RHI compliant bi-valent system - air-water heat pump with old oil Rayburn

[ajn9000]

We are looking at air-water heat pump options. One of those is to build an old oil fired Rayburn into the solution. The Rayburn is a Royal OF7 - very basic oil burner with a manual control. It currently ticks over on the lowest setting all year round, providing space heating to the room and enough hot water (gravity/convection system) for 98% of the year. Has anyone successfully designed an old Rayburn into a RHI-compliant heat pump system? If so, how was that configured with respect to controls?

 

[Nostrum]

Are you in The south west by any chance? I've seen a similar job posted somewhere else! An older property.

My issue with the proposed set up is that the Rayburn is lit continuously regardless of use, which seems wasteful. In order to achieve RHI compliance, the heat pump would need to be metered and RHI paid on usage.

It's certainly possible to connect the two systems, whether or not it's a worthwhile solution, I'm not convinced. What are the main reasons for keeping the Rayburn?

 

[ajn9000]

Yes near Callington - have been posting on the electrician's forum. We would fire up the Rayburn for cooking - but when lit it will heat water & provide some space heating. Don't want rid of the Rayburn as it is part of the character of the house.

 

[Worcester]

@ajn9000, Nostrum's in your neck of the woods and knows what he's up to

So long as the Heat Pump is metered that is all that's essential for the RHI.

From a practical point of view then a thermal store with heat in at the top from the rayburn and the bottom from the heat pump and a manual control or a temperature alarm system managing the thermal store would be straightforward, and MAY be the solution - it really needs a site visit to confirm what actually would be best.

Does the rayburn operate on a pressurised system? if not it may need an indirect coil in the thermal store and possibly a heat sink.

Effectively almost any of the solar thermal controllers are capable of the temperature control of the store. - We have often used these to manage buffer tanks for ASHP's when they don't have built in buffer tank management e.g. Sorel Solar Controllers / Pumping Stations | Navitron Green Energy - Here's a very inexpensive one: SOLAR panel differential Temperature Controller for hot water boiler & +2 SENSOR | eBay - ignore that they say solar, the key thing is that it's a differential temperature controller . If you want to get more sophisticated the Panasonic ASHP bi-valent controller is very good.

The BEST: Panasonic new HPM controller: Aquarea Manager - Panasonic - heating and cooling systems it even produces a hydraulic design and electrical control circuit - here's an example View attachment HPMtool-47132.pdf

 

[Nostrum]

Hi,

Have you had an EPC carried out recently on your property? If the answers yes, perhaps you could forward me your postcode via PM and I'll be able to get a very brief insight at the property in question.

 

[lame plumber]

if you still have a rayburn of7 i would suspect it is on its last legs, the fire bricks will be well past their sell by date unless they have been renewed at some time in its life and the boiler section may be approaching its time when it splits and leaks as they are only a lump of metal thats been corroding for the last 30 plus years. you may wish/are advised to get a rayburn specialist to inspect the old monster prior to making some expensive decisions first.

 

[ajn9000]

that's good advice thanks. The Rayburn is plumbed into a direct vented tank - in the room directly above.