Oh dear... time for school!

[AdrianUK]

Had an interesting one today ...

One of our installation engineers is due to visit a certain University, situated on the South Coast, to install one of our products... the details of the product aren't important... only that it requires a 230V supply with a capacity of at least 28A.

Our preferred way to connect this is using a 32A BS4343 'ceeform' plug & socket ... either a blue single phase or utilising 1 phase & neutral from a red 3 phase outlet. All bog standard stuff, you would think....

The Universities' "Electrician" has stated, in writing, that we cannot utilise the 32A 3P+N+E BS4343 socket in the laboratory because "its only 32A when used three phase. If you only use it single phase then it can only deliver 10A". He is being most insistent about this, saying that I don't understand electricity and shouldn't have anything to do with 3 phase if I 'cant get the basics right'

Oh dear I think he needs to attend a few classes of his own!

 

[deadshort]

Hi, how do you know it's not wired 10a per phase ?

Regards,

DS

 

[AdrianUK]

Hi, how do you know it's not wired 10a per phase ?

Regards,

DS

And it might be ... but a little 'odd' don't you think......and why not fit a 16A BS4343 if it is?

If I had fitted the outlet & had to down rate it, for whatever reason, I would have clearly labelled it with the max current available. Not an unreasonable assumption, don't you think, to expect a 32A outlet to be good for 32A?

 

[deadshort]

It's a Lab so it could be for a motor or hydraulics or just restricted to 10a due to supply restrictions.

Regards,

DS

 

[AdrianUK]

It's a Lab so it could be for a motor or hydraulics or just restricted to 10a due to supply restrictions.

Regards,

DS

True.... but his phrasing .... "you can only take 32A if its three phase" ... seems to suggest that this guy thinks you can add together the phase currents... why not simply state "sorry, that outlet is only good for 10A per phase" ......

 

[deadshort]

That's not what he said ! The phrasing of his phasing!!could be better, but i understood his meaning


DS

 

[RF Lighting]

If it's a 32A TP&N supply then there should be 32A per phase available.

Maybe the university has a 10A TP&N supply terminated on a 32A outlet, but this would be a highly unusual setup.

 

[ban-all-sheds]

Ask him to tell you what it says on the 3P breaker where the circuit originates.

 

[ericmark]

I suppose there could be a problem with phase balance if using a motor overload I seem to remember this

type does have something which means there is a maximum differential between phases. 10A does seem a little high if that is the case.

Using 3 phase 110 volt (63-0-63) I seem to remember a 16A socket had a maximum of 10A per phase when split into three single phase sockets.

At University I noted many basic mistakes. One I have talked about before was AB PLC's used without being in an enclosure. Be it no kick boards on landings and stairs or electrical faults they seem not to practice what they teach.

In different places I would get requests for supplies. 100A battery charger required a 63A supply when battery was 48 volt. It seemed rather big but it transpired it was the inrush a 32A C type would have done fine.

It is easy to make mistakes we tend to not always work out why something has happened. So if in the past the electrician had tried to use something requiring 32A and it tripped the MCB it would be easy to jump to wrong conclusions.

In one job we had problems with loads of different plugs so standardised on 5 pin 32A 'ceeform' but often the MCB's feeding the plug remained as they were. I had huge arguments over having 5 pin sockets with no neutral in the end I won them around but likely there would be the odd socket missed when we swapped back to 4 pin.

But at the end of the day you ask for a 32A supply and the University has to provide it you don't want to get involved if they have employed one of their failed students as an electrician.

Just smile and wave boys just smile and wave. (Spent too long on the Falklands)

 

[securespark]

Ask him to tell you what it says on the 3P breaker where the circuit originates.

At the risk of sounding like Pam, Oh my Christ!

Am I agreeing with Ban?

 

[AdrianUK]

Ask him to tell you what it says on the 3P breaker where the circuit originates.

At the risk of sounding like Pam, Oh my Christ!

Am I agreeing with Ban?

I have .... strangely..... there has been no reply .......... although, even if it says 'D32A' .... I suspect that he'll decide that means 3 x 10.67A = 32A !!!!!!

Its true that there could be a 'standard' of 32A TP&N plugs for everything ... even small loads. But would that not present a problem when a small load, say, 3A per phase, fitted with 0.75mm2 cable is fitted with a 32A plug which could then be inserted into a different 5pin socket which was fully rated & backed up by, say, a D32A MCB!

I did get caught out by the use-5-pin-ceeforms-for-everything-even-if-no-neutral-present in Indonesia. Took a little time before the penny dropped! Fortunately it only destroyed a control transformer.

 

[plugwash]

You could also have a circuit with an undersized neutral. Fine for a three-phase motor with a small power supply for the controls. Not so good for a large single phase load connected phase-neutral.

 

[ban-all-sheds]

I have .... strangely..... there has been no reply .......... although, even if it says 'D32A' .... I suspect that he'll decide that means 3 x 10.67A = 32A !!!!!!

Ask again.

Keep on asking.

If he keeps on ignoring you, or does reply with nonsense like that, then write to the Vice Chancellor telling him that he is employing an incompetent person and therefore the university is in breach of the EAWR and you intend to inform the HSE of this fact.

 

[AdrianUK]

You could also have a circuit with an undersized neutral. Fine for a three-phase motor with a small power supply for the controls. Not so good for a large single phase load connected phase-neutral.

True... and I agree that would pose a single phase limit..... but couldn't you only do that on distribution circuits (and not general purpose outlets) & didn't they get 'banned' after the 15th edition?

 

[JohnW2]

You could also have a circuit with an undersized neutral. Fine for a three-phase motor with a small power supply for the controls. Not so good for a large single phase load connected phase-neutral.

Is that actually allowed (for a circuit feeding a socket)? I would have thought that if there is a neutral, it would be required to be large enough to cope with a very unbalanced load, or even a single-phase one?

Kind Regards, John