Our house upstairs lighting circuit has decided to start tripping it's
circuit breakers - with no obvious cause. First suspect was that a wire
had come loose in the last light fitting installed which was a tight fit
for all the connections when it was replaced. I've removed the light
fitting and the dimmer switch, but still the problem persists.

Secondly, we have an alarm system whose power is derived from this
lighting circuit and is doing some rather strange things (spurious
alarms and modes). This alarm has been installed for years and hasn't
been seen by the installer for years either and I suspect the original
installers are no more. I know alarms have a lead-acid battery that will
eventually deteriorate.

It could be a malfunction in the alarm triggering the circuit breaker,
so calling out an electrician could be a complete waste, or it could
just be the alarm is spooked by a circuit fault.

Generally, the circuit breaker can be set, but after a while shuts off,
so I guess that would indicate some form of leakage rather than a direct
contact short.

Current plan is to disconnect the alarm from the lighting circuit and
see if the breaker still has a problem.

Any other thoughts?

Paul

"On net" wrote in message
...
Our house upstairs lighting circuit has decided to start tripping it's
circuit breakers - with no obvious cause. First suspect was that a wire
had come loose in the last light fitting installed which was a tight fit
for all the connections when it was replaced. I've removed the light
fitting and the dimmer switch, but still the problem persists.

Secondly, we have an alarm system whose power is derived from this
lighting circuit and is doing some rather strange things (spurious alarms
and modes). This alarm has been installed for years and hasn't been seen
by the installer for years either and I suspect the original installers
are no more. I know alarms have a lead-acid battery that will eventually
deteriorate.

It could be a malfunction in the alarm triggering the circuit breaker, so
calling out an electrician could be a complete waste, or it could just be
the alarm is spooked by a circuit fault.

Generally, the circuit breaker can be set, but after a while shuts off, so
I guess that would indicate some form of leakage rather than a direct
contact short.

Current plan is to disconnect the alarm from the lighting circuit and see
if the breaker still has a problem.

Any other thoughts?

Paul

Alarms usually have an internal fuse of around 1A and they should not cause
the MCB to trip. The power loss to the alarm is causing the alarm to play up
not the other way around

MCBs may fail and become weak in old age. Swap the MCB over with the
downstairs lighting MCB and see what happens.

Is there any chance that the upstairs lighting circuit is overloaded?

Adam

ARWadsworth wrote:

"On net" wrote in message
...
Our house upstairs lighting circuit has decided to start tripping it's
circuit breakers - with no obvious cause. First suspect was that a
wire had come loose in the last light fitting installed which was a
tight fit for all the connections when it was replaced. I've removed
the light fitting and the dimmer switch, but still the problem persists.

Secondly, we have an alarm system whose power is derived from this
lighting circuit and is doing some rather strange things (spurious
alarms and modes). This alarm has been installed for years and hasn't
been seen by the installer for years either and I suspect the original
installers are no more. I know alarms have a lead-acid battery that
will eventually deteriorate.

It could be a malfunction in the alarm triggering the circuit breaker,
so calling out an electrician could be a complete waste, or it could
just be the alarm is spooked by a circuit fault.

Generally, the circuit breaker can be set, but after a while shuts
off, so I guess that would indicate some form of leakage rather than a
direct contact short.

Current plan is to disconnect the alarm from the lighting circuit and
see if the breaker still has a problem.

Any other thoughts?

Paul

Alarms usually have an internal fuse of around 1A and they should not
cause the MCB to trip. The power loss to the alarm is causing the alarm
to play up not the other way around

That would be good news.

MCBs may fail and become weak in old age. Swap the MCB over with the
downstairs lighting MCB and see what happens.

Is there any chance that the upstairs lighting circuit is overloaded?

Nothing has has changed about the circuit for some time. The unit will
trip even if nothing is active (besides the alarm).

I've just remembered that we also have an exterior security light wired
to this.

