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Temperature schedule for ASHP

Air Source Heat Pumps (ASHPs)

Last Post by HarriUp 2 years ago

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John T

(@returnflow)

New Member Member

Joined: 2 years ago

Posts: 1

Topic starter 27/01/2024 8:40 pm [#1331]

Hi all, i am new here.

I have a question about temperature schedules.

We have just had our Octopus survey, waiting for quote for a Daikin system.

We currently do not heat the upstairs, hall set to 18 and rooms in use set to 20 or 21.

During the night we turn all stats down to 13. Using Hive system.

The surveyer said we only get a basic Daikin thermostat an leave it constant day and night.

Surely this is wrong.

If we move to new cosy octopus rates I would plan on boosting through the cheap periond and minimising electricity during day rate and peak rate.

We do have PV and battery but that is smal fry compared to winter heating.

So, do ASHP owners vary temperature to save energy and cost or is it normal to keep it constant?

John

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HughF

(@hughf)

Honorable Member Member

Joined: 4 years ago

Posts: 489

27/01/2024 9:59 pm

I keep it constant, I don't even have a room thermostat. It runs on weather compensation 24/7. I'm still tweaking the weather comp settings to get things just right.

Cosy is a terrible tarriff.... you'd be much better off on Go.. Heat pumps like to run long and low, boosting the heat for a couple of hours and then coasting through the expensive couple of hours isn't a good strategy in my opinion.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.

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HarriUp

(@harriup)

Estimable Member Member

Joined: 5 years ago

Posts: 108

28/01/2024 2:01 am

Your house loses heat 24hrs a day – if you heat the house for only some of those hours then you have to replace the lost heat as well, which if you have a gas boiler just amounts to using the gas at a different time, though there is a modest benefit from a lower rate of heat loss the longer you aren’t heating – so this is what most people expect to do with heating.

Because a heat pump is less efficient if it has to work harder to get the circulating water hotter, the calculations say that more energy is used to reheat up to a temperature after a period of inactivity than to maintain a running temperature.

However, many users do run a setback at night and think it doesn’t alter the efficiency too much, as temps are lower at night which decreases efficiency too. But I think there is a limit to how long you can not heat for before you struggle to bring the house back up to temp – the difficulty is that will vary depending on the weather which makes it hard to schedule.

Lowering the cost of energy is a different calculation to getting the most efficient performance from the pump by lowering the quantity of energy required. It is easier to benefit from time-of-use tariffs with UFH as that can be loaded up – if you only have radiators then you are relying on the thermal efficiency of the house to carry heat between ‘on’ periods.

Mitsubishi EcoDan 8.5 kW ASHP - radiators on a single loop
210l Mitsubishi solar tank
Solar thermal
3.94kW of PV

👍

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