• The forum software that supports hummy.tv has been upgraded to XenForo 2.1!

    This upgrade brings a number of improvements including the ability to bookmark posts to come back to later. Please bear with us as we continue to tweak things and open a new thread for any questions, issues or suggestions in Site/Forum Issues.

Electrical supply tripping out

MartinLiddle

Super Moderator
Staff member
We own a holiday home in Yorkshire that is sometimes unoccupied for several weeks at a time (although family friends visit every couple of weeks to check for problems and water house plants). The property was built in 2010 (so modern electrics) and is not in a remote location. Recently over a six month we have had two or three occurrences of the electrical supply tripping out. One of these occasions was when the property was unoccupied and the contents of the freezer were a disgusting brown mush by the time we got to them. I have two questions:

1. How do we diagnose what is causing the trips? When the property is unoccupied we turn off as much as possible so the possible culprits would be the central heating system, the fridge/freezer, the burglar alarm, the HDR-2000T PVR and the telephone answering machine (plus anything I have forgotten). We have consulted an electrician who said trial and error was the only way; any more scientific test we could try?

2. What would be the best way of remote monitoring for the power supply failing? A bit of googling found https://www.amazon.co.uk/PowerTxt-MAINS-POWER-FAILURE-ALERTS/dp/B00A7UO7AM which seems to have the required functionality but strikes me as very expensive for what it is. Any suggestions for a cheaper off the shelf option? I have also been pondering DIY solutions. I have an old computer UPS with a USB port that sends a mains power lost signal. I have been considering using that to power the ADSL modem router and a Raspberry Pi to monitor the signal and send an alert when the power fails; does this sound feasible? Any better suggestions?
 
OP
M

MartinLiddle

Super Moderator
Staff member
When you say "tripping out", is that the RCD (earth leakage) or the MCB (over-current)?
I think it is RCD; I know which breaker tripped but I am not at the property to check. Certainly what ever tripped took out all the power to the house not just a single ring main.
 

Trev

The Dumb One
Do you mean that it tripped a single breaker and the RCD? Or was it just one breaker but you are not certain which one it was?
 

Wallace

Traveler 34122
I have my cable modem and a Raspberry Pi connected to a 'cheap' APC UPS. The UPS is connected to the Raspberry by with the comms lead (USB) that came with the UPS. When/if the mains fails, the Raspberry Pi sends me an email.

Being a holiday home, you might not have an active Internet connection but I thought I would mention it anyway.
 

Black Hole

May contain traces of nut
If the RCD is more nuisance than the risk of electrocution, my vote is to disable it. I'm not sure what the current standards are, but we never used to have RCD protection and it should only trip if there is an imbalance in the current out compared to the current in (ie some has escaped to the safety earth connection or to ground).

I wouldn't put it beyond the RCD itself to be faulty, but electronics equipment which uses input mains filters (and utilise the earth as a common node) exacerbates the problem (I regard these as an illicit use of the safety earth).

Regardless, even without the RCD there should be no risk to the occupants under normal circumstances - RCDs provide a degree of protection by shutting of power if there is a problem that double-insulation and over-current protection hasn't already dealt with. I can well imagine that power disturbances (such as might be caused by lightning activity) might trip an RCD unnecessarily.
 

Trev

The Dumb One
I had an RCD that was tripping 'randomly' for no apparent reason. I changed it and haven't had a problem since. The only time it has tripped is when I have pressed the 'Test' button.
 
OP
M

MartinLiddle

Super Moderator
Staff member
I have my cable modem and a Raspberry Pi connected to a 'cheap' APC UPS. The UPS is connected to the Raspberry by with the comms lead (USB) that came with the UPS. When/if the mains fails, the Raspberry Pi sends me an email.
Now that is interesting because my old UPS is a cheap APC. What software are you using on the Raspberry Pi to send the email?
 
OP
M

MartinLiddle

Super Moderator
Staff member
Do you mean that it tripped a single breaker and the RCD? Or was it just one breaker but you are not certain which one it was?
My problem is that we arrived at the holiday home in the evening as it was getting dark and I was more interested in getting an electrical supply rather than fault finding. I know exactly which breaker it was but without the panel in front of me I can't be certain about its function. All the electrical circuits were off.

Incidentally there were power cuts in the surrounding homes at about the time the breaker will have tripped (due to road works and contractors damaging supply cables) but none of the neighbours had tripped breakers. Could a power cut (or more likely a surge as the power came on) cause a breaker to trip?
 

