EICR in a commercial premises, no RCD protection

[BBDESIGN]

we are currently completing an EICR on a currently redundant ambulance station soon to be re-opened.
The budget for the works is very tight after reading the scope, the PC for the job has said if items do not need upgrading then do not do them.

the scope stats the consumer units should be upgraded due to lack of rcd's and this will cause it to fail and EICR.

i know from previous PIR's this is not the case.

you do not need the installation to be up to current regs as long as its safe.

we have been asked to install a new kitchen ring so i know we need an rcd for this,
need some guidance on cheapest methods of going about this to safe the PC money and for us to not recommend work that will not need doing.

a suggestion was made to use dual rcd boards, but in commercial properties i prefer individual RCBO'S but again this increases costs.

help??

 

[Brightspark2]

Your making your report to current regulations...

Why do they say it needs upgrading. If it is for socket outlets for general use (but not outside use) then this would just be a C3.

Have a look at the ESC best practice guide for EICR codings...

 

[Hobsoni]

"If they are installed to a previous edition of regulations then that's ok' ( I know my quote is not word for word). BUT, do you have the testing records from when it was installed to the previous edition?

 

[SPARTYKUS]

Wilts wholesaler, "CONTROL GEAR" boards, 14 way, with main switch and 8 RCBOs, £99+ the inevitable VAT, I'm sure that money in the PC isn't that tight!!!

 

[Brightspark2]

Wilts wholesaler, "CONTROL GEAR" boards, 14 way, with main switch and 8 RCBOs, £99+ the inevitable VAT, I'm sure that money in the PC isn't that tight!!!

Now that is cheap...

 

[Farmelectrics]

And £300 to install it lol

 

[nickblake]

In commercial premises if your installing RCD then RCBO's are a must forget your dual RCD boards pain in the but and could be very costly if they trip

 

[davesparks]

In commercial premises if your installing RCD then RCBO's are a must forget your dual RCD boards pain in the but and could be very costly if they trip

If you mean SPSN RCBOs then yes, SP RCBOs are a poor alternative to a dual RCD board.

 

[Knobhead]

SP RCBO’s should never have got on the market. They’re not fit for purpose!

 

[dingledong]

Please explain , why not

 

[telectrix]

as above^^. what reasons, please, tony.

 

[Knobhead]

What is the point of detecting a N→E fault and then only disconnecting the line. The fault isn’t cleared.

 

[dingledong]

But it has notified you that there is a fault where a breaker wouldn't

 

[davesparks]

But a breaker isn't designed to and would never be expected to.

An mcb or fuse detects overcurrent or fault current flowing through the line and then disconnects the line.

A SP RCBO detects a fault between neutral and earth and then disconnects the line! What the hell does that achieve, the fault is still there and just as much diverted neutral current will be making toast of that cable.

 

[telectrix]

agree with above, but the prime purpose of a RCD/RCBO is additional protection for a situation where a person is in contact with a live part. 9 time out of 10, this would be a live part connected to the line conductor or that conductor itself. by disconnecting the line conductor from the supply, the danger is removed. it's going to be a rare occurence for the N to pose a danger if the L is dissed.

 

[Knobhead]

You can get substantial currents in a N→E fault. Not necessarily from the circuit involved. The SP RCBO will detect but not disconnect the fault whereas SPSN or DP will.

Under no circumstances should SP RCBO’s alone be used on a TT supply. I know it’s not the case here, I’m making the point.
How many times do we get threads on here “I’m changing a CU on a TT supply”? Members blithely come back with “fit RCBO’s”. The worse advice that could be given unless the type is specified.

Tel, you of all people should appreciate the problem.

 

[Silly Sausage]

You can get substantial currents in a N→E fault.

Being lazy here...
Assuming negligible conductor impedances, am I right in saying that half of the installation current would be flowing through the faulty circuit's cpc and off down the supply Earth?

Could be interesting with a 1 mil cpc.

 

[Knobhead]

In the ideal world with as you say negligible impedance then yes, half the current would take the N→E rout.
I don’t know about a 1mm CPC, it would become a fuse.

I know you’ve read the article about transformers elsewhere. I explained why impedance is introduced in to the star point of MV transformers. The N→E fault level could be of such magnitude as to melt the cable lead sheath and armourings.

 

[Silly Sausage]

I think I need to go and do some revision!

 

[dingledong]

Archy I am doing a course 3 days only 5 grand

 

[telectrix]

You can get substantial currents in a N→E fault. Not necessarily from the circuit involved. The SP RCBO will detect but not disconnect the fault whereas SPSN or DP will.

