Author Topic: Noisy power from typical backup generators  (Read 9549 times)

0 Members and 1 Guest are viewing this topic.

Offline Renate

  • Super Contributor
  • ***
  • Posts: 1460
  • Country: us
Re: Noisy power from typical backup generators
« Reply #50 on: March 03, 2021, 05:11:31 pm »
...before the voltage dropped to the cut out point at 40.4v.
Wow, you run the batteries hard, 10.1 V cutoff?
I used to see things pointing straight down as soon as I hit 11.5 V.
I guess that I'm a wimp, under 200 W load I like to keep them above 12 V.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Noisy power from typical backup generators
« Reply #51 on: March 03, 2021, 08:38:11 pm »
...before the voltage dropped to the cut out point at 40.4v.
Wow, you run the batteries hard, 10.1 V cutoff?
I used to see things pointing straight down as soon as I hit 11.5 V.
I guess that I'm a wimp, under 200 W load I like to keep them above 12 V.

Well that's determined by the UPS, at least the little ones I have don't have any way of configuring that as far as I know. I try to fire up the generator quickly enough that they get drained very little but occasionally the power goes out when I'm not home and then if it stays out long enough it will drain them all the way down like that. Setting a higher cutoff reduces the run time significantly so I'm not surprised a UPS defaults to such a low voltage.
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 811
  • Country: gb
Re: Noisy power from typical backup generators
« Reply #52 on: March 04, 2021, 02:18:43 pm »
@Renate

 I only run the battery right down to the UPS's cut off point when testing a new battery assembly to verify the expected autonomy, otherwise, with SLA batteries, it's best to avoid discharging them at all. A first time deep discharge of a new set of SLAs seems to be beneficial in doubling up their effective capacity (it seems to be more a halving of their internal resistance) going by my first encounter with this effect.

 The first time I replaced the worn out pair of 7AH SLAs in the Emerson 30 with brand new fully charged SLAs, I tested its run time with a 60W incandescent lamp load and only got 25 minutes.  The next day, with the battery fully recharged, I saw a run time of 80 minutes!

 It would seem a good idea to subject brand new fully charged SLAs to a 1C discharge test to properly condition them which, rather conveniently after a second run, provides a benchmark autonomy figure by which to compare against similar annual test runs. Otherwise it's best to avoid such deep DoD events with SLAs - LFP otoh, can be safely taken to an 80% DoD without harm until their original capacity has dropped to 80% several thousand cycles later.

 Standard practice with LFP is to limit their charging to 90% of their maximum capacity (3.2v per cell) and their discharge to no less than 10% (around 2.25 to, preferably, 2.5 volt per cell), hence the typical 80% of their full capacity that's normally used to determine their optimal total WH's worth of autonomy.

 Unlike LA battery technology, LFP offers an almost unchanging (and very predictable) WH capacity with varying discharge rates due to their much flatter discharge voltage curve and almost non-existent Peukert effect, as well as discharge/charge cycles counted in thousands rather than the tens of cycles of such abuse in the LA case. Even when you've hit, say, the 2000 cycle limit with an LFP battery, that just means you've only lost 20% of its original capacity leaving you with another 2000 cycles before you lose another 20%.

 That wear out characteristic is what makes the acquisition of secondhand LFPs such an attractive proposition. A used 120AH LFP reduced to 80% capacity is the equivalent of a brand new 96AH LFP which, if obtained through a reputable specialist battery dealer, will be a minimum and likely to have more than a 100AH's worth of remaining capacity for typically less than half the price of a new 100AH LFP with the bonus of the BMS being rated to handle 120A rather than the 100A limit of a new 100AH battery pack.

