Looking to install a 3ph supply for 2 x 6kW fryer in a commercial kitchen.

[James.B]

Hi everyone, I've looked at a job to install a circuit for a 2x 6kW fryer in a commercial kitchen and would really appreciate a second opinion on my calcs, attached in photos. Many thanks in advance.

 

[timbobelfast]

Looks OK, 6mm for me as the cost between 4 and 6 is negligible. Allows for future expansion and if terminals cable of taking 6mm. Also may consider omitting RCD

 

[plugsandsparks]

Haven't look at the calcs but if you can get two ccts in, rather than try and run two off one cct, its always better in the long run.
You can run 2 X 2.5sqmm 4 core terminate on two Rotary isolaters and put on a B16 breaker, almost impossible for that not to work (subject to calcs again. Lol
Biggest issue with a C32 is ELI

 

[Ian1981]

Do not base the ccc of the cable on 90 degree operating temperature, use the tables for Swa at a 70 degree operating temperature as the mcb and other terminals will not be rated for 90 degrees.

 

[James.B]

Thanks timbo, I appreciate your swift reply?. I thought the same about 6mm cable just to be on the safe side, but it is less than a 15m run and clipped direct and 4mm is capable of 42A installed like this, and we all know there should be plenty of buffer built in even at that, given the draw is less than 17.5Amps per phase. It's just one of those things where you'd like to be safe, it's just nice to get a second opinion sometimes as we all second guess ourselves sometimes, maybe its the beer??. Thanks again mate

 

[davesparks]

4mm is capable of 42A installed like this,

Is that the 90C rating or 70C rating?

Also if Ib is 17.3A then surely In would be 20A?

 

[James.B]

Haven't look at the calcs but if you can get two ccts in, rather than try and run two off one cct, its always better in the long run.
You can run 2 X 2.5sqmm 4 core terminate on two Rotary isolaters and put on a B16 breaker, almost impossible for that not to work (subject to calcs again. Lol
Biggest issue with a C32 is ELI

Thanks plugs and sparks, the fryer hasn't been purchased yet as I'm told it comes as a single or 3ph option, I done calcs for both but obviously best to install 3ph when you have the option as cable size for single phase comes in at 10mm. So not sure about terminal sizes etc. Could you go into more detail about your proposal please, just interested, thanks again for speedy reply?

 

[davesparks]

Haven't look at the calcs but if you can get two ccts in, rather than try and run two off one cct, its always better in the long run.
You can run 2 X 2.5sqmm 4 core terminate on two Rotary isolaters and put on a B16 breaker, almost impossible for that not to work (subject to calcs again. Lol
Biggest issue with a C32 is ELI

How on earth can you connect a single appliance to 2x circuits safely?

 

[James.B]

Do not base the ccc of the cable on 90 degree operating temperature, use the tables for Swa at a 70 degree operating temperature as the mcb and other terminals will not be rated for 90 degrees.

Thanks Ian, point noted, therefore multicore armoured @ 70 C is 33A for a 4mm cable, maybe I will go for the 6mm in that case as that states 42A ref method C. Appreciate your input mate?
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Is that the 90C rating or 70C rating?

Also if Ib is 17.3A then surely In would be 20A?

It's the 90C rating mate, but as Ian quite rightly pointed out @70 C it carries 33A on 4mm cable, so possibly will use 6mm. I'm installing it for this piece of equipment on a 32A commando with build in rotary isolator and rcd just in case of future use for something else. Also the DB is a discontinued Crabtree Polestar 125A, hence the reason for the 2 in one socket. Cheers
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How on earth can you connect a single appliance to 2x circuits safely?

I wondered that too Dave sparks, that's why I politely asked to explain in more detail?

 

[davesparks]

It's the 90C rating mate, but as Ian quite rightly pointed out @70 C it carries 33A on 4mm cable, so possibly will use 6mm. I'm installing it for this piece of equipment on a 32A commando with build in rotary isolator and rcd just in case of future use for something else. Also the DB is a discontinued Crabtree Polestar 125A, hence the reason for the 2 in one socket. Cheers

That still doesn't explain why you've selected a 32A OCPD for a 17.3A load when 20A would be the more logical choice?