replacing a faulty pump

[TinkeringRob]

Hi All

About 3 weeks ago my central heating fired up in the morning and tripped the RCD/Main Switch on my consumer unit, and it has done it everytime I have tried to fire it up since. (Notice how I'm only doing something about it now is starting to get cold!! ) Upon reading various posts on this forum I have decided it is probably the pump. To test this I removed the Neutral wire on the pump from where it connects to a complicated looking junction box (technical!) next to my hot water tank. The boiler now fires up and runs no problem (Is it dangerous to run it for a long period with no pump running?) When I place the wire back on, the pump runs for about 10 seconds and then the electrics trip again, plunging me into darkness - fortunately my consumer unit is in a sensible place to reset! So have I diagnosed the problem successfully?, or is there anything I might be overlooking? I have checked around for leaks but cannot see anything unusual.

If it is the pump this raises many more questions:
Are they all standard?
Do I have to replace like with like?
How much should I expect to pay for a new pump?
Is this something that would be easy for an amateur and his Dad (who has done quite a lot of plumbing before) to replace or am I better off getting a local tradesman in?
How much is a fair price to supply and fit a new pump?

Hope someone out there can advise me - sorry for so many questions.

Rob

 

[JohnD]

you have two questions:

1) What causes the RCD to trip?

2) How to change a pump?

You have posted this one in Plumbing, so I recommend you use the "edit" button on your post above to change the title, and edit the text so that it is just Q2.

Then post a new one on "Electrics UK" forum about your RCD tripping.

The CH people will probably want to know what sort of pump and boiler you have, and the Electricians will want to know more about your CU.

They both like photos.

 

[gas_man_gaz]

i would say yes you've diagnosed the problem successfully
and i wouldnt advise ya to run the boiler too long that way without knowing what system it is.. is it gravity hw pumped ch?
and yea, there not too tricky to replace i would fit a grundfos tho

 

[Soggy_weetabix]

i would say yes you've diagnosed the problem successfully
and i wouldnt advise ya to run the boiler too long that way without knowing what system it is.. is it gravity hw pumped ch?
and yea, there not too tricky to replace i would fit a grundfos tho

y

1: as a DIYer, can you drain the system if required.
2: Can you undo the unions on the pump?
3: Are the valves holding?

Just a few questions I ask myself before changing a pump on your system.

Cant you 'spin' it?

Dave

 

[TinkeringRob]

Thanks for the replies

I've confirmed that it is definatley the pump by wiring it directly to a plug, and the electrics trip as soon as I switch the socket on. I've been looking at pumps and am planning to buy a Grundfos 15/50 (I have no idea what these numbers mean - perhaps someone can enlighten me?) Unless anyone can tell me why I shouldn't. As far as fitting it myself goes, I will definatley enlist my Dad's help, as I think he has done it before. I think it might be wise to drain the system beforehand and change the valves just in case (there seems to be a crusty corrosion around the unions on my existing pump) I won't run the boiler anymore before I've done the job.

Rob