Trip switch tripping ..... details in message

Rollerball · 3 Jun 2011

Just over a week ago the PSU in my backup PC 'blew' and tripped the main house trip switch. I replaced the PC's PSU and it's now fine, however .........

Ever since then, whenever a certain mains block is switched on in another room, the mains trips.

Trouble is that it only happens some of the time.

I'm in the process of unplugging items from the 4 gang mains block, but as it's so random it's time consuming to isolate it.

Things that I've done so far to try and isolate the fault:

- Replaced the 2 ways mains socket (it was very old and the switches were sometimes sparking when switched on!)

- Replaced the 4 gang mains block

- Plugged the new mains block into a totally different socket in the same room

- Unplugged the scanner from the mains block

None of the above have helped.

Four items are plugged into the mains block: a PC, printer, scanner and monitor.

Is it possible that the other PC's PSU failure the other day made something more sensitive, perhaps another item elsewhere in the house or the main trip switch itself?

Is there a better way to isolate the cause?

Thanks

EDIT: Have just remembered something - my main PC (not the one on the block that's tripping or the backsup PC) has a UPS. For a long time now, whenever the aforementioned mains block is powered on, the UPS has been detecting what it refers to as 'electrical noise'. So obviously a 'noise' problem has existed for quite some time, but why is whatever is causing the fault now tripping the mains when it didn't before?

Adam_151 · 3 Jun 2011

Rollerball said:
Is it possible that the other PC's PSU failure the other day made something more sensitive, perhaps another item elsewhere in the house or the main trip switch itself?

Assuming you are talking about an RCD (you dont actually say), then sort of; if its not been tested for a while, like all mechanical devices it can suffer from slight sticking due to not being moved, if a fault occurs it might be slower than it should be tripping, but after its moved it'll probably have improved a bit by the next time.

The regulations call for a label to be fitted asking that it is tested quarterly, this not only tests the device, but keeps the mechanism moving

EngStudent · 3 Jun 2011

How much stuff is covered by the RCD? # of computers, monitors, UPS, etc. Are they all protected by the same RCD? Any appliances protected by it?

You've replaced the multi-way adaptor, but it still trips. You've tried them in a different socket, it still does it.

When all this is going on, is your PC equipment turned on? It could be that your new PSU has a higher earth leakage than your old one, and that the RCD is sensitive/you have a lot of stuff. Ideally you'd have a ramp test done on the RCD to make sure it's not that.

Edit: Did they ever get round to making a clamp meter that'll measure in mA?

Rollerball · 3 Jun 2011

EngStudent said:
How much stuff is covered by the RCD? # of computers, monitors, UPS, etc. Are they all protected by the same RCD? Any appliances protected by it?

Everything in the bungalow goes via the same RCD as far as I'm aware - items that are usually on are: 3 x PCs, 2 x LCD monitors (and 1 x CRT which is usually off), TV, Freeview receiver - then there's the usual items that aren't used that often but which have an inbuilt digital clock, such as the oven, microwave oven - then the items that are used occasionally, like the kettle.

You've replaced the multi-way adaptor, but it still trips. You've tried them in a different socket, it still does it.

Yup, that's it.

When all this is going on, is your PC equipment turned on?

Yes.

It could be that your new PSU has a higher earth leakage than your old one, and that the RCD is sensitive/you have a lot of stuff.

Sounds feasible.

Ideally you'd have a ramp test done on the RCD to make sure it's not that.

What's a ramp test? Is it something that an electrician carries out, or something that I can do with some inexpensive equipment?

Just to reiterate this point:

"Have just remembered something - my main PC (not the one on the block that's tripping or the backsup PC) has a UPS. For a long time now, whenever the aforementioned mains block is powered on, the UPS has been detecting what it refers to as 'electrical noise'. So obviously a 'noise' problem has existed for quite some time, but why is whatever is causing the fault now tripping the mains when it didn't before?"

Worth noting that the above (last para) has been going on for quite some time, long before the backup PC's PSU was replaced.[/b]

EFLImpudence · 3 Jun 2011

EngStudent said:
Did they ever get round to making a clamp meter that'll measure in mA?

Yep.

http://www.test-meter.co.uk/clamp-meters/earth-leakage-clampmeter/

EngStudent · 3 Jun 2011

Fridge, freezer, etc I assume?

Rollerball said:
What's a ramp test? Is it something that an electrician carries out, or something that I can do with some inexpensive equipment?

I guess you could hire the gear but it'd probably be cheaper to pay an electrician to do it.

I think I remember my college tutor saying the average computer leaks between 2-3mA. I can't remember if that was just the base unit or base unit + monitor. Either way, it's poor practice to have one RCD protecting an entire installation (infact, I don't think having one RCD protecting an entire installation has ever been compliant with Regs), and with the amount of stuff you have you could quite easily be nearly/over the threshold at which your RCD will trip (I think the lowest I've seen a 30mA RCD trip at was 18mA).

We love pictures on this forum. Any chance of a picture of your consumer unit?

Edit: Sorry, a ramp test will measure the level at which the current imbalance will cause the RCD to trip.

Rollerball · 3 Jun 2011

EngStudent said:
Fridge, freezer, etc I assume?

