Central Heating Bug

[Nucky]

Has anyone had and solved the following clich in a gas CH and hot water system: My system boiler frequently depressurises (pressure release valve opens) requiring frequent top-ups of water. I am on my second boiler (different manufacturer) but the same thing occurs, so the problem is not with the boiler. Any ideas where the problem lies? The pipework is small bore and eleven years old but the problem has been there since day one.

[gasman]

Could do with knowing a bit more about you're system capacity as an aditional expansion vessle may be required. But quite simply micro-bore pipe and sealed systems is very bad practice and is not recommended. There should be a bypass fitted aswell. I would recommend geting the system power-flushed for a start then check out the by-pass. Fit an automatic pressure differential one to be on the safe side. Also check out the capacity of the system to see if you need the additional expansion vessle. If you are in West Yorkshire area or near Birmingham it is possible that either myself or gucciman a fellow ABer and competent fellow could give it a once over for you and maybe help you out. If not then get it looked at and mention what has been mentioned here.

[matt1e]

totaly agree with gasman your problem most probably lies with the fact that you have microbore pipes

[Nucky]

Thanks gasman, all sounds very technical and beyond me. The whole system was put in by the developers 11 years ago in around 30 houses. I have replaced the boiler partly because it was too small and because I hoped to solve the problem. Can't help about the bypass because I don't know what it looks like. The new boiler is a Glow-worm 30si with a system capacity at 75C of 156 litres. As the problem of frequent topping up has been there since day one, will power flushing do any good? I am in York - is that near to you?

[dasman98]

hi i have come across this problem i overcome it by fitting a radiator as a by pass with 15mm pipiework at least 3m on flow and return with no stat this allowed the heat to pass as with microboar piipework restriction is taken place water is not being passed through boiler and pipework quick enough causing overheating pressure will increase
also how many radiators do you have on your system you may need an additional expansion vessel this will stop over pressure
check to make sure if there is a filling loop present that it has been disconnected when pressure has been reached when cold to 1.bar
although i think this boiler has one built in but you would be surprised to know how many people still install them

[Nucky]

Thanks for the info dasman98. I have now had an automatic bypass fitted and that appears to have made a difference. I have 15 radiators and you are right another expansion vessel may be necessary but I'm doing one thing at a time. The filling loop is manual so I just turn off the tap when the pressure reaches 1 bar.