behaviour differential switches (ELCB)
 

I have 2 differential switches (ELCB's) in my electrical system.
One is rated at 0.03 Amps; the other at 0.30 Amps.

When plugged into a 20 Amp fused circuit, protected by the 0.03 Amp switch,
my new 1600 Watt electric grass verticutter causes the switch to trip at the
slightest (physical) resistance.
When plugged into a circuit using the 0.30 Amp switch, after a short test, I
have had no problems.

This does not sound normal to me; should I be worried?
The fuse does not go, so does this mean there is a short to earth somewhere?

Robert

In article ,
"Robert" writes:
I have 2 differential switches (ELCB's) in my electrical system.
One is rated at 0.03 Amps; the other at 0.30 Amps.

When plugged into a 20 Amp fused circuit, protected by the 0.03 Amp switch,
my new 1600 Watt electric grass verticutter causes the switch to trip at the
slightest (physical) resistance.
When plugged into a circuit using the 0.30 Amp switch, after a short test, I
have had no problems.

This does not sound normal to me; should I be worried?
The fuse does not go, so does this mean there is a short to earth somewhere?

Sounds like the verticutter(?) has an earth fault.
(Never heard of one before, but I would have expected it to
be double insulated, so must be leak to the ground under it).
There are other possibilities such as incorrect wiring of the
20A circuit. Try a different high current load on it like a
kettle or 2kW heater, and see if the same happens. Since we
are suspecting there could be a wiring fault, it would be a
good precaution during such a test to assume the earthing
could be faulty, so avoid touching the test appliance(s)
when they are switched on.

--
Andrew Gabriel

Robert wrote:
I have 2 differential switches (ELCB's) in my electrical system.
One is rated at 0.03 Amps; the other at 0.30 Amps.

When plugged into a 20 Amp fused circuit, protected by the 0.03 Amp
switch,
my new 1600 Watt electric grass verticutter causes the switch to trip
at the
slightest (physical) resistance.

I dont know what a verticutter is, but presumably when this physical
resistance occurs, it is pressing against whatever its cutting, thus
making better connection with it, thus the earth leakage goes up.

When plugged into a circuit using the 0.30 Amp switch, after a short
test, I
have had no problems.

so the leakage is apx between 30mA and 300mA.


This does not sound normal to me; should I be worried?

No, just dont use your verticutter again, remove the cable etc so
no-one else does, otherwise it might fry you.


The fuse does not go, so does this mean there is a short to earth
somewhere?

yup. It wont be a wiring fault, the motor currents are too high. With a
wiring fault it would trip the instant it was switched on.


NT

Thanks for your comments, NT.
A verticutter is a scarifier with fixed steel blades, not springs.
The fact that the ELCB goes suggests leakage to earth.
Not the motor windings you say.
Any ideas how I might track it down?
R.

wrote in message
oups.com...
Robert wrote:
I have 2 differential switches (ELCB's) in my electrical system.
One is rated at 0.03 Amps; the other at 0.30 Amps.

When plugged into a 20 Amp fused circuit, protected by the 0.03 Amp
switch,
my new 1600 Watt electric grass verticutter causes the switch to trip
at the
slightest (physical) resistance.

I dont know what a verticutter is, but presumably when this physical
resistance occurs, it is pressing against whatever its cutting, thus
making better connection with it, thus the earth leakage goes up.

When plugged into a circuit using the 0.30 Amp switch, after a short
test, I
have had no problems.

so the leakage is apx between 30mA and 300mA.


This does not sound normal to me; should I be worried?

No, just dont use your verticutter again, remove the cable etc so
no-one else does, otherwise it might fry you.


The fuse does not go, so does this mean there is a short to earth
somewhere?

yup. It wont be a wiring fault, the motor currents are too high. With a
wiring fault it would trip the instant it was switched on.


NT

Robert wrote:
Thanks for your comments, NT.
A verticutter is a scarifier with fixed steel blades, not springs.
The fact that the ELCB goes suggests leakage to earth.

yep, can be pertty sure about that

Not the motor windings you say.

Im not saying that, no

Any ideas how I might track it down?

Ideally you need a megger, but you could likiely find it using a
multimeter. If its on a 2 core mains wire, the fault current is going
to the blades most likely. If its a 3 core mains wire, the fault
current is more likely to flow back down the earth wire. Either way,
divide and conquer: disconnect bits so you can find out which bit has
lowest R to earth. This will generally identify the culprit part.

Of course it needs to be unplugged when working on.


NT