Power keeps tripping out, how to diagnose?

[Energize]

So today, the sockets have gone off at least twice, my ups shows 2 blackouts and 1 electrical noise event. I have a decent multi meter, now I have been told that switching to AC microamps and connecting 1 probe to ground and 1 to the device will show current leakage, but is there a faster way of diagnosing which device is causing the fault? We haven't connected anything new to the circuit so certainly nothing is overloaded, so it must be a current leak to ground surely? Any advice would be greatly appreciated as my UPS only has so much charge.

 

[Energize]

Is it happening when certain things are on/at a specific point in their cycle?

Our dishwasher was tripping the RCD, but only about 15-30 seconds after power had been restored as it was doing something for a few seconds before turning the heating element on (that was causing the trip).

Highest chance things of tripping are:
External sockets/lights.
The appliances with water and electrics (immersion heater, washing machine, dishwasher, electric shower) so possibly try turning them off/unpluging them. IIRC if it's a fault with a heating element and water you may only see it when the appliance is switched on and using the element as at other times the element won't be "on" so the circuit for the fault probably won't be complete.

After that you have to basically go through everything.

It hasn't happened enough times to narrow it down to that yet unfortunately.

The lights and outside sockets aren't tripping, the sockets in the cellar don't go off (on a separate circuit), oven has it's own breaker, we don't have an electric shower, I'll try the kitchen appliances first as we do have a dishwasher and washing machine on that circuit.

 

[Energize]

Is it the circuit breaker or the RCD that is tripping? You haven't been very clear, and it makes a big difference in terms of diagnosing the fault.

It's number 3 that keeps tripping.

 

[Energize]

That's overcurrent, not earth leakage. Unless you're hearing a loud bang when it trips, I would diagnose that as a faulty circuit breaker.

So can I just replace the MCB is or is it an electrician call out you think?

the system resets itself ? or, rather, you know exactly when the incidents occurred ... and who was in the house

The latter yes, but everything that is plugged in switched on all the time, so I'm not sure that helps narrow it down?

 

[Energize]

The MCB will cost approx. £10, what they add for labour is another story - do you know any Sparks?

For info, you don't get nuisance trips with MCBs like you do with RCDs unless you have loaded it up to the max. What do you have plugged in to that circuit - is it heaters or something?

We don't have any electric heaters, highest rated devices are the kitchen appliances. It went out at 4am this morning when nothing was really on.

 

[Energize]

I will list the items tomorrow.

But rest assured, it is well below 32A! Apart from a fridge/freezer we have only had a few consumer electronics items and lamps connected to the circuit for months!

 

[Energize]

I highly doubt that you're exceeding the 32A. My money is on the circuit breaker being faulty; it's a cheap make that's been installed.

Story of my life.

 

[Energize]

Housemates had an electrician come around today and he said that an MCB failing was very rare and he would not expect it to just reset if that was the case.

So we are currently listing an itenary of electrical items together while plugging the fridge freezer into the kitchen circuit and praying it's that. I would have thought that it would have made economic sense to replace the MCB though anyway surely?

OK so you don't have any rcd's (maybe it's something you should consider ?) and problems not in the kitchen or the cooker.

since it's happened multiple times .. I'm surprised you haven't got a socket device where its (max) 13a fuse hasn't blown or you have the smell of burning.
so as string says maybe the cb is failing.



(in the past failing heating devices - kettles + coffee machines have tripped my rcd's but not tripped the cb's .... showing the merit of rcd's I think)

I assumed that these boxes would have an RCB built in or something? I know we have a towel heater in the bathroom on a seperate circuit with an rcd.

 

[Energize]

I'm not a qualified electrician ! - but in the picture you posted I couldn't see any reference to rcd's or is it before the consumer unit.

( I googled earlier but can't see whether officially/legally you change an MCB yourself, if you follow the appropriate checklist )

There is an RCD in the consumer unit, no6, you can only just barely make out the 0.03A marking in the photo.

I have just replaced the MCB in any case, so will see if there's any joy.

 

[Energize]

Are you sure that's an RCD, it doesn't have a test button.

