Tripping issue with new installed 13 Way Dual Split Consumer Unit 2x100A RCDs (Type A) + 12 MCBs + SPD

[Chippyminton0]

Hi, I need some help locating and resolving a fault on a new consumer unit.
I removed an existing plastic MK Sentry duel 63amp RCD unit which worked fine and replaced it with a new metal MK Sentry duel 100amp RCD unit with a SPD.

No 1 RCD I had 5 circuits. No problems all worked fine.

No 2 rcd I had 4 circuits. (There are no appliances plugged in) when I put any load on any of the circuits it trips out No 1 RCD.
When number 1 trips, number 2 doesn't but the voltage at number 2 drops to 187v
I have removed all the circuits entirely and tried each on their own on No 2 rcd and the same thing happens.
The original board (which had no problems)had 2 x 64 amp RCDs which I know work. I replaced the 100 amp pair with these and still the same problem. I have put the 100 amp pair back on but swapped them around, still the same problem.

I have removed the surge protector, same thing happens

I have now put all the circuits on to number 1 RCD and every thing works fine with no tripping. However I don't want them all on 1 rcd, I can't afford rcbo's yet. But more importantly there is still an issue there that needs resolving.

Any ideas what it might be?

I apreciate any help

 

[HappyHippyDad]

A picture with all the cables in would be better.
You may have one of the neutrals from the right RCD in the left hand neutral block.

 

[mainline]

As above, you have most probably used the wrong neutral bar.

 

[brianmoooore]

Have you split any lighting circuit that was on one MCB into two circuits on two MCBs?

 

[Chippyminton0]

A picture with all the cables in would be better.
You may have one of the neutrals from the right RCD in the left hand neutral block.

Hi Happy Hippy dad, thankyou for your reply.

Hi, I need some help locating and resolving a fault on a new consumer unit.
I removed an existing plastic MK Sentry duel 63amp RCD unit which worked fine and replaced it with a new metal MK Sentry duel 100amp RCD unit with a SPD.

No 1 RCD I had 5 circuits. No problems all worked fine.

No 2 rcd I had 4 circuits. (There are no appliances plugged in) when I put any load on any of the circuits it trips out No 1 RCD.
When number 1 trips, number 2 doesn't but the voltage at number 2 drops to 187v
I have removed all the circuits entirely and tried each on their own on No 2 rcd and the same thing happens.
The original board (which had no problems)had 2 x 64 amp RCDs which I know work. I replaced the 100 amp pair with these and still the same problem. I have put the 100 amp pair back on but swapped them around, still the same problem.

I have removed the surge protector, same thing happens

I have now put all the circuits on to number 1 RCD and every thing works fine with no tripping. However I don't want them all on 1 rcd, I can't afford rcbo's yet. But more importantly there is still an issue there that needs resolving.

Any ideas what it might be?

I apreciate any help

The 16amp mcb protected by rcd has just been put in to show the symptoms of the fault. It's 2.5mm cable and run to a double socket. The load on it is a makita charger with nothing on charge.

Have you split any lighting circuit that was on one MCB into two circuits on two MCBs?

Thanks for your reply Brian. No I havnt. I have added a video and photo

 

[brianmoooore]

Thanks for your reply Brian. No I havnt. I have added a video and photo

Won't be the common 'borrowed neutral' problem often found on stairs lighting circuits, so, in that case, HappyHippyDad is likely to be on the money

 

[DefyG]

Looks like the neutral link for the RHS RCD is taken from the wrong Neutral bar at the top (In position 8?)
It should be from the LHS Neutral bar.
The original photo shows 4No thick Blue link cables whereas the video shows 3 but 2No in the middle neutral bar.

 

[brianmoooore]

Agree. There are three neutrals in the LH neutral bar, but there should be four. One in from the main switch, one to the SP, and one each to the two RCDs.

 

[mainline]

Maybe better to call a decent electrician in to install it properly.

 

[littlespark]

I thought hes done pretty well for a non pro.

I've seen worse in the wild by those registered with a CPS.

Its just been simply a case of the wrong neutral bar, and hopefully its fixed now.



Of course, though, it will need tested and certified....

 

[mainline]

I thought hes done pretty well for a non pro.

What makes you think he's not a pro ? Doing such a nice job.

I've seen worse in the wild by those registered with a CPS.

I don't know what that's got to do with it.

Its just been simply a case of the wrong neutral bar, and hopefully its fixed now.

The first pic showed Cu pre wired initially which was then altered I wouldn't call that a simple mistake,

Of course, though, it will need tested and certified....

It needed to be tested before being energised not after.

 

[Chippyminton0]

Thanks littlespark, I'm doing my house up, ive rewired most of it just the ground floor ring left to do. The wiring I did in the consumer unit doesn't look too Tudy mainly because I've been moving the circuits about trying to work this problem out. I can tidy it up now thanks to you guy . The neutrals in the board came as they were from the manufacturer. I have read that since honey well took over MK and then licenced it out to a chinese firm that the quality had gone right down hill. I wouldn't expect them to make a mistake like that.
Any way once the wiring is finished I am going to get it tested by an electrician.
I have one more question that maybe you could help with.
I have an unprotected mcb fed from the main switch. It's not protected by the spd. I want to run a supply through an isolator near the CU and out to the garage where it would be protected by a bidirectional rcbo. Is that permitted, does it conflict in anyway with the spd?

