problems with circulation

[raljon]

can anyone offer advice please ...having serious problems with circulation here!

when the ch works it works very well but on most occasions the water isn't circulating properly and the system ends up heating up (badly/ slowly!) by gravity feed with the downstairs radiators often staying cold.

I have changed the pump (twice!) and the anti gravity valve (it doesnt stop gravity flow in the opposite direction!), and flushed the system. The system is gravity hot water, pumped ch and has a primatic tank, Potterton Myson boiler . I have bled the pump and spun the shaft too.

The only thing I have noticed is that shortly after the pump on the supply side there is a tee fitting which has a short vertical piece with what looks like a bright silver knurled knob on the end. Access is difficult and it wont turn. Is this a bleed valve and do you think that an air build up here is causing problems. The main supply pipe goes horizontal from 5cm below this and finally a with short rise to the upper level.

I am getting desparate for a solution and running out of ideas! Any help appreciated

 

[seco services]

yes thats a bleed valve

 

[twgas]

not sure what you mean by this

the anti gravity valve (it doesnt stop gravity flow in the opposite direction)

any chance of a photo of this

The only thing I have noticed is that shortly after the pump on the supply side there is a tee fitting which has a short vertical piece with what looks like a bright silver knurled knob on the end. Access is difficult and it wont turn. Is this a bleed valve and do you think that an air build up here is causing problems

 

[raljon]

the anti gravity valve looks like and is about the size of a large socket (from a socket set), say 1" accross with an arrow showing the direction of flow and is inserted after the pump.

The 'bleed valve' again looks like a large socket with a bright silver knob about 5mm accross at the top. photo may be difficult to get on here but will try later if i can. This leads nowhere and the the pipe continues off horizontally about 4" below it.

 

[raljon]

'seco services' / anyone, do you thin this could be causing the problem? There is electricity at the pump and a slight change in vibration when you turn the speed control. When the system works properly it makes a small but noticeable 'whooshing noise'when it is started ...when it doesnt it just emits a small humming noise.

 

[seco services]

why have you changed the pumps twice ?

faulty pumps, gravity check valve jamming, cold rads etc to me its pointing to sludge in the system.

 

[raljon]

pump was exchanged to rule out faulty pump.. (no difference). Anti gravity valve was changed becuase it was old and cheap to replace! Some sludge but now assumed to be mostly clear, radiators taken out and flushed in the garden.

 

[seco services]

try bleeding that valve.
my feeling is still with sludged pipes etc.
how bad was the rads when flushed was it like oil etc ?

 

[raljon]

difficult to quantify but I have seen worse. The system has had flushing solution in it for about 3 weeks and has since been drained about 3 times. Water now running fairly clear. I am hoping to be able to clamp a small mole grips on the top and I assume it would open anti clockwise to expel air? I dont understand why air there wouldnt just be pushed to the upstairs radiators where it could be easily bled out.

thanks for the ideas..please keep them coming!

 

[seco services]

don't put any more cleaning chemicals in as they shouldn't be put in a primatic system

 

[raljon]

accept the advice on chemicals but from our point of view:
1. we dont drink the hot water,
2. have no children in the house
3. If the rust/ sludge ever escaped through the airlock on the cylinder it would probably kill us anyway if we drank it!

 

[seco services]

i take it you do bath in it ?

 

[dotto]

...........also i do not think u can fit a pump in a primatic system because the air bubble will go and the primary water ( rads water) will mix with secondary water ( domestic hot water).

 

[raljon]

sorry shower only!

 

[seco services]

you can have a pump on the rad circuit but the cylinder has to be gravity.