How long should electronics last

[Simon]

My boiler has been in service for exactly 9 years. the control board just failed, in fact it appears it's ability to read a thermistor is all that went wrong. Surely it should last longer than this? It's not like a relay failed but I would assume the micro controller failed.

So how long is this stuff supposed to last? Needless to say I am highly suspicious of a built in fail timer, the whole thing worked fine, it was simply an analogue input that failed on a uC, which is hardly likely, yes the thermistor has been replaced but that worked fine. What the manual should have said in stead of "a constant yellow light means the thermistor has failed", is "replace control board"

[chriswebb]

Cynical answer: Warranty period + 1?

I think it's going to be hard to answer this question, because it will be so dependent on so many factors. Was the thing built for pennies? Was it designed to last? Will it be serviced? Was it built by people who take pride in their work? So many questions to ask to figure out the thought behind the product.

For your specific product, is it still under warranty? I see some boiler manufacturers in the US offer limited 10 year warranties and some can extend to lifetime warranties (of the product no doubt which you'd hope they'd stipulate), but I don't have much knowledge of boilers from living in apartment all of my adult life so I am not sure what they cover. Obviously for them, it's better not to have to pay out over the lifetime of the product, so they will probably build it to last. So it all basically comes back to that original cynical statement.

[Gyro]

I regard the use of 85'C electrolytics on a board inside a boiler casing as a definite case of built in obsolescence. They're usually the first thing to fail (rapid cycling of the ignition sequence, trips etc.). That's assuming that things like the relay pins were flow soldered correctly in the first place.

[chris_leyson]

I managed to get 15 years out my last boiler but it cost more in spares than the original cost of the boiler, three replacement water pumps, three replacement flue fans with a forth one sitting in a box somewhere, two diverter valves, two sets of elbow couplings with both metric and imperial threads that you can't buy anywhere, a set of manifold couplings and a repair to the controller board where one side of the PCB mounted 20mm fuse holder got so hot it turned the FR4 into toast. The final staw was a failed flow switch and that would also have needed a replacement manifold at £600 because the old one was pissing a few pints of water out everyday, at that point I gave up. It was a cheap boiler built to a price.
An Ariston washing machine that had four replacement controller boards and when the fifth one didn't work it was time to buy new one. The guy who came round to fit either the first or second controller board said they were crap and you need to fit a surge protector. I had a stab at trying to repair some of the failed controller boards but couldn't find the fault.
Consumer goods are built to a price and you have to "Muntz" the electronics and mechanics to get it down as cheap as possible. Some companies put a lot of effort into R&D in order to get 10 or maybe 15 years out of a product whereas other companies don't put much effort into R&D, you get what you pay for. EDIT: Just remembered, one of the designers at Thorn EMI Ferguson told me that they didn't fit better rated diodes around the TV line output stage because you could get 5 years life with the ones fitted.

[BrianHG]

My boiler has been in service for exactly 9 years. the control board just failed, in fact it appears it's ability to read a thermistor is all that went wrong. Surely it should last longer than this? It's not like a relay failed but I would assume the micro controller failed.

Now when you say boiler, you mean for heating your home, not hot tap water right?
I know that the hot water tanks have a microscopic thin layer of glass coating in them which supposed to last only 10 years.  After that time, as the glass thins out, and the water reaches metal, the metal eventually begins to rust and your water goes brown.  My last hot water tank began browning after 16 years of use and I switched it quick before either my tank ruptured, or, too much metal rust would permanently damage my piping and faucets.  If a heater boiler has a similar glass coating, it may have a similar lifetime expectancy, or, at least check with the manufacturer and they will tell you the life time of the tank.

[Simon]

Now when you say boiler, you mean for heating your home, not hot tap water right?
I know that the hot water tanks have a microscopic thin layer of glass coating in them which supposed to last only 10 years.  After that time, as the glass thins out, and the water reaches metal, the metal eventually begins to rust and your water goes brown.  My last hot water tank began browning after 16 years of use and I switched it quick before either my tank ruptured, or, too much metal rust would permanently damage my piping and faucets.  If a heater boiler has a similar glass coating, it may have a similar lifetime expectancy, or, at least check with the manufacturer and they will tell you the life time of the tank.

This is a gas combi boiler, it heats both radiators for heating and hot water instantly for domestic use. The controller board looks brand new, like i say a thermistor would go straight to the uC so if it's saying that the fault is there then it must be the uC itself, one of the hardiest components surely?

[Simon]

I regard the use of 85'C electrolytics on a board inside a boiler casing as a definite case of built in obsolescence. They're usually the first thing to fail (rapid cycling of the ignition sequence, trips etc.). That's assuming that things like the relay pins were flow soldered correctly in the first place.

nope simply the uC seems to have failed, silicon that lasts just 9 years..... really?.....

[grumpydoc]

Things do fail and a lot of the electronics that goes into domestic appliances is designed down to a price so components get run close to or even beyond specified ratings. In a boiler temperature is probably the biggest killer of electronics.

FWIW my boiler is 21 years old and still works. The control board is a simple all analogue affair - a couple of time delays and checks that the fan is running and pilot lit before the main gas supply is turned on. It has required two repairs by me, one to resolder the main connector which has pretty heavy pins and I think thermal cycling and the physical strain of a bulky connector eventually fractured all the solder joints. The other repair was to replace all the caps. I'll probably have to do both again, especially the caps as the only spares I had in the junk box were pretty close on max voltage (55v rated in a 48V circuit IIRC).

