Wanting to know if this theory is a load of pants or will this work??
I currently have a conventional gas boiler that heats a water tank for hot water and 8 radiators and will soon be buying a cast iron stove and want to use some of the heat from this.
The system is as follows
CH circuit: Boiler > Pump > T-piece to split upstairs & downstairs > 1 to 4 manifold > radiators > 4 to 1 manifold > T-piece to join up and down back together > return to boiler
My plan is to break into the return leg from the radiators before going back to the boiler and pipe to the stove...so in theory...cool water from radiators is then preheated (or fully heated if I'm lucky) before returning to the boiler...at which point the boiler will have minimal or no work to get up to the temp required and just keep recirculating the water without the burners running.
reasonable theory or pants....
I'm aware this will only heat the CH circuit and not the hot water tank...as I dont know how to do that one...any suggestions...ideally i want solar for that one but cant afford the panels yet.
I'm afraid it's pants. The only correctly way to use a back boiler from a stove is for the back boiler to feed a gravity circuit. This would mean replacing your existing hot water cylinder, which has one indirect coil, and replacing it with a two (twin) coil cylinder. One coil reconnect to your gas boiler and the second coil to the stove. The Cylinder must be at a higher level than the stove and any horizontal runs must have a minimum incline of 1" rise for ever 12" of horizontal run. It is also recomended to have an additional radiator on the gravity circuit to act as a heat leak, in a lot of cases this could be the bathroom radiator or towel warmer.
This heat leak radiator must not be fitted with a thermostatic radiator and idealy should be fitted with two lockshield radiator valves to prevent accidental switch off.
If you are planning to add radiator heating from the stove as well as domestic hot water I would suggest that you consult with a profesional as the control circuit requirements & wiring is very complex and can lead to a great deal of damage being done if not got right, you will need some one with HEATAS approval (the solid fuel equivalent of CORGI).
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