Rcd tripping regularly

[saveasteading]

It seems to be whenever we are away that the power goes off and the freezer contents are wasted. 

Perhaps once a month on average.

There wasn't so much trouble with the previous, very old, units but they had to be replaced.

The problem doesn't seem to be linked to bad weather or any other known reason.

 

This unit then feeds a new consumer unit which itself and occasionally trips too, but always an individual circuit.

The electrician suggested that this more distant CU (10m through the attic) might need an upgraded, feed cable but not saying why.

 

But when the circuit trips with only a fridge and central heating, it seems to me that there is an overarching problem.

Can there be surges in the mains power that cause the trip?

Problem usually the top left box, right hand or left hand trip, varies.

 

The cu box on the right has seldom any issue.

[ProDave]

Trying to work out what feeds what and what keeps tripping.

 

Is the one in the picture with the lid open the one that keeps tripping? If so post a picture of how that connects to the meter and the other CU's please.

[Radian]

You might be interested in this topic if you've not seen it before:

 

It's quite possible that the trip happens when your fridge/freezer cycles the compressor on or off. Compressors can produce transients and the presence of any digital kit on standby may be bypassing a spike to earth, or as in my case, a multi-socket adaptor with built-in surge protection. The problem with these is that surges are bypassed to earth causing the RCD to trip.

[Nickfromwales]

5 hours ago, saveasteading said:

Problem usually the top left box, right hand or left hand trip, varies.

Elaborate, please?

[Onoff]

It's not a bad shout to have fridge/freezers on their own dedicated rcbo. At least if something else causes a trip you shouldn't come back from holiday to a defrosted freezer! 

 

I ran a dedicated trunking to a double socket for this though it's currently still on the kitchen ring. 

 

 

 

[dpmiller]

If the MCB (r/h trip) is going it implies a *real* fault. What rating is it and exactly what is on that circuit? Are the cable joints/ JBs between here and where the appliances are?

[Radian]

15 hours ago, saveasteading said:

Problem usually the top left box, right hand or left hand trip, varies.

 

1 hour ago, dpmiller said:

If the MCB (r/h trip) is going it implies a *real* fault.

 

Good spot. I'd missed that 'right hand' was referring to the MCB, not the box on the right.

 

An intermittent short would be an unlikely but serious fault, however there's another possibility. Compressors can draw huge spikes of current when starting. My old fridge could pull 8A for under a second, likely more as this was recorded with a 1s sample rate. Is the fridge somewhat old?

[saveasteading]

Two fridge freezers, both fairly new.  Perhaps when away we can try consolidating to establish which, if either, is the problem.

One is a big 'american' style so prob takes more power.

 

Here is a photo of the whole box. Mains coming in at the bottom. 

The top right box is a local fuse box for this room and a few adjacent and isn't a problem. 

The top left seems only to feed the more distant CU for the rest of the house.

When there is a loss of power it is about 80% in the rcd box.....usually the rcd trip itself, or 20% a main fuse or a lighting circuit in the remote CU.

I will keep a note from now.

 

Is there a way of preventing a spike from a freezer? Just plugging in a spike prevention socket thingy?

 

The electrician suggested a switch linked to the Internet and an app so we would get an early warning and ask someone to call in and reset promptly.  But that needs power. 

[Carrerahill]

17 minutes ago, saveasteading said:

Two fridge freezers, both fairly new.  Perhaps when away we can try consolidating to establish which, if either, is the problem.

One is a big 'american' style so prob takes more power.

 

Here is a photo of the whole box. Mains coming in at the bottom. 

The top right box is a local fuse box for this room and a few adjacent and isn't a problem. 

The top left seems only to feed the more distant CU for the rest of the house.

When there is a loss of power it is about 80% in the rcd box.....usually the rcd trip itself, or 20% a main fuse or a lighting circuit in the remote CU.

I will keep a note from now.

 

Is there a way of preventing a spike from a freezer? Just plugging in a spike prevention socket thingy?

 

The electrician suggested a switch linked to the Internet and an app so we would get an early warning and ask someone to call in and reset promptly.  But that needs power. 

I think I would be looking at doing some upgrades and changes to this setup. 

 

That RCD's is protecting as entire, pretty bad way of doing it as you are finding.

