New Heat pump - v high standby consumption

[kaz911]

Hi,

I just wanted to know how other heat pumps are "performing"

I put in a 16kW Daikin Altherma R3 system with 210L water tank. But the installation (by certified Daikin tech's) seem to have left me with an incredible high standby consumption.

System is installed on a 3 phase circuit - with compressor using all 3 phases - and emergency 6kW "heater" using single phase. In the winter it can manage our underfloor heating system but in the warmer months it only does our hot water (to 54 deg c which is what the compressor can do without extra help)

Being a 210L watertank on a purely resistive element - heating from cold to hot - should cost "roughly" 9 kWh's.

So with an efficiency of >4 - my new system should do it in less than 2.5 kWh 'ish or less (outside temp 25-35c)

But standby consumption is a constant !! 120-130 w x 24h = 3 kWh! (no water circulation pumps running) - giving me a daily consumption of 5.5-7 kWh heating the tank ONLY once per day.

That is NOT the savings I expected. Some other Daikin customers have said it is due to the oil heater in the compressor that keeps the viscosity "perfect" for the compressor oil. But if that is true then all the stated figures from their datasheets are BS of the highest degree (pun intended) - as it does NOT include the power consumption for the oil heating.

Apart from that the system randomly decide to use the "emergency heat element" to heat the water with. I have not figured out why... So I'm ending up with an avg daily consumption higher than I had with my old resistive heated water tank system...

Any ideas?

/k

[Siwastaja]

Compressor heater should have thermostat control. It is not needed during summer temperatures. My ES AWC9 air-to-water heatpump for example pulls 10W at idle (according to a meter with 10W resolution, so consider this ballpark), including the stupid touchscreen computer which is probably half of that number. Only when getting near to zero deg C are the outdoor unit heating elements on - some 40-50W for compressor and some 100W for the bottom tray heating element under the evaporator coil.

120W standby even during summer is not OK IMHO. Complain and demand it getting fixed, or ask for compensation.

Is this "random" resistive heating use like once a month or every two weeks? Could be some sort of legionella cycle, aiming for higher temperature. If it's truly "randomly" and more often than that, seems like some sort of problem.

Marketing numbers likely include this "idle" consumption but they are calculated with 100% duty cycle, probably even 100% or near-100% compressor speed, which hides it. Unsurprisingly, unless you are running a public bath, the summertime duty cycle will be very low so low idle consumption matters.

[fourtytwo42]

One difference I can think of between your old and new systems is the heating of the indirect circuit and heat-pump heat-exchanger, this could add up to quite a lot depending on the size of the indirect circuit and the number of heating cycles a day.

For example with our present gas boiler (condensing) the gas consumption/time is much higher in the 1st half hour than subsequent 1/2 hours. Unfortunately I cannot measure it at closer time intervals due to "smart meter" limitations. Our boiler is out in the garage and the HW cylinder in the bathroom so quite a distance of pipe run and therefore water to be heated. 

Of course with an immersion this indirect circuit doesn't exist.

[Marco]

Not the first time I hear this about a heat pump. This should really be included in the energy ratings.

[coppice]

Why would an oil heater need to run constantly, even in winter? Surely it only needs to preheat the oil before the heat pump starts?

It sounds like you have a continuous power monitor. So, is that 120W an average, or is it being consume at a constant 120W throughout the day? Even a resistive oil heater should cut in an out by a thermostat. Its so easy to get to really low standby consumptions these days, that anything more than milliwatts is poor design. However, a lot of systems do crazy things. A lot of TVs are taking 50W day and night because some setting is keeping much of the electronics alive for a background task, like schedule monitoring. Disable that feature in the menu, and the power drops to milliwatts. They've optimised the real low power operation, but given no regard to consumption with various features enabled, even though those feature could be built to run on maybe 1W. Is your heat pump like that? Do you have something like WiFi monitoring enabled, that never lets the system really sleep?

I just checked the manual for a 1 year old LG TV. It actually warns you about possible substantial standby consumption with some menu settings enabled. One of those is to keep the bluetooth receiver running at all times. How badly do you have to design a bluetooth module to have a fearful consumption? That's how messed up standby consumption can be.

