Phase loading in a chippy

[littlespark]

What can be worse than electrical installations on a farm, or in a pub?...... Chippys!

Got a phone call from my local.... Lights and kitchen equipment not working... needs checked by a sparky before Scottish Power would attend. She'd blown a main fuse!

So ive been tasked with working out the loads across 3 phases... see which phase does what and how it can be better distributed across the phases.

I nipped in last night for a quick look. She had power but had been told not to run everything. 2 phases were at roughly 40A, the 3rd at about 25A...
Feeling the fuses with the back of my hand, the ones pulling 40A were warm compared to the 25. (no clue what the actual size of fuse is, might have to ask SP myself)

One phase runs her house through the back (of course, that was the one that blew)


All very well working out what each piece of equipment takes... but during opening hours, the power cycling through each thermostat control could throw the balance all over the place. I suspect she turns everything on at once, pulling maximum until whatever switches off on thermostat.

 

[James]

put a data logger on the supply for a week.
find out if it is even possible to balance the phases to keep inline with the the supply.
if the results suggest that a bigger supply is needed then you can advise and leave.
otherwise you could end up being the man in the middle of negotiations that are going no where!

 

[littlespark]

cheap as chips solution for a data logger?

no pun intended.... (yes... there was!)


She's not going to be running the place "as normal" for fear of blowing a fuse again.....
All i can do, if there's a severe overload on one phase when everything's added up, and very little on another.... then i can maybe move something over.. and think of a logger later.


The dumb thing is, the owner's son in law is another electrician.... but he says he's far too busy... just come back from holiday, got a big job coming etc etc to help out himself.
I think he's swerving it... doesn't want to get involved himself.

 

[James]

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[littlespark]

Had a quick look this morning, and its a dogs dinner of an install.... with addons here, there and everywhere.

The big issue is all the sockets in the chippy kitchen are off one 30A fuse... in a consumer unit which also feeds the house the owner lives in. This board off L2 for reference. Highly unlikely its actual 30A fusewire in there. The house has electric cooker and shower, but gas heating.

There are 2 cooker switches in the chippy. One feeds a commercial oven with 2 hotplates, and the other is empty... but the sockets on the switches have a burger plate, and a 2 drawer pizza oven as and when required. Both these are on L3, off a separate fuseboard

On one circuit, she has another pizza oven, 2 single fryers, a large chiller which is needing repaired and wasnt in use today... a couple of fridges, freezers.. a potato peeler and a chipper.... Not everything is on at the same time though.... and some things are only on when needed.

The main fryer is 3 phase, and draws 50A per phase as its heating up... but there is a single phase extraction fan for this wired into the isolating switch.... Surprise surprise... off L2. (that could be moved over)

Apart from a third of the big fryer, L1 doesn't seem to be doing anything.

With the place shut, and only the background fridges, freezers and whatever on in the house.... L1 and L3 were zero Amps... L2 was floating around 4.8A

With just the main 3ph fryer on and heating up... this jumped to L1 - 42A, L2 - 72A! and L3 - 50A... but i think she was boiling the kettle in the house for my cuppa at the same time.


I'm going to offer a solution of replacing the consumer unit with a 3 phase board, or additional single phase if space allows, just to separate the house from the chippy itself.
Possibility of also running an additional rfc or a number of radials through the chippy kitchen on different phases to the cooking equipment. Would have to be surface pvc trunking though.

 

[pc1966]

A 3P board makes good sense, you can decide how to allocated loads to phases as needed for sane balance.

Same for a SP board for the house. Allow separate isolation for work, and it could have a check meter on it if they need to be more precise about cost/tax reclaim on energy use.

 

[James]

Make sure the 3p board is oversized by at least 30% to allow for phase balancing