Compressor wiring. 45amp.

[illyco]

Hi all.

Just got a 36cfm twin 4HP compressor which is single phase that is replacing my 3HP (16CFM unit).
The new compressor requires a 45a supply.

My old compressor was on 32amp MK (Commando) plug, with its own supply coming off my consumer unit with a 32a MCB using 10mm armoured cable into the workshop.

My question is this (i hope you can help): Can I just swap the MCB for a 63a switch, and wire the new compressor to the fusebox in my workshop?

Thanks in advance!

 

[dobbslc]

Right I've got the regs book out! Admittedly the "old" 2nd amendment version and not the new just out 3rd amendment one....
My company's so called testing manager doesn't seem to think the testers need the latest version........WTF?
Anyway
A 10mm swa if it's 3 core single phase and clipped direct ie on a wall with cleats it will carry 67 amps. You can get 45 & 50amp mcb's too.
You must obviously upgrade the outlet to 63amps though.
I would use a D type for the inrush current on a big motor like that though.
Dobbs

 

[rikrobson]

You should have it wired into an isolator box and then back to the fusebox.

 

[illyco]

Thanks guys.

I have a 63amp rotary isolator which will be going between the compressor and workshop fusebox.

I have uprated the workshop fuse already to a 63amp - so it looks like all I need is a 45 or 50 amp MCB?

Hopefully I can get down to screwfix before it closes.

 

[Robotstar5]

A 10mm swa if it's 3 core single phase and clipped direct ie on a wall with cleats it will carry 67 amps. You can get 45 & 50amp mcb's too.
You must obviously upgrade the outlet to 63amps though.
I would use a D type for the inrush current on a big motor like that though.
Dobbs

Providing it meets the Zs for disconnection time?

 

[normspanners]

As they wont be starting up at the same time, usually there is a delay timer, could you not just wire each motor to its own 32a plug then all you would have to do is fit another mcb and 32a socket.

 

[illyco]

Yes, they start on a sequential delay.

I never got round to Screwfix, but i'm going first thing in the morning. Everything is wired up but the MBC is disconnected from the consumer board ready for when I get a 45a or 50a.

I was going to get a Type B, as thats what was there before - will a Type B be sufficient?

 

[brightspark]

go for a c type

 

[illyco]

go for a c type

Thank you brightspark, and everyone else in this thread.

On a side note, i've been lurking here a while and a lot of your posts have helped me with compressor and blasting questions! Huge thanks to you!

 

[andeep]

Sorry slightly off topic, but illyco which compressor did you go for?

 

[illyco]

Sorry slightly off topic, but illyco which compressor did you go for?

Clarke SE37C270. The twin 4HP single phase. I was about to pull the trigger on the twin 3HP, but TAITSIE from here had a VAT free code.

 

[normspanners]

Sequentially starting motors allow the unit to be run from 230v, 1ph power supply (30 amp minimum) stated off the spec from ebay
http://www.ebay.co.uk/itm/Clarke-SE37C270-Industrial-Air-Compressor-OL-/301198432356

 

[illyco]

Sequentially starting motors allow the unit to be run from 230v, 1ph power supply (30 amp minimum) stated off the spec from ebay
http://www.ebay.co.uk/itm/Clarke-SE37C270-Industrial-Air-Compressor-OL-/301198432356

I guess MM are just covering their back stating that a 45amp supply is minimum.

So in theory I could have just put my MK 32a plug on it and off I went? I'm glad i've only spend £4 on a MCB.

 

[normspanners]

Looks like it, I think they have spec'ed it for both motors starting together