[Siwastaja]

Why would an oil heater need to run constantly, even in winter? Surely it only needs to preheat the oil before the heat pump starts?

These heaters are very low power (usually 40W or so) so the pre-heat time is long, like an hour or so because the compressor has so much thermal mass. It's wrapped in some insulation, for acoustic noise reduction but also doubles as thermal insulation. The idea is that during winter the compressor would be running at high duty cycle anyway, so there is not much savings to gain. The simplest thing to do is to cut the heater using a thermostat because it's really not needed in summer.

I have been wondering why modern inverter-based heatpumps don't do this preheating by injecting DC into the BLDC compressor windings. They could use significantly higher power and thus shorter time, and save on BOM cost because then you would not need the heater itself plus a relay to drive it on the inverter board.

[coppice]

Why would an oil heater need to run constantly, even in winter? Surely it only needs to preheat the oil before the heat pump starts?

These heaters are very low power (usually 40W or so) so the pre-heat time is long, like an hour or so because the compressor has so much thermal mass. It's wrapped in some insulation, for acoustic noise reduction but also doubles as thermal insulation. The idea is that during winter the compressor would be running at high duty cycle anyway, so there is not much savings to gain. The simplest thing to do is to cut the heater using a thermostat because it's really not needed in summer.

I have been wondering why modern inverter-based heatpumps don't do this preheating by injecting DC into the BLDC compressor windings. They could use significantly higher power and thus shorter time, and save on BOM cost because then you would not need the heater itself plus a relay to drive it on the inverter board.

Modern systems measure the temperature, rather than simply switching at one temperature. They can easily predict ahead of time when pre-heating the oil might be a good idea, even if its really slow. The last Daikin air cons (cool + heat) I owned had a pre-heater, but it only came on when the ambient temperature was really low. In our environment the temperature never reached zero, and the heaters never seemed to engage at all. Those were room by room units, not a big central heat pump. They didn't heat water, and had no need to achieve temperatures warmer than the room.

[JohanH]

I have a Nibe F1255 (ground source heat pump). Standby consumption is 11 W (according to an external energy meter). It has a variable output of 1.5-6 kW. It almost never runs the 6.5 kW electrical backup heater. The tap water (180 l tank) is heated to 53 °C (top), but every second week it does a "legionella" run and heats up to 60 °C once. At these times it might use the backup heater if the compressor has a tough time, but I haven't seen it doing it in a long time.

[Marco]

Ground source heatpumps will only start up at freezing ambient temperatures in extreme exceptions regardless of what they do at idle, not really the same design considerations as air source.

[nfmax]

Something isn't right here! Have you confirmed this is real power not reactive power? If you have just measured current (in one phase, or in all 3?) it could well be reactive. Also, the idea of a 6kW phase imbalance in a domestic 3-phase supply - itself all but unheard of in the UK - is alarming in itself.

[Siwastaja]

Indeed a good question, how was this 120-130W measured?

[f4eru]

The idea of a 6kW phase imbalance in a domestic 3-phase supply

Depends. In Germany, >16A imbalance for a single device is even orbidden.
in France, and many other countries, a house is single phase in essence, and each house is balanced with the next two.....

[coppice]

in France, and many other countries, a house is single phase in essence, and each house is balanced with the next two.....

This is the case in almost all countries. Germany is an outlier, having three phase to every home. Recently Malaysia, Saudi Arabia and a few other hot countries have also been deploying domestic 3-phase as air con consumption has risen. Presumably, if all energy consumption of to migrate to electricity a lot more countries will gradually move to three phase being the norm for domestic supply.

[langwadt]

in France, and many other countries, a house is single phase in essence, and each house is balanced with the next two.....

