Acceptable incoming voltage from substation to shop outlet

[Nadz]

Hi,

I was wondering if anyone would know what the acceptable minimum and maximum on a single/three phase main incoming voltage should be. From what I have gathered you have a tolerance of +10 230V -6. Could you also quote from where it is mentioned in the wiring regs.

Thanks.

 

[Knobhead]

Could you do you're own homework?

 

[SirKit Breaker]

Uo is 230v, the answer is staring you in the face in BS7671, and it is easy to find.

Cheers..........Howard

 

[Jimmy Boy]

Hi,

I was wondering if anyone would know what the acceptable minimum and maximum on a single/three phase main incoming voltage should be. From what I have gathered you have a tolerance of +10 230V -6. Could you also quote from where it is mentioned in the wiring regs.

Thanks.

Instead of 'wondering' what about getting finger out your backside and get your nose in 7671 and learn some stuff ?..it's all there if you can be bothered to look !..ask a decent tech question and you might get a decent reply !
J

 

[Nadz]

Uo is 230v, the answer is staring you in the face in BS7671, and it is easy to find.

Cheers..........Howard

Yes, your right the answer is staring me in the face, min voltage 216.2V and max voltage 253V, the problem is someone has installed
a new A.C. unit and it doesn't power up, all the connections are correct, there is a supply of 217V at the spur. Is it possible it doesn't start due to the voltage being 217V.

thanks.

 

[HandySparks]

Yes, your right the answer is staring me in the face, min voltage 216.2V and max voltage 253V, the problem is someone has installed
a new A.C. unit and it doesn't power up, all the connections are correct, there is a supply of 217V at the spur. Is it possible it doesn't start due to the voltage being 217V.

thanks.

What else have you checked to find the fault? My guess is that supply on bottom limit is unlikely to be the problem. What exactly happens? Any indicator lights on or is it totally dead?

Have you done any fault finding inside the AC unit? How far into the unit is the supply voltage getting?

Also, what is the supply voltage at the origin of the installation? ie, is this supply voltage issue due to volt drop within the installation or is it an external problem?

 

[Knobhead]

Have you done any fault finding inside the AC unit? How far into the unit is the supply voltage getting?

That's in his next question.

 

[Engineer54]

Yes, your right the answer is staring me in the face, min voltage 216.2V and max voltage 253V, the problem is someone has installed
a new A.C. unit and it doesn't power up, all the connections are correct, there is a supply of 217V at the spur. Is it possible it doesn't start due to the voltage being 217V.

thanks.

If it's a ''New'' A/C unit, what are you messing abound with it for, get the suppliers/installers back to sort the problem out!! What is this AC unit, a split system, or an all in one wall banger??

At 217V the FCU unit would still show signs of life even if the compressor didn't.

 

[Nadz]

What else have you checked to find the fault? My guess is that supply on bottom limit is unlikely to be the problem. What exactly happens? Any indicator lights on or is it totally dead?

Have you done any fault finding inside the AC unit? How far into the unit is the supply voltage getting?

Also, what is the supply voltage at the origin of the installation? ie, is this supply voltage issue due to volt drop within the installation or is it an external problem?

The information I had was from the company installing the units which is a three phase unit, who said there is supply at the isolator and in the unit itself but because of the difference of voltage and the voltage income being low there system cannot function properly.

I have been to the premises and tested the incoming voltage supply L1 - N reads 216V which is not acceptable, L2 - N is ok, L3 - N is ok, L1 - L2 is 378V which is not acceptable, L2 -L3 is ok, L1 - L3 is ok. The problem is an external problem.

I have spoken to the client and have agreed upon righting a report in which he can issue the report to the responsible party, to increase the voltage at the substation.

This hopefully should resolve the problem.

Thanks

 

[malcolmsanford]

What protection device have you got there ...................often if your have dropped a phase the other 2 phase compensate and you still get a lower voltage reading on the dropped phase.

If you have fuse check that L1 fuse as not blown, if you have an MCB take the load out of the breaker and check to see what voltage you have then.

You maybe right and there is an external fault, but I would just check this also, after all if it is this, then your client would not be best pleased

 

[Nadz]

What protection device have you got there ...................often if your have dropped a phase the other 2 phase compensate and you still get a lower voltage reading on the dropped phase.

If you have fuse check that L1 fuse as not blown, if you have an MCB take the load out of the breaker and check to see what voltage you have then.

You maybe right and there is an external fault, but I would just check this also, after all if it is this, then your client would not be best pleased

I cannot physically get to the main fuses due to shop design not allowing access to the main fuses, even if i could the owner would not be pleased if i have to knock off the supply as the shop is open 22hrs of the day.

I will write the report anyone, who ever is responsible or who deals with incoming supplies to the building will have to send down their own engineer to verify what is on the report and they will have the same findings and I would like to see the outcome.

cheers nadz

 

[malcolmsanford]

Why are you wanting to get to the main fuses? They are not your concern.

I'm guessing that this unit is not wired directly out of the main fuses but via a distribution board, that is where I would check first for that dropped phase

 

[snowhead]

I cannot physically get to the main fuses due to shop design not allowing access to the main fuses, even if i could the owner would not be pleased if i have to knock off the supply as the shop is open 22hrs of the day.

I have been to the premises and tested the incoming voltage supply L1 - N reads 216V which is not acceptable,

So the measured voltage 216v etc is with load switched on elsewhere in the premises?

Where exactly did you measure that if you can't get near the incomer?

And what about going in during the other 2 hrs of the day / night? (must be a convenience shop?)

The DNO won't be changing Transformer tapings just because you have 216v, the rest of the customers in that area would see the increase as well.