CH & HW Problems - Air Lock around boiler?

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I've been looking at the various posts and notes around this forum to try to answer this, but am still struggling. So any help would be greatly appreciated.

Boiler is a Potterton Profile 60e
Pump is Grundfos UPS 15-90
MV's are Drayton 2 port units (2 off)

I removed and refitted a radiator yesterday. When I drained it out the water was black at the bottom, but overall not really sludgy. On reconnecting a bled it and it filled apparently normally. However, I am now in the situation that the boiler when it comes on runs only a few seconds before shutting down on its thermostat. (if I turn the setting up - it fires up again, but still soon down in seconds.) The pipes in and out of the boiler are both hot. On listening it sounds as though there could be some water boiling at the top of the pipe(??).
The pump sounds as though it is running fine. If I turn the screw on the spindle it seems to bleed out OK. It is very hot to touch. The pipe below it is hot, the pipe above slightly less hot. The motorised valves both seem to function fine. All radiators have been bled with no air coming out.
The fill tank in the roof seems to have autofilled OK to the ballcock when the radiator was drained.
I have put the immersion heater on manually, and get hot water that way, but otherwise can get no heating or hot water.

The system has occasionally been making noises that sound like the pump was rubbing on a2 Hz frequency, but on investigation they actyually seemed to be coming from the Hot Water cylinder. The noises from the pump sound like good pumping and flow and this still sounds the same now.

So is it possible that there is now an air lock around the boiler? Would this have the effect I am having? If so how do I get rid of it?
I also don't understand the valve arrangements around the hot water tank. What are the two red handled valves for? Should they both be open?

Not sure if the picture posting will work so have tried to include a link to the photo of the system as well.

Thanks,

32


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Is the pump actually turning?

Take the plug out and check before doing owt else.
 
Thanks for the amazingly prompt reply.

You are quite right. The pump with the plug out is now turning fine, and all is coming back on line. I guess it was blocked/stalled or something. I didn't realise that you could run it with the plug out to see what was happening. :oops:
Is this a sign that it probably is about to fail, or more likely need to drain and clean out the system?

Thanks anyway - hopefully that should see us through the bank hols!
 
Probably on its way out, however i have had plenty that have done that and have gone on to last for years :wink:
 

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