[Seekonk]

Ten years is a good service life. I worked for a company that built control electronics for equipment fabricators.  You can be sure that no one at the boiler company designed this.  We were given a specification and asked to quote a price for hundreds of companies like this.  There were discussions about how to make it fool proof, but never on how long it should last. I'd be in cosmic angst over adding a 1/3 cent resistor to make a module a little better. It was always a relentless push to get cost lower.  I'm surprised many things last as long as they do.  My furnace has an over temp snap disk that goes bad now and then. I just give it a whack and it runs for a couple more months. In my 50 years experience it is almost a given that switches will fail because of oxidation from low voltage and current.  There are proper materials, but you can get a reasonable service life out of low cost parts.

[BrianHG]

Now when you say boiler, you mean for heating your home, not hot tap water right?
I know that the hot water tanks have a microscopic thin layer of glass coating in them which supposed to last only 10 years.  After that time, as the glass thins out, and the water reaches metal, the metal eventually begins to rust and your water goes brown.  My last hot water tank began browning after 16 years of use and I switched it quick before either my tank ruptured, or, too much metal rust would permanently damage my piping and faucets.  If a heater boiler has a similar glass coating, it may have a similar lifetime expectancy, or, at least check with the manufacturer and they will tell you the life time of the tank.

This is a gas combi boiler, it heats both radiators for heating and hot water instantly for domestic use. The controller board looks brand new, like i say a thermistor would go straight to the uC so if it's saying that the fault is there then it must be the uC itself, one of the hardiest components surely?

Hot water tanks for domestic use have the glass lining, otherwise the hot water will begin to taste funny after 2 years or so...  You may stretch your tank to around 15 years if you fix your controller board, however, it is recommended in the industry to swap tanks every 9-10 years.  I never kept my hot water tank boiling steaming hot, so the heat from the gas burner below the tank didn't erode away the glass lining too fast (thermal stress) and I managed a 16 years.  I guess if you are in a more mild climate compared to here in Montreal, you may get away with 20 years...

[Gyro]

Things do fail and a lot of the electronics that goes into domestic appliances is designed down to a price so components get run close to or even beyond specified ratings. In a boiler temperature is probably the biggest killer of electronics.

FWIW my boiler is 21 years old and still works. The control board is a simple all analogue affair - a couple of time delays and checks that the fan is running and pilot lit before the main gas supply is turned on. It has required two repairs by me, one to resolder the main connector which has pretty heavy pins and I think thermal cycling and the physical strain of a bulky connector eventually fractured all the solder joints. The other repair was to replace all the caps. I'll probably have to do both again, especially the caps as the only spares I had in the junk box were pretty close on max voltage (55v rated in a 48V circuit IIRC).

I suspect that we have the same boilers - at least the same vintage. Cries of "They don't make 'em like they used to!" etc. 

[nali]

nope simply the uC seems to have failed, silicon that lasts just 9 years..... really?.....

You seem to be extrapolating your single event into a generic design flaw. It COULD be a random failure, or could just be bad connections as Grumpydoc had. What exactly does "ability to read the thermistor" actually mean?

[grumpydoc]

I suspect that we have the same boilers - at least the same vintage. Cries of "They don't make 'em like they used to!" etc. 

Potterton Prima - I think the 60F; late 1995/early 1996 vintage.

[JohnPen]

In Simon's case it could still be the capacitors dying as excessive supply ripple could still confuse the uC with a false reading.  Processors are usually pretty reliable, after the running in period, unless they operate long term in an excessively warm environment. This could of course be the situation in a boiler.

[Gyro]

I suspect that we have the same boilers - at least the same vintage. Cries of "They don't make 'em like they used to!" etc. 

Potterton Prima - I think the 60F; late 1995/early 1996 vintage.

Haha, knew it! Potterton Prima 50F 

Apart from the same board repairs, the only other thing I've had to do was repair the overly thin inner tube of the balanced flue which tends to rot through (worth checking). There's a remedial Flue kit for that, it is done completely from outside, no need to open the boiler...

https://www.ebay.co.uk/sch/i.html?_odkw=prima+F+flue&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xprima+F+remedial.TRS0&_nkw=prima+F+remedial&_sacat=0

[Simon]

nope simply the uC seems to have failed, silicon that lasts just 9 years..... really?.....

You seem to be extrapolating your single event into a generic design flaw. It COULD be a random failure, or could just be bad connections as Grumpydoc had. What exactly does "ability to read the thermistor" actually mean?

Well the whole thing only has 3 electrolytics all looking good. As I said you cannot tell the old from the new and i was very careful to not mix them up. the uC does not have any elecy caps near it, there are a number of SMD ceramics under the through hole PCB near the uC.

What I am saying is that for a uC to read a thermistor it only needs another resistor, so the "weakest" part in the chain is the uC (thermistor already changed). This leads me to deduce the uC failed. The boiler still produce heating water with no problem, it was specifically domestic hot water that failed. In fact the boiler cover has been off for these last 7 years so the PCB has not been overheating as it's been in a separate plastic compartment in free air. Being an efficient combi boiler there is not much heat iradiated by the combustion chamber.

no there is no tank here, it's basically a radiator with a gas burner under it, a pump, heat exchanger various solenoids and the controller. Strangely the igniter module that plugs into the main PCB is doing just fine.......

[NivagSwerdna]

My boiler has been in service for exactly 9 years. the control board just failed, in fact it appears it's ability to read a thermistor is all that went wrong. Surely it should last longer than this? It's not like a relay failed but I would assume the micro controller failed.

