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Main circuit tripped

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Clariman
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Main circuit tripped

#138716

Postby Clariman » May 13th, 2018, 9:14 am

My main question is - should I be concerned about this circuit tripping?

Circuit board has 2 banks of circuit breaker switches. Each bank is protected by a master switch. From time to time one of the master ones trips. It happened this morning. What puzzled me is that no individual circuit breaker had also tripped. Should I be concerned that there is a problem somewhere? How do I identify what is causing it?

This happens in a holiday home that we rent out. It has happened with guests staying here and the agency who handles maintenance for us thinks it is caused by the PV panels on the roof when it rains. Is that likely?

Thanks
Clariman

Clariman
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Re: Main circuit tripped

#138721

Postby Clariman » May 13th, 2018, 9:30 am

Additional info.

It is raining here today and it has tripped 3 times in last 20 minutes so clearly something that needs sorted. I have switched off circuit breaker to PV panels now. Will see if it continues to happen.

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Re: Main circuit tripped

#138722

Postby Itsallaguess » May 13th, 2018, 9:31 am

Clariman wrote:
My main question is - should I be concerned about this circuit tripping?

Circuit board has 2 banks of circuit breaker switches. Each bank is protected by a master switch. From time to time one of the master ones trips. It happened this morning. What puzzled me is that no individual circuit breaker had also tripped. Should I be concerned that there is a problem somewhere? How do I identify what is causing it?

This happens in a holiday home that we rent out. It has happened with guests staying here and the agency who handles maintenance for us thinks it is caused by the PV panels on the roof when it rains. Is that likely?


The main switch is likely (although you should confirm this....) to have an earth-leakage trip built in to it.

It sounds like one of the sub-circuits is showing an earth-leakage problem at some point (and you mentioning that this might be happening during periods where rain is present is perhaps key here), which is then tripping the main switch, rather than the sub-circuit breaker.

This often happens with outside-light circuits, but obviously it could also be affected by any rain-facing equipment, which is likey to also include your PV kit.

Obviously the key priority should be to find out where the moisture is causing the problem and eliminate the issue. If you're able to 'reset' the master switch after a period of time, this suggests that the moisture is drying sufficiently to remove the earth-leakage issue, so this should give you some hope that a better seal somewhere, where the moisture is getting in, should be something you can achieve.

Are you able to inspect the outside wiring to all exposed items? It's likely that there will be termination-points where cables enter and leave the external items, and also possibly junction-boxes where internal cross-wiring occurs, where you may see signs of moisture if you were to open those places up.

If you do find signs of moisture, then you'll need to find a way to stop the ingress of water, which should help stop these nuisance trips. Please note that these inspections should obviously be carried out with the power off....

In the longer term, if you can't source the issue itself, then you can have a think about isolating some outside circuits to see if the nuisance-trips stop, especially over wet periods where you've seen them happen before. This may at least help identify the particular circuit causing the problem.

Another option then would be to change the breaker for that circuit for one which itself contained an earth-leakage trip, but the key thing here would be to ensure that the reaction time of the sub-circuit earth-leakage trip was quicker (they are graded in millisecond timings) than that of the main breaker, and at least then, if you were unable to solve the issue itself in the short term, it would mean that just the sub-circuit would then trip under the fault-conditions, rather than the whole board....

Note that around this time of year, whilst rain can obviously be an issue, these things are often also seen being caused by condensation, rather than direct water-ingress, so just something to keep in mind during your search for the problem-area.

Good luck with your investigations.

Cheers,

Itsallaguess

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Re: Main circuit tripped

#138736

Postby Clariman » May 13th, 2018, 9:58 am

Hi Itsallaguess

Thanks for your helpful reply. I think this is all pointing towards the PVs then. It tripped 3 times this morning (when raining) and I then switched off the PV's own circuit breaker and it has not happened since and it is still raining.

Assuming it is the PVs then who is the right tradesman to look at it? Would any electrician deal with it or would it have to be a specialist PV installer?

We had some work done last year to remove pigeons who were nesting under the panels - and to put mesh around them. It is quite possible that he may have dislodged something while cleaning all the muck out.

