Potterton Problem

[Roly]

Can anyone help! I have a Potterton Neataheat Profile 60E boiler, Grundfoss UPS 15/50 pump and Honeywell V4073A1039 3 position valve. This morning the pump was making nasty screeching noises so I turned the pump speed down to a minimum.
This caused the radiators to go cold so, suspecting the pump, I bought another and replaced it tonight. I had to drain the whole system to replace the pump then refilled and switched the boiler back on. I opened a rad. bleed valve and the water gushed around and air was coming out of the radiator. After a while the overheat trip on the boiler tripped, and I couldn't reset it until it had cooled down.
The problem now is that hot water is flooding out into the header tank and not circulating. I imagine that this is causing the boiler to trip. I have opened the bleed screw on the pump but that's not solved anything, I can hear the pump working but it's struggling because it sounds like it's pumping dry.
Sorry to go on but I've tried to descibe the exact symptoms in the hope that anyone can help!!

 

[corgiman]

Blocked cold feed pipe or an airlock, have you got water in your feed and expansion tank? (the little tank in the loft)

 

[ollski]

don't shoot me but have you opened both th pump valves? and fitted pump the right way round??

 

[dal5band]

Run it cold for testing - turn the boiler thermostat to zero. Gives you more time to find the problem. Pump, air-locks, valve opening etc.

 

[ChrisR]

Alleluia for someone who can describe his system and his problem clearly!!

The solution will hopefully lie in addressing the points given above, but what is the sequence of connections , from the boiler? Does it for instance go
Boiler > Vent(22mm) > Feed(15mm) > Pump > Motorised valve?

If so, it may mean there's a blockage between the vent and the feed. Because I have one, I'd put a water-vac on the vent pipe, with the system off. This would take water the reverse direction, possibly clearing some debris.
Trickier alternatives would be to connect the mains to the feed pipe down to the system, or the vent pipe. Think about those before doing them or you'll get wet!

 

[Roly]

Thanks for all of your suggestions, answers follow;
corgiman - I do have water in the header tank, its mucky from venting the hot water. The ball valve is operating, when I push it down water comes out and water is not getting as high as the overflow.

ollski - no offence taken, the pump went in the the same way as the old one and yes the valves are open.

dal5band - thanks, good advice.

ChrisR - my setup is exactly as you describe. Unfortunately I dont have a water-vac but will work on the basis that my feed pipe is blocked and will try to clear it by any means possible!!

I will try again tonight when I get home and let you know how I get on. Kind of liked the wife getting close to me in bed though......

 

[ChrisR]

Earlex Wet and Dry vac, as in Wickes (they badge them), about £35.
Take the filter out or it'll spray out of the exhaust. Amazingly useful.