Storage heater testing

[burntwire]

Can I PAT test a storage heater ? A customer has called with a tripping storage heater problem, however it takes out the main rcd switch every time, and im not sure how to find which one is faulty except turn one off at a time. Trouble is its only tripping once every two weeks

 

[Spark123]

Providing they don't contain any sort of circuit boards - (never seen any in storage heaters before), I'd be insulation resistance testing them at 500v to see if one has a low IR.

 

[ericmark]

A storage heater is not a portable appliance but there is nothing to stop you using a PAT tester to measure earth leakage and insulation resistance.

Since they are fixed appliance they may have by design a high earth leakage using mineral insulated heaters and over 3Kw I think you are allowed about 250K ohms each so 16 heaters will drop you to 15K which can trip a 30ma earth leakage trip.

With a little leakage on each will not take too much extra to trip them.

Since the leakage tends to rise on first switch on then drop using a PAT tester does make some sense but many PAT testers are not able to handle 3Kw so can't be used.

Normally one would use an insulation tester.

 

[burntwire]

Today I went and IR tested the heaters there is 6 in total the readings were , N-L, 1) 1000, 2) 0.36, 3) 0.37, 4) 999 5) 796, 000, I have never had a lot to do with storage heaters before, altough there doesnt seem to be much to them, what part would be most likely to be causing the poor readings on 2,3 and 8 ? the thermostat on number 8 doesnt appear to be working as there is no noise when turning the dial,

Many thanks for any help !!

 

[ricicle]

, what part would be most likely to be causing the poor readings on 2,3 and 8

Elements or possibly internal wiring.

 

[Spark123]

What were the L-E readings @ 500v ?
Electrically there's not usually a lot to a storage heater, just a few elements, a thermostat and some sort of thermal cutout.

 

[burntwire]

Sorry not sure why theres a smiley face,

L - E were, 1) 75.7, 2) 75.8, 3) 75.8, 4) 736, 5)76.8, 6) 75.8 big difference on number 4 !

 

[Spark123]

Are all those readings in M ohms?

 

[ricicle]

If they are all in Mohms I'd be pretty happy!

 

[burntwire]

yep,

 

[Spark123]

Those readings are quite good.
What make of RCD is it? Does it have a functional earth wire?
Have you IR tested the installation wiring?

 

[ricicle]

Even with all those readings in parallel it should not be enough to take out a 30mA RCD - unless the element's IR is reducing when they warm up. Are you sure it is the heaters and not the associated mains wiring?
Did you do the N-E test as well or were the elements left connected when you tested them. Did you test on the heater side of the control gear so you were actually testing the elements? (although the stat should have been made if the heaters were cold!)

 

[burntwire]

I IR'd them from the fuseboard, firstly with the switch off and they were all clear as a whistle, then switches on but thermostats on low, if I turned them up readings were 0000mohms,

Its a wylex RCD,

When I took the heater in the kitchen to bits ( dimplex D83 ) there were scorch marks on one side of the casing where it had obviously been getting too hot, if thats possible,

 

[Spark123]

Was that L-N or L-E?
I don't think wylex RCDs have a functional earth, some which do have functional earths monitor voltage too so switching the power to them might cause them to trip.

 

[burntwire]

N-L Readings were 0000