gas boiler need a bit of assistance

[mark_mc]

i went to look at a house 2day and they what to fit a wood burning stove with a back boiler.
now the heating system is pressurised and there is a gas boiler system boiler with a vented cylinder upstairs

since the heating system is pressurised i would like to change it to a open vent system and put a f+e tank in the roofspace to feed the stove and then link to the central heating therefore making the gas boiler work in a vented system

will this make a difference to the gas boiler as sometimes i find they wont work without pressure.

dont worry im not touching the gas work in anyway im not gas safe reg/

 

[gasmarc]

thats an interesting one to say the least, i can see you having a couple of issues one being how to control the back boiler so you dont start boiling things also depending on what type of boiler you have it may not be suitable to convert to an open vented system, is the back boiler going to do the hot water only ?

 

[mark_mc]

the back boiler will be connected with a gravity circuit going to a twin coil vented cylinder upstairs with the vent a cold feed connected to that. and then there will be another two pipes of the back boiler (stove) to serve the radiators with a pump, this pump will only turn on when the return from the cylinder is at 45degrees and say the pump did stop working the boiler will tec not boil as it will expand via the gravity circuit and out the vent. also will fit a check valve after the pump to stop the gas boiler heating the stove when on.

i can remember the type of the gas boiler now but i knew that same are just for sealed systems and some are for both.
why dont certain gas system boilers work on vented systems

 

[gasmarc]

because they might be low water content at a guess ,others have expansion vessel fitted and low water pressure switch, pumps etc ,I dont do back boilers myself but would think correct pipe sizing and configuration is essential

 

[mark_mc]

yes pipe sizing is very important the gravity pipework as to be done in 28mm copper rising to the cylinder and then to the vent. 22 vent and 15mm cold feed.

if the boiler has be be sealed then i will think about a thermal store cylinder and link everything together will all the different coils etc will be a bit more expensive but safe

if i got the details of the boiler and rang the manufacturer they know if it could be changed to a vented system??

 

[gasmarc]

yes that will save alot of agg.good luck