electrical problem

[Peter]

A five fused fusebox in friends garage (non rcd box) is supplied from an rcd'd box in his house. The garage box supplies, 2 fountain pumps

1 cesspit pump garage doors, sockets and lights pool pump etc And auto gates

On friday his gates tripped the rcd (continues to do so) Mr autogateman finally blames one motor even though his meter finds no fault.

when the rcd was put back on neither the cesspit pump nor the fountain pumps worked but garage doors sockets and lights ok

finally after tripping all switches in the garage box and turning on one by one all starts to work again (not auto gates) until the next day when cesspit overflows.

pump extracted, floats shaken a little, nothing. cesspit pump box (seperate from fuse box) has a tripper switch off/on...pump works.

The question is are all these things related? If not are pumps and a motor really all expiring at the same time? Is there any fault in a fusebox/supply that can display these problems. Why can I switch the fountain pumps on then nothing, change nothing other than having all other trippers off then switch it on again and they work.

House is less than 10 years old.

Many thanks

Peter

[NT]

RCD trips on the total leakage current of all appliances. To find out whats causing it you need to test each appliance for leakage. You can crudely do that with a mutimeter, good enough to usually find the culprit.

NT

[Mike Tomlinson]

In article , Peter writes

sub-consumer unit with RCDs, not fuses, judging from the rest of your post ("trippers", not fuses)

If it were me, I'd be having a look inside the sub-unit in the garage. Sounds like the installer may have forgotten to tighten the screws onto the live busbar and the breakers are making intermittent contact.

Don't do this yourself, get a pro sparky in. No offence, but from the sound of your post, you're not familiar with this stuff.

[John Rumm]

ITYM MCB - miniature circuit breakers

[John Rumm]

What make are the MCBs in the garage CU?

A couple of options here; either there was power, but the pump (probably an induction motor) had stalled at start-up. Powering off and on gave it a kick and it started again. Alternatively I have also found some MCBs that go faulty in a way that means they do not actually reconnect the power every time you turn them on. This can make fault fining very confusing since they look on, but it is random as to whether they actually are.

It seems unlikely that they would all fail together. However the chap testing the gates may have been doing insulation resistance checks on the gate equipment. If he did not take care to protect devices like RCDs connected to other parts of the system, there is a small chance he may have damaged them.

Also check the supply voltage. A low supply will make it far more likely that things like pumps will fail to spin up.

[Mike Tomlinson]

In article , John Rumm writes

I did. Not enough coffee. Thanks for the correction