 

I cannot see from this image but the tails feed the little CU - then that must feed a cable which feeds the distant consumer unit, I can only assume that it's like this to protect a submain that needed protection under BS7671 but its a poor poor way of doing it. I would be getting rid of that RCD, running an armoured sub-main to the distant consumer unit, then think about having it rewired with a RCBO board ideally or split board if, and I will make the assumption, it doesn't have any RCD protection.

 

Are the freezers in a garage?

 

I would also be looking at getting those tails and things upgraded. Not sure what the "local circuits" are on the small lower CU but I am sure with a bit of thought this could all be revised and made quite a bit better. 

 

The BS88 fuse appears to be a 60 - I would be tempted to get rid of the Henley blocks and mess of old tails, run two new tails into a new 4-6 way CU - feed the local circuits from a RCBO, and feed the distant CU with an MCB - probably a 63A or 80A unit - single pole MCB's of that rating are not too easy to find but do exist. Run that out on SWA to the house distant house consumer unit. That then takes care of your submains and you can worry about the main house consumer unit at a later date. 

 

I can think of 2-3 other ways of doing this, but that is an option.

 

 

[ProDave]

+1 to re doing the submain in SWA (if not already?  Take the cover of that mini CU and post a picture inside)

  

I would probably then replace that mini CU with a switch fuse.

[saveasteading]

1 hour ago, ProDave said:

+1 to re doing the submain in SWA (if not already?  Take the cover of that mini CU and post a picture inside)

  

I would probably then replace that mini CU with a switch fuse.

This is the distant one.

The fridges are in the house.

The electrician did suggest changing the cable to armoured, though I don't understand why (can someone explain please?) 

I would have to get it from point to point which will be tricky with timber frame to get through.  Lots of holes in the plasterboard....again.

 

Everything was fine until the new "improved" metal boxes went in. All the cabling is as it was.

[ProDave]

One immediate issue is you have RCD's in the main CU and also in the CU by the meter.

 

The reason for changing the cable, is SWA does not need RCD protection. So you can dispense with the RCD at the mini CU by the meter.

 

Did your electrician do insulation test readings (he should have)

 

Everything was only "fine" before because the old CU / fuse box did not have the ability to detect an earth leakage fault.

[Jenki]

1 hour ago, ProDave said:

 Take the cover of that mini CU and post a picture inside)

  

I would probably then replace that mini CU with a switch fuse.

If DB2 only supplies (I Assume DB3) then change to switch fuse as @ProDave mentions.  Then it won't trip as its just a fuse. but then the cable supplying DB3, (do you know what cable type it is?) is only protected with a big fuse - hence the + 1 for upgrading to SWA. - but this does not necessarily fix an issue in DB3. 

as DB 3 is a new CU have you got the test results for it? 

 

This could be tripping due to brown outs, surges in O/Head power lines, many reasons really.

 

DB2 which causes the problem you mention the left or right trip?  so either the RCD trips, or the MCB trips.  to me it does point to an issues with

A,  the supply cable to DB3, (under size, failing insulation / damp)

B, a circuit in DB3 - as again I'm assuming DB2 has a standard RCD, so it trips here first

 

 

 

[saveasteading]

Thanks. The electricians were known to us, reliable and thorough from previous projects.

I didn't oversee them  but know they would have tested and told me if there was a problem. 

As you are saying what they said about the SWA I suppose they sort of were saying it wasn't ideal.

The cable through the attic is just domestic cable..

 

We are in the countryside, with lots of the grid being overhead, except when it falls down. It is likely that the underground feed is old too. (In our previous wreck up the road, we got the cable in the road changed because of low voltage....the man in the hole said he'd never seen a cable so bad, with no colours left on it). 

So it is likely that we get surges.

 

I really can't remember which switch mostly  trips....I just go to the box and reset it. But I think usually the MCB (right hand switch on DB 2), not the rcd on the left.

Must try harder.

 

DB2 is 63A. DB3 which it feeds has one 100A and another 63A RCDs which seems odd.

 

[Carrerahill]

1 hour ago, saveasteading said:

DB2 is 63A. DB3 which it feeds has one 100A and another 63A RCDs which seems odd.

 

Just what the board came with, its just the isolator rating, not an issue. Usually they are 80A and 63A or a combination of such, there is usually a bigger one for heavier loads. 

 

The issue you will also have is cascading, which RCD trips first?!? When the RCD goes, is it only ever the one at the supply and not the CU?

