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

[James.B]

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?

Hey Dave, I have selected a 32A incase it could be used for another piece of equipment in the future, if I limit it to 20A this may not be sufficient for future use. Cheers

 

[plugsandsparks]

Sorry plugs and sparks, I wasn't clear in my description, this is a twin fryer but 1 single piece of equipment, that is why I asked for you to explain, no offence intended. These fryers can be used individually or both together and come in both single and a 3ph option.

No sweat, just enjoying the joy of eletricary, 3PH is good if you can wire it that way when it arrives. As mentioned before C32 earth loop is what i would concentrate on for design, if you take a ZDb before you order the cable, it might help with sizing, alternatively drop to a C25 or even a B32.

 

[James.B]

Nothing wrong with a 32A OCPD lad, cable Ccc OK, EFLI likely to be well under the max.
If this is going to running for 12 - 15 hours a day, a 32A MCB will operate at a cooler temp than a 20A MCB in this environment.

Your the designer at the end of the day!

Agreed Timbo, as I said initially I was designing it solely for this piece of equipment but then advised to up it for the extra scope for future and so I did, I was just interested to get other people's opinions on here and obviously double check myself as it's been yrs since I've done calcs, so really appreciate your input mate?
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Interesting.. I would never describe a double socket as a 2 X13A socket, that would be 2 X single gang sockets. It would be interesting when the fryer shows up what the rating plate says.... please OP take a pic.... it might make my day ( or not) lol

I will mate?
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Many thanks to everyone for their help, much appreciated guys?

 

[James.B]

32A would be my preference, the circuit is 15m long so EFLI not going to be an issue here.
No point loading up a 20A TP MCB, he's also stated that the board and mcbs are obsolete and that he had a 32A MCB. Ccc also not an issue after correction factors applied.

Thanks again Timbo, I somehow seem to have missed this post last night?
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For what it's worth I did a 3 Phase oven and calculated 2.5 and the manufacturer insisted they always use 4mm. Maybe the manufacturer of the fryers might have some input? I suppose as it is a cafe they do tend to run their appliances at full tilt for much of the day so yeh belt and braces approach.

Sorry Vortigern, I seem to have missed this post last night too?‍. The fryer is a Parry and customer wants to purchase from Nesbitts, you were lucky to get to speak to technical, I tried twice to both Parry and Nesbitts, no one to help and no one phoned back after they said they would so?‍. Totally agree with the belt and braces approach and am guilty of over specing so good to have a mixture of tabulated figures to go by but also to be able to touch base with people who have more experience in this particular field than myself (Commercial Kitchens). Many thanks for your input.

 

[telectrix]

and as a fixed load, overcurrent protection is not required, so 32A MCB is ideal as long as In<Iz.

 

[Ian1981]

and as a fixed load, overcurrent protection is not required, so 32A MCB is ideal as long as In<Iz.

You mean Ib is equal to or less than Iz
The protective device can exceed the Iz of the cable where overload protection is not required as long as the design current is equal to or less than Iz.

 

[telectrix]

You mean Ib is equal to or less than Iz
The protective device can exceed the Iz of the cable where overload protection is not required as long as the design current is equal to or less than Iz.

sorry. i should have said Ib<Iz. what idiot put N next to B on my keyboard. just almost as bad as the caps lock next to A, so every time my fat sausage fingres type an a, EVERYTHING AFTER IS CAPS.

 

[Ian1981]

sorry. i should have said Ib<Iz. what idiot put N next to B on my keyboard. just almost as bad as the caps lock next to A, so every time my fat sausage fingres type an a, EVERYTHING AFTER IS CAPS.

I forgive you, can’t help with the keyboard situation, i always use my iPhone, spell check is a godsend ha.

 

[telectrix]

corrective text is a pain. once i had a customer of far east origin, name is Alka. i sent her a text which started as Hi AklaSeltzer.

 

[pc1966]

No sweat, just enjoying the joy of eletricary, 3PH is good if you can wire it that way when it arrives. As mentioned before C32 earth loop is what i would concentrate on for design, if you take a ZDb before you order the cable, it might help with sizing, alternatively drop to a C25 or even a B32.

As a fryer presumably has no switch-on surge of any note (maybe small motor for oil circulation?) I don't see any reason for a C-curve MCB and the B-curve version will make the required Zs far easier to meet.

 

[James.B]

Thanks Ian and Telectrix, yes my In is greater than my Ib and my Iz is greater than my In. If I used 4mm cable as mentioned before, my It would not be greater than my Iz using the 70 deg C tables, but i believe this (condition 3) unessary to meet once condition 1 & 2 are met. In saying that, I now plan to use a 6mm cable anyway therefore my It will be greater than my Iz. I see many people have mentioned about not protecting by an RCD, but I believed this was only the case where the RCD was nigated by a Risk assessment (411.3.3), personally I would prefer to fit one and would not nigated it. But would you be so kind as to maybe give reference to where the regs states this if other than by a Risk assessment? Many thanks, James?

 

[Ian1981]

Thanks Ian and Telectrix, yes my In is greater than my Ib and my Iz is greater than my In. If I used 4mm cable as mentioned before, my It would not be greater than my Iz using the 70 deg C tables, but i believe this (condition 3) unessary to meet once condition 1 & 2 are met. In saying that, I now plan to use a 6mm cable anyway therefore my It will be greater than my Iz. I see many people have mentioned about not protecting by an RCD, but I believed this was only the case where the RCD was nigated by a Risk assessment (411.3.3), personally I would prefer to fit one and would not nigated it. But would you be so kind as to maybe give reference to where the regs states this if other than by a Risk assessment? Many thanks, James?