Control boards are readily available because they do fail, presumably due to environment they live in.  I swapped a board in my boiler a few years back and it just started working again... I have the old one somewhere I should diagnose for the LOLs.  Likewise, thermistors do fail... and fans definitely fail but I guess that's not so surprising due to mechanical wear.
I have rather traumatic memories of replacing the pressure relief valve on my boiler on Christmas eve a few years back since my boiler company told me they were shut for Christmas so couldn't help, getting the parts was a nightmare, and it took me two days,... that was a job too far but it was cold...  however with a lot of stress... warm and toasty by the end of Christmas Day!  I've since had the boiler professionally serviced 
Good luck!

[Simon]

Oh my boiler is working just fine now. first i replaced the thermistor as suggested by the manual but same fault so thermistor was fine. changed the main PCB and now it's working fine (well but for the air flow switch that was faulty after just 2 years). So yes the main PCB was at fault and we all go again but for the odd requirement to reset. One day I'll open the thing up and change the pressure flow switch. Yes i managed to get parts from stock in 24 hours.

[NivagSwerdna]

One day I'll open the thing up and change the pressure flow switch.

FWIW sometimes sediment builds up in the pressure flow switch.  I fixed one issue by banging it gently to shift the gunk!  Never had to replace it!

[Simon]

One day I'll open the thing up and change the pressure flow switch.

FWIW sometimes sediment builds up in the pressure flow switch.  I fixed one issue by banging it gently to shift the gunk!  Never had to replace it!

no this is air flow, I think it makes sure air is being blown into the burning chamber so the boiler cuts out and goes to fault if there is no air being blown into the chamber, of course the safety device has proven less reliable than the device (fan) it is monitoring 

[SparkyFX]

of course the safety device has proven less reliable than the device (fan) it is monitoring 

I guess that is the second preferred outcome for a safety device, next to not failing at all. :-)
If the monitor underlies the same stresses/principles as the monitored device earlier fail might be a good thing after all.

The build-up and cycling of gunk is a science of its own, anyway.

[Simon]

This is a simple diaphram switch that picks up a small pressure difference indicating air flow into the combustion chamber

[Cerebus]

I regard the use of 85'C electrolytics on a board inside a boiler casing as a definite case of built in obsolescence. They're usually the first thing to fail (rapid cycling of the ignition sequence, trips etc.). That's assuming that things like the relay pins were flow soldered correctly in the first place.

You'd think so, wouldn't you?

I had cause to tape a thermocouple to one of the pipes inside my boiler a while back. After I'd got the readings I needed I couldn't be bothered to disassemble and reassemble the boiler to recover the thermocouple, so for a few months there was a type K thermocouple plug hanging out of my boiler.

Eventually I did need the thermocouple back and before removing it from the boiler I tried taking readings again. Low, way too low. On the pipe it was reading 50-60C, it was about 30C. So off comes the case and the tape that was holding the thermocouple had let go, leaving the thermocouple tip hanging in the breeze between the hot water outlet and the control board.

So the control board was sitting at about 30C ambient, no hotter, and in many cases  cooler than inside bits of electronics that don't have a 30 kW boiler 15 centimetres away inside the case.

Moral of the story: the apparently reasonable assumption that inside the case of a boiler is really hot is, in fact, not necessarily true.

[Simon]

Indeed. My board has not seen high temperatures. I don't know what uC they are using but really can you deliberately make such poor quality chips on purpose?

[Simon]

well you can actually, I once bought an SD card reader that lasted just 3 months.

[Seekonk]

There is no conspiracy. It sounds like the input wasn't protected enough and you suffered an extremely rare event.  I got a fairly new dishwasher from a guy who was dropping it off at recycling.  Brought it home and it had taken a massive lightning hit, board was charred and components had exploded in the line voltage section. Certainly this is classified as unrepairable in the service industry. A little clean up and some jumper wires.  Five minutes later it was working.  The microprocessor survived all that.

[Simon]

Well I'm not a conspiracy theorist but sometimes I wonder at how fast stuff breaks down when I am used to designing stuff to be indestructible and last forever. I don't know what rare event could have been suffered. On the whole the thing works as it would run the heating fine but it could no longer control the tap hot water properly reporting a non existent thermistor fault. There is a secondary thermistor apparently but it only controls to 50-55C and this was too low to run the shower that some idiot put on huge pipe sizes (3/4" I think) so a lot of heat is gone by the time the "hot" water gets to the shower head.

[Towger]

In my experience 9 years is good for a 'modern' boiler's PCB.  The build quality of Potterton, Glowworm etc is to use the technical term 'shite'.

Simon, it is probably a dry joint or dry capacitor.  I have 3 PCBs for my boiler, of different revisions.

1. Original: I managed to keep this going for 10 years, full of dry joints.  In fact I don't know how it ever worked, a couple of resistor legs were not even soldered.  It eventually decided not to detect a flame.  This was probably a dry capacitor, but after several repairs it was time to go.

2. More modern version,  with LEDs rather than neons.  This lasted two years before it started giving trouble.  A whack with screwdriver would get it going again.  In the words of Tom Baker as Dr Who 'If in douth give it a clout'.  In order to keep SWBMO happy I ordered replacement 3. 
#2 reached an unusable state before #3 arrived.  Another late night freezing cold, repair job...  It lives outside in a shed.  On inspection signs of arcing on a dry joint on a relay leg there noted and repaired, along with a number of other suspects.  Reinstalled and it is still working... well two months at this stage.

3# This is now in storage, with my growing collection of other spare and replaced parts.

