Slow HW, slow rads, boiler clunking...

Jan 01, 2008 4 Replies
J

These problems may not be related...



I have a Worcester Bosch Greenstar boiler (an early condensing combi) about 6 years old. For some months the hot water has taking about 3-4 minutes to come out hot, as if the pre-heated store isn't working. Timeswitch is set correctly, the boiler is not in ECO mode.



Also, in the last week the rads have been taking a long time to get warm. The rads upstairs get hot first while the downstairs ones are still cold. The burner comes on for about 3 minutes or so then off for



3 minutes, so the whole house is taking hours to heat up. There is a clunking noise coming from somewhere inside the boiler.

Any ideas? Pump? Sludge in the pipes - the central heating system is also 6 years old. Whihc should I check first?



Many thanks!


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H

Check the pump is rotating - Remove the silver screw ( expect some water leaking out) and see if the shaft end is rotating.

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J

Sounds like a pump problem or other obstruction in the primary water flow.

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E

I would say you probably have some flow but not enough. I'd suspect a partially detached impeller in the pump. Sludge is possibly involved but as the symptoms came on suddenly I suspect the pump.

It is often possible to change the pump head as they are often big standard grundfoss units, held by 4 allen bolts and a big o-ring.

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