Finally - is there any danger in leaving the PVs circuit on - confident that something will trip if needed during rain?

Thanks
C

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Re: Main circuit tripped

#138751

Postby csearle » May 13th, 2018, 11:29 am

Hi C,

I agree with Its's analysis especially about water ingress. I would add this though:

1. With PV systems there is a potential danger even when they are switched off. So don't assume
that because the breakers (they usually have two, one on each side of the inverter) are switched off
that it is all dead.

2. Unfortunately even if you replace the circuit breaker with one that has the residual current detection
in it too (an RCBO it's called) there is no knowing which of the two devices (or both) will trip first in the event
of a leakage larger than their rating (this regardless of their max. operation time or indeed their rating).

3. The fault-finding is also sometimes made slightly more difficult because water between the neutral (black or blue wires) and Earth will also trip the leakage-detection* so just switching off the existing trip-switch will not necessarily isolate the fault.

An electrician is the right tradesman. There are PV courses for electricians intending to install these things but I would probably just report a general RCD** tripping fault to a local electrician and let him/her get on with it. They usually know about the added danger when the sun shines. It might not be in the PV system. All you know at the moment is that it is on one of those circuits protected by that particular RCD and that there is a 99.9% chance water is involved.

I see no danger in leaving the PV system on. The RCD is doing it's job it would appear.

Regards,
Chris

*This will happen if there is any equipment switched on that slightly raises the potential of the neutral conductor above that of Earth (usually high-ish current equipment on power circuits or any equipment on lighting circuits).

**An RCD is the thing that has tripped judging by your description

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Re: Main circuit tripped

#138752

Postby FredBloggs » May 13th, 2018, 11:40 am

Myself, I know nothing about PV panels, but general DIY style troubleshooting would be to unplug them all, assuming the can be disconnected this way? Then reconnect them one by one leaving a time between reconnecting them. When it trips, the last one you connected is the faulty one. Repair the fault and repeat the process until all are connected again with no trips.

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Re: Main circuit tripped

#138766

Postby pochisoldi » May 13th, 2018, 12:00 pm

FredBloggs wrote:Myself, I know nothing about PV panels, but general DIY style troubleshooting would be to unplug them all, assuming the can be disconnected this way? Then reconnect them one by one leaving a time between reconnecting them. When it trips, the last one you connected is the faulty one. Repair the fault and repeat the process until all are connected again with no trips.


That will work if it is just one appliance causing all the problems.

The problem with RCD/RCBO nuisance trips is that it may take 30mA of leakage/imbalance to trip the device, but that could be made up of 15mA from the washing machine, 10mA from the dishwasher, on top of 10mA from ten other appliances which have an acceptable earth leakage. And this ignores the fact that your 30mA RCD might actually be tripping at 25mA or less.

The only way to weed out those problems is with experience - (1) a sensitive clamp ammeter around both L+N tails feeding the consumer unit, so you can actually measure the leakage current (see http://www.fluke.com/fluke/uses/comunid ... kagebasics) , or (2) creating a deliberate, known value leakage so that turning on a single marginally "leaking" appliance will cause a trip (suitably rated resistor with a resistance to give, say, a permanent 15mA flow between live and earth).

If you don't know what Ohms law and Watts law are, then (2) is not on option.
If you don't understand the risk of connecting a resistor between live and earth (i.e. taking exposed metalwork to 240v) , (2) isn't an option either.

While you wait for an electrician to do their checks, unplug the washing machine, dishwasher and the immersion heater (the three usual suspects).

PochiSoldi

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Re: Main circuit tripped

#138791

Postby FredBloggs » May 13th, 2018, 1:31 pm

pochisoldi wrote:
FredBloggs wrote:Myself, I know nothing about PV panels, but general DIY style troubleshooting would be to unplug them all, assuming the can be disconnected this way? Then reconnect them one by one leaving a time between reconnecting them. When it trips, the last one you connected is the faulty one. Repair the fault and repeat the process until all are connected again with no trips.


That will work if it is just one appliance causing all the problems.

