Hi i have a few issues with my Thermal store heat from leaking away via reverse thermosyphon, ie hot water is rising from flow to thermal store up the pipe in loft out to boiler outside when pump and boiler are off. Can you recommend the best non return or check valve, I have a few leftover Drayton ZA5 valves would prefer simplest and best for flow thankyou.
Preventing thermosyphon
- Thread starter speccy
- Start date
Sponsored Links
I don't see how fitting an NRV is going to stop that... the NRV needs to be fitted in the same direction of flow as what hte pump would do - and the thermosyphon appears to be in the same direction. Once the boiler is colder than your tank, the thermosyphon will stop anyway.
Presumably your boiler is gas or something 'controlled'? Motorised valve would get my vote- is the boiler driving anything else or just the thermal store? (If just the store & depending on boiler type you may need to fit a bypass between feed & return)
Sponsored Links
When you say inverted loop do you mean for example 22mm pipe out from store turning 90 downwards on the vertical how much i don't know a 180 degree bend at the bottom which feeds back up to loft?
What sort of drop must i have to stop thermosyphon.
Or i could use one of these??
https://www.bes.co.uk/water-swing-check-valve-brass-1-bsp-7464
What sort of drop must i have to stop thermosyphon.
Or i could use one of these??
https://www.bes.co.uk/water-swing-check-valve-brass-1-bsp-7464
Your original post says "hot water is rising from flow to thermal store up the pipe in loft out to boiler outside" indicating the boiler is low down and outside, the thermal store is high up.
Unless you're saying the thermal syphon is in the return to the boiler?
Nozzle
The thermal store is possibly 1ft higher over the external boiler from ground level (taking into account floor dpc/screed etc. All i know is when the WBS is running and the boiler is OFF one pipe is hot one is warm. The boiler is OFF at the isolator.
Re image below you can see i have some issues here(!), yes the pipework is a bit non standard as its still being developed, pumps are now both horizontal.
Seems i have multiple issues as the Central heating flow feed is heat leaking as is the Boiler flow pipe. I think what is exasperating this is the flow from the WBS is pumped via Ladomatt and it seems the water going in the top of the store via the flow input is flowing straight out again up the Boiler flow via thermosyphon up into loft cooling coming down into boiler on external wall.
As suggested i feel my solution here is to drop both CH and Boiler circuits down 15 inches before they go up. My only other concern is both these circuits are running through the day, will the residual hot water in the vertical sections in the wall (both flow Boiler flow and CH Flow go UP into loft) still cause enough gravity to pull cooler water from the bottom of the U or inverted loop and start to siphon again.
Last edited:
The boiler flow should have what I know to be a london loop. The pipe drops down below the store connection about 300mm and the rises up and then connects to the store.
Ahh, interesting setup. You need to keep the thermosyphon going in the woodburner circuit, the London loop sounds like a good lowtech solution to backfeeding up to the (gas) boiler in the loft. I'm sutprised you don't have motorised valves on the CH circuit- that would prevent that uncontrolled heating effect.
Thanks for your input also fyi I am using a ladomatt 11-30 bottom right of pic orange light. Was using Thermosyphon but thought I'd add the pump.
Yes this is why I posted on here pondering on whether to use loop or a few drayton ZA5 control valves.
With only a foot differential the Laddomat is pretty essential....
Loop or motorised valve- on the boiler flow the loop is (IMHO) a better fix- no moving parts, no changes to control circuits but may be a faff to retrofit. Motorised valve will work but you'll need to integrate it into the control system & cater for any pump overrun on the boiler. On the CH flow I'd go motorised valve purely for the additional control (this is assuming you have adequate heatloss arrangements elsewhere for the woodburner). Honeywell are a more reliable valve....
Loop or motorised valve- on the boiler flow the loop is (IMHO) a better fix- no moving parts, no changes to control circuits but may be a faff to retrofit. Motorised valve will work but you'll need to integrate it into the control system & cater for any pump overrun on the boiler. On the CH flow I'd go motorised valve purely for the additional control (this is assuming you have adequate heatloss arrangements elsewhere for the woodburner). Honeywell are a more reliable valve....
Agree but so far it's been sh't! It seemed to be better before when we relied on thermosyphon now i run it all day and it won't really exceed 65 degrees it would kettle at 90 degs before. Admittedly due to extra plumbing and ive now changed the connection to the FnE tank it may have introduced a thermosyphon heat leak there too, but, the boiler alone gets the TS up to 75 degrees in 1hr.
I spoke to Termoventiler about the pump and they recommended i up the 65 degree catridge to higher temp i thought that governed what temp the pump opened at only.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