I've gone into the loft and removed some of the taps of the junction box
that powers the alarm, loft lights and security light. It's behaving so
far..

...tripped again. The alarm is innocent!

The upstairs circuit hasn't changed for almost a year and it seems to
trip even with the lights off.

I'll just keep isolating bits until it behaves.

Thanks for the suggestions.

paul




Adam

On Fri, 09 Oct 2009 18:27:23 +0100, On net wrote:

I've gone into the loft and removed some of the taps of the junction box
that powers the alarm, loft lights and security light. It's behaving so
far..

...tripped again. The alarm is innocent!

So is the exterior light and loft lights.

Is this an MCB that is tripping or an RCD? If the former leave it
tripped and get a new replacement ASAP. MCBs are overload trip
devices, one tripping means significant current is going somewhere.
Significant current = significant power which could be being
disipated as heat somewhere not designed to take that heat. Yes, it
could be "tired" in which case you need a new one anyway.

--
Cheers
Dave.

In article ,
On net wrote:
Our house upstairs lighting circuit has decided to start tripping it's
circuit breakers - with no obvious cause. First suspect was that a wire
had come loose in the last light fitting installed which was a tight fit
for all the connections when it was replaced. I've removed the light
fitting and the dimmer switch, but still the problem persists.

Have you totalled up the maximum load? It's all too easy to add stuff and
forget.

--
*Everyone has a photographic memory. Some don't have film *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
On net wrote:
Our house upstairs lighting circuit has decided to start tripping it's
circuit breakers - with no obvious cause. First suspect was that a wire
had come loose in the last light fitting installed which was a tight fit
for all the connections when it was replaced. I've removed the light
fitting and the dimmer switch, but still the problem persists.

Have you totalled up the maximum load? It's all too easy to add stuff and
forget.


No, I haven't added up the load - the circuit has been unchanged now for
something like nine or ten months and the system trips without any
lights on.

In article , On net wrote:

Generally, the circuit breaker can be set, but after a while shuts off,
so I guess that would indicate some form of leakage rather than a direct
contact short.

Is this a MCB or a RCBO? If it's a RCBO it could be earth leakage - water
in an outside lamp? Or in the alarm somewhere?

Darren

On net wrote:
Our house upstairs lighting circuit has decided to start tripping it's
circuit breakers - with no obvious cause. First suspect was that a wire
had come loose in the last light fitting installed which was a tight fit
for all the connections when it was replaced. I've removed the light
fitting and the dimmer switch, but still the problem persists.

Secondly, we have an alarm system whose power is derived from this
lighting circuit and is doing some rather strange things (spurious
alarms and modes). This alarm has been installed for years and hasn't
been seen by the installer for years either and I suspect the original
installers are no more. I know alarms have a lead-acid battery that will
eventually deteriorate.

It could be a malfunction in the alarm triggering the circuit breaker,
so calling out an electrician could be a complete waste, or it could
just be the alarm is spooked by a circuit fault.

Generally, the circuit breaker can be set, but after a while shuts off,
so I guess that would indicate some form of leakage rather than a direct
contact short.

Current plan is to disconnect the alarm from the lighting circuit and
see if the breaker still has a problem.

Any other thoughts?

Paul

Update:

Disconnecting the Alarm and security light had no effect on stopping the
circuit breaker and left me scratching my head. Even with all lights off
the circuit would eventually trip.

Looking at the consumer unit I remembered that we used to have an
electrical feed to the garage that had been connected to one of the
lighting circuits (before we moved in) but that had been disconnected.
On inspection I found that the cabling had been disconnected from the
garage but still lay in a covered walkway with some exposure to the
elements - this would have been the case for a few years now.

I disconnected that cabling completely and now the upstairs circuit
hasn't tripped since about 6:30PM yesterday.

I guess the disconnected cable had been tripping the circuit with the
effects on the cable from the weather. One of those cases where the job
should have been finished properly.

Thanks for all the great suggestions - much appreciated - I'll be back
if it acts up again!

Paul