This is the case in almost all countries. Germany is an outlier, having three phase to every home. Recently Malaysia, Saudi Arabia and a few other hot countries have also been deploying domestic 3-phase as air con consumption has risen. Presumably, if all energy consumption of to migrate to electricity a lot more countries will gradually move to three phase being the norm for domestic supply.

we also have three-phase everywhere

[Siwastaja]

Same here, for an average detached house, 3x25A 230V is the most common and usually requires some balancing within the house because 25A for any single phase is easily exceeded; 1x75A would be so much easier for single-phase loads (and the USA-style 1x100A obviously even better). Some people just choose to pay a bit of premium for 3x35A, others move around some loads from one phase to another, trying to find a decent balance, and/or replace blown master fuses every now and then (25A gG does not blow that quickly with small overload!)

Having three phases used to have some advantage if you wanted to run industrial 3-phase motors at your home for some reason, but not a very common requirement. Now with VFDs, 3-phase is just a hindrance.

On grid level, averaging happens easily anyway, so having one higher-current phase per house really isn't a problem in any country which uses this convention.

Sorry for OT but having heard nothing from the OP I guess it's ok.

[nfmax]

Single-phase, 240V fused at 100A here in the southern UK. A proper 240V too, not a slightly overweight 230V!

[langwadt]

Same here, for an average detached house, 3x25A 230V is the most common and usually requires some balancing within the house because 25A for any single phase is easily exceeded; 1x75A would be so much easier for single-phase loads (and the USA-style 1x100A obviously even better). Some people just choose to pay a bit of premium for 3x35A, others move around some loads from one phase to another, trying to find a decent balance, and/or replace blown master fuses every now and then (25A gG does not blow that quickly with small overload!)

what kinds of single phase loads do you have that use that much power?

Having three phases used to have some advantage if you wanted to run industrial 3-phase motors at your home for some reason, but not a very common requirement. Now with VFDs, 3-phase is just a hindrance.

even with a VFD 3-phase is an advantage, think most VFDs that can be powered by either is only rated for half power with single phase input

[Siwastaja]

what kinds of single phase loads do you have that use that much power?

Electric heating is usually 10A/phase so that leaves just 15A per phase. All you need are two burners on a stove (out of 4, two are usually wired to the same phase) and that's it, 25A already exceeded.

Or a vacuum cleaner (a few years old pre tighter EU regulations), washing machine and dishwasher turned on at the same time, if the sockets where they happen to be are in the same phase. Cook at the same time and you are exceeding the fuse rating significantly.

Granted, fuse does not blow because of the long overload time of gG fuse, you'd need tens of minutes +50% overload nonstop (or very bad luck), but still nominal rating is regularly exceeded in many households and relying on this seems nasty IMHO.

Control boxes which measure phase currents and temporarily turn off stuff like boiler, central electric heating, sauna stove or similar to protect the 25A fuses have been semi-common here for surprisingly long time, before the Internet era (let alone IoT), because on some areas 35A contracts were so much more expensive per month (or not available at all). This is still a front-page advertised add-on feature on many large heatpumps sold on Nordic markets.

230V 25A is just mere 5.8kW (and yes, if balancing is not thought at all, then the worst case reduces to just 25A single phase). The US/UK 100A single phase stuff is 24kW so much less to think about.

[Marco]

With inverters in pretty much everything all three phase accomplishes in residential is causing expensive problems to save a few cheap electrolytic capacitors.

[kaz911]

It is the real power measured with 3 current clamps and voltage and phase measurement on each phase at the same time.

Apart from that it is very visible on our electricity bill - just in standby we are paying Euro 30-40 more per month (compensated for price difference) than we used to do.

Just had official Daikin technician here - he could not do anything about the standby consumption. He said I should have asked before buying it... (It is not in their specifications or installations manual)

[zilp]

16 kW? Compressor electric power? Are you heating a castle?!

I have a 4 kW Daikin Altherma 3 R ECH2O, single-phase 230 V, that idles at ~ 12 W, measured by the power company's meter, which includes everything, controller, pumps, compressor, and load shedding contactor (which already takes a watt or two, I don't remember), hot water circulation deactivated.

So ... yeah, 120 W seems gigantic. Really, I think the 12 W are kinda excessive already. Watching one temperature sensor shouldn't need 12 W, should it? Like, that's already some 50 kWh over a summer that should be trivial to avoid at relatively minor BOM costs.

