Bypass circuit... solid fuel stove... thermal store...

[Dan Robinson]

They were bought up by Specflue - most of the engineering, patents, and technical staff and assets were moved over, and the business side was let go.

Good products - rubbish business sense is what killed them IIRC.

 

[RWhites]

I think I've got there.... from a combination of most of your replies.

The main reason I'm wanting the 'pump circulating to dump heat' safety system to work is because a) I've got it, so may as well make some use of it; and b) I don't want to rely on just one safety system that kicks in at 95deg in a 350lt store; and c) If I can avoid washing the heat down the drain, so much the better!

Like I said, I think most of my questions have been clarified to one degree or another, both on here and via some external research. I've concluded that a fairly simple 3rd pipe to rad - entering at the top, opposite the return should work - no reason I can think of why it won't, and confirmed on here by Mysteryman.

This pipe to be 'normally closed', with a 3-port valve opening the pipe when the 90deg overheat stat on the store triggers the pump to do it's safety work. I need to add this valve to the system.

So, under normal day-to-day conditions (including when the solid fuel stove is not lit), I'll have a fully TRV'd system (plus I'll add an ABV because my new pump is not modulating as far as I can tell).

If the stove is lit, and the store gets to 90 deg, and I have electricity, the 1st safety system (already fitted to the store at the factory) will kick in - it will start the radiator pump (to all rads), and it will also bypass one TRV on a large rad (just in case all TRVs are closed). In effect this is like having a 'permanently' open dump rad - but only when conditions dictate that I need it open.

If I do not have electricity, the 1st safety system will not work at all - no pump, no diverter valve, no circulation - so it is irrelevant whether the port valve will work or not. This is where the 95deg power-free quencher coil (also fitted at the factory) will kick in and pour lots of hot water down the drain.

End result - I need to add a 3 port valve and a run of pipe to the top of the relevant rad. I'll keep the port valve near the store so I can test it periodically. I also need to add an ABV (but not for the reasons I'd originally suggested).

I think that covers it....

Many thanks again to you all for your input. I'll post back in due course to let you know if it works ok - unless it kills me

 

[SimonH2]

First, I'd suggest you stuff a modulating pump in. I put a thermal store in the flat and the modulating pump (Grundfoss AlphaII) along with TRVs on all rads makes for a virtually silent system.

Your plan for a third pipe to a large rad sounds good to me - just be aware that you'll have a rad that gets flippin hot if the system kicks in ! Simplest way to wire it is with a 2 port valve, motor (brown and blue) connected to permanent supply via overheat stat, and switch (orange & grey) connected in parallel with heating time switch (ie turns on pump when valve open).

As an alternative to consider, there are valve sets available for WBSs which combine several functions - including an overheat divert to a heat dump. Rather than overheating the store and then cooling it, one of these would allow for a passive heat dump on the WBS primary circuit itself.