Intermittent Central Heating

[SomeoneElse]

I have the most strange problem, where my central heating sometimes works and other times the rads simply do not get hot

The heating system is a closed combi boiler system.

So far I have:

1. Removed all radiators and flushed with a pressure hose
2. Added a cleaner which now makes my water a bit orange but not excessively.
3. Opened the screw on the pump only a trickle escapes and checked that it turns. occasionally feels a tiny bit gritty but the pump definitely does seem to work i.e. it turns under its own when on.

If I leave the system to go cold it sometimes is enough to get up and running again.

Another odd thing is that although I have flushed the rads when the system does work the bottom of some rads takes longer than the top to heat. Which I though was potentially down to sludge but I ran the water clear through these puppies??

A rad was removed downstairs and the pipes are sealed not joined, I don't believe this is a problem but though I should mention it. As problem only manifested after this....

I hope someone has a clue even if it is down to faulty pump despite it spinning?

 

[gassafeengineer]

i have come across the impellor on the pump coming loose and intermittently working also they sometimes shear off completely

valve pump off and remove 4 allen bolts remove pump head, may take a clout with the hammer and inspect the impellor

 

[SomeoneElse]

Thanks for the reply,

I don't think the problem is the impeller as it spins even when the system isn't working

Is it possible for the impeller to spin happily away and yet still be a failed/failing pump?

 

[gassafeengineer]

when you remove the screw from the pump head that is the shaft that is spinning you need to remove the head to see the impellor it may have come off the shaft

 

[SomeoneElse]

Thanks for giving me something to check.....

I'll let you know how it went.

 

[SomeoneElse]

hmmm... head is off, and thing is loose complete and fancy free

What now?

 

[SomeoneElse]

not sure if this might help but it sounds a little like its raining inside the pipe between the pump and the heat chamber..... is it possible there is some sort of back steam pressure preventing water flow?