Central heating not working. Help needed.

[Chickenman]

I have an open vent central heating system which was working fine. I have done some remedial work but now the system is pumping over. Once it starts pumping over, the feed and expansion ball cock feeds the system and the over flow cannot cope.
I have turned the pump to its lowest setting. What do you think the causes are ?
My initial thoughts were an air lock in the system but doubtful. I have lowered the F and E tank by half a meter which means the F and E tank is only about 2meters above the pump.
Before I alter all the pipe work again I would really appreciate some guidance.

Thanks
Pete

 

[JCplumb]

What 'remedial' work did you do to the system?
Sounds like pump is in front of f/e connection and pumping into the tank instead of pumping round the system.
''Once it starts pumping over, the feed and expansion ball cock feeds the system and the over flow cannot cope.'' This bit doesn't make any sense, if it's pumping over, the float valve would be closed due to the level of water in the tank rising from the pumping over.
The 2m head from the pump to the f/e tank is fine as long as the system is piped properly and the pump is pumping away from the f/e pipe.

 

[Chickenman]

What 'remedial' work did you do to the system?
Sounds like pump is in front of f/e connection and pumping into the tank instead of pumping round the system.
''Once it starts pumping over, the feed and expansion ball cock feeds the system and the over flow cannot cope.'' This bit doesn't make any sense, if it's pumping over, the float valve would be closed due to the level of water in the tank rising from the pumping over.
The 2m head from the pump to the f/e tank is fine as long as the system is piped properly and the pump is pumping away from the f/e pipe.

Thanks for swifty reply. Nothing has been changed on the pump side. It's worked this way for 20 years. The system is not old. It was changed about 5 years ago in the same configuration. The reason the ball valve continues to run is due to an error on my part. I put the vent for the central heating system into the f/e for my back boiler. This tank is situated next to the other and will be fixed tomorrow. This of course led to the situation why the ball valve was not shutting off and continiued to run. It would have stopped if the valve was in the same tank. This still does not resolve the problem of pumping over and the only thing I can think of is the tank being lowered.

Thanks
pete

 

[stevetheplumber]

Thanks for swifty reply. Nothing has been changed on the pump side. It's worked this way for 20 years. The system is not old. It was changed about 5 years ago in the same configuration. The reason the ball valve continues to run is due to an error on my part. I put the vent for the central heating system into the f/e for my back boiler. This tank is situated next to the other and will be fixed tomorrow. This of course led to the situation why the ball valve was not shutting off and continiued to run. It would have stopped if the valve was in the same tank. This still does not resolve the problem of pumping over and the only thing I can think of is the tank being lowered.

Thanks
pete

do you have some details of which boiler it is ? some boilers have ways to deal with low head situations

 

[JCplumb]

So the float operated valve that is continuing to run is the one in the tank that is not being filled from the new f/e pipe? i.e. the water from the f/e is going into the wrong tank causing that one to overflow, but the other tank is having to replenish the water lost from the f/e filling the wrong tank? Wow, that hurt my head
There could be new resistance from either an airlock or sludge movement during this work, which could be causing the f/e issue. Might be an idea to flush the system then use some of the tricks shown on this site recently to refill carefully or backfill the system.
Does the new f/e pipe still have the same clearance over the new f/e tank water level that it used to have befor you moved the tank? That f/e pipe will be full of water up to the level of water in the f/e tank, so if the pipe used to peak 8 inches above the tank before you lowered it, the new pipework should peak 8 inches above the new level.

 

[JCplumb]

do you have some details of which boiler it is ? some boilers have ways to deal with low head situations

That's interesting. I wouldn't have thought about the boiler in a million years with it being a pumped open vent system.

 

[SafeGasInstall]

try turn water of to cwst in the loft and drain it down !

 

[Chickenman]

Hi to all

Sorry for not responding I was having a bite to eat after a day of scratching my head!....well an evening at least. To answer you many kind replies the boiler is around 24 years old and to be honest even the manufacture had no info on it when I called....hard to belive ...

