Hi all I am involved in a self build and currently trying to sort out chimney design for a stove with a wrap around boiler. Stove has 4 connections at back A - B at top and C - D at base left to right. Do I need to leave space to side of chimney for two 28mm pipes that will T off approx 1m away from point B at back of stove up 28mm to cylinder down 22mm to pump for rads (hot) and the same for point D approx 1m away expansion cistern 28mm up and 22mm down linking return off rads - therefore blanking off A and C

Or will all four A B C & D be used 2 for 28mm pipes for gravity and 2 connections for central heating therefore requiring spaces on left and right of chimney which is to directly above stove

And finally is a high and low pipe stat recommended a bloke over a pint mentioned should be thinking of a motorised valve.

I am not expecting to do all the plumbing work myself but may source some of the components and will be doing the block work myself

Thanks Simon

Hi Simon

Sune's advice is sound and I would agree with most of his comment. With the caveat that you don't give enough design info to assess boiler tapping situation. What stove make/model do you have? If the saddle boiler is just that - a single boiler, you may be best off using two TBOE tappings for thermo-syphon to cylinder and heat-leak rad (aim for 20% of total boiler output min.), using these pipes for V and CF/Exp to header tank. Use the other two tappings for pumped flow and return. This would be pref as boiler is then a natural neutral point in the system between pump and gravity plumbing.

BUT if the boiler is a split saddle aka Woodwarm, a popular range of stoves, then you will need to join both top pipes as flow, and both bottom return pipes, and split the gravity/pumped circuit another way. Several ways to skin that cat...pref via a mixing valve of some kind, or if you want to go cheap, an injecta T works perfectly well, and your plumber can make one for pennies.

Both stat suggestions will work - there are arguments both ways. We have used 'minimax' hi-lo stats for years with success in limiting condensation in the boiler (longevity factor), but if using an hydraulic mixing valve like, say, the Laddomat, they can provide a flue stat. My only liking for a high-limit stat as belt and braces here (bah gum-tree lad) would be if the residual heat in the boiler after a hot bout of stoking caused localised boiling. It happens, and is unpleasant. But less so on a tarry boiler...sigh!

My preference therefore if I was having to part with my filthy lucre - low temp protection with flue stat and boiling protection with a high-limit stat. One advantage of a low stat would be that it would allow the pump to extract residual heat in the boiler more efficiently than thermo-syphon can, without the risk of condensation. Whether that outwighs the parasitic pump consumption involved is another argument.

You pays your money....

Regards

Crusoe

Hi Crusoe sorry did not reply earlier missed your response. The stove I have is the Clearview 750 wrap around boiler approx 13 kwh to water which probably equates to 10 ?? to be connected to a 260 - 300L thermal store with seperate pumped rad circuit and 60 X 47 solar tubes. The recession has cetainly meant you are able to haggle over the price, it was reading on forums that help me to decide. At times I wish I had gone for a modern gasification boiler for the front room but that would mean too many sacrifices in other areas.

I have read threads about the Landdomat and it has certainly been popular with people with large stores but for now, my current thinking is that I will try without.

If you could confirm which setup you think best it would be appreciated. Just starting on lighting haha see many more nights online, cheers

Hi Simon

I think the Clearview will give you the output they claim - just ensure the front room itself is not too small that you have to turn the stove down, as if that happens, your boiler output drops correspondingly. I would say, given both stove and ST output, that your thermal store is on the small side, as if you intend to keep the solar running (as opposed to stagnating), there will be times with that array when you have to bleed heat off.

I am assuming that the TS is vented (header tank) and will be for rads and DHW? (Or is the cylinder you mention a separate DHW indirect?) In which case, as the CV boiler is a single integrated unit, you need only take TBOE 2 x 28mm pipes to the TS - just worth checking with the mfr that they are ok with that. If you don't want to gravity extra rads, 300 litres is sufficient of a heat-dump - just ensure that in power-fail conditions you allow heat out of the store as well as into it - a connection from near the top of the store with a fail-safe open valve like Honeywell's V4043B (note suffix, this is not a standard 5-wire MV with end-switch) will fail open and allow egress of heat from the store to your chosen gravity circuit.

As far as overheat protection goes from the stove TO the store, don't put the pump directly in the return, but in a loop of pipe adjacent to it, with an injecta T built in. whisper me your email and I'll send you a diagram, but please clarify points above first.

There have been threads on this forum and a lot of guesswork re. themo-syphon (ie gravity) pipework and it's really not the black art it's purported to be. Experience is good though, especially as these 2 pipes will incorporate your cold feed and vent facilities, so maybe this bit you could get help with?

Regards, Crusoe