heated water running into central heating header tank

silver fox · 9 Oct 2006

I have a problem with my heating, when I turn on the hot water switch on the controller, heated water from the boiler comes out of the expansion overflow into the heating systems header tank

the system is oil fired boiler fully pumped with a 3 port valve (mid position) and tank stat all the rads have trvs except the one in the bathroom

I have turned the speed of the pump down which seems to have stopped the the problem but I feel there must be an underlying cause

can anyone shed some light on this problem??

many thanks

bathjobby · 9 Oct 2006

I have a problem with my heating when I turn on the hot water switch

heating / hot water ? which. Suggest you read what you have written, because its confusing.

Bamber gaspipe · 9 Oct 2006

silver fox said:
I have a problem with my heating when I turn on the hot water switch on the controller heated water from the boiler comes from the expansion overflow into the header tank

the system is oil fired boiler fully pumped with a 3 port valve (mid position) and tank stat all the rads have trvs except the one in the bathroom

I have turned the speed of the pump down which seems to have stopped the the problem but I feel tere must be an underlying cause

can anyone shed some light on this problem??

many thanks

Someone turned your pump speed up?

Rob · 9 Oct 2006

its all down to the configuration of your cold feed and open vent. not really alot you can do yourself except precisely what you have done. its also possible that the cold feed has become blocked.

test your rads do they heat up on slow pump speed, if so you have the option to leave it as it is, no reason why not, or call out a heating engineer who understands a simple 'H' sysytem

Agile · 9 Oct 2006

Its almost certainly because you system has become sludged up.

The normal cure is a power flush!

Tony

Bamber gaspipe · 9 Oct 2006

If it was a problem with the pipework configuration I would think that this problem would have manifested itself before now.I can`t see it being a blocked cold feed because no mention has been given of being unable to vent rads, a blocked cold feed wouldn`t make it pump over in an open vented system anyway. Have you had any work done recently heating or plumbing wise?

silver fox · 10 Oct 2006

to clarify by turning on the hot water I mean turning on the part of the heating system that heats the dhw

no pipework has been done since the system was installed about five years ago

nobody has turned up my pump speed

the only work done recently was a boiler service

could be sludged up but when bleeding rads the water is clear no smell of inhibitor tho!!

I suppose it could have always done this without my noticing!

thanks for all the answers

anyone know of any desludging products that work well?

Bamber gaspipe · 10 Oct 2006

silver fox said:
I have turned the speed of the pump down which seems to have stopped the problem but I feel there must be an underlying cause

job`s a good `un

bathjobby · 10 Oct 2006

heated water from the boiler comes out of the expansion overflow into the heating systems header tank

What is the level of the water in the expansion tank and how high above the tank does the vent pipe go before it 'U's over at the top ?
The level of water in this tank should be low, just enough to cover the feed pipe at the bottom; being a gravity system the level of the water in this tank is also the level of the water in the expansion pipe, therefore, the higher the level the less expansion needed for it to 'overpump'. By the same token the higher the expansion pipe goes above the top of the expansion tank, again, the more expansion required before 'overpumping'.
Ideally at least 2' (60cm'ish) above top of tank but nothing wrong with going to 3' / 1 mtr.

silver fox · 10 Oct 2006

the tank is one of those combination jobs with two small headers and a dhw tank all in one box,

there is very little clearance between the roof and the top of the tanks hence the u is not very much higher than the tank 6 inches max

I'll try reducing the level of the water in the header tank

thanks for the tip

diynot

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heated water running into central heating header tank

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