RCD Nuisance tripping

[sterod1971]

I have consumer unit with an RCD that protects the entire house and of late it has started tripping for no apparant reason. When reset the MCB for one of the rings (downstairs lounge, hall, front and middle bedrooms) trips and when I reset it it gives a spark. I went round and unplugged everything reset the MCB and RCD then plugged each appliance in one by one untill everything was back on. Niether the RCD or the MCB tripped. THis has happened on a few occasions and as my better half works from home every time it happens she has to reboot the pc etc to carry on working which is annoying for her as she loses work etc. Short of calling out a sparks to check the wiring what is the best way (easiest) of identifying the fault?
Steve

 

[EdwardCurrent]

Hello,

As you know, it could be a host of things. A process of elimination may be your best way forward.

Does your kitchen have its own circuit ? Or is it on the same 'ring main ?
If it is, it may well be worth starting off with your 'wet' appliances, fridge, freezer, washing machine etc etc.

Are you sure that there is no 'pattern' emerging of when it trips ?

Sorry I cant be of more help but sure the other folk on here will steer you in the right direction.

Good Luck

Ed

 

[sterod1971]

Hi
Kitchen is on its own ring but we do have a mini fridge in the office and a small freezer in the spare room for the dog food

the house is split into 5 circuits front to back. Lights front, lights back, ring front ring back and the kitchen is on its own ring.

The wiring is quite old except for the kitchen which is less than 5 yrs (coincidentally when we had the new consumer unit fitted)

I assumed it was the front ring where the problem was as its the mcb that sparks when reset the front ring which provides power to the sittining room (lcd tv, dvd, dvrfreeview box, vhs, 3 lamps, phone).Bedroom (2 lamps, adjustable beds, crt tv, dvd, alarm clock, phone) hall, office( (3 pcs, 4 moniters, CCTV recorder, 2 laptops, 2 printers, speakers for pc, fan, credit card machine, shredder, router, broadband hub, 3 phones and mini beer fridge) And hence went round un plugging and replugging everythin on this circuit. the MCB didnt trip at all on replugging everything back in and so far this motning its been ok.
As to patterns. the nuisence tripping occurs at different times and under different loads so there isnt as yet a pattern. (we do however get tripping whenever a bulb blows and assumed this was normal)

 

[kkynaston]

It may be the IT equipment that is the cause here.

PC's tend to leak quite a bit to earth therefore tripping the RCD.

Is the whole install protected by an RCD or do you have some sockets that are not RCD protected?

Can you take a pic of your consumer unit for us.

 

[JohnD]

it is very undesirable to have a single RCD that protects the whole house, for the very reason you have observed. It also increasesd the risk of nuisance tripping because you may have several tiny, insignificant leaks on different circuits that sometimes add up to enough to cause a trip.

when we see the pic of your CU we will be able to suggest improvements to the design, but changing this is notifiable work and needs a suitably qualified electrician. For the moment I agree about unplugging appliances. If the fault is caused by an appliance, it is most usually a "watery" one like a kettle, immersion heater, washing machine, dishwasher, shower, fishtank, boiler or CH pump; or one with a heating element such as immersion heater, washing machine, dishwasher, shower, microwave or oven.

Outdoor circuits such as lighting, sheds and fountains are very prone to getting wet. It can also be caused by rodents gnawing cables, often under floors.

Try unplugging half the appliances one day; and half the next day, and if this changes the tripping pattern you can start plugging appliances back in one at a time, for a day.

I would also look into a basic UPS for the computer, but you need our "Hardware" forum for that.

 

[sterod1971]

View media item 7538working left to right
Landing socket (nothing plugged in) radial circuit
Back ring main
Front ring main (this is the one that sparks)
RCD protects whole house
Lights
Lights
Lights
Shower (no longer used)
Main switch

 

[kkynaston]

Is it possible for you to switch off a couple of PC's for a while and see if it still trips?

 

[JohnD]

it is not laid out as a whole-house RCD. It looks like a split-load.

when the RCD trips, the lights should still work. Do they?

