Hot boiler, cold pipework

[Binman]

Hi, Can anyone help?

The System

I have 14 year old central heating system:-

Glow-worm Space Saver 60BR Mk 2, fully pumped, hot water cylinder, British Gas Multi Head 2 pump (replaced Jan 2002?), Honeywell Diverter Valve F5-9738 (old?, looks like current V4044 model), Potterton EP2000 Programmer.

The Problem

The boiler fires up OK and runs for a while then cuts out (overheat thermostat?). The pipework doesn't heat up, though, at least not initially but after a couple of minutes the f and r pipework coming out of the boiler gets hot but only close to the boiler.

I can hear the pump running when switched on and hear bubbles passing through.

The box on the diverter valve gets warm when the system (ie. pump) is switched off but the power to the programmer is connected. The lever on the box of the diverter valve rests at mid-way, neither staying at the "auto" side or the "manual" side.

At the end of the last heating season the heat to the radiators used to stop from time to time. I could get it going again by switching off for a few minutes and then switching back on again (I should have done something about it then!!). Over the summer we just used the boiler for hot water and all was well.

On trying to start up the space heating recently, again not working but now it didn't respond to the switching off and on trick! Also I couldn't then get the main burner to light. I put in a new thermocouple and that got the main burner lit - but again no circulation. I noticed some minor leaks at the flow and return connections to the boiler. I drained down and fixed these, refilled the system. The current situation is that the main burner lights up OK but there is no circulation of hot water. The pipework from the boiler travels vertically up at first and then horizontally to the cylinder and pump.

My thoughts are that I have either got an airlock above the boiler or the diverter is jammed in an "off" position (if that is possible).

Many thanks to anyone who can suggest which way to go.

Regards,

Binman.

[/u]

 

[oilman]

The pump is not moving the water for whatever reason. At that age the system probably needs cleaning anyway, and the pump may be nearly blocked up, Take the pump off and see what it's like inside.

 

[Binman]

Many thanks, Oilman.

I'll take a look inside the pump tomorrow.

Does the cold f and r pipework at the boiler suggest that there is air in these pipes rather than water? I'm only a layman but wouldn't heated water in the boiler quickly conduct heat through the water a little way along the f and r pipes even if the pump was not moving the water at these places?

You didn't mention the diverter - I presume that you don't suspect this a being the cause of the problem?

Thanks again for your reply - much appreciated.

Regards,

Binman[/u]

 

[Binman]

I took out the pump and the diverter valve today. The pump looked clear. It turns OK by hand or electric power. The diverter had just a minimal amount of sludge inside, which I cleaned out. The pump is on the flow side, both isolating valves are open and I've bled the pump. The pump spins freely and I heared a slight noise of water passing through it when the system was full again and switched on. Still, though, the heat from the boiler is not travelling along the pipework. The boiler gets hot but the heat doesn't reach the pump.

When I was repairing leaks at the boiler/f&r joints I drained the system at the boiler. Am I right to assume then that the f&r pipes are clear of any blockage?

Has anyone any suggestion?

Many thanks in advance,

Binman

 

[Binman]

I left it alone for an hour or so and switched on again - not expecting any change - the heat reached the pump and beyond. It's heating up the radiators and the cylinder. I've switched it off and on a few times and the system is firing up and working well. I suspect there had been an airlock, which cleared itself.

Thanks again to Oilman.

 

[Bahco]

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