 

[Chippyminton0]

Looks like the neutral link for the RHS RCD is taken from the wrong Neutral bar at the top (In position 8?)
It should be from the LHS Neutral bar.
The original photo shows 4No thick Blue link cables whereas the video shows 3 but 2No in the middle neutral bar.

That's done the job, thankyou.

 

[Chippyminton0]

What makes you think he's not a pro ?


I don't know what that's got to do with it.

The first pic showed Cu pre wired initially which was then altered I wouldn't call that a simple mistake,

It needed to be tested before being energised not after.

Hi Thanks for your comments. Just to be clear the first pic was a screen shot from screwfix's website. It was a generic photo of the type of CU which i bought. The second one was my consumer unit, although I had not removed any of the neutrals from the neutral bar. The way you see it was the way I received it. I knew there was a neutral issue because it just made sense but it didn't occur to me that a manufacturer like MK would make an error like that. Which is why it wasn't obvious to me. Sometimes another set of eye will see the immediately even if it is staring me in the face. For peice of mind the whole house wireing will be tested. I apreciate your comment

 

[Chippyminton0]

Hi, I need some help locating and resolving a fault on a new consumer unit.
I removed an existing plastic MK Sentry duel 63amp RCD unit which worked fine and replaced it with a new metal MK Sentry duel 100amp RCD unit with a SPD.

No 1 RCD I had 5 circuits. No problems all worked fine.

No 2 rcd I had 4 circuits. (There are no appliances plugged in) when I put any load on any of the circuits it trips out No 1 RCD.
When number 1 trips, number 2 doesn't but the voltage at number 2 drops to 187v
I have removed all the circuits entirely and tried each on their own on No 2 rcd and the same thing happens.
The original board (which had no problems)had 2 x 64 amp RCDs which I know work. I replaced the 100 amp pair with these and still the same problem. I have put the 100 amp pair back on but swapped them around, still the same problem.

I have removed the surge protector, same thing happens

I have now put all the circuits on to number 1 RCD and every thing works fine with no tripping. However I don't want them all on 1 rcd, I can't afford rcbo's yet. But more importantly there is still an issue there that needs resolving.

Any ideas what it might be?

I apreciate any help

It works a treat now, thankyou for all your help. I'm not sure I would bother with MK anything in future

 

[littlespark]

Was it on special price?
You might have been able to get a Proteus, Fusebox or Hager full RCBO board for not much more.

You will need to fill the gap at the end though. Is that a bell transformer?

 

[littlespark]

What makes you think he's not a pro ? Doing such a nice job.


I don't know what that's got to do with it.

The first pic showed Cu pre wired initially which was then altered I wouldn't call that a simple mistake,

It needed to be tested before being energised not after.

His profile says “electrical enthusiast/ unqualified hobbyist” So, no, he’s not a pro. With a name like Chippy Minton, he’s either a joiner or lives in Camberwick Green

Just an observation. Not all sparks that are cps members are competent… in my opinion…
It’s like the cps give membership on however much the fee is, and the evidence of 1 job per year… which could cover dozens of workers.

Unintentionally altered. Once disconnected, it wouldn’t be hard to mistakenly put it in the wrong bar.

True. Maybe I should have said “report done on the house”

 

[plugsandsparks]

Unlucky for a DIYer to pick up a CU, wrongly pre-wired. I think an electrician would have said "what the *uck" when they opened the box and saw how the neutrals were wired, clearly incoming and outgoing neutral leads to the say bar was never going to work, i would hope a pro would have spotted it as they were mounting it.
Generally i take all the guts out anyway to mount the enclosure, do all the knock outs etc, so a wrongly wired Cu from factory is neither here no there.

 

[DefyG]

Generally i take all the guts out anyway to mount the enclosure,

Same as

 

[littlespark]

Your last question on message #12 that I don’t think anyone else has responded to….
The 32A mcb next to the mainswitch is for the SPD. You’ll need to connect that back up, and not use it for the outbuilding.
It’s not there as a spare.

Depending on how it’s wired, the supply to the the outbuilding may need to be rcd protected.
The final circuits from the outbuilding WILL need to be rcd protected.

 

[brianmoooore]

Apart from anything else, with the link to the SPD in the 'out' side of the MCB, it would probably be physically impossible to get another cable of the required size into that terminal.

 

[DefyG]

Your last question on message #12 that I don’t think anyone else has responded to….
The 32A mcb next to the mainswitch is for the SPD. You’ll need to connect that back up, and not use it for the outbuilding.
It’s not there as a spare.

Depending on how it’s wired, the supply to the the outbuilding may need to be rcd protected.
The final circuits from the outbuilding WILL need to be rcd protected.

Agreed and it isnt shown on the Screwfix screenshot! which doesnt show a mcb between the MS and SPD so again something doesn't quite ring true!
There are also 2 (albeit MK) mcb's installed that do not look like the sit well and may therefore not be compatible with that actual CU?