 That set of 7AH SLAs I'd bought to test the compatibility between my ancient SmartUPS2000 and the Parkside inverter genset will be my last purchase of SLAs. My next UPS battery will definitely be an LFP battery pack. I've had a gut full of the concept of the expensive SLA battery pack as "A Consumable" with a service life at best (2.25v per cell float charging voltage) of 6 years tops.
« Last Edit: March 21, 2021, 08:50:43 pm by Johnny B Good »
John
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 8973
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: Noisy power from typical backup generators
« Reply #53 on: March 04, 2021, 02:45:11 pm »
Standard practice with LFP is to limit their charging to 90% of their maximum capacity (3.2v per cell) and their discharge to no less than 10% (around 2.25 to, preferably, 2.5 volt per cell), hence the typical 80% of their full capacity that's normally used to determine their optimal total WH's worth of autonomy.
LiFePO4 is normally charged to 3.6V/cell with 3.45V/cell being a good derating, you might be confusing it with LTO.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 811
  • Country: gb
Re: Noisy power from typical backup generators
« Reply #54 on: March 04, 2021, 04:32:05 pm »
@NiHaoMike,

 Thanks for that reminder. I was being a little lax in referring to the "Nominal 4 cell battery pack" 12.8 voltage equivalent to the 12 volt SLA it replaces. It's been a few weeks since I last researched LFP battery usage for UPS, Solar power and off grid, so am a little hazy on the finer details.

 Now you mention it though, ISTR seeing figures of 3.6v (and even 3.65v for a complete 100AH 16 cell battery pack I'd tried bidding on back then). Also, ISTR that battery pack, which went for 10 times my upper bid limit, had a low voltage cut off set to 40v. I suspect its BMS had been tuned for use with a 48v powered UPS to allow it to remain in control of the low battery shutdown process rather than chance  'having the rug pulled out from underneath it'.

« Last Edit: March 21, 2021, 08:50:18 pm by Johnny B Good »
John
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 811
  • Country: gb
Re: Noisy power from typical backup generators
« Reply #55 on: April 01, 2021, 10:24:06 pm »
I have built a number of alternator sets over the years mostly using stamford brand of alternator, now part of cummings power, I never had any trouble with noisey power from them and they use electronic AVR's or transformer type regulation on the smaller units. All the rotors have had a slight helical form to the windings which i understand helps with delivering a smoother waveform.

 Have you ever tested the effect of connecting a 4.7uF PFC capacitor across the output? You might be shocked by the result. These generators can handle resistive and inductive loads ok but can end up overvolting due to the self excitation effect caused by the leading current produced by a capacitive load which in my case was the 9.4uF's worth of capacitance across the mains input of a SmartUPS2000 line interactive UPS which would be disconnected when it transferred  to battery power due to the incoming generator voltage going north of the 240v mark by some 30 volts or more.

 I couldn't figure whether these caps could be safely disconnected or not and their exact function remains a mystery. It's possible that modern line interactive UPSes may have eliminated the need for such a large amount of capacitance on their mains input circuit (that SmartUPS is well over a quarter of a century old now) so you might not see the overvolting issue I'd suffered with my own setup if you're feeding the generator's output into the mains in socket on a modern UPS.

 As for my own thoughts on how to add a fuel priming bulb to that Parkside inverter genset, it has occurred to me that I could have saved on the T adapters and just plumbed it into the fuel line (before or after the pulse driven lift pump), assuming the one way valves don't create an excessive pressure drop. I'll test the simple series arrangement first but my original parallel arrangement might well prove to be the only viable alternative to the more usual arrangements.

 Such arrangements being that it's plumbed into an extra hose nipple on the carb to let it suck the fuel through to prime it and send the excess back to the tank or else simply to squirt extra fuel into the inlet port to make up for a dry bowl and make it easier to start.

 It seems I've come up with a third alternative that's never been mentioned in any of the youtube videos I've watched (the only source I could track down that offered even so much as a clue as to how these pulse driven fuel lift and priming bulb pumps work) in relation to priming such small engine kit relying on a (crank case pressure) pulse driven fuel lift pump. I'll report my results here in a week or two's time after I've had a chance to work on the generator.


 I can now report on my fuel priming experiments with that priming bulb kit. Sorry for the delay being a fortnight longer than I'd estimated but I do at last have something positive to report even though the upgrade still requires another length of 2 by 3.5mm fuel line to complete the final version.

 I was going to follow my original idea of using the priming bulb kit to refill the carb float bowl via the fuel feed line but this was sidelined by the presence of a mystery clear plastic tube, dangling out of the bottom of the base plate alongside of the float bowl drain tube, connected to a nipple on the carb body which looked temptingly like it could have been a 'priming port'. Succumbing to this temptation, I connected the primer bulb's outflow to this nipple and plumbed the input into a T adapter connection to the fuel tank feed line.

