Potterton Boiler/Heating Issues

[nickjc]

Hi Folks,

I hope someone can give some advice on this issue.

My heating system comprises of a potterton sumprima boiler, 3 way valve & the top up tank in the loft - I assume its a sealed system.

I have had to replac the 3way valve and the automatic air vent both located in the airing cupboard. System was drained, new parts fitted and then refilled. I also had the famous pcb issue with the boiler so this was replaced too.

The problem I now have is when the boiler is ignited it appears that the water within the boiler water tank is heated to the point of boiling and then the boiler cuts out (as I assume is has reached temp) - but there isnt any water circulating. The boiler makes some loud banging noises when it cuts out.

I have taken the face of the pump off to check its working/spinning.

There is a bleed valve located above the boiler, but running a length of hose from that into the sink doesnt run off any water - no idea if thats normal as it appears to be the hot "exit" pipe from the boiler.

I cannot get any more air out of the system via the radiators. I have drained the system twice to double check everything.

So... anyone with any thoughts. If nothing else its been interesting, but after 3 week of no hot water I really need to get a professional in unless there is something obvious I am missing.

Any help would be appreciated.

Thanks all.

 

[seco services]

did you bleed the pump ?
is the pump running ? just cause it spins when its out don't mean its working.

 

[nickjc]

I did check the pump (its a Myson) but unscrewing the black centre cap and got a regular drip. I also took the front of the pump off this evening and briefly put power to it, so the impellor is spinning ok.

 

[seco services]

when the system is running is the pipe to the pump and pipe from the pump both getting hot ? if you say the pump is running try it at a different speed 3 etc.

as you say just cause its working it may not be turning under load.

you can useally feel them if they are working.
or unscrew the nut in the centre and pull it outwards and it will
lock into the spindle and if the pumps runing it will rotate as well.

 

[nickjc]

I tried the speed change, figured 3 would be better than 2, but still no joy.

The pipes either side of the pump do get hot, but the pump is also hot. Not sure if thats just the heat of the pump transferring up/down (the pipe)

Just about to link to a pic which may help.

 

[nickjc]

 

[nickjc]

 

[seco services]

that above you boiler is a draincock. and you'll probably find the rubber washer jammed in the end thats why it won't let water out.

the pump how far up the pipe is it getting hot ?
not at all, or to the valve etc ?
what have you got it on heating only, hw only ?

is the air valve open in the airing cupboard ?


i would say your airlocked at the motorised valve.

 

[nickjc]

If I connect a hose to that draincock, i get a slow trickle. Fills up a mug in about 1 or 2mins. The water is red hot. Should it run out faster?
I do have another one next to the hot water tank. Neither let any water out at any speed...

The heat transfers about 8" up and down the pipe, so not very far. Again, this is red hot! It doesnt get as far as the 3way valve.

The air vent is open slightly all the time. When the system was first filled lots of air escaped & i have left it in the same position.

Maybe the key is the draincock above the boiler?

Thank you for your help so far, much appreciated.

 

[seco services]

leave the draincock for now.

the heat is getting to the pump but not the valve. as air rises you won't get it out of the draincock down near the boiler.

if both pipes either side of the valve are cool/cold i would.

turn boiler etc off
get a towel lay it on the pump
get a container that will fit between valve and the vertical pipe.
push the lever on the valve over till it locks in the man position.
and slacken the nut on the horizontal pipe above the pump to the valve. (only a turn or two)
then just pull the pipe slightly till the water releases only need a trickle
and it should release any air trapped at the top pipes.

remember the pipe will get hot as the air releases and the hot water rises.

then push the pipe in tighten nut and switch on
and make sure that both the valves on the end of the pump are open.

tell me how you get on

 

[nickjc]

As the heating system is switched off, the boiler is cold and the pipes are also cold. I opted to pull apart both the horizontal pipes to try and make sure no air is in the valve. Fired up the system on hot water only and the boiler lasted amount 1 min then mad loads of banging and shut down. I couldnt hear any air in the system from the airing cupboard.

None of the pipes are warm as I guess the water didnt have time to get that far. The outlet pipe from the boiler is hot though. Pretty sure there isnt any water heading up that pipe though. Sounds like residual water inside is getting heated over and over.

Out of interest, not sure what the fitting is in the pic, would it be a check valve?

 

[seco services]

its an air seperator

 

[seco services]

its an air seperator releases any air from system.
that pipe gos up to the loft tank
i take it you have a combined feed/vent pipe.

your pipework is a basic layout and all vertical so should not really airlock.

im still thinking the pump is an issue

the boilers direct below your pump if the pump was running there is no reason why the water in the boiler won't circulate and so boiler keep on running.


when you released the pipework from the valve did water come out both sides ?
the loft tank has got water in ?
did it drain and re-fill ok ?
if you run the system and hold the pump and change the speeds can you feel it ?
and you didn't shut the pump valves at all ?

 

[nickjc]

The boiler is across from the airing cupboard, so the pipes must run horizontal for 15ft(ish).

I took each side of the valve off seperately, there was plenty of water coming out. Incidently, when I took the face of the pump off then refitted and turned back on the valves the air bled instantly out of the bleed valve. That would have had to go thru the 3way valve (i assuming!)

Just one note, the bottom valve directly below the pump doesnt really open/close. I havent touched it in this whole process. But it only turns a few mil either way. The one above the pump turns 5+ times. Is that normal? As I havent touched it i dont assume it to be a problem.

I have checked the loft tank (top up one) and yes, there is the usual level of water in there. I kept on eye on it throughout.

Puzzling !

 

[seco services]

now you say you have about 15ft of horizontal pipework from boiler to the bottom of airing cupboard.
and i take it you can't get to these and they don't have a bleed valves ?

a nice length for an airlock to gather in i would say.