I think I know what could be the problem with my heating.......please let me know if you agree. Ok I have doen nothing major to the sytem...except two things, the header tank is now slighty lower and the expansion is now in another header tank...Here is what I think could be wrong, though I need to check tomorrow.

All was working well until I move the expansion to another tank, in reality the expansion could or has always pumped over for the first few mins as the heating circuit settled down. This was all ok when the expansion was in the same tank as the ball-valve feeding the same system......trouble is now the expansion is in another tank....so this will mean the system will never equal out at first, ie on firt start up after filling a bit of water may go into the F and E tank.....but if they share the same tank the exesspumped over water will bring the float up so the tank cannot feed the heating system......so alll settles down. But with the way I messed up the excess water pumping over goes to another F and E tank....so the ball -valve on the heating Fand E opens and fills the heating Fand E........but will just keep filling as the water.


Hope that makes sense..


ATB

pete

 

[SafeGasInstall]

I think is time for a upgrade to your system

 

[ecowarm]

You are saying you have put the heating expansion pipe to another cistern? Maybe the CWSC ? I dont think you should be messing with the pipes if you dont know what your doing. Get a plumber to come and sort out this mess ASAP

 

[Mike Jackson]

Pumping over when it first starts up is a major problem. This introduces air into the system and promotes corrosion. By lowering the cistern you have probably made this worse. By putting the expansion pipe over another cistern you are creating even more problems by diluting any inhibitor and adding still more air.

If this is a cold water storage cistern that you have been pumping over into you have also contaminated the potable water within your property.

It's time to get someone in that knows what they are doing before you destroy your heating system any more or poison someone cleaning their teeth.

 

[SafeGasInstall]

pumping over when it first starts up is a major problem. This introduces air into the system and promotes corrosion. By lowering the cistern you have probably made this worse. By putting the expansion pipe over another cistern you are creating even more problems by diluting any inhibitor and adding still more air.

If this is a cold water storage cistern that you have been pumping over into you have also contaminated the potable water within your property.

It's time to get someone in that knows what they are doing before you destroy your heating system any more or poison someone cleaning their teeth.

and your house

 

[Chickenman]

and your house

Thanks for the replies gents but this thread has kind off gone away from what I originally asked. Just to clarify a couple of things. I have not at any stage said I put the expansion into the domestic hot water header tank and yes I agree this would create a health hazard but you would have to drink from the hot water tap for this to occur of course.

Secondly I understand your concerns about me detroying my system but as I am actually here asking for help with the system wpould point to me realising there is something wrong with the system, rest assured the system is an open vented two pipe return and wont be going pop....as I say it is vented and the vent is clearly working, hence my problem. The system doesnt need renewing, the whole system was renewed 5 years ago and has worked sterling since .

Another thing I would like to point out is I am a time served plumber with alot of heating experience but that was 20 years ago and although I can retain most of my knowledge and have never had any problems with any of the work I have done on my property, this one has me a little confused. But as I stated earlier I think it is a simple can of me putting the expansion into the F/E for the solid fuel, the coil shares the same cylinder.

My way forward is to simply put the vent into the correct F/E and if that doesnt cure the promlem raise the F/E....do you agree with this?

Many thanks

Pete

 

[ecowarm]

Put it back to the correct F&E and raise the vent, also feed and expansion may not be piped correctlly

 

[PlumbBobBob]

what was happening before your remedial work was carried out which caused you to carry out remedial work?

 

[Hardy1]

I have an open vent central heating system which was working fine. I have done some remedial work but now the system is pumping over. Once it starts pumping over, the feed and expansion ball cock feeds the system and the over flow cannot cope.
I have turned the pump to its lowest setting. What do you think the causes are ?
My initial thoughts were an air lock in the system but doubtful. I have lowered the F and E tank by half a meter which means the F and E tank is only about 2meters above the pump.
Before I alter all the pipe work again I would really appreciate some guidance.