[Simon]

Well this one is well made, like i say it still worked but for a small failure whos cause it not traceable to any assembly issues but is enough to put the kibosh on the whole thing. for £190 they are probably not worth repairing. The only thing I can think of is a filter ceramic capacitor in the thermistor input could have shorted internally but somehow I doubt it.

[grumpydoc]

Indeed. My board has not seen high temperatures. I don't know what uC they are using but really can you deliberately make such poor quality chips on purpose?

Probably not temperature per se but temperature cycling can kill things relatively quickly.

[Monkeh]

I am used to designing stuff to be indestructible and last forever.

The only thing I can think of

These two statements don't add up. You're used to designing stuff to last but you can't think of failure modes?!

Open pull-up resistor.
Shorted ceramic cap.
Open ceramic cap.
Silver leeching causing termination failure of SMD caps or resistors (potential cause of above opens).
Fractured via.
Fractured solder joint.

Just a few random thoughts. We'll ignore the 'good looking' electrolytics, and the assumption there's no additional circuitry in the thermistor input.

Oh, and it's also possible at some point in the last 9 years of services and repairs someone has given the chip a nice belt and the damage is finally apparent.

[danadak]

There is extensive literature on long term reliability integrated circuits
on the web, just google "long term reliability integrated circuits", tons
of hits.


Regards, Dana.

[chris_leyson]

Glad you got it fixed Simon,

Well I'm not a conspiracy theorist but sometimes I wonder at how fast stuff breaks down when I am used to designing stuff to be indestructible and last forever

I think a lot of engineers would rather over engineer things to make them last but there comes a point where you have to stop especially if the engineers are working to tight budgets or timescales. If your product is connected to mains 24/7 you've got to test for brown outs, surges, fast triansients and more, then there are all the what if questions, if a component goes open or short will it fail safe and sometimes small details might get overlooked. I think the Seiki 39" TV with the impressively bad PSU failure is one example where profit was more important than safety and reliability, maybe they just copied bits and pieces from other designs without putting any real engineering effort into the design. On the other hand I still have a DAC90A that is well over 50 years old and it just needs a re-cap, after all paper caps weren't designed for a 50 year life span.

[tecman]

One thing not mentioned are tin whiskers.  They are a common cause of "failure" that is a gift of lead-free solder mandates.  They can cause shorts between pins resulting in a bad input or signal, up to a large short circuit.  Many in the industry are not aware of the issue, but it has been around for decades.  I was exposed to it years ago designing some mil hardware.  All hi-rel mil and space equipment still use lead based solder for that reason.  Sometimes you can see the whiskers under a microscope and try to remove them, but often it is looking literally for a needle in a haystack.  One repair mitigation is to flux and reheat (reflow) the unit.  The whiskers will pull back into the joints.

As I said many "failures" are caused by diagnosed whishers.

https://nepp.nasa.gov/WHISKER/background/index.htm

Paul
 

[chris_leyson]

I've only even seen one tin whisker, it had been happily growing inside a hermetically sealed relay, once the top of the relay was filed off you could see it with the naked eye if the illumination was just right so it must have been quite big by tin whisker standards. From what I've read pure tin plating is the most likely cause of tin whiskers and not lead free solder, http://www.indium.com/blog/pb-free-solders-are-not-the-cause-of-tin-whiskers.php
I think in the case of the relay you've got stamped and formed tin plated parts which have residual mechanical stress and lead free solder just adds to the stress, the whisker wasn't growing out of a solder joint.

[james_s]

Sometimes stuff does just fail for no readily apparent reason. Several years ago I fixed a Bosch dishwasher with an unusual fault, the "fix" was adding an external pullup resistor to one of the IO pins on the microcontroller and today it still works just fine. I know of several other identical dishwashers that have not had any electronic faults at all so I'm not inclined to believe that it was the result of a design flaw. Failure analysis is a complex topic, there are so many factors that come into play.

[Simon]

I am used to designing stuff to be indestructible and last forever.

The only thing I can think of

These two statements don't add up. You're used to designing stuff to last but you can't think of failure modes?!

Open pull-up resistor.
Shorted ceramic cap.
Open ceramic cap.
Silver leeching causing termination failure of SMD caps or resistors (potential cause of above opens).
Fractured via.
Fractured solder joint.

Just a few random thoughts. We'll ignore the 'good looking' electrolytics, and the assumption there's no additional circuitry in the thermistor input.

Oh, and it's also possible at some point in the last 9 years of services and repairs someone has given the chip a nice belt and the damage is finally apparent.

As i've repeatedly said this board is in excellent condition, it has not been overheated or thermically cycled for that matter as most of it's life has been spent in a room so it has seen nore more than 40C and no less than 0C, not really what you would call thermal cycling.

I didn't design this board so I don't know what mitigation went into it's design. What is more astounding is not what if the electrolytic capacitor 20mm away that may have little to do with the uC has fasiled but there is no sign of bypass capacitors at all unless i am to count one of the small (maybe 0.1uF) ceramics. I've not tried to reverse engineer it. As I've also said it is strange that this one input has failed yet several others are obviously working fine, I'll have to get my meter and test the ceramics, maybe one is shorted internally but for that the only other failure mode i can think of is the uC failing which.... now that I have removed the firmware label from it i can tell you is an ST72C216G1B so not some won-hung-lo thing.

[Simon]

oh and the cap is rated for 105C

[Simon]

And there are movs on the mains input.

