EICR codes - school

[snipersmith87]

Hi all

Currently carrying out an EICR on a senior school. I constantly find myself questioning my codes as I always go on the side of caution and appreciate I can possibly be a bit too harsh? From the minute I got my testing I was thrown out on my own and have pretty much self taught since then....Just after some feedback guys.

T and E clipped direct low level around around skirting in classroom - C2 (minimal mechanical protection - cable susceptible to damage)
FP cable clipped direct in canteen to low level socket - C2 (cable susceptible to damage from external influences resulting in potential danger. Cable also has No RCD protection)
MICC cable run low level around class wall - C3 (cable susceptible to damage from external influences - unlikely to result in potential danger / RCD protected)

I have coded these as 90% of the circuits in a school are run in conduit or trunking. For the obvious reason of mechanical protection.

16Amp MCB - Radial supplying 4 x 13Amp twins also supplies a 16Amp Commando (C2 - Commando is currently supplying a double 13Amp socket with a 16Amp plug on a piece of equipment. No signs of thermal damage. However my outlook is if ever the layout changed there’s the potential to overload cable if a 16Amp piece of equipment was plugged in)

No RCD protection for socket outlets for internal use - C3
What are views on RCD protection in schools?
The majority of the RCD are also AC type. Should I be coding these a C2 with the potential of DC current masking a fault and RCD not tripping?? (Computers , Printers etc.)

.....Help me

 

[davesparks]

Hi all

Currently carrying out an EICR on a senior school. I constantly find myself questioning my codes as I always go on the side of caution and appreciate I can possibly be a bit too harsh? From the minute I got my testing I was thrown out on my own and have pretty much self taught since then....Just after some feedback guys.

T and E clipped direct low level around around skirting in classroom - C2 (minimal mechanical protection - cable susceptible to damage)
FP cable clipped direct in canteen to low level socket - C2 (cable susceptible to damage from external influences resulting in potential danger. Cable also has No RCD protection)
MICC cable run low level around class wall - C3 (cable susceptible to damage from external influences - unlikely to result in potential danger / RCD protected)

T&E is designed to be clipped direct, what exactly is the source of the mechanical damage you can forsee for this? Is there any sign of damage having occurred? In what way is this potentially dangerous? I would have said it a recommended improvement (C3) at best.

Again FP200 is designed to be clipped direct, and has the advantage of an earthed metallic screen. Are there any particular potential sources of mechanical damage you can see or is there any sign of damage having occurred? The cable does not require RCD protection.

MICC is the most mechanically strong cable you could install, and as far as impact from blunt objects go it is equal to if not better than steel conduit. No code for this.

 

[Dustydazzler]

There does seem to an urban myth surrounding twin & earth that it must never be installed direct on to brick work and if you come across it then code it dangerous.
twin and earth was pretty much designed to be clipped onto stuff.
it only becomes a danger if it has been mullered by some careless numpty kicking or bashing it...

 

[snipersmith87]

Its more the environment thats my concern.

The T and E is clipped low level skirting then up onto window sill which is being used for storage also. Approx 10m run.

The FP again is located canteen by seating area. No signs mechanical damage.

Its just the norm for us to install in conduit or trunking in schools etc. Hence why i feel its not sitting right with me to see clipped direct. More the environment.

 

[Dustydazzler]

I once did was on a big new school project and we used 20mm white pvc conduit for all the drops etc.
Went back a few years later for other works and during that time someone had been in to fit powered white boards and run black flex cable tied all down the outside of the conduits to the sockets to plug into...

 

[snipersmith87]

There does seem to an urban myth surrounding twin & earth that it must never be installed direct on to brick work and if you come across it then code it dangerous.
twin and earth was pretty much designed to be clipped onto stuff.
it only becomes a danger if it has been mullered by some careless numpty kicking or bashing it...

......it’s the latter part of your reply that I’m worried about!!!

