Pub/restaurant kitchen diversity

jedisparks · Mar 26, 2020

Hi all,

Not sure if I've posted this in the right place or not. Just looking for a bit of help please.

I need to move a dist board in a gastro pub/restaurant ready for a new kitchen to be installed. I'll not be involved in the Kitchen install itself but need to make sure I put in a suitable supply and board so its ready to go. This board will also be supplying lighting & small power throughout. So that's a bar, restaurant and 3 B & B rooms upstairs with minimal loads.

Currently on site is a 100amp 3 phase supply at the cut out. Then an 80amp switch fuse for a sub main to the existing dist board around 15metres away, the cable for which I had planned to divert and extend slightly for the new board. I told the kitchen specifier to go easy on electrical cooking appliances and use gas wherever possible. They've come back with mostly gas appliances apart from:

1 x combi/steam oven at 32A 3ph (the main ovens are gas)
1 x pizza oven at 20 3ph
1 x dishwasher at 20 3ph

There are a number of other appliances listed as requiring 13amp supplies (a bit vague I feel) for:

2 x hot cupboard
extractor fan
chillers
cellar cooling
coffee machine
fridges
glass washer
fridges behind the bar

Lighting load throughout building is minimal due to all being LED.

I'm happy with the smaller loads but its those 3 x 3 phase appliances I'm not sure what sort of diversity to consider for them. OSG append 4 suggests 100% full load of largest, then 80% of 2nd, then 60% of remaining for small hotels. Might this be a suitable approach? Am I pushing it with the 80amp sub main fuses?

Any help greatly appreciated. Thanks

GBDamo · Mar 26, 2020

One thing to consider with commercial kitchens is they have a habit of turning everything on at once to warm up.

So where they have multiple electric ovens, grills, plate warmers, hot cupbards, baine maries etc then they will all pull full load for 15-20 mins before they all start cycling.

Had to demonstrate this at a very large pub kitchen. They had added and added to an existing installation and eventually overloaded the TP C63 protecting the distribution circuit. All phases were overloaded when the kitchen staff started up.

The quote is still being "considered" to put it right, in the meantime they are following a staged start up procedure.

jedisparks · Mar 26, 2020

GBDamo said:
One thing to consider with commercial kitchens is they have a habit of turning everything on at once to warm up.

So where they have multiple electric ovens, grills, plate warmers, hot cupbards, baine maries etc then they will all pull full load for 15-20 mins before they all start cycling.

Had to demonstrate this at a very large pub kitchen. They had added and added to an existing installation and eventually overloaded the TP C63 protecting the distribution circuit. All phases were overloaded when the kitchen staff started up.

The quote is still being "considered" to put it right, in the meantime they are following a staged start up procedure.

Thanks GBDamo,

That's interesting. I think I'll chat to the kitchen designer about the likely hood of the pizza oven and the steam oven being started up at the same time or if the gas ovens are the main focus. Expect the dishwasher will fire up later into the service but will check this too.

Any other views really appreciated. Although the work is more or less a doddle ill admit it's been a while since I've worked on commercial kitchens and a little uneasy about all this hanging off of 80amp fuses.

Many thanks

pc1966 · Mar 26, 2020

Remember also that the fusing time for an 80A fuse is something like 2 hours at 100A and 10 minutes at 120A (anyone got a useful calculator for this?) so if you are a few percent over it is not going to be sudden death!

telectrix · Oct 8, 2021

might be an idea to stagger the switching on like previously mentioned. then 100A/phase may just do it. find out from client the intended use of the 3ph,32A combi. it may be only intermittent use.