Wiring for a compressor

[dunny]

Hi all, hope you had a great Xmas.

I am taking delivery of my new compressor next week and I need to plan how it will be best wired. It is going in the garage and requires a minimum of 45 amp fuse. Already in the garaage is an isolator switch with a few fuses in and I was wondering whether it is therefore just a case of putting a larger fuse in? The current fuses run some lights and some sockets but there is a spare.

Thanks

D

 

[Adam_151]

It is unlikely to be as straight forward as you anticipate!

It would be helpful if you could post the full electrical specification of the compressor in question along with photographs of the distribution board in the garage as well as the one in the house.

Be prepared that you are most probably going to need an electrician out to sort the supply out, but at least we will be able to give you an idea of what is likely to have to be done

 

[Robin0577]

Without further information we can only speculate, but you may well find that you've just opened a rather large can of worms....

IF this is a typical domestic garage arrangement supplied from the house, then it is quite likely that the whole supply to the garage will be of less than 45 amps capacity....

 

[Taylortwocities]

Yes photos please

Where is your consumer unit and incoming supply in relation to the garage?

 

[dunny]

And in the garage:-

 

[dunny]

Yes photos please

Where is your consumer unit and incoming supply in relation to the garage?

Its on the other side of the wall so its easy enough to get to. The mains power cable from the over head pole comes into the garage and then into the house. I will be gettintg itr all rewired and getting the pole removed but not for a while.

It would be helpful if you could post the full electrical specification of the compressor in question

It has just arrived!! What am I looking for in terms of the spec?

Thanks

D

 

[Adam_151]

You are looking for a rating of the motor in KW or HP. And also number of phases.... we hoping that this is one, not 3!

Are you able to clarify that all of your pictures except the last one are in the house?

 

[dunny]

It would be helpful if you could post the full electrical specification of the compressor in question

Single phase 230v , 2 4HP motors:-

 

[dunny]

You are looking for a rating of the motor in KW or HP. And also number of phases.... we hoping that this is one, not 3!

Are you able to clarify that all of your pictures except the last one are in the house?

Thats correct

2 x 4HP motors (3KW) start sequentially and Clark say needs 45A fused protection.

D

 

[Adam_151]

Single phase 230v , 2 4HP motors:-

Is that a mis-print. Or does it it use two separate motors? If its the case... is it more like two compressors with a motor each going into a common receiver? Or are they combined in some other way? Does only one start if air demand is low or do both start and run together all the time. It may help to have the model number of the machine so that we may see exactly what you have

 

[Robin0577]

From the spec, my guess is it's this one https://www.machinemart.co.uk/p/clarke-se37c270nd-36cfm-270-litre-industrial-a/

The motors cannot start at the same time but can run at the same time.

 

[Robin0577]

So, we're looking at a 6kw running load, plus allowance to start one motor with 3kw already being used by the other.

 

[Robin0577]

45A sounds quite reasonable for that. So, that'll be entirely new wiring and switchgear back to the meter for your compressor then, none of your existing fuseboxes is capable of providing a 45A circuit. The switchfuse in the garage is only rated for 20A and the Wylex boards in the house take 30A fuses maximum.*

This work will be notifiable to building control. The additional loading should, strictly speaking be notified to your electricity distributor too.

*It's possible but unlikely, the 8 way one might have one 45A capable slot at the end nearest the switch.

 

[Taylortwocities]

You will need a new switchfuse at the electric incoming service head. Probably 10mm² cable to a suitable connector at the point where the compressor will be located.

As above. This is a new circuit and notifiable (you'll need a registered electrician to plan and do this work) as I'm guessing that you don't have the level of competence to DIY this!

Also, you will need to seek permission from the DNO for this additional load, especially as your supply is "overhead". They will not want all the lights in the other houses on the same supply dimming everytime you start the compressor!
Do you know what the supply type is, do you have an earth rod outside the house?

 

[Robin0577]

P.S. Slightly off topic - did anyone else spot the problem with the wiring exiting from the newer looking MEM switchfuse that's apparently being used as the main switch?