Heat pump hot water / underfloor heating settings

[jonm12345]

Hi - I have moved into a new build and inherited an air source heat pump, 390L hot water tank, solar panels, a hot water return/circulation pump and I have an EV / am on Octopus Intelligent Go.

 

The system is controlled by a NIBE SME 20 controller.

 

I come from boiler / radiator world so bear with me...

 

The installer told me not to touch any of the settings - so obviously...

 

I have no issues with the heating or hot water but looking at the settings can't help but think I'm running this inefficiently especially as we have a household of 3.

 

1) The hot water is set to Smart Control on the NIBE with scheduling off. This allegedly learns hot water behaviour and heats the tank at the most efficient level. Do these settings work? Given we are a household of 3 I was thinking there could be no more efficient way than setting it to heat from 3:30-5:30am when we get 7p/khw on the EV tariff. Is the answer to try it and see?

 

2) The hot water return/recirculation pump is set to come on 6-9am and 4-10pm. I get having it on in the morning when we shower but we don't really need instant hot water from the taps further away from the tank between 4-10pm. Is the only downside to switching it off having to wait a bit for hot water? If so I'll just set it to 7-8am which is when we tend to wake up / shower etc. but want to make sure I've got the right idea here.

 

3) The underfloor heating is set to run 24/7 at the same temperature. Each room has its own (limiter) thermostat but no timer controls - that would have to be done via the NIBE. The heat curve etc. has all been set and the installer claims that leaving it running 24/7 and not adjusting / lowering temperature overnight is the way forward. Coming from boiler / radiator world this sounds odd but is this the right advice?

 

Thanks for bearing with me this far!

[JohnMo]

38 minutes ago, jonm12345 said:

running 24/7 and not adjusting / lowering temperature overnight is the way forward

Generally 24/7 on weather compensation is best. Setback are likely to be cost neutral, so no point.

 

Other ways to run are batch charging the floor on cheap rate.

 

But I would get used to the house for a month or two before messing with things.

 

 

[Luke1]

I have the same controller, but have not used the HW smart control, which I think can only be used with solar connected to the system.

I would guess that it heats the water when solar is at a peak. I'm not sure if its predictive for weather, and what happens in the case of no solar?

 

I would probably schedule this to the cheap rate period over night. You may be better off doing it this way if you have solar export that is higher than overnight import rates?

If you don't run out of hot water in the day, you could also look at tweaking the HW setpoint down to increase COP, likewise up if you do run out and it re-charges in the day when you don't want it to.

(This can be accessed in the installer settings by holding the back arrow for 7 seconds from the home screen).

 

In respect of the 24/7 heating, we tend to batch heat over night into the floor slab so that the heat pump doesn't run as much in the day during peak rate electricity. In the shoulder seasons we should be able to heat over night only. 

I do this by scheduling a temperature increase / curve increase for the overnight period. (Which one you see is dependant on whether you have an internal temp sensor connected to the unit.)

 

 

[jonm12345]

Thanks - yes our export is 15p/KWh vs 7p import overnight

[jonm12345]

7 minutes ago, Luke1 said:

I have the same controller, but have not used the HW smart control, which I think can only be used with solar connected to the system.

I would guess that it heats the water when solar is at a peak. I'm not sure if its predictive for weather, and what happens in the case of no solar?

 

I would probably schedule this to the cheap rate period over night. You may be better off doing it this way if you have solar export that is higher than overnight import rates?

If you don't run out of hot water in the day, you could also look at tweaking the HW setpoint down to increase COP, likewise up if you do run out and it re-charges in the day when you don't want it to.

(This can be accessed in the installer settings by holding the back arrow for 7 seconds from the home screen).

 

In respect of the 24/7 heating, we tend to batch heat over night into the floor slab so that the heat pump doesn't run as much in the day during peak rate electricity. In the shoulder seasons we should be able to heat over night only. 

I do this by scheduling a temperature increase / curve increase for the overnight period. (Which one you see is dependant on whether you have an internal temp sensor connected to the unit.)

 

 

 

Thanks - yes our export is 15p/KWh vs 7p import overnight

[Beelbeebub]

I did see a YT vid where the guy had fitted a small home battery system that was large enough to power his HP through the high periods (so maybe 5-10kwh) so that all his HP (plus a big chunk of domestic) was at the half price octopus cosy rate.  That means your cop only needs to be about 2 to be as cheap as gas.

 

Obvs need to invest in the home battery system.

[jonm12345]

On 04/03/2025 at 13:11, Beelbeebub said:

I did see a YT vid where the guy had fitted a small home battery system that was large enough to power his HP through the high periods (so maybe 5-10kwh) so that all his HP (plus a big chunk of domestic) was at the half price octopus cosy rate.  That means your cop only needs to be about 2 to be as cheap as gas.

 

Obvs need to invest in the home battery system.

thanks. Yep, batteries are next!