 After priming with a few presses, I was able to start it 'first pull'. Unfortunately, the engine didn't pick up speed after opening the choke obviously running on an over-rich mixture before it eventually died after about a minute or so. Obviously, this 'mystery nipple' wasn't intended for use with a fuel priming bulb as I'd hoped so it was back to my original plan.

 Cascading the priming bulb in series with the fuel tap connection to the carb fuel line was the easiest plumbing arrangement (no need to use a pair of Tee adapters either side of the fuel lift pump which is plumbed in between the fuel tank and the fuel shut off tap). This seemed to work with only some minor bother to start with but after allowing it to run the carb dry and cool down for a couple of hours to retest the "Start from bone dry" stone cold condition, it became obvious that it was suffering fuel starvation due to excessive flow restriction from the primer bulb.

 I had to call a halt on further work for lack of sufficient fuel line and time. It's now finally become obvious that the only viable option that remains is the more complicated plumbing of the primer bulb in parallel with the original fuel lift pump. This arrangement removes any question of flow restriction and the one way valves in both pumps means they should function perfectly fine in this arrangement.

 If I hadn't been tempted by that extra plastic pipe connection to the carb and gone straight for the parallel arrangement, the job would have been done and dusted by now. Still, my experience here may help someone else considering a similar enhancement to make pull starting these cheap inverter gensets as easy as it should have been to begin with. I've placed an order for a metre length of the 2x3.5mm fuel line so it's just a matter of awaiting delivery and some dry warmish weather to resume the modification - it's a task best worked on out of doors rather than indoors for very obvious reasons.

 As for that mysterious plastic pipe connection to the carb, I think it must be an atmospheric pressure equalisation vent tube but why such a plastic tube would be deemed necessary when the more usual system of pressure balancing with a small vent hole into the float chamber above the normal fuel level beats the hell out of me. Presumably there IS a good reason for this bit of extra plumbing. Maybe someone here knows the answer to that question?

 Looking at the long range weather forecast for the UK, it looks like it may be another couple of weeks yet before I can make a final report. Small parts orders from UK sellers rarely take longer than a week to be delivered in spite of the Covid 19 restrictions. Often they will arrive with 2 or 3 days of being ordered, barring Bank Holiday silliness and such like. Even if the fuel line turns up this Saturday, the weather forecast for this weekend and into the following week looks extremely bleak for any such outdoors work so don't hold your breath on my next report. :(

 BTW, I didn't waste this opportunity to connect a DSO to the alternator and a a 3 turn sense winding over the exposed end of the ignition coil core in order to record waveform  traces to let me answer the question "How many stator poles - 18 or 21?". The number is typically 18 or 21 in virtually all such inverter gensets. In this case, as you will see from the attached screen shots, the answer is 21 (with 7 pairs of magnets embedded into the flywheel).

 In this case, there is an ignition pulse every revolution rather than every other revolution. It's not at all surprising since the waste spark is of no consequence and simplifies ignition timing and accuracy - triggered directly from a flywheel sensor without any additional anding with a camshaft derived signal to restrict it to the start of the power stroke.

 Although I have my answer to let me order that TI sensor pre-programmed for a 7 by 3 pole stator BLDC hall sensor emulation (or to DIY a 3 hall sensor array with a 17.143 degree spacing around the flywheel periphery, assuming sufficient leakage flux exists), I rather doubt I will ever bother trying to take my electric starter project any further.

 Looking at those screenshots, I suspect I'd need to provide supplementary battery power to the ignition circuit to get a reliable spark at the 200 to 240 rpm cranking speed I'd hoped to get at best. In itself, such a low cranking speed should still be enough but without a reliable source of sparks, it's a no go as things stand. My best guess, looking at those traces, is that it needs a 500 rpm minimum cranking speed just to generate a reliable source of ignition pulses in the absence of such supplementary battery power to the ignition circuit.

 That low cranking speed ignition issue is the final nail in my DIY BLDC direct drive electric start project's coffin. That's not to say such an electric starting technique couldn't be employed in future models where the manufacture can modify the alternator with additional heavy duty low voltage starter windings to allow a 12v starter battery to directly power the starter windings with a minor modification to the ignition circuit to be powered from the battery/charging generator output. However, that does rather put it out of reach of all bar the most dedicated of DIYers prepared to do whatever it takes no matter the cost.

