PIR codes

[IQ Electrical]

Have you used the adiabatic equation (if permissable) to determine the minimum cpc size that would comply?

 

[monkeyelectric]

Have you used the adiabatic equation (if permissable) to determine the minimum cpc size that would comply?

I think he's done a runner after posting the same question 3 times

 

[IQ Electrical]

I think he's done a runner after posting the same question 3 times

Ah well, his loss!

 

[kobie1978]

Pme vs TT

Hello all first post so go easy. I am presently carrying out condition reports on a chain of pubs my company started doing them 5 years ago when I joined my firm last year I was made aware I would be doing most of testing. I was quite happy about this got me outta the filth same money but rewarding in my eyes. Anyway what's your take on this Pub has Pme but was lacking power for domestic/commercial kitchen. Well there's a caravan plot next door owned by pub where a nic company took a supply including staked earth and run a sub main to pub Pme origin. This to me is **** but hey a few stickers and I would be of with it. But to take 2 x10mm earth's from switch fuse in pub straight into Pme met block! And here is my problem it's been bugging me I graded this with c2 potential danger should it be a c1 immediate danger due to what is essentially a high risk situation waiting for a fault to occur and kill someone.
I appreciate any and all responses

 

[Richard Burns]

I think that this is an inappropriate situation but as you have said it is "waiting for a fault to occur and kill someone" therefore it is a C2 as there is no immediate danger unless a fault occurs.
I am pretty sure that connecting an existing supply to the DNOs PME earthing is not legal might be interesting to put that in comments (but check legality first!)

 

[NoSparks]

Re: Pme vs TT

there's a caravan plot next door owned by pub where a nic company took a supply including staked earth and run a sub main to pub Pme origin. .... But to take 2 x10mm earth's from switch fuse in pub straight into Pme met block! And here is my problem it's been bugging me I graded this with c2 potential danger should it be a c1 immediate danger due to what is essentially a high risk situation waiting for a fault to occur and kill someone. I appreciate any and all responses

I don't think there is any danger here at all.

First make sure I understand the configuration: Switch fuse in Pub close to supply head with final earth consisting of 2x10mm cables. Sub main from pub to caravan with CU in caravan. Caravan CU earthed with local earth rod. I cannot make out if you imply the submain has an earth and if it is also connected to the earth in the caravan CU. I am assuming that the caravan is fixed and is being considered as an Mobile Home (or outbuilding) rather than a Caravan as described in Reg 721.

First the 2x10mm earths. My understanding is that it is permissable to use two thinner cores wired in parallel to form a cable so long as they are of equal length and will therefore share the load correctly. In this case 2x10 being 20mm total exceeds the requirement for a 16mm earth (assuming a 25mm supply).

Second the earthing of the caravan. There have been many discussions on this board re "exporting" the equpotential environment of the supply head, some beleiving that you should do this, some beleiving you should create a seperate equipotential environment by installing a TT system in the out building. I don't know if there is any recent edict on this, but look at it in these ways. If the earth of the sub main is connected in the caravan then the earth rod can be considered as an extranious item of mental connected to the caravan (even if only through its own cable) and must therefore be bonded with a minimum of 10mm. If the earth of the submain is not connected then it is a TT system, should be fitted with a 100mA RCD and earthed with a minimum of 2.5 or 4mm (according to mechanical protection). To me both approaches are valid and present no risk.... or have I misunderstood somthng?

A side issue would be the size and nature of the earth conductor in the sub main. If it is for example a 10mm T&E supply then the earth would be undersize to act as bonding, while a 10mm core of a SWA cable would be. Then again some supply companies will not accept the earth included in a SWA cable as a bonding cable and require a seperate bonding cable connected directly to the met, exactly as shown in the Regs. Note also though that if the caravan were considered to be within the scope of Reg 721 then the bonding of the caravan must be to the earth of the incomming supply.