The electrician tells me my supply is 60A, so I'll need 16mm tails when I put in the new consumer unit. He also mentioned that if the supply had been 100A, or if the checks on my rewiring layout showed I'd need a 100A supply, then I'd need 25mm tails. Can anyone tell me how this would be calculated?
How to check max supply
- Thread starter regsmyth
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How what would be calculated?
I think you mean 'Maximum Demand'.
It may be that 60A was derived from the sticker on the side of the main fuse. This sticker may or may not be telling the truth.
If you do mean Maximum Demand - it is the total current demand of your installation after taking into account diversity on some circuits - e.g. light circuits (i.e. not all lights are likely to be on at the same time so we can make an allowance for them of 66% of maximum).
Assessing Maximum Demand is a refined art - some say a dark art. It's most likely the case that no two electricians would assess maximum demand to be the same on the same installation (though they shouldn't be too far apart).
It may be that 60A was derived from the sticker on the side of the main fuse. This sticker may or may not be telling the truth.
If you do mean Maximum Demand - it is the total current demand of your installation after taking into account diversity on some circuits - e.g. light circuits (i.e. not all lights are likely to be on at the same time so we can make an allowance for them of 66% of maximum).
Assessing Maximum Demand is a refined art - some say a dark art. It's most likely the case that no two electricians would assess maximum demand to be the same on the same installation (though they shouldn't be too far apart).
I got the impression from the electrician that once my layout, no. of circuits etc had been worked out, it could be the case that the 60A supply wouldn't be sufficient, and if so, the elec company would need to put a bigger fuse in(?).
So I just wondered if it was just a simple case of adding up the Amp rating of the MCBs (my guess is "No". Stupid question I'm sure, but all helpful answers are gratefully received.)
So I just wondered if it was just a simple case of adding up the Amp rating of the MCBs (my guess is "No". Stupid question I'm sure, but all helpful answers are gratefully received.)
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Does the big main electric board fuse holder have 60A on the outer casing, the one with the E board seal on possibly
DO NOT PULL IT OUT TO LOOK THOUGH
DO NOT PULL IT OUT TO LOOK THOUGH
Some electricians estimate Maximum Demand on the high side, (alas)often on the very high side.
If you list all the circuits you have and the rating of their MCBs, I'm sure we could offer two things:
1. an assessment of Maximum Demand
2. a subsequent disagreement on the figures for Maximum Demand
If you list all the circuits you have and the rating of their MCBs, I'm sure we could offer two things:
1. an assessment of Maximum Demand
2. a subsequent disagreement on the figures for Maximum Demand
For what it costs I would use 25mm ,at least it will be there for you,if you do need an upgrade to a 100 amp supply in the future,
the main swith of the new cu will most likely be 100 amp rating
the main swith of the new cu will most likely be 100 amp rating
Sound advice.
OK thanks,
this is the way it's looking..
1. Lighting 6A (4 beds, ensuite, wardrobe lights)
2. Lighting 6A (outside lights)
3. Lighting 6A (extension, kitchen)
4. Lighting 6A (hall, bathroom, toilet, extractors, airing)
5. Radial 16A (utility w/machine, t/drier, ironing, sitting room, study)
6. Ring 32A (4 beds, hall sockets)
7. Ring 32A (kitchen sockets, extractor, d/washer, kickspace heater, workshop sockets, dining room sockets, upstairs (one room) sockets, lobby socket.)
8. Cooker
9. Shower
10. Smoke detectors
11. Central heating
12. Immersion
I realise some of these can be joined, but I'll probably go for a MK 17 way split load, so can afford to keep things separate.
this is the way it's looking..
1. Lighting 6A (4 beds, ensuite, wardrobe lights)
2. Lighting 6A (outside lights)
3. Lighting 6A (extension, kitchen)
4. Lighting 6A (hall, bathroom, toilet, extractors, airing)
5. Radial 16A (utility w/machine, t/drier, ironing, sitting room, study)
6. Ring 32A (4 beds, hall sockets)
7. Ring 32A (kitchen sockets, extractor, d/washer, kickspace heater, workshop sockets, dining room sockets, upstairs (one room) sockets, lobby socket.)
8. Cooker
9. Shower
10. Smoke detectors
11. Central heating
12. Immersion
I realise some of these can be joined, but I'll probably go for a MK 17 way split load, so can afford to keep things separate.
Very true.
After diversity you'll find that a general household comprising of shower, cooker, 3 ring finals, heating, 2 lighting circuits and an alarm will add up to more than 100A. An overall diversity assessment should then be made.
It's amazing how many so called 'electricians' will just give the sum of all the protective devices in total.
nope.
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