 Since I'm not quite into that class of extreme DIY, that now puts an end to any further work on my BLDC direct drive electric starter folly leaving me to concentrate upon fixing the unconscionable lack of a priming bulb pump perpetrated by the manufacturer, Parkside.

 As it happened, it was rather fortuitous that I'd spotted the opportunity to wrap three turns of a croc clip test lead around the ignition coil core to save using a microphone by the vacant spark plug hole to detect a timing reference as I'd originally intended since it let me spot the low revs ignition issue in time to avoid expending any more effort on what had threatened to become a rather more complex modification than I'd ever originally imagined it would ultimately turn into.

 Considering the poor or unreliable ignition pulses at low cranking speeds, it seems surprising that a kickback risk should still be present but I think just enough voltage must be getting generated to produce a possibly mis-timed spark if a poor technique is employed to pull start it. I would say all that ignition circuit needs is an undervolt lock out with a power ramp up ignition retardation set to a few degrees past TDC for the first two or three power strokes in order to eliminate the kickback risk of a fixed advanced ignition timing optimised to the eco and max output engine speeds without any consideration for the pull start kickback hazard this presents to the end user. Just adding a priming pump goes a long way to mitigating this rather spiteful shortcoming.

« Last Edit: April 02, 2021, 04:40:34 pm by Johnny B Good »
John
 

Offline EmptyHead

  • Newbie
  • Posts: 4
  • Country: us
Re: Noisy power from typical backup generators
« Reply #56 on: April 02, 2021, 04:09:58 pm »
Quote
As for that mysterious plastic pipe connection to the carb, I think it must be an atmospheric pressure equalisation vent tube but why such a plastic tube would be deemed necessary when the more usual system of pressure balancing with a small vent hole into the float chamber above the normal fuel level beats the hell out of me. Presumably there IS a good reason for this bit of extra plumbing. Maybe someone here knows the answer to that question?
Sometimes, the atmospheric pressure equalization vent will allow fuel to exit the carb:
A) when unit is tipped over it will allow gasoline to exit
B) if carb float or needle has an issue it will allow gasoline to exit carb without flooding engine(if engine is sitting level)
Many "suitcase" type generators route the hose to exterior of the generator to prevent gasoline from collecting inside the housing.
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 811
  • Country: gb
Re: Noisy power from typical backup generators
« Reply #57 on: April 02, 2021, 04:53:11 pm »
@EmptyHead,

 Thank you very much for that answer. It makes good sense to provide such a vent/drain tube with a 'suitcase' type generator now that I think about it. The open frame types don't really need such a tube but it's all too painfully obvious now you've reminded me of the distinction. :palm:

 BTW, I've added a couple more paragraphs to that post (I was only going to slightly improve my phrasing of the final paragraph but got a little carried away). I think I can resist any more tinkering now. ::)

John
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 811
  • Country: gb
Re: Noisy power from typical backup generators
« Reply #58 on: April 16, 2021, 03:29:07 am »
 Well, the parts arrived over a week ago but the weather didn't didn't permit any outdoors work until yesterday when I was finally able to install the priming pump bulb in parallel with the original fuel lift pump. As expected, I didn't have any fuel starvation issues with this more complex arrangement and, joy of joys, starting is now a less arduous task after a long lay up with a drained down carburettor float chamber (typically done by shutting the fuel off to let it run dry).

 I tested by allowing it to cool down after my first test run and draining the remaining 2 or 3 cc of fuel from the float chamber having let it run dry to terminate the test run. Since I'm using the priming bulb kit in a non-standard way to refill the carburettor float chamber from bone dry, it seems to need about 6 to 10 pumps rather than the more usual 2 or 3 when it's used as originally intended simply to squirt a bit of neat fuel into the venturi. I'm fine with this since those extra 4 to 7 presses are a damn sight easier to apply than pulling on the starter cord 4 or 5 times with kill switch operated to inhibit the ignition until I'm ready to chance my arm (literally!) to give it one good full strength yank to fire it up.