[kaz911]

16 kW? Compressor electric power? Are you heating a castle?!

I have a 4 kW Daikin Altherma 3 R ECH2O, single-phase 230 V, that idles at ~ 12 W, measured by the power company's meter, which includes everything, controller, pumps, compressor, and load shedding contactor (which already takes a watt or two, I don't remember), hot water circulation deactivated.

So ... yeah, 120 W seems gigantic. Really, I think the 12 W are kinda excessive already. Watching one temperature sensor shouldn't need 12 W, should it? Like, that's already some 50 kWh over a summer that should be trivial to avoid at relatively minor BOM costs.

kind off - the calc said between 9 and 12 kW. But it is noise sensitive here - so a larger compressor = less noise as the inverter runs more silent when it does not have to go full pelt. So we got offered 11 or 16 kW at the time. It covers UFH and hot water. But we have an semi-open garage below that cant be insulated - so it takes a bit to keep floors cosy in the winter.

Specs sheet says 23 watt standby - (found spec sheet after a lot of digging as it seems like Daikin already took our outdoor unit off the market again. I can only guess why.)

[zilp]

kind off - the calc said between 9 and 12 kW. But it is noise sensitive here - so a larger compressor = less noise as the inverter runs more silent when it does not have to go full pelt. So we got offered 11 or 16 kW at the time.

Is that really a problem, though? I mean, the compressor only runs at full power when it's freezing cold outside ... i.e., when neighbours presumably keep their windows closed?!

It covers UFH and hot water. But we have an semi-open garage below that cant be insulated - so it takes a bit to keep floors cosy in the winter.

Specs sheet says 23 watt standby - (found spec sheet after a lot of digging as it seems like Daikin already took our outdoor unit off the market again. I can only guess why.)

Hehe. Have you looked into interfacing the controller and somehow influencing it into less insane behaviour? Like, my Altherma has a CAN bus that you can use to read and write config values and read sensor values, so maybe you can just use a raspberry pi or something to watch the temperature and configure some less power consuming mode while the hot water is hot enough ...

Though, really, this just sounds like a defect to me, but no idea what rights you would have under UK law.

[kaz911]

no the compressor would run full speed every time it makes hot water. Not only when it is cold outside.

But you can de-rate the compressor by running it in "silent mode" which is then roughly equal to loosing 30% of it's capacity giving a net output of 16 - 3.8 = 12'ish kW - slightly above worst case winter temp requirement.

But it is a LOT more quiet than a 12 kW running full speed.

But yes I think my unit have an issue. And I think it is the compressor that has an issue.

I don't want to fiddle with it until I know if I'm taking Daikin on via the courts.

[coppice]

no the compressor would run full speed every time it makes hot water. Not only when it is cold outside.

But you can de-rate the compressor by running it in "silent mode" which is then roughly equal to loosing 30% of it's capacity giving a net output of 16 - 3.8 = 12'ish kW - slightly above worst case winter temp requirement.

But it is a LOT more quiet than a 12 kW running full speed.

But yes I think my unit have an issue. And I think it is the compressor that has an issue.

I don't want to fiddle with it until I know if I'm taking Daikin on via the courts.

If you have found a spec of 23W, I'd try looking through the configuration again. Many modern products have so many options, with funky interactions. Most of the installers and maintainers only know the little they need to.

[zilp]

no the compressor would run full speed every time it makes hot water. Not only when it is cold outside.

Would it? Mine pulls ~ 2 kW at current outdoor temperatures, so far from full power. Though no idea how that's dristributed between compressor and fan.

Also ... 210 l takes ~ 244 Wh to heat 1 K, so if we assume 10 K hysteresis, full power 12 kW at CoP of 3 would heat that thing in 4 minutes!? Or rather, it wouldn't, because I'd think that small-ish tank can't absorb 36 kW at reasonable supply temperatures!?

[Siwastaja]

You surely must have some consumer protection laws, and authorities you can talk to, without taking it to the court?

