Turn Off Heat Pump at night?

Baldlygo

We have had our oil boiler replaced with a heat pump six months ago. It just heats the existing 7 radiators. I'm reasonably pleased with its performance even when the temperature drops below zero. However, our electricity usage has almost trebled in those coldest months.
The Heat Pump runs 24/24. I used to set a timer to turn off our oil boiler between 10 pm and 7.30 am and felt this made savings by not having heat generated at night. We are retired so we do need the heat in the house during the daytime every day. Another consideration is that the radiator pump also runs 24/24 and it does make a continuous sound.
My question here is would it save us some money or could it cause harm to our Heat Pump if we turned it off every night?

Netexporter

Low and slow is the mantra for heat pumps (also applies to some degree to conventional boilers). It is better the have a temperature set-back, of about 3 degrees, during the night, rather than shutting off completely.. Having a shallow heating curve set will also help efficiency, but you will need to give the pump longer the reach "daytime" temperature.

What is your flow temperature? Is there any scope for lowering that?

born_again

What do you use to heat the water?

Baldlygo

I do not know what a flow temperature is but my regular setting is 20 degrees and I have the option to manually change it up or down temporarily. I am presuming that the pump is either on or off at any one time and depends on the controlling thermostat. In other words - it makes no difference to the electricity used if I set the temperature to a high 25 degrees for example - it just means it will be on longer. Not sure if I have explained that very well

Baldlygo

born_again said:

What do you use to heat the water?

Electric ballon

Netexporter

The flow temperature should show in the settings menu of the control panel. You should also have been given the design information by the installer, which should show what flow temperature is required to reach the specified room temperatures with the particular emitters (radiators/UFH) that you have. If they kept the existing radiators from the oil system, then the flow temperature is likely to be quite high, possibly 50 degrees+, which will never give you a good COP for the system. You want a flow temperature as near to 30 degrees as possible, to achieve a COP of over 4, which may require larger radiators to compensate.

What is the refrigerant used in the ASHP?  R290 (propane) might give you a fighting chance of a reasonable COP at higher temperature, but other refrigerants, like R32, work better at lower flow temperatures.

Patrol

You can turn a heat pump off overnight but what is likely to happen is that it works hard to bring the property up to temperature each morning and that can be less efficient than leaving it on overnight. Your oil boiler is likely to have been much more efficient at this sort of morning reheat than a heat pump will be

As a matter of interest how much did your electricity bill go up by and how much would you have spent on oil

What make / model heat pump is it, someone here might be able to advise further if they know that. Do you have a manual for it, that might provide meaningful information for you

The flow temperature is how hot the water supplied to your radiators is and the lower that temperature the more efficient / economical the heat pump is likely to be. That also assumes your radiators are suitable for low flow temperature (i.e. oversized compared to radiators supplied by conventional gas/oil boilers)

There is probably a setting to reduce the flow, room, and hot water temperatures overnight

Not sure what you mean by Electric ballon. Could you be clearer e.g. heating this with the heat pump, immersion, or something else like back boiler or solar thermal

Spoonie_Turtle

Our ASHP was a retrofit (although with rads installed for the first time with it) and doesn't have a setback setting so we do turn it off at night (via the heating schedule, it's not allowed to kick in between certain times) because it was feeling like a huge waste to have it heating to the same temperature at night especially during colder nights - whirring away at -ve℃ outside to keep inside at 18℃ at 3am, for instance. 
[The circulation pump does still keep going overnight for antifreeze or defrost.]

But your heat pump is newer than ours so if it is a model with a setback option, that would be more efficient than turning the heating off altogether.

In terms of energy usage, I don't have exact data.  Our heat pump's usage has gone down since changing it to the heating off at night, but I also changed the hot water settings at the same time, so that may have made some or all of the usage difference, I really don't know.

Netexporter

Yes, the hot water settings could account for quite a bit of usage, for various reasons. If the DHW temperature is set unnecessarily high, if the legionella cycle is employed too often, or if it is using immersion heater assistance.

Reed_Richards

Many people combine heat pumps with underfloor heating.  UFH is very slow to respond so it needs whatever heat source it uses to be on pretty much all the time.  People often confuse the needs of UFH with the way you should run a heat pump but they are two completely separate things.

I have only radiators.  I set back my heating by a few degrees between 22:30 and 04:30; this has the effect of turning off the heat pump for six hours unless it is very cold outside.  This does no harm whatsoever.  When the heat pump comes back on it works continuously to bring the house back to temperature and I think this is more efficient then the rest of the day much of the time, because when it is warmer out it has to cycle on and off to keep its output low enough but when it is warming up the house it can settle down into gentle and continuous operation.  Anyway, whether it is more or less efficient it is operating with electricity the costs me 7.5 p per kWh until 07:00.  I also heat my water with this cheap rate electricity.

 

Baldlygo

Netexporter said:

The flow temperature should show in the settings menu of the control panel. You should also have been given the design information by the installer, which should show what flow temperature is required to reach the specified room temperatures with the particular emitters (radiators/UFH) that you have. If they kept the existing radiators from the oil system, then the flow temperature is likely to be quite high, possibly 50 degrees+, which will never give you a good COP for the system. You want a flow temperature as near to 30 degrees as possible, to achieve a COP of over 4, which may require larger radiators to compensate.

What is the refrigerant used in the ASHP?  R290 (propane) might give you a fighting chance of a reasonable COP at higher temperature, but other refrigerants, like R32, work better at lower flow temperatures.

I'm sorry Netexporter but that all sounds too complicated for me. Our setup is a Themor Aerolia 8 with a thermostat in one room,