Commercial tests

[r.bartlett]

I was asked by a maintenance manager today:

"If we added an additional 20a single phase supply on an existing consumer unit to power an air conditioner isolator to outside (we are doing the a/c install only) what test certificates of the new circuit are a legal requirement? "

The board is within it's inspection due date

He asked his subbie electricians (two different companies) and got two different answers..

Which isn't surprising as they both quoted for another job one insisted 32mm armoured was needed and the other said 16 mm was ok according to his calc...But we won't go into that and you can guess who won the job!

TIA

 

[RF Lighting]

EIC covering the new circuit only.

 

[ricicle]

There is no such size as 32mm². 35mm² is the closest. How far is this point/how is it routed from the distribution board as even 16mm seems way over the top ?

 

[securespark]

Even with a fair route round the building, I wouldn't envisage more than 10mm2...unless there are some serious derating factors in play.

 

[Lectrician]

I assume the A/C chap is confusing 16amp & 32amp with cable sizes.

 

[Iggifer]

Guys the SWA sizing calc was for another job, not the HVAC install

 

[r.bartlett]

Guys the SWA sizing calc was for another job, not the HVAC install

Yes you are right it was for a 100a supply running about 150m or so..

 

[r.bartlett]

I assume the A/C chap is confusing 16amp & 32amp with cable sizes.

no I made a simple mistake as it was 35mm sq not 32mm but as I say I am not involved in the electrical side

 

[r.bartlett]

EIC covering the new circuit only.

thanks

is this a legal obligation though??

 

[Iggifer]

yes

 

[r.bartlett]

yes

thanks.

 

[ricicle]

Yes you are right it was for a 100a supply running about 150m or so..

I hope the 16mm guy didn't get it .....?

 

[Iggifer]

he totally did!

 

[RF Lighting]

Yes you are right it was for a 100a supply running about 150m or so..

I hope the 16mm guy didn't get it .....?

I hope the 35mm² guy didn't get it either

 

[r.bartlett]

he totally did!

Of course he did!

however this was part of a 5 year project and as it stand is running at max 18 a. the guarantee will be long gone when the rest is installed -although we expect a max running of 45a tops then in any case... (assumes these phases get signed off)

It's just a manufacturers hang over from over spec'ing the fuse rating.
IE spec a 32a 3p+n for a unit which runs at max 18a and is inverter driven so start current is less than 1a. Why?

Daikin used to spec 16a supply for an indoor unit which drew 1.2a on high fan!(outdoor unit has to be fed from elsewhere)Madness