 

[James]

sometimes we need a reality check.
how many times have you been called out to repair a bit of twin and earth that has been clipped to a wall and damaged?
in my case it is rare to the extreme. I am not sure if it has ever happened.

trailing cables run over by office chairs, extension leads under desks, the flex on a vacuum cleaner that is constantly wound round the handle then unwound again, isolators that are plastic with things leant up against them.
damaged and broken all the time, often taped up many times before being called in to fix them.

regular inspection and maintenance is important, most issues can be picked up visually by the on site maintenance team but often they prefer to take a step back and say the installation is safe because I have a certificate that says so, from 18 months ago and is not due to run out for another 18 months.

sometimes in our quest to cover our own back sides we will err on the side of caution and declare something that is in all honesty 99% safe as a defect "just in case"

 

[davesparks]

16Amp MCB - Radial supplying 4 x 13Amp twins also supplies a 16Amp Commando (C2 - Commando is currently supplying a double 13Amp socket with a 16Amp plug on a piece of equipment. No signs of thermal damage. However my outlook is if ever the layout changed there’s the potential to overload cable if a 16Amp piece of equipment was plugged in)

Is the cable correctly sized for the 16A MCB? If so then how can it be overloaded when the overload protection is set at 16A?

 

[snipersmith87]

Is the cable correctly sized for the 16A MCB? If so then how can it be overloaded when the overload protection is set at 16A?

Currently no....potentially yes. My concern is if the layout changes and they supply a 16Amp piece of equipment amongst the sockets that are already supplying items, the cable and the MCB could ‘potentially’ be subject to pulling more than designed for. A 16A MCB operating above its rated capacity, however not tripping the breaker. Likewise for the cable.

 

[GBDamo]

Currently no....potentially yes. My concern is if the layout changes and they supply a 16Amp piece of equipment amongst the sockets that are already supplying items, the cable and the MCB could ‘potentially’ be subject to pulling more than designed for. A 16A MCB operating above its rated capacity, however not tripping the breaker. Likewise for the cable.

Couldn't the same be said for any multi-point socket circuit?

Am I missing somerhing, is it the 16A socket or the cable or both you're concerned about?

If it was a 16A socket on a larger MCB then yes, potential for the socket to be used exceeding it's design rating.

Which ever way, surely the 16A MCB protects?

 

[snipersmith87]

Couldn't the same be said for any multi-point socket circuit?

Am I missing somerhing, is it the 16A socket or the cable or both you're concerned about?

If it was a 16A socket on a larger MCB then yes, potential for the socket to be used exceeding it's design rating.

Which ever way, surely the 16A MCB protects?

The same way in how any cable can be subject to overload despite being protected by an ocpd. Poor design can overload a cable and not trip the breaker. Its a 16A mcb....protecting 5 x twins and a 16amp commando. My argument is if they happen to plug in a 16amp piece of equipment amongst the twins already supplying various equipment. The cable could be subject to overload and the MCB operating above it capacity whilst not tripping. I would normally install commandos on dedicated circuits for the very reason im stating... they draw more current.
[automerge]1572561591[/automerge]
Would you install a 16amp oven on a radial amongst 5 x twins??

 

[ipf]

[automerge]1572561591[/automerge]
Would you install a 16amp oven on a radial amongst 5 x twins??

Maybe not but, even if in such a case, a 16 amp mcb would suffice, as long as the cable is up to it. IMO

 

[Deleted member 122525]

The RCD protection is an interesting point within schools, I do a lot of work in schools, refurbs, new builds and EICR, when doing EICR, if there is no RCD protections on sockets, its always a C3 within West Sussex schools, with the exception of science labs (10mA RCD to be used) and food tech kitchen (30mA RCD to be used) on sockets, as long as the earth fault loop values are correct for the Circuit. The Gray area that I have picked up on is, if you are able to plug an extension lead into a ground floor socket and take it outside, or corridor sockets where cleaners may be plugging in hoovers or floor polishing machines. Where I would still put this as a C3 but with a foot note explaining my findings and concerns.

 

[snipersmith87]

Thankyou for the replies.
The general feedback I'm feeling is that im possibly going 'too' worse case scenario due to the environment and perhaps not the way I'd install it but not neccessarily wrong. Its always good to have a sense check amongst fellow professionals. I find EICR can be a lonely game at times.

Are people coding AC type RCDs?? Just making a comment?? Where do we stand with this??

 

[davesparks]

The same way in how any cable can be subject to overload despite being protected by an ocpd. Poor design can overload a cable and not trip the breaker. Its a 16A mcb....protecting 5 x twins and a 16amp commando. My argument is if they happen to plug in a 16amp piece of equipment amongst the twins already supplying various equipment. The cable could be subject to overload and the MCB operating above it capacity whilst not tripping. I would normally install commandos on dedicated circuits for the very reason im stating... they draw more current.
[automerge]1572561591[/automerge]
Would you install a 16amp oven on a radial amongst 5 x twins??

Any general purpose socket circuit has the same potential for overload. A twin socket on a 16A MCB could be overloaded the same way.

