Pump or just capacitor?

[GeeTee]

A quick update. Put the new capacitor in and the pump starts right up fine and is nigh on impossible to stop from turning with the "finger test". Reinstalled to boiler, bled everything of air and appears all is well, central heating is toastily up to temp and warming the house nicely as I type. Looking forward to a nice hot shower in a bit

Just for reference - those Maplin capacitors don't quite fit right in the wiring box atop the pump. Thanks to having a lip around the base that the original doesn't have the lid of the wiring box sits a mm or so proud on that side.

Thanks for everyone's help

 

[GeeTee]

AARGH! I spoke too soon.

After about 30 mins running fine on CH the whole boiler went dead. Turned out the fuse at F1 had blown on the wiring board (behind lower door). So I followed the diagnostics in the back of the service manual, replaced the fuse, then on demand for heat the divertor did it's exercise routine, then right when the pump should have spun up the same fuse popped again. I've no more spares of that fuse now (T2E250V) so can't replicate that again until I get some. The diagnostic flow at this point simply states "Check/replace pump".

I've not pulled the pump back out yet, but checked the resistances from the end of the lead that plugs into the wiring board.

Live->Neutral 60 Ohms
Live->Earth 40 Ohms
Neutral->Earth 60 Ohms

That's not right is it? Surely there shouldn't be any path to earth from L or N??

 

[Agile]

Exactly!

Sounds as if the pump is seriously faulty !

Did you measure it when disconnected from the PCB ?

Powering the pump directly from an alternative sourse with a 3A fuse is often informative.

Measuring the current taken is useful too ( I use a clamp on non invasive meter for that )

 

[GeeTee]

Exactly!

Sounds as if the pump is seriously faulty !

Did you measure it when disconnected from the PCB ?

Powering the pump directly from an alternative sourse with a 3A fuse is often informative.

Measuring the current taken is useful too ( I use a clamp on non invasive meter for that )

Yes, I disconnected the pump lead connector from the board for those resistance tests above. Yesterday when I had the pump on the coffee table the resistance from L->N was ~200 Ohms at the terminals in the box on the pump. I didn't check resistance to earth though, just L->N to make sure it wasn't fully open or closed circuit.

I'll pull the pump head out again later on and lash it up to a plug with a 3A fuse and some flex. Shame that can't be done without removing the pump head from the boiler - the box is on top with no room to remove the cover screw and access the terminals.

I don't have a clamp on meter and my multimeter only seems to have the capabiity to measure DC current draw - it's one of these cheapies http://www.youtube.com/watch?v=kzAHzwETlXc

I'm rapidly coming to the conclusion I need a better meter as my simpleton device has twice been thwarted in this one discussion

Back to the basin and kettle for sanitation - I didn't even get to have that shower - still if stuff is shorting out, that could have been a shocking experience!

 

[DP]

Gee tee, good chance there is moisture/ water in the area were the electricity is applied. Sure if you put a 3 amp fuse, perhaps a 13 amp fuse, or even a six inch nail where the fuse should be, the pump will run and wetness around the electrics will be a witches cauldron. Forget the clamp meter- even is you were going to measure the current flow, how will you know if measured current is what it should be?

Option for you is to drop the boiler pressure to zero, remove the Allen screws to revolve the head to a position that permits opening the termination cover. Ensure any spillage is contained and does not flood areas that will create their own issues

 

[Agile]

Try taking head off and removing terminal cover and put it somewhere quite warm like an electric oven for an hour and see if it will dry it out.

But usually water in the windings is caused by a seal failure and will probably leak again when refitted.

A bridge rectifier will enable your test meter to measure AC current!

Tony

 

[matt1e]

Try taking head off and removing terminal cover and put it somewhere quite warm like an electric oven for an hour and see if it will dry it out.

But usually water in the windings is caused by a seal failure and will probably leak again when refitted.

A bridge rectifier will enable your test meter to measure AC current!

Tony

from the ops earlier post the terminal cover is already half off, well at least not on properly as the cap he has fitted is physically too big

ps Tony you mean Voltage not current

Matt

 

[GeeTee]

OK, pump is off again - and yes there is some moisture in the pump wiring box. It was definitely bone dry when I last refitted it and there is no sign of any moisture external to the pump, so I can only think it has made its way up from the pump via the connector between pump and box.

The short to earth seems to be in the pump rather than the box though.

With the box attached to the pump I now get:
L->N 70 Ohms
L->E 35 Ohms
N->E 70 Ohms

If I remove the 2 screws attaching the box to the pump but leave the box still plugged in to the pump connector I get:
L->N 50 Ohms
L->E & N->E both no circuit

One of those 2 screws certainly appears to serve to connect the box circuitry to the pump (presumably as an earth).

I have to assume a seal has gone in the pump itself. I think I may to admit defeat

 

[DP]

Matt, you having a laugh? You cannot be serious !!

ps Tony you mean Voltage not current

Our Tony does NOT make a mistake

 

[Agile]

Quite right Danny, of course I did say and mean current!

I try not to make any mistakes. Although replacing the PRV in that Worcester boiler at my standard charges seems to have been a mistake!

 

[matt1e]

Quite right Danny, of course I did say and mean current

Ok Then Tony if you would kindly post a sketch or description of how you would read the current draw of a piece of equipment running on ac using a dc ammeter and a bridge rectifier, I'd be happy to have been taught something new

Matt

 

[GeeTee]

One last thing if you would be so kind

Anyone ever used HSS (Heating Spares Specialists http://www.hssspares.co.uk) for parts?

They seem to be the cheapest I can find for a new pump. Any other recommendations also welcome.

 

[GeeTee]

One last (hopefully final!) update on this particular thread.

New pump unit installed after a bit of cleaning of seal surfaces - heating and DHW is working well. (Thankfully the new pump came complete with a new auto de-aerator, on removing the old I found crusty deposits down the back where it had been weeping / leaking).

I have a couple of other questions to ask but I'll put them in another thread.

 

[andytw]

A bridge rectifier will enable your test meter to measure AC current!

Tony

Was this tongue in cheek ?? I don't see a smiley

Even as a standalone statement outside of the context of this thread the statement does not hold up, as once it is introduced, there is no AC current.

Just in case anyone reads this thread in the future and sees it as good advice ...

It would not be possible to connect a bridge rectifier in series with a pump as it has 4 connection points so that is a no go.
Assuming, therefore, that you connect the bridge rectifier to Live and Neutral and then the + and - outputs to the pump then, yes, you will now have DC voltage and DC current.
However connecting the DC voltage to the AC pump would be a very bad idea indeed, as the pump is an AC device. The DC current now measured as passing through the, now non running pump, would be very high and of no relevance to it's it's true AC current when connected to it's intended AC supply.

andytw

 

[matt1e]

A bridge rectifier will enable your test meter to measure AC current!

Tony

Was this tongue in cheek ?? I don't see a smiley
andytw

Nah he meant it,with Tony even the impossible is possible, I asked for a schematic but it must be a secret

Ps there are only two connection points on a single phase pump (not including earth) the amount of windings etc has nothing to do with it as everything is contained within and drawing current from a single source.
Everything else you have said holds true though

Matt