Air Source Heat Pump Freezing

BellaBlondykeTheThird

matt_drummer said:

BellaBlondykeTheThird said:

@matt_drummer could I suggest you put a link to your heat pump mega thread to these chats otherwise they all appear to regurgitate the same info.

This also goes for the other heat pumpers here that have existing long threads about their heat pumps and setup.

Otherwise it all becomes.about their setup and what they are doing next and the same info repeated and it is not always relatable to the original issues. The threads go off topic.

Just my opinion bin the idea if you like.

I agree.

But I was asked specific questions and i thought it would be rude not to answer them.

Threads often develop and widen in scope.

Anyway, when somebody asks me directly if I would have been better off with GCH and do I regret getting a heat pump I think it deserves an answer, don't you?

Anything else I posted was relevant to heat pumps icing in freezing conditions as far as I can remember.

Anyway, you don't need to worry too much as I don't intend to be posting very often so you won't be skipping past my boring regurgitated information on a regular basis.

I'm not worried lovely, just sometimes posts need pulling back on track and don't let my words stop you posting often. Have a lovely weekend and the weather is in the double digits tomorrow here so less freezing up of heat pumps?

JSHarris

FWIW we've heated our home using a monobloc heat pump for nearly ten years now.  As delivered the performance was abysmal.  No amount of talking with the pretend manufacturer (Glowworm) achieved anything.  Out of frustration I took the covers off the thing and found that the internal parts were labelled Carrier.  Turned out that what we have isn't a Glowworm heat pump at all, so it was not surprising that the (expletive deleted) Glowworm people weren't knowledgeable.

I take my hat off to Carrier, though (they know their stuff - Willis Carrier invented these things well over a century ago).  Following their advice I was able to adjust the settings (a bit as @Spoonie_Turtle described above, but with some deeper tweaks into the installer menu) and those completely transformed the performance.

As an example, it's been getting down to between -5°C and -8°C here overnight (and we only run our ASHP overnight) yet our electricity consumption has never exceeded 21kWh per day for everything, heating, hot water, all the usual stuff, and we have no other source of energy.  Also, we keep the house at around 22°C, as we like to feel warm.

Cost per day (all our electricity is at the off-peak rate) for the past week has averaged about £3.30, much higher than normal for the time of year, but I don't think that's too bad given the sub-zero weather over the past week.  Key seems to be getting the heat pump set up correctly, together with decent insulation and proper sizing of the heat emitters.

Patrol

AuntyPolly said:

Ok thanks, will look at posting a new thread. Didn't want to double up as it at first seemed to be same issue. Freezing ASHP. 

I think I'll dig out calculations too. Obviously the current error and not working is a different issue to the low room temp due to freezing conditions which was our original connection to the OP. 

And this is something we will probably need further advice on as likely to still be present after, unless by some chance the board fault contributed to the lower room temps someway. 

If you do raise your own thread. As it's an old property were you living there prior to the heat pump being installed, and if so do you know how much gas or oil was used per year as that would be a good indication of what is required to heat the house assuming you are looking for a similar temperature. Plus whether the radiators were upgraded when the heat pump was installed and if so was it a minor change or significant increase in capacity

BobT36

matt_drummer said:

From a cost point of view, taking my daily consumption, it's no different from gas if I was on a standard variable tariff. I could buy gas cheaper on something like Octopus Tracker but then I could do the same with electricity.

Thanks Matt, an informative post. The quoted bit is really interesting for me since I'd seen a lot complain about the cost, but again it seems more to do with the setup. (again this is disregarding Solar and "not burning things" benefits). Ofc when add solar, underfloor heating and all that, then it makes even more sense.

I'm personally someone who just turns the heating on "when I need it", rather than having it on low and constant, but you are right that it can get a bit TOO hot and stuffy when put it on "for a blast" so I imagine a low & constant comfortable temperature is better, providing the cost is alright, which it seems isn't actually too bad! 

I guess now that the tech itself is getting a bit better, a lot of the problems will be resolved on the installer-end, having them be better trained and fit appropriate models for each specific house. But of course it seems the owner needs to put in some "work" too to fully understand it. With my GCH I just set a temperature (max lol) and flow temp of ~70c and then just flip it on / off as I need it. 

How is it for hot water? Do you need a "cylinder" setup? I presume they can't just heat "on demand" like a Combi? I've never had a cylinder since I was little, so always just been used to hot water (washing hands, pots, showers) on demand. 

Thanks also Spoonie_Turtle for your perspective. 
Although some may seem regurgitated information, I think it's important to have some real-world perspectives (positive or negative) as otherwise when people like me (who've never even seen one) see these threads with big problems, you just think "oh my god why would I ever bother with one of those?" lol. 

