Air Source Heat Pump Freezing

Spoonie_Turtle

Er … I am not an expert and I could be totally misunderstanding this, but that '2000W' … does that not mean it's a 2kW unit?  If so, no wonder it struggles to get to temperature!  Ours is 8 or 9kW for a 3-bedroom house!

I have no advice, but I'm so sorry to hear you've had such a bad time of it.  I doubt anybody is laughing, because you trusted professionals to know what they were doing and it sounds like you have been badly let down.  Not your fault at all, and no laughing matter to be cold in winter!

doodling

Hi,

Spoonie_Turtle said:

Er … I am not an expert and I could be totally misunderstanding this, but that '2000W' … does that not mean it's a 2kW unit?  If so, no wonder it struggles to get to temperature!  Ours is 8 or 9kW for a 3-bedroom house!

I have no advice, but I'm so sorry to hear you've had such a bad time of it.  I doubt anybody is laughing, because you trusted professionals to know what they were doing and it sounds like you have been badly let down.  Not your fault at all, and no laughing matter to be cold in winter!

It is 2kW (max) electrical which under the circumstances specified on the label could be 5.8kW thermal.

The questions are:

1) How much heat does the property require?

2) Were the radiators changed to ones about twice the previous size when the heat pump was installed so that it had some chance of actually delivering its specified output?

Answering the first question will require someone to do some maths based on the size / construction of the house.

MultiFuelBurner

At first glance it appears you have the smallest unit that company produces going by the maximum power it can draw. (Manual link below)

I would suggest this is under powered for a 4 bedroom property with kitchen and Lounge unless your property is very high up on the efficiency scale and almost passive house status.

I suspect you have been mis-sold on the unit and you need either one or two up the run for power output to heat your home sufficiently.


https://en.ahi-carrier.gr/wp-content/uploads/2021/05/IOM_30AWH_HO.pdf

QrizB

Another vote for a heat pump with a 5.8kW nominal output being quite small for a four bedroom house, particularly if the radiators weren't replaced with higher-output ones matched to the heat pump.

Do you run the heat pump non-stop? If the radiators are marginal, you shouldn't try running it like a gas boiler for only a few hours a day. Just switch it on and let it do its thing for a few days, and see if your house warms up.

Netexporter

Get one with R290 refrigerant. It will deliver higher flow temperatures with less of a COP penalty.

Scot_39

Spoonie_Turtle said:

Er … I am not an expert and I could be totally misunderstanding this, but that '2000W' … does that not mean it's a 2kW unit?  If so, no wonder it struggles to get to temperature!  Ours is 8 or 9kW for a 3-bedroom house!

I have no advice, but I'm so sorry to hear you've had such a bad time of it.  I doubt anybody is laughing, because you trusted professionals to know what they were doing and it sounds like you have been badly let down.  Not your fault at all, and no laughing matter to be cold in winter!

You might be confusing input power from mains ratings - and effective heat output ratings.

Its rating plate suggests a 2kW input - 5.8kW effective output at the air temperature / flow output temperature - if I understand the power label correctly.

Think the figures for heating mean at 7C external / 45C flow COP of 3, at 7C external / 35C flow - COP of 4.2 - but no expert - and don't have an ASHP.

Those COP figures are likely to drop with differential as outside temperatures drop.

The 1.18 change in COP for dropping flow temps from 45 to 35 in line with other posters who have said 5C on external temp drops around 0.5 on COP.

And of course the frost heating - like those models who used to run condensor heat belts - will consume an additional "vampire load" - not directly giving any heat to home.

(But better to have a system theat keeps working - than say a frozen condensor pipe on a gas boiler - never really understood why the don't fit trace wire heaters in them for winter).

If say COP dropped to 2 - at say -3C external (taking the 10C to the air side - again not 100% sure it's that simple) - that would be 4kW output - 4kWh per hour - 96kWh per day - so in deepest winter in a large 4 bed home - suspect its underpowered.

Reed_Richards

The air passing through your heat pump should go in through the grill at the side and out via the fan.  Neither of these appear to have ice, your ice is right down the bottom suggesting that it might be the condensate water that is freezing.  But that doesn't offer an explanation as to why your heat pump is not working properly.

In order to defrost, the heat pump will draw warm water from inside the house.  Many heat pump systems have a buffer tank or a volumizer tank to make sure there is enough hot water for this.  If you don't have either of these the heat pump may be forced to rob hot water from your central heating system and cool the inside of the house.

If the engineers you tried won't respond promptly, you need to find other engineers.    

AuntyPolly

Hi, I was very intrigued to stumble on this thread whilst seeking advice 

We too have recently had an ASHP installed and it is struggling to keep the house at 18c.  Unlike Curly legend we have a unit twice the size (I'm not sure of spec, but it has two large fans).  

The problem we are finding is that as outside temp drops, the defrost cycle kicks in (obviously using the heat from the house/radiator circuit to defrost). The problem is that the system does not seem to be able to get the house temperature back up before it has to start the next defrost again, meaning that the overall house temperature is slowly declining dropping a little more with each defrost cycle. So over a cold period of several days the house has been down to below 16c.  Unfortunately for us there is no back up system as described in the techologyconn thread that was shared, so we are unsure on what we can do to help raise the house temp, apart from light a log fire, but that defeats the object of having a greener energy installed.

We therefore need advice to help resolve this issue (the installers are not returning calls).

Like curlylegend states, the cost of the electricity feels like a waste on these days. I wonder would it be better just using electric fan heaters in each room maybe?

Reed_Richards

Heat pumps either have a fixed target temperature for their water output or this output temperature is varied according to the outside temperature.  You can maximise the output from your heat pump by using a fixed target temperature and making that the maximum that your heat pump allows.  Three possible things will then happen:

1.  Your house will reach your desired temperature
2.  Your house will remain cold but your heat pump will run in relatively short cycles of heating the house.  This would indicate that your radiators are not large enough to give you the heat you need, the return water gets too hot and the heat pump has to take frequent breaks to avoid overheating
3. The heat pump runs for long periods between defrosting but the house remains too cold.  The return water remains 5 degrees or more lower in temperature than the output.  That would indicate that your heat pump does not have sufficient output power to cope with the current outside temperatures.

     

AuntyPolly

The installers set up all the parameters and it has a fixed target temp. They also did all the room measurements and relevant calculations to ensure that they also installed the new correctly sized radiators in every room. 

So that leaves the unit itself, but again the installers assessed this prior to ordering.

The heat pump is running as expected in temperatures above 4C and we are happy with that regard, it is just this cold weather issue and even then the pump appears to be working ok, it's not stopping or anything, so maybe we are in a location that may require a hybrid system with backup as we are in a very humid area.

On the positive side the installers have now arranged for someone to inspect it next week.  But if weather warms up above 4c it will not be an issue. We have taken photos of declining room temps etc. My husband also had temperature probe on flow pipe and apparently that is not reaching temp.  Installers set to 50 and Max output over past few days has been 37.