Blocked cold feed ?

[datamile]

Does this sound like a blocked cold feed ? I've not been able to track the pipework yet to mag test it but.

Potterton 80 downstairs, pump upstairs about the level of bottom of rads, F&E tank in loft.

Boiler started resetting, it was hot , pump was hot but rads were cold and the header tank was full and cold. The pump is spining, and vibrating, but not removed it to check impeller blades

Lots of air in the system, so I try to drain and flush it but removing rad from ground floor. Very little water came out unless I unscrew a bleed tap from a ground floor rad.

During this time the header tank level did not change (ballcock tied up).

I refilled the system via a air vent which is above the pump, and got all the air out the rads. (it took a lot of water)

One switch on the system did run with the CH coming on for 1 min, and then the pump trying to move it around the system. The heat was very slow to move around the system. Sometimes when the pump was off you could hear water flowing back into the boiler.

This worked for about a day before the boiler started resetting itself again.

Does this sound like a blocked feed pipe ?

Its a Grundfos pump, if the feed is blocked does that mean that there would be insufficient head in the system for the good pumping ?

 

[ChrisR]

Does this sound like a blocked feed pipe ?

SOunds quite likely. Magnet you know about.

Its a Grundfos pump, if the feed is blocked does that mean that there would be insufficient head in the system for the good pumping ?

No, a system that's really full of water doesn't need any more so it works ok.
Could be there's still some air - primaries by HW cyl?

If you're a good christian, turn off the pump valves, pray they work without leaking, and remove the head of thepump (allen screws x 4). See if it's got gunge between the discs of the impeller.
Pump valves always leak for me - god gave up.

 

[felix]

"Very little water came out unless I unscrew a bleed tap from a ground floor rad."

There's a big clue in there. Water isn't getting out of the header tank into the rest of the system. This could indeed be a blocked cold feed but it could also be an airlock. All it takes is a slight uphill section in the feed pipe. You are left with a column of air trapped in the pipe below and your head of water is reduced to the depth of the tank only.

I learnt this the hard way when an incompetent plumber moved our cold storage tank. there was a barely detectable upward slope in the cold feed from the tank but it was enough to stop any water coming out of the hot taps. I cleared my airlock by coupling hot and cold taps together and, very carefully, blowing the air out through the tank. Unfortunately, this problem will keep coming back as air collects in the feed ppe.

 

[datamile]

Can't do the tap thing on a CH system ;( Gave the pipe a shake, but no joy. Still think its blocked.

 

[kevplumb]

just cut out 2m of 15mm for the same problem

 

[oilman]

You'd better put up a "THIS WAY" sign for the water. Otherwise without the pipe it won't have a clue which way to go.

 

[kevplumb]

ok i replaced is

sa