Reed_Richards

BobT36 said:

How is it for hot water? Do you need a "cylinder" setup? I presume they can't just heat "on demand" like a Combi? I've never had a cylinder since I was little, so always just been used to hot water (washing hands, pots, showers) on demand. 

I'm not trying to pre-empt Matt but all heat pumps systems need a hot water cylinder.  But these give you hot water "on demand" for almost all practical purposes.  The advantage is that you can most likely run more hot taps at once than you can with a combi boiler.  The disadvantage is that if you take three baths in quick succession you might run out of hot water, because you are using it faster than the cylinder can be reheated.  

QrizB

Reed_Richards said:

BobT36 said:

How is it for hot water? Do you need a "cylinder" setup? I presume they can't just heat "on demand" like a Combi? I've never had a cylinder since I was little, so always just been used to hot water (washing hands, pots, showers) on demand. 

I'm not trying to pre-empt Matt but all heat pumps systems need a hot water cylinder.

The alternative, if you don't have space for a HW tank, would be to fit an instantaneous electric hot water heater, working much like your combi boiler. Far more expensive to run but cheaper to install and can be tucked away somewhere, in a cupboard or under a sink.

JSHarris

Reed_Richards said:

BobT36 said:

How is it for hot water? Do you need a "cylinder" setup? I presume they can't just heat "on demand" like a Combi? I've never had a cylinder since I was little, so always just been used to hot water (washing hands, pots, showers) on demand. 

I'm not trying to pre-empt Matt but all heat pumps systems need a hot water cylinder.  But these give you hot water "on demand" for almost all practical purposes.  The advantage is that you can most likely run more hot taps at once than you can with a combi boiler.  The disadvantage is that if you take three baths in quick succession you might run out of hot water, because you are using it faster than the cylinder can be reheated.  

I've been running an ASHP very effectively since 2014 and we do not have a hot water cylinder, so I'd question whether the highlighted words in your quote are accurate (perhaps leave out the "all"?).

I use an electrically heated thermal battery for hot water, either powered by off-peak electricity or from excess PV generation.  Excess PV generation accounts for about 70% of the thermal battery charging over the course of a year, so the reality is that I pay about 4p to 5p per kWh for hot water, a bit cheaper than using gas (if gas was available here).

matt_drummer

I agree with @Reed_Richards and @QrizB

You will need some source of DHW, a heat pump cannot provide DHW directly on demand like a combi boiler.

I did see at least one example where the home owner had air to air heating and a small gas powered instantaneous water heater fitted. There is a video on YouTube. The a2a replaced the gas central heating if I remember correctly.

You don't save the gas standing charge but it is quite a neat solution to DHW.

JSHarris

I think the whole idea of having heating and hot water provided by the same device needs a re-think.  We're only used to this because for boilers this happens to work (although it's often far from efficient at some times of the year).

I started from the fundamental principle that I only need a heating system for about 4 months of the year, whereas I need a hot water system all year around.  In addition I only need a heating system to deliver low level heat, whereas I need a hot water system to deliver water at maybe double that temperature.  It seemed a bit daft to mess up the efficiency of either system by such an extreme difference in requirements.

To that end I installed a fairly cheap air source heat pump (cost around £1,000 installed) to run my underfloor heating, where it only needs to deliver warm water at around 30°C.  I installed an electrically heated thermal battery (works like a combi boiler and heats water on demand from stored heat) that is more efficient than a hot water cylinder (much lower losses) and provides hot water at 55°C on demand.

This works well for me as I have solar panels, so for most of the year the hot water is free and for the remainder it's heated by off-peak electricity.  I don't regret having chosen to install completely separate systems for heating and hot water, ten years later it still seems to me to be an entirely logical thing to do.

Reed_Richards

QrizB said:

Reed_Richards said:

BobT36 said:

How is it for hot water? Do you need a "cylinder" setup? I presume they can't just heat "on demand" like a Combi? I've never had a cylinder since I was little, so always just been used to hot water (washing hands, pots, showers) on demand. 

I'm not trying to pre-empt Matt but all heat pumps systems need a hot water cylinder.

The alternative, if you don't have space for a HW tank, would be to fit an instantaneous electric hot water heater, working much like your combi boiler. Far more expensive to run but cheaper to install and can be tucked away somewhere, in a cupboard or under a sink.

Those instantaneous water heaters can draw quite a lot of power, particularly if you want a decent flow of hot water.  Heat pumps can also draw quite a lot of power when running at full tilt.  You might need to check that running both together couldn't exceed the capacity of your mains supply.