The blue button at the top of it is the test button.

 

[Energize]

As said before. Get an electrician in to diagnose the fault and replace the consumer unit at the same time as its looking pretty tired.

Also if that is an rcbo then you have no rcd’s for anything other than your lighting circuit.

Mcbs stop your house burning down but rcds Will save your life.

Electrician has already been and has echoed the earlier suggestions that each device needs to be ruled out on the circuit.

 

[Energize]

If there is a short to neutral though rcd won't trip will it? I think we have a plug adaptor that records peak current draw would that be useful?

I wasn't there there at the time, but I was told that he said what is connected (various computers, tvs, an amplifier, low power consumer electronics and led lamps) was well below the 32A limit, only thing he mentioned was that sometimes UPS devices can cause trips due to the transformer, but turning the UPS on and off at the socket hasn't caused the breaker to trip so far.

 

[Energize]

Yes, it would trip with neutral short - that's one of the main advantages. However, disregard "RCD plug adapter" comment as it makes no sense. If you really want RCD protection then change out the consumer unit.

I thought they tripped when there was a difference between the current supplied to the device and the current returned? If all the current in a device was going from the live and shorting so that all that current went back to the neutral there would be no delta n would there?

 

[Energize]

They detect earth leakage, so yes. MCBs do not detect earth leakage, they detect overcurrent. Using an RCD to diagnose why an MCB keeps tripping would be like using a thermometer to take someones blood pressure.

That would result in short circuit fault current, which would trip your 32A MCB. An RCD would not trip under L-N short circuit fault current.

Ah right, sorry got confused as to which sentence of mine your original comment referred to. So a plug in RCD will not trip if there is a short to neutral whereas a plug-in current sensing device will show the over current and potentially trip correct?

It hasn't tripped since I replaced the MCB so I am hoping that's all it was.

When I do eventually get around to having the consumer unit replaced I would certainly like to have more circuits so each floor of the house is on it's own circuit, the tediousity of this I cannot tell you!

 

[Energize]

Yeah, just edited my post, obviously not quick enough.

I'll have to fish it out tomorrow and see what it's specs are.

 

[Energize]

Could you link to the products or post part numbers?

By the way, I assume the new MCB has held up so far?

Actually, could you recommend any particular diagnostic product? With Amazon prime I might as well order something that could come in handy in future for diagnosing similar faults.

 

[Energize]

To be honest, no. The test equipment that I own and use costs £1000+ and it isn't plug and play as such - it requires an experienced technician to use it.

If I were you, I wouldn't invest any more time into this unless the replacement MCB starts tripping.

Unfortunately after replacing the MCB it has tripped a couple more times. Every device has been now unplugged one at a time so that seems to rule out any device as being faulty and I have checked that the continuity on all the sockets between earth live and neutral is correct, so it looks like we're going to have to call out an electrician again. Wonder if it's a problem with wiring somewhere in the house, maybe damaged insulation on the cables?

 

[Energize]

Having ruled out a faulty MCB, and with no apparent damage to equipment, I would be looking for loads that have high starting current. What have you actually got plugged in?

You could plug each individual device into one of these, set it to amps, and see if anything spikes momentarily as it is switched on.

FLOUREON Power Meter UK Energy Monitor AC 230V~250V Power Consumption Meter Energy Cost Calculator Watt Voltage Amp Meter[Energy Class A+++] - 1pack https://www.amazon.co.uk/dp/B01DSQ30FO/ref=cm_sw_r_cp_apa_i_M3RADb3HR0CM0

Just consumer electronics and lamps.

A couple of tvs, game consoles, 2x desktop computers and monitors going through a UPS, amplifier + speakers, subwoofer, network switches, external hard drives, a printer. That's about it.

Computers and stuff in the UPS are left on 24/7 so there's nothing really being turned on or off there. Yeah I've got one of those and have thought about doing that, it's just that it doesn't seem to trip at the point anything is switched on.

Did the electrician that came do any insulation resistance tests on the circuit?, if not then get a new electrician!

