Any heating engineers / plumbers about

Mark_The_Yid

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I've got a problem with my central heating. Only some of the radiators are getting any heat at all and not necessarily properly hot. The boiler overheat stat is kicking in after not very long and there is a knocking sort of noise from the pipework when the boiler fires up (which I am assuming must be air). One pipe at the boiler is red hot and the other is only warm. The pump seems to be running ok.

Am I right in thinking it sounds like an airlock in the system and if so what would have caused it and how can I get rid of it?
 
tried a few and they seem to bleed ok. Even ones that are stone cold
 
Sounds like the pump impeller has seized - CH pump impellers are not usually on a shaft but dragged around magnetically. If it's been off for a while you may be able to free it up by giving it a clout with a mallet or block of wood. Not too hard, the pump body is cast lol
 
You can feel the pump vibrating though and when you turn the speed down on it the vibrating gets lower and faster when you turn the speed back up.
 
You can feel the pump vibrating though and when you turn the speed down on it the vibrating gets lower and faster when you turn the speed back up.

Yes, but is the impeller spinning? It's not on a shaft so the motor could turn and the impeller not?

If one side of the pump is hot and the other side gets quickly cooler the further from the pump you check it's likely shagged.
 
Is there any way to tell? I whacked it a bit but nothings changed
 
If it rapidly gets cooler as you follow the pipe away from the pump it's likely shagged. Can you see the flow arrow that indicates the direction of flow?
 
Yeah can see arrow. Pipe is still red hot approx 1.5m along as it enters the floor.

Dunno if it matters but predominantly all the working rads are upstairs and cold ones are downstairs
 
Can the pump be bled. Seam to remember doing this once by loosening the big slot screw in the center of the pump
 
Yeah can see arrow. Pipe is still red hot approx 1.5m along as it enters the floor.

Dunno if it matters but predominantly all the working rads are upstairs and cold ones are downstairs

Sounds like it's in thermo-syphon, pump not working, hot water rises so the upstairs gets warm and downstairs doesn't. Without a nose that's my best stab M8.
 
I would be inclined to agree with HH tbh, especially if there is a big temperature difference between the two pipes at the boiler
 
I've opened up the pump and got a little water come out. With the screw out I put a screwdriver inside and something was turning as it was grating against the screwdriver blade. Does this mean the pump is ok or still not prove anything? I don't really wanna do £120 on a pump and find its not the problem
 
I've opened up the pump and got a little water come out. With the screw out I put a screwdriver inside and something was turning as it was grating against the screwdriver blade. Does this mean the pump is ok or still not prove anything? I don't really wanna do £120 on a pump and find its not the problem

One, you need someone to take a look and two £120 for a pump is over the top!
 
Screwfix want £115. I was hoping to not have to find the cash to get someone in.
 
defo the pump as regards the price look to pay around 75 + vat as all pumps are now a rated you wont find a 25 pound job anymore as these were phased out about a year ago as regards to energy efficiency
 
defo the pump as regards the price look to pay around 75 + vat as all pumps are now a rated you wont find a 25 pound job anymore as these were phased out about a year ago as regards to energy efficiency

With @JimmyP here, just changed mine and bought from PTS, £70+vat. Easy DIY job especially if isolators are sound :)
 
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What are your thoughts on ebay item 171223489450? Or should I stick to grundfos?
@JimmyP I'm in Essex.
 
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