[Zero999]

Now when you say boiler, you mean for heating your home, not hot tap water right?
I know that the hot water tanks have a microscopic thin layer of glass coating in them which supposed to last only 10 years.  After that time, as the glass thins out, and the water reaches metal, the metal eventually begins to rust and your water goes brown.  My last hot water tank began browning after 16 years of use and I switched it quick before either my tank ruptured, or, too much metal rust would permanently damage my piping and faucets.  If a heater boiler has a similar glass coating, it may have a similar lifetime expectancy, or, at least check with the manufacturer and they will tell you the life time of the tank.

This is a gas combi boiler, it heats both radiators for heating and hot water instantly for domestic use. The controller board looks brand new, like i say a thermistor would go straight to the uC so if it's saying that the fault is there then it must be the uC itself, one of the hardiest components surely?

Hot water tanks for domestic use have the glass lining, otherwise the hot water will begin to taste funny after 2 years or so...  You may stretch your tank to around 15 years if you fix your controller board, however, it is recommended in the industry to swap tanks every 9-10 years.  I never kept my hot water tank boiling steaming hot, so the heat from the gas burner below the tank didn't erode away the glass lining too fast (thermal stress) and I managed a 16 years.  I guess if you are in a more mild climate compared to here in Montreal, you may get away with 20 years...

That sounds like a very odd set up to me. I don't have a hot water tank at my house, but my parent's do. The tank is made from copper and is situated in an upstairs cupboard, over 5 metres away from the boiler. The water in the tank never mixes with the tap water. Water circulates from the boiler, through a coiled pipe, inside the tank, which acts as a heat exchanger. The tank does have a heating element (immersion heater), which can be used in case the boiler or gas supply fails.

[Monkeh]

Now when you say boiler, you mean for heating your home, not hot tap water right?
I know that the hot water tanks have a microscopic thin layer of glass coating in them which supposed to last only 10 years.  After that time, as the glass thins out, and the water reaches metal, the metal eventually begins to rust and your water goes brown.  My last hot water tank began browning after 16 years of use and I switched it quick before either my tank ruptured, or, too much metal rust would permanently damage my piping and faucets.  If a heater boiler has a similar glass coating, it may have a similar lifetime expectancy, or, at least check with the manufacturer and they will tell you the life time of the tank.

This is a gas combi boiler, it heats both radiators for heating and hot water instantly for domestic use. The controller board looks brand new, like i say a thermistor would go straight to the uC so if it's saying that the fault is there then it must be the uC itself, one of the hardiest components surely?

Hot water tanks for domestic use have the glass lining, otherwise the hot water will begin to taste funny after 2 years or so...  You may stretch your tank to around 15 years if you fix your controller board, however, it is recommended in the industry to swap tanks every 9-10 years.  I never kept my hot water tank boiling steaming hot, so the heat from the gas burner below the tank didn't erode away the glass lining too fast (thermal stress) and I managed a 16 years.  I guess if you are in a more mild climate compared to here in Montreal, you may get away with 20 years...

That sounds like a very odd set up to me. I don't have a hot water tank at my house, but my parent's do. The tank is made from copper and is situated in an upstairs cupboard, over 5 metres away from the boiler. The water in the tank never mixes with the tap water. Water circulates from the boiler, through a coiled pipe, inside the tank, which acts as a heat exchanger. The tank does have a heating element (immersion heater), which can be used in case the boiler or gas supply fails.

US/Canada. Odd is normal.

[Cerebus]

That sounds like a very odd set up to me. I don't have a hot water tank at my house, but my parent's do. The tank is made from copper and is situated in an upstairs cupboard, over 5 metres away from the boiler. The water in the tank never mixes with the tap water. Water circulates from the boiler, through a coiled pipe, inside the tank, which acts as a heat exchanger. The tank does have a heating element (immersion heater), which can be used in case the boiler or gas supply fails.

US/Canada. Odd is normal.

Forty years ago a hot water tank was the norm in UK houses and flats. The switch to combi boilers started en-masse in the 80s for new build and replacement of existing boilers.

[Simon]

my dad still has a tank because the wankers that did his free boiler replacement simply replaced the old boiler with a newer design that is more efficient (along with fucking up everything they could in the process and then dissapering). with the old "boilers" they were so inefficient that in the summer i found it would be cheaper to use the electric element and permanently turn off the pilot light for the gas.

[Gyro]

There are still a lot of us with the benefit of having the remains of a tank of hot water when the boiler goes out. I've no intention of changing - the water is far too hard around here!

[Zero999]

Now when you say boiler, you mean for heating your home, not hot tap water right?
I know that the hot water tanks have a microscopic thin layer of glass coating in them which supposed to last only 10 years.  After that time, as the glass thins out, and the water reaches metal, the metal eventually begins to rust and your water goes brown.  My last hot water tank began browning after 16 years of use and I switched it quick before either my tank ruptured, or, too much metal rust would permanently damage my piping and faucets.  If a heater boiler has a similar glass coating, it may have a similar lifetime expectancy, or, at least check with the manufacturer and they will tell you the life time of the tank.

This is a gas combi boiler, it heats both radiators for heating and hot water instantly for domestic use. The controller board looks brand new, like i say a thermistor would go straight to the uC so if it's saying that the fault is there then it must be the uC itself, one of the hardiest components surely?

Hot water tanks for domestic use have the glass lining, otherwise the hot water will begin to taste funny after 2 years or so...  You may stretch your tank to around 15 years if you fix your controller board, however, it is recommended in the industry to swap tanks every 9-10 years.  I never kept my hot water tank boiling steaming hot, so the heat from the gas burner below the tank didn't erode away the glass lining too fast (thermal stress) and I managed a 16 years.  I guess if you are in a more mild climate compared to here in Montreal, you may get away with 20 years...