Black Hole

May contain traces of nut
All the electrical circuits were off.
The MCBs protect the individual rings, so that means the RCD.

Could a power cut (or more likely a surge as the power came on) cause a breaker to trip?
An RCD - maybe. MCB - unlikely.

The likelihood is that you have an over-sensitive RCD, and if you replace it your problems will go away. If they don't, you have a more serious wiring issue (but I would expect such an issue to be constantly tripping the RCD). If you want to maximise reliability over safety (but it's still safe), ditch the RCD altogether (fusewire fuse boxes never gave us these problems).

Regarding monitoring, instead of rigging up something to give you active monitoring, why not just have something you can ping every now and then? No response (because the router is off) means intervention is required. Maybe the router has sonething you can ping.
 

xyz321

Well-Known Member
I wouldn't ever recommend trying to defeat a safety device (e.g. RCD), it could save someone's life at some point (e.g. when poking around inside a PVR with the power on).

I have had an RCD trip repeatedly but it was always caused by a fault elsewhere. Faulty cooker elements (old type) or a mains suppressor which had a cracked casing.

An MCD could trip due to surge currents, if the power is restored, typically with lots of switch mode power supplies hanging off it.
 

Black Hole

May contain traces of nut
The events an RCD protects against are not normal circumstances. You have to have taken some measure to defeat the first level protection and then induce a second level of failure to be at risk. 30 years ago we never had RCDs, and we all made it this far.

That said, I have no doubt they are required by current ultra-cautious building regs (which are a product of first-world modern sophistication which will ultimately price us out of the market).

A fusebox MCB shouldn't trip due to inrush currents. If it does, it is the incorrect quick-blow type - but it doesn't seem likely that they would blow on all the circuits.
 

MikeSh

Well-Known Member
I don't see how any of these suggestions and diagnoses are of much value until we know exactly which device(s) tripped. All we seem to have is that all the power was off and that one(?) switch was reset to restore it.
 

BMAX

Member
The events an RCD protects against are not normal circumstances. You have to have taken some measure to defeat the first level protection and then induce a second level of failure to be at risk. 30 years ago we never had RCDs, and we all made it this far.

That said, I have no doubt they are required by current ultra-cautious building regs (which are a product of first-world modern sophistication which will ultimately price us out of the market).

A fusebox MCB shouldn't trip due to inrush currents. If it does, it is the incorrect quick-blow type - but it doesn't seem likely that they would blow on all the circuits.
A RCD is the only protection against the effects of accidental (or deliberate) human contact with the mains and they are designed to trip at current levels considered to be non-lethal in the majority of cases. To disable such a facility borders, it seems, to quote a well known Vulcan, "illogical"
 
Last edited:

Mike0001

Well-Known Member
I believe RCD protection is legally required in new homes, isn't it? Possibly in rewired homes too, since 2008.
 

kev7378

Member
I believe RCD protection is legally required in new homes, isn't it? Possibly in rewired homes too, since 2008.
Yes: new builds and rewired homes.

But also "possible" yes: As I understand it, if you have a new circuit added or substantial work on an existing circuit/installation, then there are parts to the regulations controlling whether or not the installation needs to be brought up to date. I think the regulations indicate RCD has to be present in all such cases, and so the easiest way to go is to install a full modern "consumer unit" if the property does not already have one? Best to get an approved electrician to do it than doing it yourself these days (you need a certificate afterwards anyway).
 
Last edited:

kev7378

Member
The events an RCD protects against are not normal circumstances. You have to have taken some measure to defeat the first level protection and then induce a second level of failure to be at risk.
But it is precisely the occurrence of "not normal circumstances" that the RCD is intended to protect us against. Let us consider a scenario: a loved one is plugging in a "wall wart" charger for their cell phone/other device; the plastic casing comes apart just as it slides in and, you know how it is, the socket is still switched on, and it's one of those chargers that does not have sealed insides or protected pin heads... RCD or no RCD (can they be saved by the fuse in an old type fuse box (post #12): no)?

Note that an RCD is not a guaranteed protection against electrocution: https://en.wikipedia.org/wiki/Residual-current_device#Testing_of_correct_operation

30 years ago we never had RCDs, and we all made it this far.
Have we all made it this far?
 
Last edited:
Top