Commando sockets don't draw more current, they load connected to them draws the current.

Maybe I'm looking at it differently because it's perfectly normal for us to install 13A, 15A and 16A outlets on the same circuit.

 

[snipersmith87]

Any general purpose socket circuit has the same potential for overload. A twin socket on a 16A MCB could be overloaded the same way.

Commando sockets don't draw more current, they load connected to them draws the current.

Maybe I'm looking at it differently because it's perfectly normal for us to install 13A, 15A and 16A outlets on the same circuit.

I agree. However General purpose sockets do get overloaded. Extension leads get overloaded. Worse case scenario an overload that isnt enough to trip the ocpd and create a fire hazard. It does happen. We all design circuits to prevent overload or minimise it to short durations.
In my head a 16amp commando is to supply a piece of equipment that is potentially gonna draw more than 13amps....hence why its not on a 13amp plug top.
Put that load on a 16amp mcb. Along with a tea urn... etc etc. The mcb could be operating above its 'designed' loading due to additions over time.

 

[Dustydazzler]

I agree. However General purpose sockets do get overloaded. Extension leads get overloaded. Worse case scenario an overload that isnt enough to trip the ocpd and create a fire hazard. It does happen. We all design circuits to prevent overload or minimise it to short durations.
In my head a 16amp commando is to supply a piece of equipment that is potentially gonna draw more than 13amps....hence why its not on a 13amp plug top.
Put that load on a 16amp mcb. Along with a tea urn... etc etc. The mcb could be operating above its 'designed' loading due to additions over time.

Once you get to about 18-20 amps for even a relatively short period most 16a mcbs will operate. Most cable attached to a 16a device should be good for at least 20 amps for a good while.
I saw a test where JW put 80+ amps through some 1.5 csa cable and it took ages for it to start smoking and melt.
20 ish amps wouldn’t even make a dent

 

[davesparks]

I agree. However General purpose sockets do get overloaded. Extension leads get overloaded. Worse case scenario an overload that isnt enough to trip the ocpd and create a fire hazard. It does happen. We all design circuits to prevent overload or minimise it to short durations.
In my head a 16amp commando is to supply a piece of equipment that is potentially gonna draw more than 13amps....hence why its not on a 13amp plug top.
Put that load on a 16amp mcb. Along with a tea urn... etc etc. The mcb could be operating above its 'designed' loading due to additions over time.

Yes that could cause an overload, however the ocpd will operate according to its tripping curve.
The tripping time of the OCPD is taken in to account in the current rating of the cable, they don't reach ignition temperature the moment they see 0.1A more than the ocpd rating.

A 16A socket is used to supply anything with a 16A plug on it, there's more than one reason for doing this.

In the OP you say that it is currently supplying a 16-2x13A adaptor, so it's no different having another 13A twin socket on the circuit.
Yes the layout could change in the future, but then it could also stay the same for the next 10 years, that's unpredictable.
By this same logic you could say that any circuit could be altered in the future and therefore should be coded.

 

[snipersmith87]

Yes that could cause an overload, however the ocpd will operate according to its tripping curve.
The tripping time of the OCPD is taken in to account in the

Yes that could cause an overload, however the ocpd will operate according to its tripping curve.
The tripping time of the OCPD is taken in to account in the current rating of the cable, they don't reach ignition temperature the moment they see 0.1A more than the ocpd rating.

A 16A socket is used to supply anything with a 16A plug on it, there's more than one reason for doing this.

In the OP you say that it is currently supplying a 16-2x13A adaptor, so it's no different having another 13A twin socket on the circuit.
Yes the layout could change in the future, but then it could also stay the same for the next 10 years, that's unpredictable.
By this same logic you could say that any circuit could be altered in the future and therefore should be coded.

I agree Dave. Just overthinking as usual...(Or underthinking!)

 

[Lucien Nunes]

Which ever way, surely the 16A MCB protects? The same way in how any cable can be subject to overload despite being protected by an ocpd.

If the Iz of a cable is 16A after the necessary factors are applied, it means that it is large enough to be adequately protected by 16A OCPD, not that its absolute limit is 16A. In effect, a cable that the calcs say is derated to 16A will actually carry at least 16 x 1.45 = 23A. But you can't use it at that current if it's protected by (e.g.) a 60898 because to be guaranteed to trip at 23A, you have to use a 16A device which makes 16A the maximum usable Ib.

And re MICC, if that needs protection against school pupils, the school has bigger problems than its EICR results.