xtrafast 120 - How to test pump is working

[jmuk]

Hi All. Under pressure from the wife I fired up the central heating yesterday evening (why - it's only September!) for the first time since last winter.

Unfortunately the majority of the radiators haven;t come on, only the three nearest the boiler (I suspect due to heat conduction as opposed to water flow). I can't hear any swishing noises and the boiler heats up the water in short bursts - i,e, 5 secs to heat to set temp, then off until temp drops -suggesting it is only heating a small amount of water, and that the pump is not working. Is that a reasonable diagnosis? Theie are no fault indications on the boiler.

First impression are it could be the pump - so I'm going to drain the system (and flush it whilst I'm at it), remove the pump and have a look - is their anything I should look for when checking the pump? I'm going to take it into work and get the sparky to bench run it - is that not a good idea (dry running it)?

Other alternatives are the bleed valve on top of the pump (its missing its cap - could that cause a problem), or the flow sensor (if that was faulty would it stop the pump?).

Thanks in advance. Jim

 

[picasso]

Your pump is probably just jammed, first make sure that there is water in the system then undo the big screw in the middle of the pump keep a towel handy as there will be some water, use a small flat headed screwdriver and spin the pump anti clockwise, the pUmp should start up.

 

[jmuk]

Thanks picasso - Will check tonight.[/img]

 

[jmuk]

See photo - instead their is a serrated cap - I've slowly unscrewed it but a lot of water started coming out - so it looks as though i may have to bleed it down and remove it - unless anyone knows what to do with this type of pump.

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• jmuk
• 27 Sep 2012
• 1

 

[jmuk]

The black knob on the front was actually a dust cover - onve removed their is a sprung screw which connects with the pump - which is turning. I can also turn the pump by, hand using the screw (shwn power to the pump is off).

Now have 3 upstairs and 2 downstairs rads working - no luck on other 4 downstairs rads though. Have drained system from 3 downstairs drain points, plus removed on rad and wired up a drain to where TRV was - and flushed the system in all cases - still no joy with remaining radiators though - I guess it's just a case of systematic bleeding and waiting.

Is it possible the pump is not generating enough flow?

The water heats from 35 to set 75, holds 75 for only a few secs, and then drops back down to 35 - is that a sensible cycle or should it hold 75 for longer?

 

[jmuk]

After taking out the 3 valve internals I sussed it was siezed - I've freed it and will see if it works - unfortunately the pump appears knackered as well - I've taken it out and when you turn the end screw their is a grating noise.

I suspect that when I;ve been pressing the screw in to determine if the pump is turning its shaved some plastic off the shaft end - and that is whats causing the grating - the plastic is stuck between the impellor and caseing - unfortunately I cannot take the sealed casing off to check.

I've tried flushing the pump but but it still grates.

With pump installed the boiler reports fault 05 - shich is symptomatic of faulty thermister (I swapped the DHW and CH around so couldn't be that), or blocked/stuck pump. The pump is turning but probably not fast enough tp generate enough flow?