 I can now (at long last!) conserve my energy for a full strength pull that's guaranteed to fire it up first go and worry less about just how much life remains in that much abused pull starter cord. :)
« Last Edit: April 16, 2021, 03:31:02 am by Johnny B Good »
John
 

Offline IDEngineerTopic starter

  • Super Contributor
  • ***
  • Posts: 1924
  • Country: us
Re: Noisy power from typical backup generators
« Reply #59 on: April 19, 2021, 11:10:21 pm »
Had our first power outage (due to high winds) last night since getting the large inverter generator. It fired right up, and after warming up for a few minutes I powered the house with it.

Worked perfectly! Economy mode worked as intended, keeping the engine RPM's (and fuel consumption) down during lighter loading. But when a refrigerator fired up, or another large load kicked on, there was none of the UPS beeping and other complaints by electronics in the house. The engine would adjust its RPM's to accommodate but otherwise such things were non-events. As intended!

I had my wife use the ~1000W microwave oven a couple of times while I monitored the generator's behavior. I could tell when the load came and went, but nothing in the house complained at all.

The layout of this unit is interesting. The inverter is mounted directly below the fuel tank and above the engine (?!?) with a nice large heat sink on the engine side. The thing is, heat sinks work both ways... they lower thermal impedance in BOTH directions, and the way this one is mounted appears like it would absorb waste heat from the engine directly below. I didn't check the heat sink temperature, but I will next time.

I'm attaching photos of the top and bottom of the inverter, as best I can photo them without disassembly. For some reason I can't get them to inline, despite the message editor offering that option, even when I've downsized them.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Noisy power from typical backup generators
« Reply #60 on: April 19, 2021, 11:18:05 pm »
I'm guessing they mounted it there to make use of the airflow from the engine cooling fan. Heat soak when shutting the unit off probably is an issue to some degree, although I'm guessing in most cases it will not exceed 100C.

I do love inverter generators, mine is only 2kW but has proven adequate since outages are fairly rare here and most of my appliances are gas. If I have it in eco mode the UPS's will kick in for a moment most of the time when the refrigerator starts but that's a small price to pay. I'm tempted to install a ESP8266 relay in there so I can remotely switch it out of eco mode when I know I'm going to fire up a larger load but it hasn't been a priority since I have UPS's on the important stuff.
 

Offline IDEngineerTopic starter

  • Super Contributor
  • ***
  • Posts: 1924
  • Country: us
Re: Noisy power from typical backup generators
« Reply #61 on: April 19, 2021, 11:43:10 pm »
I'm guessing they mounted it there to make use of the airflow from the engine cooling fan. Heat soak when shutting the unit off probably is an issue to some degree, although I'm guessing in most cases it will not exceed 100C.
Yep, I thought of that but haven't checked the airflow direction yet. Seems like they could have easily mounted it as a "wall" on one side of this "open frame" unit but I wasn't on the design team, so who knows.

Quote
I do love inverter generators, mine is only 2kW but has proven adequate since outages are fairly rare here and most of my appliances are gas.
Ours too - everything that CAN be NatGas is. My motto is "if you want heat, burn something". Electricity is a terrible way to generate heat unless it needs to be very carefully controlled, like in aluminum smelting or soldering or welding. We have NatGas water heater, oven, cooktop, clothes dryer, whole-house furnace, the works.

Quote
If I have it in eco mode the UPS's will kick in for a moment most of the time when the refrigerator starts but that's a small price to pay.
As noted earlier, that's why I transitioned to the large inverter. We too have a 2KW "suitcase" inverter but it's not sufficient to power the entire house in a worst case situation (both refrigerators running at the same time, a few lights on, maybe someone uses the microwave, etc.). Since I was buying a new unit anyway I wanted to go as big as possible because our previous 6KW unit would labor once in a while, though that may have just been due to transient startup loading. This is the largest inverter unit I have found, and "I've never wished for a smaller whole house generator" so the more margin the better - and ECO mode means the engine isn't running WOT all the time so it's likely more efficient than a smaller traditional generator anyway.