 

[littlespark]

None of the screwfix pictures show an mcb for the SPD… so maybe it doesn’t need one??

My comment still stands for possibly needing rcd protection for outbuilding cable.

 

[Avo Mk8]

The 32A mcb next to the mainswitch is for the SPD. You’ll need to connect that back up, and not use it for the outbuilding.
It’s not there as a spare.

The H6820s Sentry dual SPD (and their single module version) has an internal fuse, and according to MK (though difficult to find the info) does not require additional MCB protection.
Just thought I'd mention for the OP's benefit.
Sorry - posted before I saw your amendment above!

 

[Chippyminton0]

Your last question on message #12 that I don’t think anyone else has responded to….
The 32A mcb next to the mainswitch is for the SPD. You’ll need to connect that back up, and not use it for the outbuilding.
It’s not there as a spare.

Depending on how it’s wired, the supply to the the outbuilding may need to be rcd protected.
The final circuits from the outbuilding WILL need to be rcd protected.

Hi little spark once again thankyou for your reply. The sdp doesnt have an mcb. There wasnt one connected to it and i checked on MK's website which says that type of SPD doesnt need one. I put the 32 amp mcb in between the spd and the main switch as there was enough slack to move the spd over a bit. I was hoping to leave it unprotected and conect it to the main switch with a busbar. I wanted to use it feed the garage . At the other end in the garage is a consumer unit with a main switch and a 32 amp 30ma bidirectional rcbo for protection. It was my understanding that having the garage supply running protected by a 32a 30ma rdc at the main consumer unit end and a 32a 30ma rcbo at the garage consumer unit would cause tripping issues.

(The bidirectional rbco is for a small solar invertor for a future project after the circuits have been tested by an electrician)

 

[Chippyminton0]

Was it on special price?
You might have been able to get a Proteus, Fusebox or Hager full RCBO board for not much more.

You will need to fill the gap at the end though. Is that a bell transformer?

I was being lazy/cautious maybe. I didn't want to extent the tails to the meter. The main switch on the MK was on the same side as the original which meant I could use the same tails. I bought a fuse board CU for the garage. It's seems like so much better quality than the MK. Ref to the RCBO board you are right. That is what I should have done

 

[Chippyminton0]

Was it on special price?
You might have been able to get a Proteus, Fusebox or Hager full RCBO board for not much more.

You will need to fill the gap at the end though. Is that a bell transformer?

Shelly 3em

 

[Chippyminton0]

Was it on special price?
You might have been able to get a Proteus, Fusebox or Hager full RCBO board for not much more.

You will need to fill the gap at the end though. Is that a bell transformer?

The gap filler was broken when I took it out on the box. I'm going to get one from screwfix today

 

[Chippyminton0]

Agreed and it isnt shown on the Screwfix screenshot! which doesnt show a mcb between the MS and SPD so again something doesn't quite ring true!
There are also 2 (albeit MK) mcb's installed that do not look like the sit well and may therefore not be compatible with that actual CU?

Well spotted, I was short 2 6 amp mcb's. I put two of the ones from the previous CU in it yesterday until I could get 2 new ones today.
When I got the cu there where two small pieces of plastic rattling around in the box. It turns out they where the clips for the back of the blanking cover for the gap at the end of the rcds. My guess is either MK really does have appalling QC or someone has had that box already and returned it back to screwfix.
Apparently that sdp doesn't need a mcb. I squeezed it between the main switch and SPD with the intension of supplying it from the main switch with a busbar and using it to supply the garage where it would be protected with a bidirectional rcbo.
Would that work or do you think I should take it out and forget about the idea?

 

[brianmoooore]

It is preferable that the supply to the garage isn't RCD protected, but that depends on whether the cable between the two is required by its type or installation method to be so protected. SWA doesn't need RCD protection, as long as the supply earthing isn't TT.

 

[Chippyminton0]

It is preferable that the supply to the garage isn't RCD protected, but that depends on whether the cable between the two is required by its type or installation method to be so protected. SWA doesn't need RCD protection, as long as the supply earthing isn't TT.

Hi Brian,

The cable is 6mm 2core and earth armoured swa. It will be earthed back to the main CU which is earthed to the incoming main as in the photo.
I have to mention though the I have installed a separate earth rod purely for off grid DC, solar panels, mttp charge controller and Battery which is in/on the garage. This rod is 20m away. Could that potentialy cause an issue?

 

[littlespark]

That photo looks like the incomer from the street.

 

[Chippyminton0]

Joiner

 

[Chippyminton0]

Joiner

His profile says “electrical enthusiast/ unqualified hobbyist” So, no, he’s not a pro. With a name like Chippy Minton, he’s either a joiner or lives in Camberwick Green

Just an observation. Not all sparks that are cps members are competent… in my opinion…
It’s like the cps give membership on however much the fee is, and the evidence of 1 job per year… which could cover dozens of workers.

Unintentionally altered. Once disconnected, it wouldn’t be hard to mistakenly put it in the wrong bar.

True. Maybe I should have said “report done on the house”

That photo looks like the incomer from the street.

It is the incoming main from the street