Hybrid oil/ ASHP smart system

[111cookie111]

Hi all, 

 

Im hitting brick walls with my research, so thought i would see if anyone else has solved this one. 

 

Looking to put together a hybrid (bivalent) oil/ heat pump system for the new build im half way through. (ive got a new oil boiler and tank already installed onsite feeding old house)

 

Ive got a warmflow oil boiler so thats the only bit im tied to. 

 

Im after a 'smart' system though that will switch between source based on outside temp. and tariff. 

 

I think the only one that comes close is the Valliant VRC 700 with Aerotherm HP. Im yet to deep dive into the 'smartness'. 

 

Looked at Tapo, but heard they run HP inefficiently. 

 

All advice/ feedback welcome. 

 

Nick 

[Dillsue]

Our LG Therma V from 2020 has a back up boiler feature that is documented as shutting the HP down and switching a volt free contact at a configurable outdoor temperature. I guess later versions will/may have that?

 

I beleive some of the electricity suppliers offer tariffs where they can control your heat pump in return for a discounted rate. My brother has just moved his new Vaillant on to that type of tariff with Ovo.

 

Whether you can get both temp and tariff switching in one HP I don't know but LG and Vaillant may be worth looking at to get your research going.

[JohnMo]

I had a gas boiler and installed a heat pump for cooling. Had 2 years of data from gas only, then ran a year on ASHP only then configured to run hybrid for a year.

 

Concluded after running for a while heating season and doing all the costs I was way cheaper and simpler to run pure weather compensation from ASHP.

 

The complexity of having two heat sources isn't worth the time and money. Stick to oil or do the environment a favour and just go ASHP don't bother mixing the two. A new build just doesn't need it.

 

Spend the money on a battery and run cheapest rate electric 365 days a year with monobloc ASHP.

 

To.mske an oil boiler work in a new build you need a thermal store - charging a thermal store via an ASHP costs too much in CoP impact.

 

KISS keep it simple....

[sharpener]

1 hour ago, JohnMo said:

To.mske an oil boiler work in a new build you need a thermal store - charging a thermal store via an ASHP costs too much in CoP impact.

 

Don't understand this comment. A thermal store is useful for time-shifting, but that doesn't apply to oil bc the price is the same 24/7.

 

The tariff difference easily covers the loss of efficiency in charging up the TS: at this time of year I am only heating it to 45C which is enough to warm up the bedroom after the cheap period ends at 0700.

 

2 hours ago, 111cookie111 said:

I think the only one that comes close is the Valliant VRC 700 with Aerotherm HP. Im yet to deep dive into the 'smartness'. 

 

There are occasional comments about hybrid systems on the Arotherm plus FB group, worth posting a query there I would say. It's possible you would save by running the boiler during peak tariff times and the HP otherwise, but in a new build you might find the thermal time constant is sufficiently long to ride through the peak times anyway. 

[JohnMo]

37 minutes ago, sharpener said:

Don't understand this comment. A thermal store is useful for time-shifting, but that doesn't apply to oil bc the price is the same 24/7.

Heating loads are so low in a new build and modulation of oil boiler not the best, lots of short cycling is very likely without a volume of water to work with. Or you can do thick screed and simply batch charge the floor, but you need a boiler that will happily put out about 35 degs for a few hours at a time to make it work efficiently. A minimum output of 15kW doesn't really make this option realistic.

 

40 minutes ago, sharpener said:

but in a new build you might find the thermal time constant is sufficiently long to ride through the peak times anyway

As said I have been and done it with hybrid - just isn't worth the hassle doing hybrid on a new build. It's bad enough managing a heat pump that doesn't modulate the best, an oil boiler could be an utter pain. Just looked at the Warmflow range of oil boilers and minimum output of the entire range looks to be 15kW. When a typical 200m² new build house will need no more than about 5 to 6kW maybe less, built to minimum building regs, the boiler is huge. A well built house will be 3kW or lower heat demand, so boiler could be 5x oversized.

[sharpener]

5 hours ago, JohnMo said:

Just looked at the Warmflow range of oil boilers and minimum output of the entire range looks to be 15kW. When a typical 200m² new build house will need no more than about 5 to 6kW maybe less, built to minimum building regs, the boiler is huge. A well built house will be 3kW or lower heat demand, so boiler could be 5x oversized.

 

I tend to agree. But the OP has already got the Warmflow so it is a sunk cost and might have a role to play. I don't think they mind the cycling, I used to have a ?80,000 BTU/hr Archie Kidd and it was quite happy running 5 mins on 15 mins off indefinitely. More important was the min temp to avoid condensation, I guess less of an issue with a more modern condensing type.