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32A single and 3 phase supplies feeding catering heat lamps via grid fuse modules.

hertzal123

I have been asked wire 300W heat lamps that are mounted over restaurant kitchen hot plates.

The loading of the lamps can be up to 6kw and will include dimmer switches for groups of lamps.

I was planning to supply the lamps via MK grid fuse modules with 13A BS1362 fuses and 2M of 4mm  3 core or 5 core

ho7.Assuming the the fuses will protect the lighting wiring.I was wondering if the grid fuses are suitable in this situation

in particular ,with the 3 phase 32A supplies?Thanks for any advice.

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    A few things intended to help ...

    First, ambient temperature around the BS 1362 fuses should be limited to 40 deg C maximum, and not exceed 35 deg C mean over 24 hours (this is the stated service conditions in BS 1362). You might also need to consider ambient temperature for the selected cables vs their service conditions ... also that the fuses themselves dissipate up to 1 W of heat at their rated current. As to how much load you might want to put on each fuse, perhaps worth looking at this article: electrical.theiet.org/.../

    hertzal123 said:
    My customer,the steel fabricators are told if the commando socket in the kitchen is 3 phase 32A or 1 phase 32A.I then make up a lead with 3 pin or 5 pin commando plug to supply the grid fuse box.If 3 phase ,I may use 3 fuse units and a connector block for the neutral to supply the banks of heat lamps.All lighting circuits are single phase.My concern was if the fuse units are suitable for the 3 phase use?

    Second, based on this, BS 7671 may not be the correct standard to apply, because it sounds like a pre-manufactured assembly. A suitable product standard should be selected and certified against.

    Third, one thing to be aware of, if you are using the BS 7671 approach for overload protection (which, if there are filament-type lamps being used, is perhaps important), Cf for a BS 1363 fuse  is 0.76 (from BS 1362, I2 = 1.9 × In). The same would also apply to BS 646 fuses.

    Fourth, your installation instructions for the completed product might also want to stipulate what type of backup protection you need from the protective devices in the electrical installation supplying the socket-outlets in the kitchen, to cover the (admittedly very rare) cases where the prospective fault current at the socket-outlet might exceed 6 kA. (BS 1362 fuses have a rated breaking capacity of 6 kA). I was just thinking that in some large sites, such as large shopping centre, airport, etc, there might be cases where the restaurant just happens to be near to the transformer and prospective fault current is unusually high.

  • 0 in reply to gkenyon

    Thanks for the informative reply Graham.

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