Integrating ASHP into existing heating system

[Fly100]

I’m interested in exploring the possibility of integrating and ASHP into my current system.

 

 

Background

 

New build property in 2017 @272 m2. 80% of the West walls are glass and very open, with little protection from the wind. Currently oil boiler, no mains gas.

Ground floor is 172 m2 all under floor heating with 150mm insulation flow temps @ 40c

Upstairs has radiators which are not used other than that to take the chill of the rooms and ( rads) sized with the ASHP in mind in the future.

 

The house is very well insulated but very open with little protection from the wind.

 

it was sized for 2 x 8.5kw ASHP. This would have resulted in more Planning Permission applications and after 3 years of battles with the locals we decided to put an oil boiler in and await ASPH Technology to improve to see if a single unit would ever emerge.

 

I’m interested in some sort of Hybrid setup that would use the ASHP on the milder days with the Oil Boiler helping out when the ASHP cant provide the required heat output.

 

 

Pipe dream or is this a possibility ?

 

Thanks,

 

FLY

[Gav_P]

Hi Fly,

Certainly is possible. Plenty of hybrid setups out there. 
 

Im sure someone will be along soon who can provide some tangible advice.  

 

 

[ProDave]

The easiest way to achieve this might be to investigate the Grant Hybrid combined oil / ASHP though that might be an expensive sollution?

 

You could fit a single ASHP and have a changeover scheme, that could either be manual valves or more automated.  That largely depends on who is doing it and their knowledge, I doubt you will find many people who routinely combine 2 different heat sources.

[Nickfromwales]

+1 on getting a hybrid, and subsequently saving a LOT of complex integration and balancing......... Plus, the existing oil boiler will sell relatively easily.

[Fly100]

5 minutes ago, Nickfromwales said:

+1 on getting a hybrid, and subsequently saving a LOT of complex integration and balancing......... Plus, the existing oil boiler will sell relatively easily.

 

I was with you all, but those VortexAir's are close to £10k.

 

I should add I have 6.2Kw of PV Solar on the Roof too.

Edited November 23, 2020 by Fly100

[ProDave]

What is your typical annual usage of oil?  that would let us work out you actual real world heating needs and see if an ASHP is viable on it's own.

[TonyT]

Can you not isolate the flow and return from the boiler and tie in a standard ASHP.

 

Have a large buffer tank with PV immersion dumps 

[Fly100]

The PV doesnt produce that much in the colder months, we put everything into the DHW tank and some days it cant bring that to up to a decent temp if its low cloud on little sun.

As for Oil usages I suggest it will be 900 - 1200 L depending on the Winder Temps.

 

Im exploring the option,

A there is an RHI incentive

B Borris's Carbon Plan.

 

Thanks,

FLY

[Nickfromwales]

On 23/11/2020 at 23:46, TonyT said:

Can you not isolate the flow and return from the boiler and tie in a standard ASHP.

 

Have a large buffer tank with PV immersion dumps 

Nope.
25% max PV productivity in winter, so PV > heating = no chance whatsoever. That tank will sit dormant all year. 
PV dump > hot water is the only sensible option and just face facts that you’ll have to purchase some energy in winter. Large buffer will only be any good really if you have Solar Thermal or multiple ( reliable ) fuel inputs.

You’d only want an isolations on the flows and to keep the returns linked ( grouped ) so the system is one unified body of water always sharing one filling loop / expansion vessel / pressure gauge etc for simplicity. That can be done with a 3-port diverter valve ( NOT a mid-position valve ) and a simple light switch to change between oil > ASHP. At that point I’d buy the cheapest modulating ASHP I could find and see if you can get 10+ years out of it. 

[AliG]

I don't think you need such a large ASHP.

 

If your house is well enough insulated that 40C flow temperature works and you use 1200l of oil a year, which looks like around 13000kWh then a 12kw ASHP would probably suffice.

 

A 12 kw ASHP running 24 hours a day is going to put out 288kWh of heat. This is equivalent to around 25l of oil, maybe 30l allowing for boiler efficiency.You might want a 16kw to allow for lower output on days wells below 0. You can get these as single units, although they are the big two fan units, maybe this is what you were thinking of by 2x 8.5kw.

 

Unless you have days where you use over 30l of oil then this would seem large enough. I guess I would be wrong if you let the temperature fall a lot overnight, but it seems unlikely from the figures given.

 

 

Edited November 25, 2020 by AliG