That sounds like a very odd set up to me. I don't have a hot water tank at my house, but my parent's do. The tank is made from copper and is situated in an upstairs cupboard, over 5 metres away from the boiler. The water in the tank never mixes with the tap water. Water circulates from the boiler, through a coiled pipe, inside the tank, which acts as a heat exchanger. The tank does have a heating element (immersion heater), which can be used in case the boiler or gas supply fails.

US/Canada. Odd is normal.

Forty years ago a hot water tank was the norm in UK houses and flats. The switch to combi boilers started en-masse in the 80s for new build and replacement of existing boilers.

I didn't say having a water tank was odd. Read Brian's post I was responding to, which you removed. It's odd to have a steel hot water, which is heated directly by a gas flame. I've never seen that before!

[Rick Law]

Sometimes stuff does just fail for no readily apparent reason. Several years ago I fixed a Bosch dishwasher with an unusual fault, the "fix" was adding an external pullup resistor to one of the IO pins on the microcontroller and today it still works just fine. I know of several other identical dishwashers that have not had any electronic faults at all so I'm not inclined to believe that it was the result of a design flaw. Failure analysis is a complex topic, there are so many factors that come into play.

I know you did not say it is a design flaw in the quote - I quoted it because it makes one think about the term "design flaw" - that "it is a design flaw" or not is really a matter of the requirement.

If you are tasked with designing (for example) a water heater to last 10 years, your design based on analysis would last 20 years.  The result then is not the product requested.  Presumably, cost can be brought down by reducing the life expectancy.  If the customer had wanted it to last 20 years, they would have brought the 20 years model.

Similarly, if one is tasked to design a DMM with +-2%.  It would be a waste to spend the extra for 0.1% parts if the model is only rated for +-1%.  Of course with exception where it is necessary to have 0.1% parts there to achieve the +-1% end goal.  By sourcing lower cost parts, they can afford to make this model cheaper if the source cheaper parts.

Even in cases where you know re-doing the layout of that area of the PCB would increase durability, you need to put into consideration that the durability is worth the investment to re-do by both the manufacturer and the end user.  Lower cost with lower durability and/or lower quality do have its place in the market.

So I am not sure if it is correct to interpret it as a design flaw or meeting designed criteria unless the design criteria is known.

[Simon]

To be honest my initial point was about the actual life span of parts, the silicon devices and basic passives like resistors and capacitors. It's not like this thing has seen vibration or heat and seems reasonably designed.

[Cerebus]

Now when you say boiler, you mean for heating your home, not hot tap water right?
I know that the hot water tanks have a microscopic thin layer of glass coating in them which supposed to last only 10 years.  After that time, as the glass thins out, and the water reaches metal, the metal eventually begins to rust and your water goes brown.  My last hot water tank began browning after 16 years of use and I switched it quick before either my tank ruptured, or, too much metal rust would permanently damage my piping and faucets.  If a heater boiler has a similar glass coating, it may have a similar lifetime expectancy, or, at least check with the manufacturer and they will tell you the life time of the tank.

This is a gas combi boiler, it heats both radiators for heating and hot water instantly for domestic use. The controller board looks brand new, like i say a thermistor would go straight to the uC so if it's saying that the fault is there then it must be the uC itself, one of the hardiest components surely?

Hot water tanks for domestic use have the glass lining, otherwise the hot water will begin to taste funny after 2 years or so...  You may stretch your tank to around 15 years if you fix your controller board, however, it is recommended in the industry to swap tanks every 9-10 years.  I never kept my hot water tank boiling steaming hot, so the heat from the gas burner below the tank didn't erode away the glass lining too fast (thermal stress) and I managed a 16 years.  I guess if you are in a more mild climate compared to here in Montreal, you may get away with 20 years...

That sounds like a very odd set up to me. I don't have a hot water tank at my house, but my parent's do. The tank is made from copper and is situated in an upstairs cupboard, over 5 metres away from the boiler. The water in the tank never mixes with the tap water. Water circulates from the boiler, through a coiled pipe, inside the tank, which acts as a heat exchanger. The tank does have a heating element (immersion heater), which can be used in case the boiler or gas supply fails.

US/Canada. Odd is normal.

Forty years ago a hot water tank was the norm in UK houses and flats. The switch to combi boilers started en-masse in the 80s for new build and replacement of existing boilers.

I didn't say having a water tank was odd. Read Brian's post I was responding to, which you removed. It's odd to have a steel hot water, which is heated directly by a gas flame. I've never seen that before!

I didn't say that you said that it was odd.

I didn't even say that anything anybody said was odd.

I did think that several people about here are a little odd, but I didn't say it.

Removing seventeen layers of posts is just a simple courtesy to people who don't want to have to wade past 50 lines of text to read my one or two liner, not an attempt to cunningly conceal what you really said, so that I can entrap you into appearing odd, or an odd-sayer, or even to reveal you as the secret seasonal turkey snacker that we all suspect you to be. 

[tpowell1830]

Indeed. My board has not seen high temperatures. I don't know what uC they are using but really can you deliberately make such poor quality chips on purpose?

In a perfect world, where handling and installing uC on the PCB is done with perfect precision and care, the uC would live very, very long. However, there could have been a micro-fracture undetected in the silicon of this single chip and installed and constant cycling and stress from handling and installation could have made it worse. Even though the PCB was not in a very hot environment, as you say, the PCB has some movement and heat fluctuations over time and this could have further stressed the chip until finally it did not function.