 

[sterod1971]

Yes the lights still work

 

[JohnD]

you would have to get a qualified electrician to do it, but one thing you could do is to move whichever Socket Circuit is used for the PCs onto that spare position on the non-RCD side, and have it protected by an RCBO. An RCBO is a single device that contains both an MCB and an RCD. Or run a new circuit to the PC room on an RCBO in that position. Then it would have its own RCD and would (mostly) be unaffected by faults on the other circuits on the RCD side.

Proteus is rather a budget brand and I don't know how readily available RCBOs are to suit.

If it turns out that the multitude of PC equipment is causing the trips, look for a UPS that isolates the PCs from the supplying circuit. Or use fewer of them. All PCs cause a certain amount of earth leakage due to the way their power supplies are designed.

 

[Steve]

Definitely get a UPS though.

 

[radioredcat]

A ups is a must for pc's as i know well living in powercut alley iv'e lost a few hard drives because of power cuts.
So i bought a trust 800va ups power goes off ups bleeps every ten seconds pc stays on,This ups gives about 25mins with a pc and a crt monitor but you will need a bigger one for several pc's.
my ups has run down during a powercut while iv'e not been at home and there has been no damage to the pc when it's run out of power.


andy

 

[Taylortwocities]

Proteus RCBOs are made
http://www.proteusswitchgear.co.uk/product_details.asp?product=1251

and you can buy em at CEF

 

[sterod1971]

Thanks for all your help guys,
Turns out last trip was caused by security light (B&Q special) blowing its bulb.
After discussing this with SWMBO weve decided to take the plunge and have the entire house re-wired, Weve not got enough sockets in any of the rooms anyway so this will be the best way to A. satisy the gadgets need for power, B. stay safer by not using loads of multiway plugs.

This is what id like to do.
1 ring for lounge (lots of power need here and only 2 double sockets at present)
1 ring for Kitchen
1 ring for office
1 ring for master bedroom
1 Ring for garage
Supply to outside for lights pond pump and filter
Supply to shed for light and alarm
Lighting circuit split up/down rather than back/front as at present
boiler on its own circuit
shower on its own circuit
rest of downstairs on ring (hall. dining room)
rest of upstairs on ring (rest of bedrooms and landing socket)

Is this doable within the regs or does a ring have to cover a certian square meterage?

Cheers
Steve

 

[ban-all-sheds]

1 ring for lounge (lots of power need here and only 2 double sockets at present)

Lots of power, or lots of outlets? Have you really got several kW of load in your living room?

Ditto the master bedroom?

Is this doable within the regs or does a ring have to cover a certian square meterage?

You may have as many circuits as you like - the guidelines specify a maximum area served by socket circuits, not a minimum.

And don't get too hung up on the idea of rings - if you're having lots of circuits then you almost certainly won't need the capacity of a ring, and radials are better for future modifications.

Good idea to put all wiring in conduit for ease of future changes. And if you specify metal conduit for switch drops, or BS 8436 cable it removes the need to have RCDs where you'd rather not.

Think hard about where to have sockets - it's difficult to have too many, and also about what circuits to have. The items on the list below won't all apply to you, but they are worth thinking about:

• Upstairs sockets
• Downstairs sockets
• Kitchen sockets
• Circuit for appliances
• Cooker circuit
• Non-RCD circuit for F/F
• Non-RCD circuit for CH boiler
• Dedicated circuit for hifi
• Dedicated circuit for IT equipment
• Upstairs lights
• Downstairs lights
• Immersion heater
• Loft lights
• Shower
• Bathroom circuit
• Alarm
• Supply for outside lights
• Supply for garden electrics
• Supply for shed/garage

Plus any peculiarities brought about by your house layout & construction - e.g. in mine because of solid floors and where the rings run, I have a radial just for a socket in the hall, the doorbell and the porch lights.

Unless you want to go to the expense of RCBOs throughout, the CU should have at least 3 sections, 2 on RCDs and one not into which you can install a mix of RCBOs and MCBs.

If you live somewhere where supplies are dodgy in the winter, have the lights, the boiler supply, and a socket in each room wired to a separate CU, or a separate section in a large one, that can be supplied by an emergency generator - lights, heating, TV and a kettle/microwave make life a lot more bearable.