I've found a small oil leak in the valve cover, but haven't investigated in detail yet. It's maybe two drips per hour hitting the concrete, so it's not going to risk low oil level before I change it regularly anyway.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Noisy power from typical backup generators
« Reply #62 on: April 20, 2021, 12:14:41 am »
I'm guessing they mounted it there to make use of the airflow from the engine cooling fan. Heat soak when shutting the unit off probably is an issue to some degree, although I'm guessing in most cases it will not exceed 100C.
Yep, I thought of that but haven't checked the airflow direction yet. Seems like they could have easily mounted it as a "wall" on one side of this "open frame" unit but I wasn't on the design team, so who knows.

Quote
I do love inverter generators, mine is only 2kW but has proven adequate since outages are fairly rare here and most of my appliances are gas.
Ours too - everything that CAN be NatGas is. My motto is "if you want heat, burn something". Electricity is a terrible way to generate heat unless it needs to be very carefully controlled, like in aluminum smelting or soldering or welding. We have NatGas water heater, oven, cooktop, clothes dryer, whole-house furnace, the works.

Quote
If I have it in eco mode the UPS's will kick in for a moment most of the time when the refrigerator starts but that's a small price to pay.
As noted earlier, that's why I transitioned to the large inverter. We too have a 2KW "suitcase" inverter but it's not sufficient to power the entire house in a worst case situation (both refrigerators running at the same time, a few lights on, maybe someone uses the microwave, etc.). Since I was buying a new unit anyway I wanted to go as big as possible because our previous 6KW unit would labor once in a while, though that may have just been due to transient startup loading. This is the largest inverter unit I have found, and "I've never wished for a smaller whole house generator" so the more margin the better - and ECO mode means the engine isn't running WOT all the time so it's likely more efficient than a smaller traditional generator anyway.

I've found a small oil leak in the valve cover, but haven't investigated in detail yet. It's maybe two drips per hour hitting the concrete, so it's not going to risk low oil level before I change it regularly anyway.


Who knows, I've seen all kinds of questionable design decisions, I try to assume the engineers knew what they were doing but sometimes it's impossible to say. I would try checking the temperature just to satisfy my curiosity. If heat soak turns out to be a problem then maybe a small battery powered fan could be an option.

One reason I went with the 2000W instead of the 3000W (aside from cost) is that the fuel consumption at the same low load is significantly less on the smaller unit, BUT you're right, it will still be lower than the smallest reasonably sized conventional generator. At constant high load a conventional generator is going to beat out an inverter generator, but in real world domestic use a generator will typically spend 90+% of the time running at less than 25% load and in this case inverter will win every time over the long run.

Is there a local dealer? If it's brand new and you can get it fixed locally I would be inclined to take it in to have it serviced. An oil leak from the valve cover is usually a pretty trivial problem to deal with but it's one you shouldn't have to deal with. In the old days they'd send somebody out to fix it for you but that probably isn't gonna happen.
 

Offline Renate

  • Super Contributor
  • ***
  • Posts: 1460
  • Country: us
Re: Noisy power from typical backup generators
« Reply #63 on: April 20, 2021, 12:23:04 am »
There's no reason a refrigerator or an air conditioner has to start with a big "THRUMMMMM".
The Japanese killed it with their mini-split air conditioners.
For RVs there are mods that fiddle with the currents to the air conditioner windings to make them start easier and make a ginormous generator less necessary.
I think most people with non-inverter generators would be surprised what low percentage of power they are using.

And for that fridge, just use a nice Dometic water/ammonia/hydrogen thermal cycle fridge, nice and quiet.

Does anybody make a VFD fridge???
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 8973
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: Noisy power from typical backup generators
« Reply #64 on: April 20, 2021, 12:56:47 am »
Does anybody make a VFD fridge???
Quite a few do, very common in the higher end ones for their superior temperature regulation.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Offline PaulAm

  • Frequent Contributor
  • **
  • Posts: 938
  • Country: us
Re: Noisy power from typical backup generators
« Reply #65 on: April 20, 2021, 01:32:11 am »
There are also soft start devices for large compressor appliances like heat pumps.  I had one on my geothermal unit that took a 100+A starting surge down to 30A.  It made my backup generator a LOT happier.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Noisy power from typical backup generators
« Reply #66 on: April 20, 2021, 02:25:05 am »
And for that fridge, just use a nice Dometic water/ammonia/hydrogen thermal cycle fridge, nice and quiet.