 

This is why my garage is on a 50A SWA submain fed from an MCB in the house CU. So when I drop my extension cable in a bucket of water only the RCBO for that circuit in the garage goes and because I used RCBO's for each circuit, I still have lighting on in the garage to go reset the small power RBCO!

[saveasteading]

Got some good news on this....I think. but more tech help needed.

I don't think we need to change the main cable that links the 2 units

(I have just about worked hot how to get it up through the stud wall with least mess, but hoping not to.)

 

The circuit  continued to trip. Sometimes there would be a week with no problems, on another day several, and occasionally it would refuse to reset....then 10 minutes later all was well.

 

It occurred to me that this was wet weather related. We have a pole in the garden that has an outside light and from which a spur has been taken to our newish electric gate.

The box faces south west, and is fully exposed to driving rain.

 

At first I blamed the light, as PIR boxes don't last long until the plastic fails. so I disconnected the light. It was wet inside the box, and put some tape round the duct.

 

Then last night it went again.....and as I had to go out I noticed that the trip coincided with triggering the gate....maybe 10 times.

 

Turned off the fuse for that circuit, and all was well....apart from manual override required  to the gate.

 

I will post photos in the next post, as is easier from the phone.

 

The new question:

 

I was about to fit a new connection box, with proper closure glands on it, but I noticed the more complex connection from the armoured cable at bottom right with some sort of sleeve and a nut inside the box.. This is outwith my knowledge....Does it need the nut? what is going on inside the sleeve?

I also noticed it was wet on top of the internal tape I put in yesterday, so def coming in the upper trunking.

 

To summarise....the feed cable comes from underground and up in the trunking to the light on the pole. The gate contractor spliced into it and added the box. From this an armoured cable goes down again, and off to the gate.

 

BTW power-wise it is all fine. Originally there was a 300W lamp, but now it is a 20W led.

 

[saveasteading]

Pics.

[saveasteading]

[Onoff]

That is a ****fest. Not even proper glands used for the conduit, just a hole. Is that SWA actually earthed to the banjo?

 

Neighbour paid a fortune for oak swing gates and the wiring looked just like that.

 

Tbh I'd use flexible conduit and come in from the bottom in 3 holes.

[Onoff]

Mine:

 

 

OK, it's not finished yet...

[saveasteading]

10 minutes ago, Onoff said:

from the bottom in 3 holes.

Nice simple idea.

 

13 minutes ago, Onoff said:

Is that SWA actually earthed to the banjo?

 

Yes.  Should it not be?

 

Do you think they have joined a domestic cable to the armoured, in that sleeve? And why the screw connection?

[Onoff]

12 minutes ago, saveasteading said:

Nice simple idea.

 

Yes.  Should it not be?

 

Do you think they have joined a domestic cable to the armoured, in that sleeve? And why the screw connection?

 

So you have the mains feed coming in bottom right? Looks like twin and earth, explain how that's run please.

 

Top right more twin and earth to the light?

 

Bottom right, armoured to the gate?

[saveasteading]

Bottom left and top were the original feed to the light from long before we bought it.

The trunking was already there, and cut for the box installation.

 

It comes from somewhere in the house (switch at front door) , then under the garden about 20m.

I have not investigated if and where it might change to swa. It must be quite deep as I haven't yet cut through it when gardening.

 

The box and the bottom right armoured cable were put in by the gate installer.

[ProDave]

6 minutes ago, saveasteading said:

Bottom left and top were the original feed to the light from long before we bought it.

The trunking was already there, and cut for the box installation.

 

It comes from somewhere in the house (switch at front door) , then under the garden about 20m.

I have not investigated if and where it might change to swa. It must be quite deep as I haven't yet cut through it when gardening.

 

The box and the bottom right armoured cable were put in by the gate installer.

Contractor wants shooting.

 

He has taken an inadequate, not fir for outside feed to a light, fitted a crappy non waterproof box, without even trying to waterproof the conduit entries and joined his SWA gate feed to it.

 

It is full or water, witness the rusted SWA gland.

 

you have found the solution to your tripping.  Rip it ALL out and start from scratch with SWA from the house.

[Onoff]

F*** me, potentially worse than I  thought 😂

 

Until now I thought my neighbours was the worst I'd ever seen. They used push fit pvc conduit and glands but nothing was sealed/glued. Does this circuit have it's own breaker/fuse?