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Rotary isolator sizing

Baldyhugh

Hi

is it acceptable to use a rotary isolator which is a larger rating than required eg. Using a 32a isolator for a 16a or 20a circuit? Dependant on manufacturer, the higher rated ones are physically larger and offer more space inside for wiring. With my wholesaler there is only a couple of pounds difference in price, so it seems sensible to use the larger one but was curious if there was a regulation reason why I shouldn’t.

 

thanks

 

Peter

  • 0

    Normally we might  call using the next size up conservative design. Generally, apart from cost, it is a good thing, bigger contact areas  run cooler, last longer.

    Note that larger terminals may need the wire doubling over or something to get a decent grip.

     The only situation where it might be a source of confusion is if there is a combined switch and fuse, and it may encourage the unskilled to fit an oversized fuse. clear labeling helps then.

    no reg as far as I know that ever prohibits you, further  I'd  suggest it is actually  a good idea if the project budget can stand it.

    Mike.

  • 0

    Certainly acceptable to my mind. In the old days we'd use 20A round joint boxes on 5A lighting circuits - no one bothered with the 5A ones as they were far too small and fiddly to get more than a couple of cables into.

    Likewise, isolators don't come in all the same ratings as MCBs, so often you'd have no choice but to use a higher rated one.

       - Andy.

  • 0
    Thanks for your replies, much appreciated. Yea for the matter of a couple of pounds difference, I tend to go for the larger rates ones. Some off the cheaper brand of isolators are badly designed in my opinion and leave very little room to manipulate the cabling into the terminals so would go for the larger which offers more space. Thanks again
  • 0

    I always go for the larger size, simply because terminating a 6.00mm multicore SWA into a 32A rated one is next to impossible, so up a size we go. Makes life easier all round.

  • 0

    im about to spec up 20 or so isolators on a job, balking at the cost of Schneider steel ones, I'm going plastic, but will spec 32a, even though almost all of them only need 16a supplies

     

    its about £2 difference at the most

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