[woodchips]

I bought a Hydropro Premium 14 swimming pool heat pump heater at an auction. Output 14kW. The controller was dead, but a new replacement included and just tried it, new controller doesn't communicate over the serial bus, error.

Anyway, pretty simple inside, connect mains to compressor and fan and off it goes. In this mode it is actually cooling the water, and gets impressively cold. Only using a few gallons of water in a bucket with a small circulating pump.

There is a 4 way valve, operating that and changes to heating. Again impressive performance on the limit water, hets too hot to put a finger on the compressor pipe so >60C.

Measured consumption at 240V was about 11A on cooling and 15A on heating.  This ties in reasonably well with the stated consumption.

Question, why is the heating consumption greater than the cooling consumption? The four way valve just reverses the direction of gas flow through the compressor?

On a very quick test it would seem that these swimming pool heat pumps are a good thing. Air to water so easy to get into the house to use the heat. What needs some more testing is how well it works with an air temperature below 10C, not at 25C.

[Siwastaja]

I bought a Hydropro Premium 14 swimming pool heat pump heater at an auction. Output 14kW. The controller was dead, but a new replacement included and just tried it, new controller doesn't communicate over the serial bus, error.

Anyway, pretty simple inside, connect mains to compressor and fan and off it goes. In this mode it is actually cooling the water, and gets impressively cold. Only using a few gallons of water in a bucket with a small circulating pump.

There is a 4 way valve, operating that and changes to heating. Again impressive performance on the limit water, hets too hot to put a finger on the compressor pipe so >60C.

Measured consumption at 240V was about 11A on cooling and 15A on heating.  This ties in reasonably well with the stated consumption.

Question, why is the heating consumption greater than the cooling consumption? The four way valve just reverses the direction of gas flow through the compressor?

On a very quick test it would seem that these swimming pool heat pumps are a good thing. Air to water so easy to get into the house to use the heat. What needs some more testing is how well it works with an air temperature below 10C, not at 25C.

I'd say open a new thread. Anyway, are you sure the thing doesn't have an EEV (electric expansion valve, basically a stepper motor)? If it does, to recreate the dead controller, you also need to feedback the EEV to keep the process in control (usually measuring and keeping superheat constant). If you fail to do that, worst case you get refrigerant enter the compressor in liquid form, killing the compressor in little time. If the thing has capillary tube or TEV (thermal expansion valve), then you don't have to do anything.

[woodchips]

Thanks for your reply.

Yes, it has a connector marked Electronic Expansion Valve, 5 wires , but disappears into the depths of the heat pump and can't see what it is or does.

When I first tried to get it working I just paralleled the compressor, fan and 4 way valve together and connected the mains. Quickly started making I am not happy noises. If I delay operating the 4 way valve for 30 seconds or so then runs quietly. The 4 way valve swaps between heating and cooling.

[Siwastaja]

Thanks for your reply.

Yes, it has a connector marked Electronic Expansion Valve, 5 wires , but disappears into the depths of the heat pump and can't see what it is or does.

When I first tried to get it working I just paralleled the compressor, fan and 4 way valve together and connected the mains. Quickly started making I am not happy noises. If I delay operating the 4 way valve for 30 seconds or so then runs quietly. The 4 way valve swaps between heating and cooling.

A great way to get the compressor destroyed. EEV absolutely needs to be properly controlled, otherwise compressor sucks in liquid refrigerant which removes the oil and it's permanently dead soon after that.

[langwadt]

Thanks for your reply.

Yes, it has a connector marked Electronic Expansion Valve, 5 wires , but disappears into the depths of the heat pump and can't see what it is or does.

When I first tried to get it working I just paralleled the compressor, fan and 4 way valve together and connected the mains. Quickly started making I am not happy noises. If I delay operating the 4 way valve for 30 seconds or so then runs quietly. The 4 way valve swaps between heating and cooling.

A great way to get the compressor destroyed. EEV absolutely needs to be properly controlled, otherwise compressor sucks in liquid refrigerant which removes the oil and it's permanently dead soon after that.

https://www.macscool.co.za/compressor-failures-liquid-slugging/