Yes, sorry, of course - knew I'd forget something! 1 x fridge, 1 x chest freezer.

Re ramp tester - thanks.

I think I remember my college tutor saying the average computer leaks between 2-3mA. I can't remember if that was just the base unit or base unit + monitor. Either way, it's poor practice to have one RCD protecting an entire installation (infact, I don't think having one RCD protecting an entire installation has ever been compliant with Regs), and with the amount of stuff you have you could quite easily be nearly/over the threshold at which your RCD will trip (I think the lowest I've seen a 30mA RCD trip at was 18mA).

I see. Well, it's quite a small bungalow so there's only the electrical items that I listed - would all of those really push it to the limit?

And why does it only trip some of the time, even though the same units are always on?

Also, there IS another RCD - forgot that there is a separate one in the room that has the washing machine, dishwasher and chest freezer - would need to trip it to determine which sockets it's handling. So at least I have two RCDs, it's just that most of the power seems to be going through the one that's tripping.

We love pictures on this forum. Any chance of a picture of your consumer unit?

Do you mean the RCD? It's made by Wylex - I can get a picture if you like.

A few other things worthy of note:

a) If my wife's PC is already switched on (the one that's maybe causing all the problems) and then I switch off my main PC, backup PC and monitors, then switch them back on, the power has NEVER tripped. It's ONLY tripping when my wife's PC machine and its gang socket are switched on (and then only intermittently).

c) A week or so ago the mains tripped during the night, the aforementioned PC and mains block were NOT switched on, OR the TV or Freeview receiver - we don't know when it tripped, perhaps when the boiler came on?

d) Worth noting that if the trip goes and then it's turned back on (WITH EVERYTHING STILL SWITCHED ON) it doesn't re-trip at that point.

It's almost as if something is causing a momentary mains spike (or whatever).

EngStudent · 4 Jun 2011

Do any of your PCs have WOL enabled?

Personally I'd be calling someone to do a ramp test on the RCD and test the insulation resistance of your installation. Failing that, I presume you've had a look inside the base unit to ensure that there's no contact between any cables/components and the chassis of the PC? (Unlikely but you never know!)

Rollerball · 5 Jun 2011

No, I don't think that any have WOL enabled.

Rollerball · 18 Aug 2011

Further to this (and a recap with more info):

My wife's PC sometimes trips the mains power when it's powered on - sometimes it only instigates an 'electrical noise' warning on my own PC's APC UPS. Sometimes her PC powers on just fine. This has been ongoing for a few months.

It's definitely the PC as it happens in various mains sockets, etc. No other electrical items cause this in the house.

I bought and fitted a new PSU but no luck - the intermittent mains tripping fault remains. Replaced the mains cable, etc but still no luck.

It ONLY happens when this particular PC is switched on (although I noticed that when powering on the scanner yesterday (RARELY used) that the APC UPS software blipped up an electrical noise error). However, just to reiterate, it's only when the PC is powered on at the mains socket that the mains trips, as determined by plugging it into a wall socket (ANY wall socket) on its own.

So what to do now?

It's tough to track it down due to the intermittent nature of the fault as it doesn't always trip the mains.

Is there anything that I can plug into the mains socket for this PC which will somehow prevent the problem from occurring, or at least stop the mains from tripping?

bernardgreen · 18 Aug 2011

All good quality switched mode power supplies that have an earth connection will create a small amount of earth leakage current in their filter circuits. One PC should not trip the average 30 mA RCB. Ten PCs or other items with switched mode power supplies are close to the 30 mA limit.

You probably have some earth leakage in your wiring and the "leakage" in the PC is the final straw. Finding leakage in the wiring requires test equipment and knowledge of how to test the wiring. Can be a DIY task but an electrician will ge faster and have the necessary equipment.

Rollerball · 18 Aug 2011

To add to that, the RCD that is tripping is right next to the main fuse box - on it is printed:

80 Amp load, 100 milliAmp Trip

bernardgreen · 18 Aug 2011

A picture would be very usefull. 100 mA suggests this might be a very old system. If no picture then does the RCB have

[1] four large cables, two at the top and two at the bottom

[2] 6 cables, four large and two small ones that are maybe green yellow. Two large and one small at the top and two large and one small at the bottom.

If you cannot see the cables do NOT remove any covers.

Rollerball · 18 Aug 2011

What's the difference between an RCB and an RCD?

Here's a pic of the RCD:

http://i59.photobucket.com/albums/g319/Dalek99999/P8180320.jpg

bernardgreen · 18 Aug 2011

RCB was my typing error.

Almost all equipment that has an indicator to say it is on standby will have its input filter connected and creating some earth leakage. Unplugging is the one way to ensure the equipment's filter is nor contributing to earth leakage.

I think you need an electrician to inspect your installation. That RCD has an exposed live terminal at the top. That needs to be corrected.

The cover of the adjacent fuse box is upside down which suggests the arrangement inside has been modified to bring the main switch to the right hand side when normally it would have been on the left hand side. That modification if not done properly could mean errors in the wiring of the fuses. As the "electrician" has left live terminals exposed I fear his work inside the fuse box may be jsut as poor quality.

Pictures of the meter and main fuse would help to assess the quality of workmanship

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Trip switch tripping ..... details in message

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