Thanks
Pete

Get a heating engineer out mate..your best bet.

 

[Chickenman]

Get a heating engineer out mate..your best bet.

The reason for the work is the original header tank was in a bad state so I replaced it. I also fitted a better F/E tank for my solid fuel which as I say has a coild in the same cylinder. I suspect that dropping the central heating F/E has caused this problem and I am raising it at this time.If I have to get a central heating engineer in to solve this I really need my head kicking in lol...its not beyond me I am pretty sure I will sort if. After all the suggestions here are all pointing in direction I am going. I will let you know the out come.

ATB

pete

 

[ecowarm]

Its on a seperate system, 1st coil and wood burner, 2nd coil gas/ oil boiler. You can't put expansion into the other F&E cistern.

 

[Chickenman]

Its on a seperate system, 1st coil and wood burner, 2nd coil gas/ oil boiler. You can't put expansion into the other F&E cistern.

Yes I know they are on seperate systems, one coil is for the Oil fired CH with its own header tank and the other is the middle coil for the solid fuel with its own independant header tank. There is also a third coil for a solar tube system which isnt fitted as yet.

Anyway I seem to be getting some where! I changed the pipe work so it is as before and correct, ie the two heating vents go to the F/Es they should. Now I have just fired up the system and for the first 3 mins it was pumping over but only the odd spurt, it has now settled down and seems to be ok, all be it a bit noisy with the air at the moment. As I sasi earlier I am by no means a Heating Engineer , just a plumber with experience of it, mainly installations so not much trouble shooting, give me old fashioned gravity systems and I am ok lol. Anyway is it normal to have the odd spurt of water from the vent when starting some systems?

Cheers

Pete

 

[Chickenman]

Ok turned system off and restarted and it pumped over again, also noticed one rad failing to heat up so checking the valve. Could all this possibly be an air lock in the system so pumping over and stopping the rad heating up?

 

[Mike Jackson]

An airlock stopping one rad from heating up won't cause pumping over. It's either incorrect pipework configuration or the pumps too big for the system. It's possible that the pumping over has introduced air into the system and caused an airlock or the constant air ingress has caused corrosion and the rad is sludged up.

My first port of call would be the boiler instructions to see what minimum head is required over the F&E tank. I see loads fitted where the minimum head requirements haven't been complied with.

 

[Chickenman]

Hi Mike

Thanks for your reply. I sorted the radiator out it was a tiny grain of muck that had blocked the bleed nipple, unfortunatley as you said it hasnt cured the pumping over problem. Regarding the head to the boiler the system that is in my house is a bit odd as the cold feed doesnt go to the boiler downstairs, the system fills via a cold feed in the airing cupboard upstair into the heating ring near the clyinder flow, the vent then tees off that, I have never seen this before. I kinda feel this is where the problem lies and think the pump is indeed situated in the wrong place, which is on the flow around 3 metres under the F/E. At this rate I might have to arrange for a heating engineer to come and help me sovle this, oh and give me that kicking for not sussing this out lol.

I am thinking that this problem may have been here all the time but I only noticed it due to the fact I was working in the roof space when it occurred. It bloody frustrating to say the least.

Cheers

Pete

Regarding the bolier it a crappy old Potterton that came from the Ark

 

[SafeGasInstall]

you will be ok chikenman , I can see your a really timed served plumber even been 20 years ago

 

[Chickenman]

you will be ok chikenman , I can see your a really timed served plumber even been 20 years ago

Well I have admitted defeat and just called a heating engineer. I am pretty certain its the pump thats wrong but dont want to arse the system up more by messing around with it. Maybe it is fate but the guy I called stopped me when I was giving him my address and said ,,,no need to carry on with your address, I am at your next door nieghbours tomorrow to quote for a job....small worl eh!

Thanks for all your help gents.

Pete

 

[jtsplumbing]

Is it possable that you have a fault with one of the coils in the cylinder ?