411.3.3 is the regulation you want for omission of additional protection by a risk assessment

 

[telectrix]

Thanks Ian and Telectrix, yes my In is greater than my Ib and my Iz is greater than my In. If I used 4mm cable as mentioned before, my It would not be greater than my Iz using the 70 deg C tables, but i believe this (condition 3) unessary to meet once condition 1 & 2 are met. In saying that, I now plan to use a 6mm cable anyway therefore my It will be greater than my Iz. I see many people have mentioned about not protecting by an RCD, but I believed this was only the case where the RCD was nigated by a Risk assessment (411.3.3), personally I would prefer to fit one and would not nigated it. But would you be so kind as to maybe give reference to where the regs states this if other than by a Risk assessment? Many thanks, James?

how will the fryers be connected? hard wired or on plug? and will cable be buried <50mm in wall?

 

[plugsandsparks]

As a fryer presumably has no switch-on surge of any note (maybe small motor for oil circulation?) I don't see any reason for a C-curve MCB and the B-curve version will make the required Zs far easier to meet.

I think the only issue i can see is getting TP B curve breakers for that board, TBH its getting harder and harder to meet ELI with the values dropping as they do. Did an EICR on an office ring that was put in 10 years ago on a c32, failed today just outside ELI, its a MEM board , nothing wrong with the cct, hey ho

 

[James.B]

As a fryer presumably has no switch-on surge of any note (maybe small motor for oil circulation?) I don't see any reason for a C-curve MCB and the B-curve version will make the required Zs far easier to meet.

Hi PC, the reason for me using C Type 32 was because I have one, and the DB is the old Crabtree Polestar 125A, discontinued about 10 yrs ago, but point noted and I agree. With a Ze of 0.1 on a TN-C-S and using a 4 core 6mm swa using the armour as my cpc cleated direct on a run of less than 15m I'd expect a pretty decent Zs, sub 0.2, so hopefully no foreseeable issues and will also be RCD protected, cheers James?
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411.3.3 is the regulation you want for omission of additional protection by a risk assessment

Thanks Ian I thought that was the only reg alright, appreciate your time mate?

 

[marconi]

JamesB: I admire the care you are taking with the required analysis and that you record it too ( - I assume) for posterity - just in case. Well done , Sir.

Plenty of great advice from some leading runners in the game.

Did your client consider 'induction fryers'? A lot more efficient and quicker.

Induction Fryers, Buy Online UK | Nisbets Induction Cooking Machines - https://www.nisbets.co.uk/catering-appliances/cooking-equipment/induction-cookers/induction-fryers/_/a33-4

View: https://www.youtube.com/watch?v=7GcMRCUw2J0


I recommended 2 x 3kW to my brother-in-law to make best use of a very limited single phase power supply to cook chips at football ground catering van.

 

[James.B]

how will the fryers be connected? hard wired or on plug? and will cable be buried <50mm in wall?

Hi Telectrix, fryers will be wired via a 32A 5 pin plug and socket, with rotary interlock switch and RCD protected. Using a 4 core 90 deg thermosetting swa cleated direct and with pirana locking nuts. With the rotary isolator being of plastic construction I'll gland into a metal J.Box first and into the isolator from that, unless there's a better option on the market these days that I don't know about??? Open to other options, and appreciated, many thanks?

 

[telectrix]

if the 32A socket is dedicated to the fryer, my thoughts are that RCD may not be required. A written RA might be advisable.

 

[James.B]

JamesB: I admire the care you are taking with the required analysis and that you record it too ( - I assume) for posterity - just in case. Well done , Sir.

Plenty of great advice from some leading runners in the game.

Thank you Marconi, yes some good advice from people that I appreciate, to be able to so called, bounce off, things change so quickly in this industry and it's good to be able to come on here and if you have an issue or a doubt, then put it out there. As they say that's what this forum is all about, and everyday is a learning day, none of us know everything and sometimes can even forget our basics no matter how much experience we have?. A guy said to me many years ago, cover your --- and sign any legal document as if you are standing in a court of law. I guess old habits die hard ?. Appreciate your feed back, thanks James?
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if the 32A socket is dedicated to the fryer, my thoughts are that RCD may not be required. A written RA might be advisable.

It is dedicated to the fryer, at this moment in time, the problem is I know the owner and I also know he changes his mind like the wind and it may be used for something else in the future, therefore I'd prefer to cover my --- as they say, I know there is the cost element, but that's on him and I walk away with a clear conscience knowing all is well. In saying that I appreciate your informative info, many thanks again?
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JamesB: I admire the care you are taking with the required analysis and that you record it too ( - I assume) for posterity - just in case. Well done , Sir.

Plenty of great advice from some leading runners in the game.

Did your client consider 'induction fryers'? A lot more efficient and quicker.

Induction Fryers, Buy Online UK | Nisbets Induction Cooking Machines - https://www.nisbets.co.uk/catering-appliances/cooking-equipment/induction-cookers/induction-fryers/_/a33-4

View: https://www.youtube.com/watch?v=7GcMRCUw2J0


I recommended 2 x 3kW to my brother-in-law to make best use of a very limited single phase power supply to cook chips at football ground catering van.

Thanks Marconi, I did see these when I was looking up the fryer he speced, I'm sure he's seen them but seems adamant about this particular one, another reason why I speced a 32 breaker instead of what would have been a 20 for this load was that there is a twin 9kW fryer available, so I wouldn't put it past him to go for that ??, cheers anyway?