General Question - Linkup heating system gas/solid fuel.

[Dan Le Moignan]

Afternoon guys, is anyone on here clued up/ hetas qualified for solid fuel wet systems?.
I'm linking up my current solid fuel heating system upto a combi boiler.
I'm doing this via a heat exchanger so the rad circuit stays pressurised and the solid fuel side stays open vented.
The system was spec'd by a hetas guy via stoves online website.
Now I need it fitted ASAP the fitter I rang said it doesn't sound safe as one heat leak rad may not be enough to stop the system boiling in the event of a power cut losing the pumps.
The only thing I can think is that I didn't make it clear that the solid fuel system is staying open vented? It will have a large capacity copper header tank also.

Here's the schematic I have for the system

ImageUploadedByTapatalk1375715300.574053.jpg

Thanks for any feed back. I'm running out of time as I need this done by mid September. I may have to just fit the combi and tie in the wood burner when winter is over.

[chriswrc51]

Hi mate,
Not HETAS etc, but i run a heating firm, we do Domestic but mainly commercial and use very similar systems to this.

The fact the solid fuel side is remaining OV will allow for expansion of the system content in the event of pump failure so you will definately be ok... remember though, the OV MUST NOT have any valves or obstructions along its entire length.

However, if you wanted an extra bit of protection (this is what we do on commercial plate to plate heat exs) , fit a combined temp/pressure relief valve on the solid side pipe work, the combi boiler will have a pressure relief built in that you pipe to atmosphere, the T&P Valve is similar, but has a heat sensing rod that lifts the valve at 95c/4 bar and releases the water, so again if piped to atmosphere would just bleed water off until the system temp dropped (be quite quick as the tank would be introducing cold water again).

this would also offer some protection for should the heat ex ever fail and pass water from the sealed combi side to the OV solid side..

Hope that makes sense!
cheers
chris

[Dan Le Moignan]

Chris thanks for the reply!
The actual solid fuel circuit will not have any valves, but i will run a honeywell mov on the heat leak circuit triggered from a pipe stat, it will also be a fail open valve so in the event of powerloss it will fail in the open position.
I was looking to fit T&P valve as i now cant quench via the hot water cylinder but i can only find ones at 95 deg/c, i was wondering if this was slightly to low? as i was planning the pipe stat for the heat leak to maybe trigger at 95 or is this to high?.
I think i really need to get the system running and monitor the temps as iam slightly worried that before the burner was heating 7 rads and a hot water cylinder and the return pipe to the burner was still nice and hot, now it will be a short circuit with the only heat transfer being the plate exchanger.
I have been told the exchangers are very efficient and almost all the heat will be transfered through it, but part of me still thinks i may end up boiling the water.
I have run out of time for now so i have booked a plumber to fit a combi set up and i will link up next year as the pipework will be fairly easy to change.
I think i will do most of it myself as i was a marine plumber/ pipefitter before so have good knowledge of piped service systems. I would do it all if i could and maybe just get it signed off at the end if this is possible?

[chriswrc51]

Chris thanks for the reply!
The actual solid fuel circuit will not have any valves, but i will run a honeywell mov on the heat leak circuit triggered from a pipe stat, it will also be a fail open valve so in the event of powerloss it will fail in the open position.
I was looking to fit T&P valve as i now cant quench via the hot water cylinder but i can only find ones at 95 deg/c, i was wondering if this was slightly to low? as i was planning the pipe stat for the heat leak to maybe trigger at 95 or is this to high?.
I think i really need to get the system running and monitor the temps as iam slightly worried that before the burner was heating 7 rads and a hot water cylinder and the return pipe to the burner was still nice and hot, now it will be a short circuit with the only heat transfer being the plate exchanger.
I have been told the exchangers are very efficient and almost all the heat will be transfered through it, but part of me still thinks i may end up boiling the water.
I have run out of time for now so i have booked a plumber to fit a combi set up and i will link up next year as the pipework will be fairly easy to change.
I think i will do most of it myself as i was a marine plumber/ pipefitter before so have good knowledge of piped service systems. I would do it all if i could and maybe just get it signed off at the end if this is possible?

Hi mate,

I would say set your Pipe stat lower than 95, usually boiler flow temps now are left around 75-80c, this helps the diff between flow and return meet on the Delta T curve for condensing mode more effectively, therefore if you aimed to run a similar temp on the solid fuel side, you could set your pipe stat to 85c, heat sink via a BIG rad in an unoccupied area (Garage to keep the Cos warm!), you should hopefully then not get upto anywhere near the 95c setting on the T&P, or boil up..
Regarding the DIY side, technically its against the gas regs to even hang the boiler on the wall even in your own home if your not Gas Safe (boilers are classed as a "Gas fitting") however, everybody does, how can they stop you when they sell boilers to the public in B&Q etc!! I would see if theres a local friendly fitter around, do all the pipe work yourself bar the last meter of gas each end, get them in to connect and commission etc shouldnt be a problem as you obviously know the crack, only stumbling block is the boilers now have to be registered with Building control, the installer does this via gas safe and they issue a compliance cert which you would need if you was to ever sell/move as its forms part of the HIP pack..
Hope this all helps!!
cheers

[Dan Le Moignan]

Sorry Chris what I meant was I would do the solid fuel side myself.
I'm leaving the combi side to a gas safe regd plumber next month!.
With regards to combi boiler return temp I'm running a spirozone manifold which will indirectly mix the flow and return to try and achieve a 50degc return temp to keep the boiler in condensing mode.
I will run a 5k plus heat leak rad in the loft with copper header to keep the mice warm! A lot like this;
ImageUploadedByTapatalk1377123150.785155.jpg

I have no garage at the moment so car is in storage!
Think I would end up messing about with the pipe stat to see what temp is best, would an aqua stat be a better option?

[chriswrc51]

Sorry Chris what I meant was I would do the solid fuel side myself.
I'm leaving the combi side to a gas safe regd plumber next month!.
With regards to combi boiler return temp I'm running a spirozone manifold which will indirectly mix the flow and return to try and achieve a 50degc return temp to keep the boiler in condensing mode.
I will run a 5k plus heat leak rad in the loft with copper header to keep the mice warm! A lot like this;
[ATTACH]10214[/ATTACH]

I have no garage at the moment so car is in storage!
Think I would end up messing about with the pipe stat to see what temp is best, would an aqua stat be a better option?

Yeah you may be better with an Aquastat actually, a lot more accurate with a faster response, the Honeywell L6188A2010 has a higher range also, 40-110c, so greater scope to set as you wanted..
The heat sink set up looks good too, should more than do the job.. Im not that familar with the Spirozone manifold, obviously on Commercial we loose a lot more heat through the system, so wouldnt usually have to blend down.
cheers