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Reading a Meggr

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Gregory

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I have a megger analog when I test a oven element which is 1500W 240V
I test the element for earth resistance should the element read on the megger 1.5K oms using 500V meg oms setting.
I am not shore as to when the element is good or not
If it is a short to earth it is no good or a open circuit.
how do you work out what the reading on the megga should read and the reading when the element is no good
 
The resistance form one end of the element to the other should be 38 Ohm.

The resistance fromthe element to its casing (earth) should be high.
What is "high" ?

1000Mohm would be very good
100Mohm would be OK
1Mohm I would regard with suspicion but is probably OK.

Less than 1 Mohm, buy a new one it is on its way out.

Less than 10k ohm, it is scrap, replace it NOW.

JimB
 
I agree with Jim B(eam);)

but an other way of testing it if you don't have a megger is to power the element up after a ELCB (earth leakage circuit breaker) (30 mA)

if that one trips throw it out

Robert-Jan
 
A more accurate method is to connect it to the live wire via a DVM set to read AC current the case to protective earth and no neutral connection. The meter will indicate the leakage current - if it reads over 0.25mA then throw it out.
 
A more accurate method is to connect it to the live wire via a DVM set to read AC current the case to protective earth and no neutral connection. The meter will indicate the leakage current - if it reads over 0.25mA then throw it out.

And if there is short circuit between element and case?
Bye Bye DVM!!:eek:

JimB
 
Easiest way is a PAT tester - but if it reads that low a leakage to earth on a Megger, then it's duff anyway.

My Megger has a handle you wind, and a War Department stamp in the leather case! :D
 
Easiest way is a PAT tester - but if it reads that low a leakage to earth on a Megger, then it's duff anyway.

My Megger has a handle you wind, and a War Department stamp in the leather case! :D

Which war would that be.:D

I used to have one of those, you can get a really good belt [ and I dont mean the martial arts kind] if you mishandle those old meggers.
 
Which war would that be.:D

I've always presumed WWII :D

It's made by Record, and says Ref. 5G/203

I used to have one of those, you can get a really good belt [ and I dont mean the martial arts kind] if you mishandle those old meggers.

We always demonstrate it to work experience kids! :p

As I understand it modern electronic ones give a greater shock?.
 
And if there is short circuit between element and case?
Bye Bye DVM!!:eek:

JimB

That's what fuses are there for.

The 250mA fuse in the meter shouldn't last for long enough for any damage to be done.

If you're worried about this then add a 100W bulb in series with the live.
 
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