HRC fuse

rick · 2022-09-03T22:18:59+00:00

The incoming tails from Meter cab go to a Switch Fuse (MEM 100ESSCF)This is fitted as standard with 100A HRC fuse.I am not sure what physical type of fuse this is ..... but can it be changed to 80A ? (labelled appropriately)As supply fuse is 80A having 100A fuse at this point is of no value.Fuse Carrier has 'MEM Type CM' printed on it.

Sep 03, 2022 Last reply: 3 years ago 24 Replies

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rick 3 years ago

The reason would be to be able to run circuits with 16mm2 rather than 25mm Appreciate the cable runs to a protective device (MCB etc.) I have a circuit with 6mm2 from switch fuse to RCD/and 40A MCB, he would not certify it as although anything downstream was protected by MCB ... the actual cable link to switch fuse was 6mm2 and as Switch fuse had

100A fuse he classed it as under sized under fault condition.

I did point out supply fuse was 60A (uprated this week to 80A) but he said that was irrelevant as fuse could be changed in the future.

He certified everything downstream but not to the switch fuse, it was his comment that I should use 25mm2 had me thinking of downrating fuse so I can use 16mm2 rather than 25mm2.

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John Rumm 3 years ago

With 1000A+ fault currents, all bets are off. Fuses tend to vaporise very quickly - so either or both could go.

(there have even bee cases where a fault in an appliance on the end of a

13A plug have taken out the household 100A incomer leaving the plug fuse still working!)

Once into fault conditions, MCBs use a different trip mechanism. As you said, magnetic rather than thermal. So fuses and MCBs do not always discriminate in the way you might expect.

(properties with very high prospective fault currents (i.e. low supply and earth impedances) do strange stuff since the I^2t let through energies can be so high).

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Brian 3 years ago

The two that did mine seemed fine. We had a chat about PME etc - they spotted I have a local extra earth bond to my radio earth system. They couldn’t have have been more helpful. I even sent an Email to the company complimenting them on the service etc.

We have an overhead supply in our road.

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rick 3 years ago

I did originally request & pay for a 100A supply So I could ask Western Power to increase to 100A ....... I don't need it now, but could be useful if I ever need to add an EV charger They have just rebranded as National Grid.

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Andy Burns 3 years ago

I did start to notice "WesternPower ... A NationalGrid company" on the vans a while ago

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