The problem with RCD/RCBO nuisance trips is that it may take 30mA of leakage/imbalance to trip the device, but that could be made up of 15mA from the washing machine, 10mA from the dishwasher, on top of 10mA from ten other appliances which have an acceptable earth leakage. And this ignores the fact that your 30mA RCD might actually be tripping at 25mA or less.

The only way to weed out those problems is with experience - (1) a sensitive clamp ammeter around both L+N tails feeding the consumer unit, so you can actually measure the leakage current (see http://www.fluke.com/fluke/uses/comunid ... kagebasics) , or (2) creating a deliberate, known value leakage so that turning on a single marginally "leaking" appliance will cause a trip (suitably rated resistor with a resistance to give, say, a permanent 15mA flow between live and earth).

If you don't know what Ohms law and Watts law are, then (2) is not on option.
If you don't understand the risk of connecting a resistor between live and earth (i.e. taking exposed metalwork to 240v) , (2) isn't an option either.

While you wait for an electrician to do their checks, unplug the washing machine, dishwasher and the immersion heater (the three usual suspects).

PochiSoldi

Agreed, typically in a scenario such as you paint, it isn't a DIY job any more. The DIY approach can tell you whether you need a sparky or not at just the cost of a possible wasted afternoon though. General DIY warning - do not monkey around with anything electrical unless you have some knowledge of what you are doing.

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Re: Main circuit tripped

#138805

Postby Itsallaguess » May 13th, 2018, 2:09 pm

FredBloggs wrote:
General DIY warning - do not monkey around with anything electrical unless you have some knowledge of what you are doing.


Clearly the safety aspect is critical in a task such as this when it involves electricity, but if this issue has just reared it's head, and let's say perhaps that there are a couple of obvious external junction-boxes in the PV circuit, then taping a couple of carrier bags around the jb's and seeing if that relieves the nuisance-tripping the next time it rains heavily can definitely be something that a competent and safety-concious DIY'er can achieve without initially invoking the cost and hassle of getting a tradesman out.

Water-ingress is happening somewhere that didn't happen to the same degree before. There's lots of ways to isolate the location of the possible issue without actually opening a single electrical cover...

Cheers,

Itsallaguess

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Re: Main circuit tripped

#138814

Postby FredBloggs » May 13th, 2018, 2:40 pm

Itsallaguess wrote:
FredBloggs wrote:
General DIY warning - do not monkey around with anything electrical unless you have some knowledge of what you are doing.


Clearly the safety aspect is critical in a task such as this when it involves electricity, but if this issue has just reared it's head, and let's say perhaps that there are a couple of obvious external junction-boxes in the PV circuit, then taping a couple of carrier bags around the jb's and seeing if that relieves the nuisance-tripping the next time it rains heavily can definitely be something that a competent and safety-concious DIY'er can achieve without initially invoking the cost and hassle of getting a tradesman out.

Water-ingress is happening somewhere that didn't happen to the same degree before. There's lots of ways to isolate the location of the possible issue without actually opening a single electrical cover...

Cheers,

Itsallaguess

Absolutely, if you are confident what you are doing, go right ahead. How about spraying a hose on the units to simulate rain? No, I guess not, but you never know............

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Re: Main circuit tripped

#138928

Postby Clariman » May 14th, 2018, 8:48 am

Thanks everyone. That is all very helpful.

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Re: Main circuit tripped

#139068

Postby csearle » May 14th, 2018, 8:38 pm

Clariman wrote:Thanks everyone. That is all very helpful.
FredBloggs's idea with the hose is a good one if you are struggling to reproduce the symptoms. C.

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Re: Main circuit tripped

#139159

Postby Meatyfool » May 15th, 2018, 11:26 am

If mucking out the pigeon detritus was the cause, this could be a major hassle. I suspect at least some of the pv panels will need to be removed from the rack in order to be able to check the wiring connections underneath them.

If you have to, whilst there, get "shrink wrap" covers for the connectors. A little bit of heat shrinks the plastic wrap over the connector all but eliminating any means by which water can get to the connector.

Meatyfool..


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