32a mcb on a 2.5m radial

Iona222 · Apr 2, 2021

Is the above OK, its feeding a fused spur downstream with a combi boiler attached to the spur. Cheers

buzzlightyear · Apr 2, 2021

No it should be on a 16amp or 20amp.

westward10 · Apr 2, 2021

Think we need a bit more info on the set-up.

Julie. · Apr 2, 2021

Radial or spur?

Radial no
Spur yes (but not recommended as someone may convert to a Radial - it would be an easy error)

Iona222 · Apr 2, 2021

As I said its a 32amp mcb, feeding a fused spur downstream. Connected to a combi boiler, obviously the reason I'm asking as I think its to high, im going to change it to a 20 amp. Cheers.

Vortigern · Apr 2, 2021

433.1.204 Accessories to BS 1363 may be supplied through a ring final circuit, with or without unfused spurs,
protected by a 30 A or 32 A protective device complying with BS 88 series, BS 3036, BS EN 60898, BS EN 60947-2 or BS EN 61009-1 (RCBO). The circuit shall be wired with copper conductors having line and neutral conductors with a minimum cross-sectional area of 2.5 mm2 except for two-core mineral insulated cables complying with BS EN 60702-1, for which the minimum cross-sectional area is 1.5 mm2. Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20 A and if, under the intended conditions of use, the load current in any part of the circuit is unlikely to exceed for long periods the current-carrying capacity (Iz) of the cable.

James · Apr 2, 2021

If it is a spur from a ring, even if it is spurred off from the origin, then it is ok

Vortigern · Apr 2, 2021

Note top left quadrant

Soi disant · Apr 3, 2021

Vortigern said:
Note top left quadrant

Informative, not normative.

Soi disant · Apr 3, 2021

Vortigern said:
433.1.204 Accessories to BS 1363 may be supplied through a ring final circuit, with or without unfused spurs,
.

And they may be supplied through radial final circuits.

Soi disant · Apr 3, 2021

Iona222 said:
As I said its a 32amp mcb, feeding a fused spur downstream. Connected to a combi boiler, obviously the reason I'm asking as I think its to high, im going to change it to a 20 amp. Cheers.

So the overload protection is downstream of the cable. It will prevent an overload.

The 32A device will provide fault protection for the cable.

The arrangement is fine.

But totally pointless. Change it to a 20A if you want. Will need testing and certifying.

Ian1981 · Apr 3, 2021

The arrangement is acceptable as long as the conductors are adequately protected for fault protection, overload current can be omitted and in any case is afforded by the nature of the final load and fused spur

Vortigern · Apr 3, 2021

Soi disant said:
not normative

Most of the hundreds of commercial business units I have entered have such an arrangement as standard for router power etc. adjacent to comms box. Usually direct from the MCB

timhoward · Apr 3, 2021

Even though it's fine I'd agree with downrating the breaker simply to save arguments and reduce confusion in future. It will instantly look suspicious in an inspection as it stands.

Soi disant · Apr 3, 2021

timhoward said:
It will instantly look suspicious in an inspection as it stands.

Only to people who should not be doing inspections.

So yeah - put a smaller one in - there are too many numpties around.

32a mcb on a 2.5m radial

Iona222

buzzlightyear

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westward10

Julie.

Iona222

Vortigern

James

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Vortigern

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