Under no circumstances should SP RCBO’s alone be used on a TT supply. I know it’s not the case here, I’m making the point.
How many times do we get threads on here “I’m changing a CU on a TT supply”? Members blithely come back with “fit RCBO’s”. The worse advice that could be given unless the type is specified.

Tel, you of all people should appreciate the problem.

i do, up to a point, but was just pointing out that a SP RCBO will do it's job in the majority of cases by dissing the L and removing the immediate danger when used for additional protection. fault protection is a different kettle of fish, especially in industrial installations.

 

[Knobhead]

i do, up to a point, but was just pointing out that a SP RCBO will do it's job in the majority of cases by dissing the L and removing the immediate danger when used for additional protection. fault protection is a different kettle of fish, especially in industrial installations.

You may as well say the fuse will only blow on Wednesdays.

It’s got nothing to do with industrial.

I’ve had a domestic N→E fault passing 25A. A SP RCBO would detect but not disconnect the fault.

Now do you see why they are not fit for purpose?

I can’t see how you can defend something with such a basic design flaw.

 

[jamie-spark]

One thing that puzzles me. It's great if the circuit requires rcd protection. What if it doesn't, N-E fault will still go undetected.

 

[Silly Sausage]

One thing that puzzles me. It's great if the circuit requires rcd protection. What if it doesn't, N-E fault will still go undetected.

Good point!

 

[Knobhead]

It is a good question.

You’re the domesticated lads, what protection would you normally use and what are the consequences of not protecting a circuit?
The only way I can think of is DP MCB’s. They will trip given a N→E fault of the magnitude that will cause damage to cables.
For some reason I can’t see you all rushing down that rout. There will be the usual cry of “it’s too expensive!” which is the usual cry with DP RCBO’s.

It all comes down to “how much are you willing to pay for safety?”

Not many circuits on an industrial site will be RCD protected. At the foundry I can only think of nine bits of kit on the two sections I looked after that was portable and therefore needing RCD protection. Not many considering the size of the plant.
Anything else that was portable was 110V from fixed transformers.

 

[Richard Burns]

The UK system is predicated on safety being disconnection of the line conductor, this obviously removes the shock hazard of the presence of a significant potential difference.
The hazard of having an undetected N-E fault (which I would expect to be present in about 50% of old domestic installs) is the ccc of the cables through which the fault current runs, the integrity of the connections of those cables (since earths generally tend to be ignored!) and the risk of sparking giving rise to fire.
In an otherwise well constructed installation an NE fault would split the current via N and E, since this halves the current in any conductor this helps avoid overcurrent problems, but the chance of the current from high powered circuits flowing through the cpc of say a lighting circuit brings the risk back up.
If all the connections are OK then there should be fewer problems with terminations than ccc of cables, particularly on earlier joints that tend to have a much larger terminal than strictly necessary for the current.
Again a good connection of all cables lowers the risk of arcing at faulty joints, though it is is often the main worry in thatched properties.

In general I am happy that single pole disconnection does not cause undue hazard, but in more modern installs the presence of RCD protection makes the nuisance value of unexpected tripping much higher because the single pole RCBO is not clearing the fault, the fault will be shifted to the next upstream device and cause unnecessary disconnection of non faulty circuits.
Single pole RCBOs may significantly reduce the fault current since the disconnected circuit is not generating a fault current and the fault point will be the highest resistance in the current path for the stray current so limiting the current flow via the fault.

 

[jamie-spark]

I work in industrial commercial installations. The only double pole RCBO,s and DP+MCBs configurations we install are EX or agricultural installs

Ex because of the hazardous area
Agricultural DP rcbos are install for discrimination of the back up 300ma rcd

In industrial it generally is only the socket outlets that require rcd protection. So as I said any other N-E fault would go undetected. Although sp rcbos would highlight the N-E fault by not resetting( although as others have stated the fault would still be in circuit )

 

[jamie-spark]

I work in industrial commercial installations. The only double pole RCBO,s and DP+MCBs configurations we install are EX or agricultural installs

Ex because of the hazardous area
Agricultural DP rcbos are install for discrimination of the back up 300ma rcd

In industrial it generally is only the socket outlets that require rcd protection. So as I said any other N-E fault would go undetected. Although sp rcbos would highlight the N-E fault by not resetting( although as others have stated the fault would still be in circuit )