central heating help

[alim1]

hello all. i have drained and refilled my c.h system which has a worcester 14/19 cbi boiler, hot water cylinder and header tank etc.

the prob is the boiler ignites and runs as normal for a few mins and then the burners go off with only the "demand" light still on, no errors flashing.

i can hear and feel the the ch pump working. blead the radiators but can't bleed the pump as the vent screw is worn.

please help

 

[Dan Robinson]

Do the pipes come out of the top or the bottom of the boiler? If the latter, then there is a bleed point (white plastic) on the U-shaped pipes to the left of the boiler.

If air is stuck in the pump try flicking the speed selector backwards and forwards - it might help tease the air out.

 

[alim1]

the pipes come out of top. did as you suggested but still no luck! it seems the pump is unable to pull the water from the boiler?

cheers

 

[alim1]

silly question guys. can the 2way motorized valve stop water circulating
on both the hot water and central heating at the same time?

i still can't seem to get the water out of boiler through the pump and out?

is there a way i can test the pipe for a blockage without cutting the pipe?

cheers

 

[Space cat]

silly question guys. can the 2way motorized valve stop water circulating on both the hot water and central heating at the same time?

No it can't. It blocks one or the other or neither.

is there a way i can test the pipe for a blockage without cutting the pipe?

If it wasn't blocked before, it's unlikely to be blocked now. Your problem is almost certainly caused by one or more airlocks. One round of bleeding doesn't always do the trick. The pump can't shift air so the first thing you have to do is get water in it. (That worn vent screw would have been really useful. )

I would start with the pump off but the three port valve in mid-position (use the override lever) then bleed whatever you can, starting with the cylinder coil. Go round until no more air will come out of anything. Next, get the pump running and do it all again.

 

[alim1]

thanks for that mate.
i have now put a new pump in, traced the flow pipe from boiler to pump and
found an elbow on the pipe which has a vent hole.

i pumped air through this and it came out ok from drain holes on the boiler
and under the pump. so that pipe is not blocked ?

i have again refilled the system and blead it 3 times now and it does not work!

any ideas guys?

 

[alim1]

sorted now. it was an airlock.

the one vent i missed was the one under the floorboards, did that and all others for a number of times and it is working, got heat and water. wife is happy

thank you guys for your help.
cheers