Heat Pump - Is it working or is it just rubbish?

Bad_Pump

So I had a new heat pump installed in November. I have two issues:
1. I appreciate they have to work harder in winter but my house always feels cold. Occasionally it's 'not cold' but it's never warm. My radiators never feel hot like they did with my old gas boiler. They just feel warm at best. Is that normal? Is the idea constant low level heating or is the HP just not doing it's job?
2. My combined energy bills have skyrocketed. Like 50%+ higher than they were pre-HP. My gas is almost nothing, but the electricity is huge. November's use was 829kWh. These things are supposed to give me a return on my investment but not at this rate. Again I appreciate it's winter. Maybe that balances out over the warmer months? I could accept the higher bills if my house was toasty warm all the time but it's not.
So, is this all sounding normal or is something wrong?
Thanks!

FlorayG

I would suggest you get back to your installer. 
The radiators will not be as hot, that's normal, but they should heat the room by being on longer. If you are switching them on and off as you did the gas then that's your problem. You should set the temperature you want and then leave them alone, they will run for longer to reach room temperature.
If you are doing that it will also account for the high bills

Bad_Pump

FlorayG said:

I would suggest you get back to your installer. 
The radiators will not be as hot, that's normal, but they should heat the room by being on longer. If you are switching them on and off as you did the gas then that's your problem. You should set the temperature you want and then leave them alone, they will run for longer to reach room temperature.
If you are doing that it will also account for the high bills

We have the thermostat set on the AI setting so it should be adjusting as it goes along. 

Keep_pedalling

Did you simply swap out a boiler with a heat pump with no upgrade to the radiators? 

FreeBear

Bad_Pump said:

So I had a new heat pump installed in November. I have two issues:
1. I appreciate they have to work harder in winter but my house always feels cold. Occasionally it's 'not cold' but it's never warm. My radiators never feel hot like they did with my old gas boiler. They just feel warm at best. Is that normal? Is the idea constant low level heating or is the HP just not doing it's job?

I've been running my gas powered central heating with low flow temperatures this winter - At one point, as low as 30-45°C just to see if I could. Took a long time for the house to heat up after cooling down overnight, but it never felt cold. The radiators felt as if they were barely warm, yet room temperatures steadily increased - Have temperature sensors throughout the house and log the data..

Low temperature heating systems are slow & steady (think tortoise & hare), taking time to heat a place up. But to do it effectively requires a system that has been properly specified and configured. One would assume that your installation was specified by an MCS accredited installer, so radiators should be large enough. Quite possible that the system hasn't been tuned properly to maximise efficiency & temperatures. In which case, get them back to adjust the settings.

Bad_Pump

Keep_pedalling said:

Did you simply swap out a boiler with a heat pump with no upgrade to the radiators? 

Yes. But we were going along with the advice of our installers.

FreeBear

Bad_Pump said:

Keep_pedalling said:

Did you simply swap out a boiler with a heat pump with no upgrade to the radiators? 

Yes. But we were going along with the advice of our installers.

Did they do a proper detailed heat loss survey on each room ?

QrizB

Bad_Pump said:

2. My combined energy bills have skyrocketed. Like 50%+ higher than they were pre-HP. My gas is almost nothing, but the electricity is huge. November's use was 829kWh.

How much electricity would you expect to have used in a November before having your heat pump? 200kWh? 300?

And how much gas would you expect to have used? 1000kWh? 1500?

Bad_Pump said:

 hese things are supposed to give me a return on my investment but not at this rate.

Are you sure about that? Did someone promise you that it would?

A heat pump with a middle of the road COP of 3-ish will cost a bit more to run than a mains gas boiler, assuming the current standard Ofgem-capped tariff.

matt_drummer

FreeBear said:

Bad_Pump said:

So I had a new heat pump installed in November. I have two issues:
1. I appreciate they have to work harder in winter but my house always feels cold. Occasionally it's 'not cold' but it's never warm. My radiators never feel hot like they did with my old gas boiler. They just feel warm at best. Is that normal? Is the idea constant low level heating or is the HP just not doing it's job?

I've been running my gas powered central heating with low flow temperatures this winter - At one point, as low as 30-45°C just to see if I could. Took a long time for the house to heat up after cooling down overnight, but it never felt cold. The radiators felt as if they were barely warm, yet room temperatures steadily increased - Have temperature sensors throughout the house and log the data..

Low temperature heating systems are slow & steady (think tortoise & hare), taking time to heat a place up. But to do it effectively requires a system that has been properly specified and configured. One would assume that your installation was specified by an MCS accredited installer, so radiators should be large enough. Quite possible that the system hasn't been tuned properly to maximise efficiency & temperatures. In which case, get them back to adjust the settings.

It is not actually the low flow temperature that makes the home take longer to warm up with a heat pump compared to the gas/oil boilers they often replace.

The emitters (radiators/ufh) if big enough put out plenty of heat even at very low flow temperatures. It's actually the dT between flow and return temperatures and the flow rate that determine the heat output, the actual flow temperature is irrelevant to the heat output as long as the emitters can cope.

The main reason it takes longer to heat up with a heat pump is that their maximum output is usually pretty close to the heat loss of the home at the coldest temperatures.

That means not much extra heat is available when it is coldest to raise the indoor temperature.

We are used to gas and oil boilers that have much bigger heating outputs that are capable of raising indoor temperatures very quickly.

I have a heat loss of about 4kW at -3c but had a 28kW gas boiler.

Obviously, the house would warm up more quickly with 28kW of heat compared to only 4kW from the heat pump.


If your radiators were bigger than they are now then your gas boiler could put in even more heat, it is just restricted by the radiator outputs.

Once you replace your gas boiler with a heat pump your limiting factor will be the maximum heat output of your chosen heat pump. When it is close to design temperatures it will need to run continuously to keep the home at the designed indoor temperature, if you don't, and with no spare heating, you'll never raise the indoor temperature with the heat pump alone.

born_again

Bad_Pump said:

FlorayG said:

I would suggest you get back to your installer. 
The radiators will not be as hot, that's normal, but they should heat the room by being on longer. If you are switching them on and off as you did the gas then that's your problem. You should set the temperature you want and then leave them alone, they will run for longer to reach room temperature.
If you are doing that it will also account for the high bills

We have the thermostat set on the AI setting so it should be adjusting as it goes along. 

Maybe drop the AI setting & set to a temp that you find comfortable. 

matelodave

I don't honestly think that a heatoump will actually give a return on the investment, especially compared with gas or oil at the moment. They aren't rubbish, but they need to be set up and operated correctly but, IMO, any claims about them saving money are greatly exaggerated.

They are being sold on the premise of saving energy, which may be true, but as the energy they use presently costs four times that of a gas or oil boiler they are unlikely to save money unless you can run them very efficiently/

leccy is around 25p/kwh whereas gas is about 6.5p and AFAIK oil is also around 6.5p, so you need an SCOP of 4 just to break even. However you need to understand that SCOP is an average over the whole year. COP is the instantaneous value, so will be a lot less during the winter than it will be in the summer. 

As suggested above, run the unit for longer and not on and off like a gas boiler,  but you should still expect some pretty high daily electricity usage when it's everso cold outside.

On Sunday 12th Jan we used about 50kwh of electricity for heating = £12.50. Being generous and assuming I'm achieving a COP of three, that's probably equivalent to around 150kwh of gas = £9.75 but we have our system pretty well set up and we know how to use it properly. 

Bear in mind also that you probably didn't really take much notice of how much gas you used in kwh (or even the cost) but now you've got a heatpump you are trying to measure something and comparing it without using a similar kwh baseline.