Also, as you pointed out, the capacitors look new and clean, however, I have seen very clean and new looking caps have very low ESR over time, which diminishes the filtering ability. Also, over time, the capacitance diminishes, therefore diminishing the filtering ability. The uC has a tolerance that allows voltage pops and the caps provide this protection, until it doesn't and the uC can take no more and breaks.

There are 10s if not hundreds of other scenarios in which this uC could have failed, mostly related to handling, electrical, installation and environmental stress conditions.

When you think of all of the conditions in which you have a perfect PCB, the probability of meeting all of the perfect conditions is so astronomically large that the devices will not eventually fail that it is what I would call a success that you got 9 years of service from this system.

Just my 2 cents...

[SparkyFX]

If your product is connected to mains 24/7 you've got to test for brown outs, surges, fast triansients and more,[...]

... which are hard to be predicted or quantized. I mean, ten years ago i rushed to disconnect the devices when there was a thunder and lightning nearby. Very few things broke (maybe a power brick), but the chance of devices breaking is higher with more devices connected to mains. Does that statistic outrun the allegedly less resilient devices or the use of microelectronics?

Especially transient protection is neither perfect nor completely reliable, apart from expectations regarding surge protectors. Of course, after the last failed attempt at washing machine repair, i better put an extra surge protector in front of it, just to increase chances. Those LNK304 DC/DC converters seem to violently loose their chip package right often in Whirlpool devices, people on ebay specialized in sending the repair kits/spare parts in envelopes.

[chris_leyson]

Those LNK304 DC/DC converters seem to violently loose their chip package right often in Whirlpool devices

I'm going to to be testing a Power Integrations flyback in the new, hopefully the MOVs will do their job, we'll see.

[coppice]

Those LNK304 DC/DC converters seem to violently loose their chip package right often in Whirlpool devices.

Is this a problem with the Whirlpool products, rather than the Power Integration device? I've seen customers use those Power Integrations devices in some high volume long life applications with pretty solid results. Solid enough that it was hard to displace them.

[BrianHG]

I didn't say having a water tank was odd. Read Brian's post I was responding to, which you removed. It's odd to have a steel hot water, which is heated directly by a gas flame. I've never seen that before!

Read line 1 of the features of this natural gaz water heater tank at this site:
http://www.gsw-wh.com/en/products/atmospheric-vent
Or google 'glass lined water heaters'
With a quality glass lined tank and installation, you hot tap water is as clean to drink as your normal cold water, that is until enough of the glass lining fractures/dissolves (it's vapor deposited to only a few microns thick) over time and will still be ok as most tanks are stainless steel, but, the heating eventually begins to break this down.

[SeanB]

Those steel tanks with the glass lining typically just make it out of warranty before failing, despite having a sacrificial anode in there. They are not make out of stainless steel, just regular mild steel with a coating of glass fused to it. They suffer from pressure cycling crazing the glass, and are pretty much going to fail from the get go, especially as they are run at a high pressure.

To find a manufacturer that makes a non mild steel tank at any price other than insane is near impossible, though there are still a few around that make copper tanks, that essentially last nearly forever, but are limited in being gravity flow only.

[Seekonk]

This is getting way off topic, but if you replace the anode rod in a heater every 5 years the tank will easily last 40 years. If you pull yours out right now it is likely there is nothing there. This is only likely possible if when the heater is new you remove the anode rod and reseal it with a good non hardening thread sealant. Installers don't even try to unscrew anything from an old water heater.  Another tip. The cold water inlet has a plastic feed pipe inside. This takes cold feed water to the bottom of the tank.  These have a tendency to break off with age.  This causes you to run out of hot water quickly from feed water instantly mixing with hot.

[SeanB]

I had a unit that was just out of warranty ( 5 years 1 month, thank you Kwikhot) and the element failed with leakage to the grounded casing. There was still half of the anode left, but that cold water baffle came out as white plastic powder and crumb as I undid the element from the bottom where it was mounted. New element in, new thermostat ( 50C instead of the as new setting of "just short of boil") plugged in and a little insulation to reduce standing loss, and the tank itself failed 6 months later, leaking from most likely the pipe stub welds rusting through, as the glaze is thinnest there. Put in a new one, which is even more plastic than the old one.

Scrap yards literally only take those at no payment or you pay them, as they spend a week there stripping the sleeves and insulation off them before compacting the 10m high pile into around 50 cubes of steel, and then have to pay for dumping the removed foam in a landfill site.

[Zero999]

I didn't say having a water tank was odd. Read Brian's post I was responding to, which you removed. It's odd to have a steel hot water, which is heated directly by a gas flame. I've never seen that before!

Read line 1 of the features of this natural gaz water heater tank at this site:
http://www.gsw-wh.com/en/products/atmospheric-vent
Or google 'glass lined water heaters'
With a quality glass lined tank and installation, you hot tap water is as clean to drink as your normal cold water, that is until enough of the glass lining fractures/dissolves (it's vapor deposited to only a few microns thick) over time and will still be ok as most tanks are stainless steel, but, the heating eventually begins to break this down.

No, I've never seen one of those before. In the UK the water tank is normally separate from the boiler.

[tggzzz]

The longest boiler guarantees I have seen are for 9 years.

The  most reliable brands are Worcester-Bosch and Vaillant.

Draw your own conclusions.

[Simon]

I didn't say having a water tank was odd. Read Brian's post I was responding to, which you removed. It's odd to have a steel hot water, which is heated directly by a gas flame. I've never seen that before!

Read line 1 of the features of this natural gaz water heater tank at this site:
http://www.gsw-wh.com/en/products/atmospheric-vent
Or google 'glass lined water heaters'
With a quality glass lined tank and installation, you hot tap water is as clean to drink as your normal cold water, that is until enough of the glass lining fractures/dissolves (it's vapor deposited to only a few microns thick) over time and will still be ok as most tanks are stainless steel, but, the heating eventually begins to break this down.

In the UK all plumbing including tanks is copper. We use plastic for pipes as well now.

[coppice]

I didn't say having a water tank was odd. Read Brian's post I was responding to, which you removed. It's odd to have a steel hot water, which is heated directly by a gas flame. I've never seen that before!

Read line 1 of the features of this natural gaz water heater tank at this site:
http://www.gsw-wh.com/en/products/atmospheric-vent
Or google 'glass lined water heaters'
With a quality glass lined tank and installation, you hot tap water is as clean to drink as your normal cold water, that is until enough of the glass lining fractures/dissolves (it's vapor deposited to only a few microns thick) over time and will still be ok as most tanks are stainless steel, but, the heating eventually begins to break this down.

In the UK all plumbing including tanks is copper. We use plastic for pipes as well now.

Most UK radiators are steel. Many houses still have galvanised steel header tanks, although the majority have been replaced. The incoming pipe in millions of houses is still lead.

[Zero999]

I didn't say having a water tank was odd. Read Brian's post I was responding to, which you removed. It's odd to have a steel hot water, which is heated directly by a gas flame. I've never seen that before!

Read line 1 of the features of this natural gaz water heater tank at this site:
http://www.gsw-wh.com/en/products/atmospheric-vent
Or google 'glass lined water heaters'
With a quality glass lined tank and installation, you hot tap water is as clean to drink as your normal cold water, that is until enough of the glass lining fractures/dissolves (it's vapor deposited to only a few microns thick) over time and will still be ok as most tanks are stainless steel, but, the heating eventually begins to break this down.

In the UK all plumbing including tanks is copper. We use plastic for pipes as well now.

Most UK radiators are steel. Many houses still have galvanised steel header tanks, although the majority have been replaced. The incoming pipe in millions of houses is still lead.

Radiators work as a closed loop, so corrosion is less of an issue.

[coppice]

Most UK radiators are steel. Many houses still have galvanised steel header tanks, although the majority have been replaced. The incoming pipe in millions of houses is still lead.

Radiators work as a closed loop, so corrosion is less of an issue.

Corrosion is only a minor issue with radiators because there is corrosion inhibitor in the closed loop. Without that, the radiators rot through quite quickly. I guess if 100% of the heating loop were steel this wouldn't happen, but mix metals and one of them is going to fail fast.

[SparkyFX]

Is this a problem with the Whirlpool products, rather than the Power Integration device? I've seen customers use those Power Integrations devices in some high volume long life applications with pretty solid results. Solid enough that it was hard to displace them.

Hard to tell from a single sample in my case, but google "LNK304 repair kit" and the compatible device list gives you quite some impression.

Checked my photos of the PCB again, there is an intact looking MOV included in the circuit, even a non-aging SIOV type, so the cause might not be transients at all. Degrading related to overheating might be an issue, the machine has got an included 12h timer which i use quite often, so it is in operation (providing DC power) longer than just the one cycle.

[Towger]

In my experience 9 years is good for a 'modern' boiler's PCB.  The build quality of Potterton, Glowworm etc is to use the technical term 'shite'.

UPDATE:

PCB 2 died this morning.  A 400v capacitor let out the magic smoke and molten polystyrene. 

Life = 3 Years. The date on this board is 2011.

I installed PCB 3 tonight, same version (7) but 2016, different brand capacitors.

Symptoms: Heating started, but did not heat for long.  Over temp tripped.  Reset.  Restarted.  Pump did not appear to be running.  Assumed pump failed (original 20? years old).  Checked voltages.  No power going to pump.  Replaced PCB.  Wife happy again :-)

[cdev]

How old is old? My water heater is a few years old and Ive been thinking about doing this (replacing the anode) now.. its maybe (guessing) five years old.. Its still a current model..

It still works fine.. no issues.. have not tried to remove it.

This is getting way off topic, but if you replace the anode rod in a heater every 5 years the tank will easily last 40 years. If you pull yours out right now it is likely there is nothing there. This is only likely possible if when the heater is new you remove the anode rod and reseal it with a good non hardening thread sealant. Installers don't even try to unscrew anything from an old water heater.  Another tip. The cold water inlet has a plastic feed pipe inside. This takes cold feed water to the bottom of the tank.  These have a tendency to break off with age.  This causes you to run out of hot water quickly from feed water instantly mixing with hot.

[paulca]

This is a gas combi boiler, it heats both radiators for heating and hot water instantly for domestic use. The controller board looks brand new, like i say a thermistor would go straight to the uC so if it's saying that the fault is there then it must be the uC itself, one of the hardiest components surely?

Mine went bang about 2 years ago.  Dead, no status lights nothing.  Plumber replaced the board, showed me the old one.  It had a huge black charred mess that looked like it was close to actually catching fire, the board was nearly charred though.  I wasn't into electronics at the time so I have no idea what failed in such a horrible way.

Fire is not something you want near a gas boiler.  I can only assume the gas value fails shut.