Quiet and very dependable, but aren't they horrible in terms of efficiency? I remember my grandparents had one in their old motorhome and it put out a ferocious amount of heat. It could run on either propane or electricity and the energy to feed the cycle entered in the form of heat.
 

Offline Renate

  • Super Contributor
  • ***
  • Posts: 1460
  • Country: us
Re: Noisy power from typical backup generators
« Reply #67 on: April 20, 2021, 02:44:03 am »
I remember my grandparents had one in their old motorhome and it put out a ferocious amount of heat.
They have a chimney flue for the heat.
Unless you put your hand under the flue cap you can hardly notice the heat.
The flame is like a disposable cigarette lighter goosed up to about twice the flame.
It runs me about 7.5 US gallons of propane a month ~$30 with tax (in an expensive area).

You've got me thinking though.
It does have 120 VAC switchover, but no 12 VDC switchover
There are certainly times where my solar panels are throwing electrons to the wind.
I'll have to consider that.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Noisy power from typical backup generators
« Reply #68 on: April 20, 2021, 05:03:53 am »
I remember my grandparents had one in their old motorhome and it put out a ferocious amount of heat.
They have a chimney flue for the heat.
Unless you put your hand under the flue cap you can hardly notice the heat.
The flame is like a disposable cigarette lighter goosed up to about twice the flame.
It runs me about 7.5 US gallons of propane a month ~$30 with tax (in an expensive area).

You've got me thinking though.
It does have 120 VAC switchover, but no 12 VDC switchover
There are certainly times where my solar panels are throwing electrons to the wind.
I'll have to consider that.

Well the motorhome was a 1965 model and the refrigerator was original, it's possible things have improved since then. This was also 25 years ago so my memory could be a little fuzzy. At one point they made domestic refrigerators using the same process that burned kerosene using an Aladdin mantle lamp burner. Never saw one in the flesh, I only came across them when I was looking for parts for my oil lamp.
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 811
  • Country: gb
Re: Noisy power from typical backup generators
« Reply #69 on: April 20, 2021, 05:28:17 am »
@Renate

 Regarding VFD compressor fridges, when I checked what was available here in the UK about a year back, there wasn't a single one. Even looking for high spec (overpriced) fridge/freezers I could only find one (maybe two) VFD compressor models. Needless to say, this was all in aid of eliminating the 1KW or so (measured with an analogue MetraWatt power meter) startup surge of our under counter fridge to save that cheap inverter genset from tripping out to a 1200W plus overload.

 Once the fridge compressor had kicked in, the loading swiftly dropped to 140W. At the time I was testing the compressor startup surge and running loading, it was maintaining temperature on a one hour run with one hour off cycle, averaging 70W consumption. I didn't bother testing the chest freezer since I could probably run it on a daily schedule with the thermostat turned to a lower temperature to allow it to remain safely shut off for 18 to 20 hours per day, allowing me to pick the best time of the day to minimise loads before disconnecting the generator from the SmartUPS2000 to concentrate all of its energy on starting the freezer back up before reconnecting to a lightly loaded UPS.

 You can't really manage a fridge this way like you can a chest freezer which can safely keep its contents frozen through a 24 to 48 hour mains outage depending on the thermostat setting and how often you feel the need to extract items of frozen foodstuff from it.

 I haven't actually tested whether the inverter genset can actually start the fridge compressor, in part because of it lacking a priming bulb pump but mainly on account I'd have to wait for it to cut out on the thermostat to avoid disruption to the temperature regulation and allow a half hour or so for the compressor to cool down enough to allow a normal restart before firing up the genset for another half hour of run time for the 'stat to restart the compressor in the usual way with my missus giving me earache over the noise disturbance to our neighbours.

 Also, since it was late Spring / early Summer, it was low down on my priority list and could wait for when she wasn't around - as per usual when a job is put on the back burner, the test never got run. However, since fitting that priming bulb pump has removed all the hassle I'd originally suffered with starting the generator, I'm a lot more inclined to take advantage of her absence next time she's visiting friends or family, given a dry weather day.

