Testing a pump with a multi meter

[Nostrum]

Hi Lads,

Got a chance to do some contract breakdown work and just been trying to remember all the stuff I used to do has made me realise i've forgotten a bit! All the new stuff i've learnt must have pushed the old stuff out my ears!

How do you test a pump with a multimeter to confirm it's knackered or lazy? The old screwdriver trick might sound a bit slap dash if they ask me!

Cheers in advance

Sam

 

[Nostrum]

Just in case that doesn't make sense, an seeing a the edit buttons off sick, I mean the resistance of the windings (i think)

 

[mfgs]

I have never tested one with a multi meter. I do the screwdriver trick, or more often than not you can tell by the sound.

 

[Dotty]

I've had a couple of boilerhouses drown in the bad weather recently (completely flooded!). I had to buzz a lot of stuff out including 3 phase pumps. I didn't worry about resistance of the windings, I was just looking for continuity and whether or not they were earthing down.

 

[so-solar]

If there is 240 to the pump and she aint spinning, she needs binning!

 

[Puddle]

If there is 240 to the pump and she aint spinning, she needs binning!

Could it not be the capacitor ? :mellow:

 

[zeebeedee]

The only time I test pumps is when something is blowing fuses on a s or y plan!

 

[diamondgas]

Knackered pump will usually give you a resistance to earth L-E or N-E as croppie has said... Also infinite L-N or 0 ohms L-N is knackered too!

Lazy pump wouldn't show much I doubt as it's more likely mechanical rather than pump windings IMHO

 

[BLOD]

A new pump should show about 150 ohms across the windings.
The higher the ohms the slower the pump will be working

 

[Dannypipe]

Remember, resistance readings will alter with the speed settings of the pump.

As Diamond has said, if you have a short curcuit, then it's time to replace the pump. As a rule of thumb you can assume:
(On a Grundfos 15/50 set at speed 3)
[FONT=Calibri,Calibri][FONT=Calibri,Calibri]Less than 1 Ohm = Motor windings burnt out – Replace pump or pump head
Mega Ohms/Infinity/Overload = Motor windings burnt out – Replace pump or pump head
120 – 200 Ohms = Motor windings O.K.


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[GrahamM]

A new pump should show about 150 ohms across the windings.
The higher the ohms the slower the pump will be working

Is it not something like 160 ohms on first speed to around 60 on third speed? Or there abouts.

 

[Dannypipe]

I've always assumed that my readings as above are about right.

If it's not infinity or closed circuit, then the chances are it's ok.

There's a lot to be said for the old screwdriver test!! At least for us domestic plumbers.

 

[Nostrum]

Cheers all for the input. I thought I had a figure of 100 ohms kicking about in there somewhere, but the above will do me fine thanks. Just need to have it tattooed across my knuckles bad boy biker style so I don't forget again .