I would suspect fixed wiring at fault rather than equipment, while a 13A plug top fuse is pretty poor at discriminating with a B32 breaker, at least sometimes a fault would take out both, and if you are saying its happened multiple times (how many), even if it doesn't blow the plugtop fuse, it'll stress it, and eventually it will go alongside the breaker. I would expected that at somepoint the 13A fuse would have gone, the fault would be disconnected and you'd know what is not working.

I'd also rule out inrush in a domestic situation taking out a B32 unless you have industrial kit, or a server farm or something, if it was a B16 i'd be bit more wary, even 3kva site transformers don't take out B32s, the 5Kva ones do sometimes.

I'd suspect cable damage, and you are likely to see a poor IR even when the breaker is holding in, there is a possible fire risk (especially without any RCD protetcion), so it ought to be addressed as a priority

Where in the UK are you? there might be someone on here local who can diagnose it

Hasn't run any insulation tests as far as I know, but I have contacted an electrician I personally know through a social group to ask him if he can take a look rather than the randomer my housemates got in!

It's not even a 13A fuse in the plugs, it's 3A or 5A for everything connected to the circuit!

It's tripped 14 times in the past couple of weeks according to my UPS logs.

 

[Energize]

still don't understand - you are manually resetting it though - so you know exactly when it happens .? .. obviously you don't see a pattern

still think I would get an rcd adapter and see if that fired under the theory that current is not exclusively being returned to neutral.

I have a (maplin) energy meter wouldn't know if these are fast enough to capture short duration current peaks (they are probably integrating over a period of time)

Yeah I am manually resetting it, and don't see a pattern. Psb.

Month Day _Year_ Hour Minute Event Description
8 30 2019 13 24 Battery backup transferred to AC utility power.
8 30 2019 13 4 Battery backup transferred to battery power due to blackout.
8 28 2019 13 2 Battery backup transferred to AC utility power.
8 28 2019 12 58 Battery backup transferred to battery power due to blackout.
8 28 2019 8 57 Battery backup transferred to AC utility power.
8 27 2019 21 19 Self-test Passed.
8 26 2019 9 12 Battery backup transferred to battery power due to blackout.
8 25 2019 11 49 Battery backup transferred to AC utility power.
8 25 2019 0 45 Self-test Passed.
8 24 2019 11 30 Battery backup transferred to battery power due to blackout.
8 22 2019 20 26 Battery backup transferred to AC utility power.
8 22 2019 20 22 Battery backup transferred to battery power due to blackout.
8 22 2019 10 32 Battery backup transferred to AC utility power.
8 22 2019 10 31 Battery backup transferred to battery power due to blackout.
8 21 2019 20 49 Self-test Passed.
8 21 2019 13 15 Battery backup transferred to AC utility power.
8 21 2019 13 8 Battery backup transferred to battery power due to blackout.
8 21 2019 9 35 Battery backup transferred to AC utility power.
8 21 2019 9 35 Battery backup transferred to battery power due to blackout.
8 20 2019 15 6 Battery backup transferred to AC utility power.
8 20 2019 15 4 Battery backup transferred to battery power due to blackout.
8 20 2019 4 16 Battery backup transferred to AC utility power.
8 20 2019 3 52 Battery backup transferred to battery power due to blackout.
8 19 2019 21 32 Battery backup transferred to AC utility power.
8 19 2019 21 31 Battery backup transferred to battery power due to blackout.
8 19 2019 18 56 Battery backup transferred to AC utility power.
8 19 2019 18 47 Battery backup transferred to battery power due to blackout.
8 19 2019 17 53 Battery backup transferred to AC utility power.
8 19 2019 17 32 Battery backup transferred to battery power due to blackout.

 

[Energize]

So after further testing I found one socket which isn't being used with live and neutral reversed, touching the screw on the socket with my electrical screwdriver lights it up! After opening it up I was shocked to see that there is an uninsulated earth wire connecting to the socket and the backplate which I guess must be making the whole of the backplate and the screws connecting to it live.

Question though, why does my multimeter show 37v ac when only one probe is touching the shorted earth wire?