 Even if the generator can only cope with no other loads connected, I can always rig up a load shedding relay to dump the UPS load for the half minute required to ensure the compressor startup surge has been overcome as a work around solution to keeping the fridge running during an extended Winter outage (the only time I'm concerned with due to the increasingly marginal UK grid capacity at that time of the year).

 If it can't cope, then there's no point in rigging up such a work around. If it's a severe winter outage we'd probably do just as well by using the fridge as a "Coolbox" fed with cooler packs chilled by exposing them to the outside freezing temperatures.

 Aside from the increasing risk of winter outages, loss of mains supply is very rare in urban areas of the UK. We've only ever witnessed one actual loss of supply some thirty years ago as a result of a fault in the locality which was cleared just four hours later. My family think I'm wasting my time in making some token gesture of preparedness against what they can only see as an extremely unlikely event, hence all the flak from my ever loving' wife. :(

 We'll probably never see any winter blackouts, especially now I'm prepared to a limited extent to mitigate such events, due to Sod's Law. That's fine by me since the hundred quid investment in the generator is chump change in the larger scheme of things anyway.
John
 

Offline Renate

  • Super Contributor
  • ***
  • Posts: 1460
  • Country: us
Re: Noisy power from typical backup generators
« Reply #70 on: April 20, 2021, 10:32:53 am »
Regarding VFD compressor fridges, when I checked what was available here in the UK about a year back, there wasn't a single one.
I used to really hate the sound of a refrigerator cycling.

If it gets much above 100°F here I might run the air conditioner.
Fortunately, at that temperature it doesn't cycle but runs 100%!

FYI: The 120 VAC heater on my fridge is 180 Watts.
The run time on propane is somewhere around 50%.
 

Offline SeanB

  • Super Contributor
  • ***
  • Posts: 16272
  • Country: za
Re: Noisy power from typical backup generators
« Reply #71 on: April 20, 2021, 10:47:13 am »
With the abnsorbtion fridge you can simply replace the 120VAC element with the dual voltage version, which is the same size, but has 2 separate nichrome element sets in it, and a 4 wire tail. Common on caravan units, where you have a choice of gas when stationary at a park, or mains as well if you are wanting to save the gas as electric is part of the service, or 12V for use to keep it working during towing, where you cannot use the gas. Typically a 60 to 100W heater cartridge, though if you cannot get the 12V version you can have them made by almost all of the industrial heating suppliers, as they are quite used to making custom cartridges, though they likely will have it in stock off the shelf or next day.
 
The following users thanked this post: Renate

Offline Renate

  • Super Contributor
  • ***
  • Posts: 1460
  • Country: us
Re: Noisy power from typical backup generators
« Reply #72 on: April 20, 2021, 02:03:58 pm »
... mains as well ...
Oh, yeah, I remember this "mains" stuff. I plugged in once a few years back. >:D

... to keep it working during towing, where you cannot use the gas.
I run the fridge on gas while running down the road.
I don't consider it a safety problem and it never blows out.
Even if it did, the interlocks work just fine.

One thing that always pissed me of was that the "Auto" LED and the "Check" (i.e. fail to ignite/no gas) were both amber.
Now the Check LED has a nice bright red.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Noisy power from typical backup generators
« Reply #73 on: April 20, 2021, 05:32:44 pm »
FYI: The 120 VAC heater on my fridge is 180 Watts.
The run time on propane is somewhere around 50%.

My home fridge draws around 130W and the duty cycle is pretty close to 50%, so average draw about 65W for something much larger than a typical RV refrigerator. Very rough guess is a comparably sized absorption fridge would draw about 400W vs 65W for the compressor based one, that goes along with my impression that the absorption refrigerators are not very efficient. They offer some very compelling advantages for RVs though.
 

Offline Renate

  • Super Contributor
  • ***
  • Posts: 1460
  • Country: us
Re: Noisy power from typical backup generators
« Reply #74 on: April 20, 2021, 05:56:36 pm »
Hmm, you may have a point.
I just rechecked the spec for the 120 VAC heater and it's 325 Watt!
I don't think that I'll be messing around with 12 VDC heaters.
Maybe a big plastic Fresnel lens and some mirrors? >:D

I actually did this graphic a while ago to demonstrate the amount of stored energy that I'm driving around with.
(Ignoring the truck battery. The two GC2 AGM batteries are pretty serious.)
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf