Uprating electric supply

dil1976

robatwork wrote: »

If only! A sadly boring answer that my sparks has to move my consumer unit and has advised uprating from 60 to 100.

Back on topic, i wouldn't bother. as I said earlier your house has run fine on what is already there so there shouldn't be any problems in the future unless you have any major electrical works done. But this would be advised before any works commenced.

DVardysShadow

dil1976 wrote: »

And the relevance to the OPs question is?

:rotfl::rotfl::rotfl::rotfl::rotfl:

That your contribution:

dil1976 wrote: »

A 60 amp fuse BS 1361 type 2 fuse would quite easily take 80 amps for a reasonable amount of time.

is not relevant to the OP's question.

dil1976

Well mentioning that having a 45 amp shower so will blow a fuse is hardly constructive when, if you were as knowledgeable as you make out should know that firstly it would never draw that higher current, secondly 60 amp fuses are more common than folk think and there has never been a mass roll out to change them, therefore they are more than adequate in probably more than 95% of domestic premises that they are fitted.

DVardysShadow

dil1976 wrote: »

Well mentioning that having a 45 amp shower so will blow a fuse is hardly constructive when, if you were as knowledgeable as you make out should know that firstly it would never draw that higher current, secondly 60 amp fuses are more common than folk think and there has never been a mass roll out to change them, therefore they are more than adequate in probably more than 95% of domestic premises that they are fitted.

A little knowledge...

If a 45A shower circuit never drew more than 45A, of course, you would not need to fuse it in the first place.

But you do need to fuse it - and fusing needs to take into account cable faults just as much as appliance faults - if not more so. A 45Amp fused circuit, if correctly designed will have a minimum fault potential of 900A at its far end [BS7671 Appendix 12 and a simple % calculation].

So you are making a bit of a brass of yourself to suggest that it is not constructive to suggest that a 45A shower circuit could never draw enough current to blow a 100A fuse.

Although 60Amp service fuses are quite common, if the OP does indeed have a 45A final subcircuit, I have shown that the service fuse should be at least 100A for correct fuse discrimination.

Of course, if you don't see any benefit in fuse discrimination, then a 60A fuse will do. The fact that there has never been a mass rollout of upgraded service fuses has more to do with it being the customer's responsibility to request and pay for the upgrade when they have final subcircuits fused above 30A. The downside of 45A circuits on a 60A company fuse is that if a serious short occurs on a final subcircuit, it can take out the company fuse. Which [to bring it back to relevance to the OP's question] is probably why the electrician is recommending that the company fuse be upgraded to 100A.

Ectophile

DVardysShadow wrote: »

:rotfl::rotfl::rotfl::rotfl::rotfl:

That your contribution:



is not relevant to the OP's question.

It's totally relevant, and I struggle to see why you would think otherwise.

In the real world, a 60A fuse will not blow if you occasionally put 80A through it while having a shower. So upgrading to a larger fuse may well cost the OP money which need not be spent.

dil1976

DVardysShadow wrote: »

A little knowledge...

If a 45A shower circuit never drew more than 45A, of course, you would not need to fuse it in the first place.

But you do need to fuse it - and fusing needs to take into account cable faults just as much as appliance faults - if not more so. A 45Amp fused circuit, if correctly designed will have a minimum fault potential of 900A at its far end [BS7671 Appendix 12 and a simple % calculation].

So you are making a bit of a brass of yourself to suggest that it is not constructive to suggest that a 45A shower circuit could never draw enough current to blow a 100A fuse.

Although no diversity is allowed on instantaneous water heaters, where, lets say the the oven, heating and hot water are all gas. Where would you use 15 amps in a house otherwise, even a kettle and iron on at the same time would struggle to to pull that.

So yes I would leave the 60 amp fuse in place. It really would take something to blow the main fuse. Sometimes common sense has to over take anything else.

DVardysShadow

Ectophile wrote: »

It's totally relevant, and I struggle to see why you would think otherwise.

In the real world, a 60A fuse will not blow if you occasionally put 80A through it while having a shower. So upgrading to a larger fuse may well cost the OP money which need not be spent.

You are totally mistaken here. The 80Amps is dil1976's red herring. I am certainly not arguing that a brief period at 80A will blow the company fuse, because it probably won't. But this is irrelevant to determining the correct size of company fuse for the installation.

The real current to be considered is a dead short on the shower cable. This certainly can blow a 60A company fuse, even if the 45A final subcircuit fuse blows. Which is why a 100A company fuse is required.

DVardysShadow

dil1976 wrote: »

Although no diversity is allowed on instantaneous water heaters, where, lets say the the oven, heating and hot water are all gas. Where would you use 15 amps in a house otherwise, even a kettle and iron on at the same time would struggle to to pull that.

So yes I would leave the 60 amp fuse in place. It really would take something to blow the main fuse. Sometimes common sense has to over take anything else.

The argument you quote is about fuse discrimination. But you now discuss Diversity. Diversity is another matter altogether. It has been raised as something which may have influenced OP's electrician. We don't have enough information to do a diversity calc for OP's installation. So we cannot say one way or the other whether 60A is adequate.

dil1976

DVardysShadow wrote: »

The argument you quote is about fuse discrimination. But you noe discuss Diversity. Diversity is another matter altogether. It has been raised as something which may have influenced OP's electrician. We don't have enough information to do a diversity calc for OP's installation. So we cannot say one way or the other whether 60A is adequate.

Whereas if OP has a 45A circuit, we can say that a 60A service fuse is not adequate to provide fuse discrimination..

Exactly which goes back to what I said earlier, if the house has been fine for several years now. I see no point in upgrading the fuse. Should works be carried out in the future then it may need upgrading.

Seeing as it only moving a DB I can't see why it needs it.

DVardysShadow

dil1976 wrote: »

Exactly which goes back to what I said earlier, if the house has been fine for several years now. I see no point in upgrading the fuse. Should works be carried out in the future then it may need upgrading.

Seeing as it only moving a DB I can't see why it needs it.

Indeed, your logic is overwhelming. If none of the fuses have blown for several years, when the sparky moves the consumer unit, he need not bother with fuses at all, because the house has been fine for several years.

Fuse discrimination is only important when fuses blow. If you don't believe the fuses will blow, then don't bother about it. After al, the 200ms when a fuse blows is only 0.000006% of the once in 10 years that it blows, so it is totally disproportionate to spend money on it.

Not that I accept your logic.