testing storage heaters

[Falcon69]

Hi whats the best way to test storage heaters if tennant complaining of not working? Any advice welcome. Thanks

 

[Apache]

Look here

http://www.talk.electricianforum.co.uk/showthread.php?t=1666

If you have a specific problem give us the details and we will help

(note to admin - why not move the above thread into the storage heaters sub-forum?)

 

[Falcon69]

OK, thanks.

What resistance/continuity reading would you expect for a good element in storage heater?

Also when testing immersion elements, 11 inch one usually, approx 18-20 ohms if ok. Have had 200-300 ohms & 5 ohms, which I take as no good. Is this correct?

If do insulation resistance on element between live & earth or neutral & earth & reading 0.00M ohms would this mean element breaking down, even if sometimes its not tripping mcb?

 

[NozSpark]

Storage heater elements are in the reigon of 800w

As V squared / wattage = resistance

52900/800 = 66 ohms

Immersion elements are in the reigon of 3kW

52900/3000 = 17 ohms

Obviously there is a +/- tolerance, but not a great deal... any significant differences then I would say the element is faulty..

 

[SPECIAL LOCATION]

Storage heater elements are in the reigon of 800wAs V squared / wattage = resistance

52900/800 = 66 ohms

Immersion elements are in the reigon of 3kW

52900/3000 = 17 ohms

Obviously there is a +/- tolerance, but not a great deal... any significant differences then I would say the element is faulty..

I would concur with you there Noz...

just one minor error in your calc..

the 3kw rating value refers to the old money nominal voltage of 240v..

if you look at a new one it also states 2.7kw @ 230v

(for compliance with our new 'official' nominal voltage of 230v! :| )

your calc had a bit of each... so if we just do quick amendment..

230v x 230v = 52900 / 2700 = 19.56 ohms

but

240v x 240v = 57600 / 3000 = 19.2 ohms

which is near a need be to Falcon's 20ohms!

Many modern electric appliances have a power rating quoted for both 230v & 240v!...

e.g. look at a new shower box

 

[NozSpark]

BlushingBlushingBlushingBlushing

Aw sh1t..............and I did my calcs at 230v as well

 

[Falcon69]

Thanks for info.

Any thoughts on ins res testing on immersion elements?

Thanks.

 

[SPECIAL LOCATION]

Thanks for info. Any thoughts on ins res testing on immersion elements?

Thanks.

yep sorry... from your earlier post..

If do insulation resistance on element between live & earth or neutral & earth & reading 0.00M ohms would this mean element breaking down, even if sometimes its not tripping mcb?

First tripping MCB?...

don't get confused between overload & leakage.

e.g.

If an element is breaking down on the neutral side to earth..

there may be no overload thus MCB would not operate..

but there would be leakage & an RCD should trip!

If an element is breaking down on the live side to earth..

most probably a near "live-Earth" short.. and thus overload so MCB will operate!

Second Insulation resistance test to earth should be;

open circuit, OL, or greater than highest value on your meter! e.g. >200Meg etc..

If you are getting a low or 0.00Meg it is a dead-un!

I generally think it is best to disconnect the heater from the circuit..

because there is often a neon back at the switch.. which can sometimes give you a false reading.

Also don't forget about the thermostat switch inside the element this can go open circuit & stop working!

So often best the check each of the three key components:-

1/ Take the heat resistance flex out of the switch / connection box and test across the end of the flex..

sometimes a fault may be in a bit of dodge flex customer has fitted..

non-heat resistant & gone brittle / poor loose connections etc..

had towels & stuff dragged across it and broken down somewhere.

2/ Check continuity across the thermostat..

as you turn the temp adjust bit you can see it go open & closed circuit with your continuity meter.

3/ Check the element. NOTE;

assuming you have proved the continuity of the element approx 20ohm..

with it diss from circuit it is irrelevant which end of the element, (L or N),

you test to earth.. cuz there is only 20ohm between the L & N connection points.

 

[Falcon69]

Thanks for the detailed explanation, much appreciated