Circuit Design For 15.5kw Cooker?

[nlbhoy]

I looked at a job today in commercial kitchen.

They want power run to a 15.5kw cooker, now obviously this would come in around 67a. Applying diversity
it comes to around 27amps.

Would you use a 32amp mcb with 6mm t&e?

Or would you recommend 40amp mcb with 10mm? since it's not a domestic dwelling.

Cable will be run in trunking with conduit drops.

 

[davesparks]

When you say cooker, what exactly is it? What sort of load profile are you expecting from it? I'm surprised that a commercial cooker needs a SP supply, they generally tend towards TP supplies unless it's a single element oven or similar.

In trunking and conduit I would be using singles, possibly lsf if it's commercial, rather than T&E.

 

[not clever]

If using trunking I'd consider using singles terminating to a rotary isolator & commando with cable drop to oven in sy

 

[davesparks]

If using trunking I'd consider using singles terminating to a rotary isolator & commando with cable drop to oven in sy

SY is not appropriate for such an installation, an HOFR sheathed flex such as H07-RNF or good old butyl would be far more suitable.

What properties of SY do you think will make it suitable for this particular scenario?

 

[nlbhoy]

It's definitely single phase. It's just a oven and hob.

It's a catering company who lease a commercial kitchen unit.

The connections on the cooker are rated at 40a.

I was thinking as it's probably used more and for longer periods of time (compared to domestic) to allow for
less diversity and rate the mcb at 40A?

 

[Octopus]

What make and model?

 

[Paul.M]

@ the OP. Are you sure it is single phase at 15.5Kw????

 

[nlbhoy]

@ the OP. Are you sure it is single phase at 15.5Kw????

Yeah, it's definitely single phase.

 

[davesparks]

It's definitely single phase. It's just a oven and hob.

It's a catering company who lease a commercial kitchen unit.

The connections on the cooker are rated at 40a.

I was thinking as it's probably used more and for longer periods of time (compared to domestic) to allow for
less diversity and rate the mcb at 40A?

Do you understand how the diversity on a cooker actually works?

How is this to be connected? Is it to be on a plug and socket connection or a hard wired connection?

 

[nlbhoy]

Do you understand how the diversity on a cooker actually works?

How is this to be connected? Is it to be on a plug and socket connection or a hard wired connection?

I believe it's 10amps plus 30% of the total load. Add 5amps if there's a socket.

In my case 10amps plus 30% of the remaining 57amps which is 27.1 amps??

It would be hard wired.

 

[davesparks]

I believe it's 10amps plus 30% of the total load. Add 5amps if there's a socket.

In my case 10amps plus 30% of the remaining 57amps which is 27.1 amps??

It would be hard wired.

No, that's just the calculation for applying diversity, I'm talking about the theory behind that calculation and why it works. The cycling of the elements and suchlike.

 

[hightower]

No, that's just the calculation for applying diversity, I'm talking about the theory behind that calculation and why it works. The cycling of the elements and suchlike.

Hi Dave, if you've time to type it up I'd love to hear? I thought it had something to do with an element would only need to be on to get up to temperature, and then it's only on intermittently to keep the oven at temperature and hence you can apply diversity. Probably a mile off with this theory though so look forward to being corrected.

 

[telectrix]

Hi Dave, if you've time to type it up I'd love to hear? I thought it had something to do with an element would only need to be on to get up to temperature, and then it's only on intermittently to keep the oven at temperature and hence you can apply diversity. Probably a mile off with this theory though so look forward to being corrected.

you're quite right. as the elements switch on and off by their thermostats, they will not all be on simultaneously.

 

[nlbhoy]

So I went to the job today and had a better look around as the kitchen had closed.

The unit is has a 63 amp supply. Told the client I couldn't wire the cooker (15kw) as this
would put here well over 80amps, well I got a mouthful of abuse from her about how
much she had paid for this oven, and how she will find a "better" electrician to wire
this for her lol.

Did I do the right thing not wiring this?

How would you handle a client like this?

 

[HandySparks]

If I got a mouthful of abuse from a potential client before the job started, they wouldn't be a client any more.

 

[Andy78]

So I went to the job today and had a better look around as the kitchen had closed.

The unit is has a 63 amp supply. Told the client I couldn't wire the cooker (15kw) as this
would put here well over 80amps, well I got a mouthful of abuse from her about how
much she had paid for this oven, and how she will find a "better" electrician to wire
this for her lol.

Did I do the right thing not wiring this?

How would you handle a client like this?

So the appliance has a full rated current of 67A, connections rated at 40A, with diversity applied requires a circuit capable of 27A, yet can't be connected because it requires a 63A supply ?

 

[Martin Kerr]

So I went to the job today and had a better look around as the kitchen had closed.

The unit is has a 63 amp supply. Told the client I couldn't wire the cooker (15kw) as this
would put here well over 80amps, well I got a mouthful of abuse from her about how
much she had paid for this oven, and how she will find a "better" electrician to wire
this for her lol.

Did I do the right thing not wiring this?

How would you handle a client like this?

Design the circuit for the load calculated , install as per instruction and charge accordingly
When the incoming fuse pops , tell her I told you so .....

 

[Leesparkykent]

Obviously diversity can still be applied but the sum given in the OSG is for a domestic cooker.

 

[i=p/u]

Understand the manual as you can price accordingly . Push to the limit

 

[davesparks]

So I went to the job today and had a better look around as the kitchen had closed.

The unit is has a 63 amp supply. Told the client I couldn't wire the cooker (15kw) as this
would put here well over 80amps, well I got a mouthful of abuse from her about how
much she had paid for this oven, and how she will find a "better" electrician to wire
this for her lol.

Did I do the right thing not wiring this?

How would you handle a client like this?

I'm a little bit lost here, what unit has a 63A supply? I thought this was a commercial kitchen?

What is the existing maximum demand?