Old house, new cooker...

We are currently renovating our old-ish house. Recently we had a new electic meter installed, and the chap who did it \\\'down-graded\\\' our main breaker to 60Amps. Apparently the tails weren\\\'t big enough to support more.

I now want to install a new range cooker, and the one I have my eye on rates at 14.7Kw (Max - when all added up), which is 63.91 Amps (if I\\\'ve worked it out right). Does this mean that I can\\\'t get this cooker? With diversity is it possible, or even sensible? I\\\'m not sure if the hob and oven sections can be wired seperately. In which case maybe I could wire two isolated circuits, one for each?

Any suggests or tips?

Thanks

David.

elliethespyder said:

We are currently renovating our old-ish house. Recently we had a new electic meter installed, and the chap who did it \\\'down-graded\\\' our main breaker to 60Amps. Apparently the tails weren\\\'t big enough to support more.

I now want to install a new range cooker, and the one I have my eye on rates at 14.7Kw (Max - when all added up), which is 63.91 Amps (if I\\\'ve worked it out right). Does this mean that I can\\\'t get this cooker? With diversity is it possible, or even sensible? I\\\'m not sure if the hob and oven sections can be wired seperately. In which case maybe I could wire two isolated circuits, one for each?

Any suggests or tips?

Thanks

David.

Click to expand...

Is Hob seperate from the Oven?

What is the wattage of the Hob?

What is the wattage of the Oven?

What is the cable length from the cooker position to the CU?

Can you run another cable to the CU, if you need to?

The simplest solution is to get an electrician out to upgrade your meter tails (25mm) and get the DNO back to upgrade the fuse. Your service fuse will probably take the 63A of the cooker (while on full load) for quite a while, but you still have the rest of the house to consider...

Whether you wire the cooker and hob separately won't alter the power consumption, you will still want to use them both at the same time. But regardless it would be a good idea to wire 2 radials for the cooker.

Diversity for cookers: 10A + 30% of remaining load + 5A if you have a socket at the cooker switch.

So:

10A + 16.17A = 26.17A or 10A + 16.17A + 5A = 31.17A

This is fine and won't cause you any problems as long as you have appropriate cable and a suitable MCB.

Davy

Thanks for the speedy replies! Mosez, in answer to your questions, I'm assuming the hob and cooker are all in one, but don't know. It's a freestanding rangecooker, so I'll have to go see one, or at least see the installation instructions to know if they can be seperated. I think hob and oven sections were roughly half and half power-wise, of the 14.7kw (off the top of my head). As for distance from the CU it's about 4m (as the crow flies, probably 5m for the wiring) so not far. No problem running another cable if required.

Dave, thanks for the heads up on getting things upgraded. I'm surprised the guy from the board didn't suggest it at the time. That might be the best idea. Is it possible that the supply to the building is not capable of more than a 60Amp load? I.e. would it be likely that the board would have to replace the main feed to the house in order to allow a 100Amp load?

Anyway, excellent responses! Many thanks.

David.

elliethespyder said:

Dave, thanks for the heads up on getting things upgraded. I'm surprised the guy from the board didn't suggest it at the time. That might be the best idea. Is it possible that the supply to the building is not capable of more than a 60Amp load? I.e. would it be likely that the board would have to replace the main feed to the house in order to allow a 100Amp load?

Click to expand...

The guy who replaced the meter probably didn't mention it because they don't care, they are only there to do what they were told to do - the things they fail to 'mention' to the property owner boggles the mind.

Anyway, if you had a larger fuse originally then there shouldn't be any reason for them not to put it back. I'm assuming the tails connecting the meter to the consumer unit are either 16mm or possibly a length of twin & earth? If you upgrade those then you should be up to standard and they should upgrade the fuse no problems. The only reason they wouldn't upgrade the fuse after the tails are replaced would be if main supply cable wasn't substantial enough, in which case they should never have fitted the larger fuse in the first place.

Just give your DNO a ring and find out from them what the situation was/is.

Diversity for a cooker is as stated 10A + 30% of rest + 5A for an outlet, while you'd probably be ok doing so*, I'd probably not take it to this extreme for a individual cooker circuit and would probably install 10mm² cable on a B40 breaker

*remember that heating elements cycle on an off, etc

But there is no probablem in using this diversity across the whole installation, if you want to add it all up, cookers are as above, lights are 66% of total, sockets are 100% of the first (biggest) circuit and 40% of the rest and immersion heaters the full load (13A)

This will probably come out quite high, a better way is a clamp meter around one of the tails for real world figures (or sometimes the sparky makes an educated guess at max demand)

Quite often adding up diversified circuits will give you a figure of 150A or so with a house that has a 60A main fuse, doesn't often burn out in practice, normally you won't be pulling 60A for any length of time in a standard house** (and besides, you need to pull more than 60A to make it fail and for quite some time)


** This obviously doesn't apply if you run 'ahem' a gardening business from your attic.... etc

If you upgrade the tails (you'll have to have the DNO pull the fuse an open up the meter then its likely that they can stick a bigger fuse back in for you )



As a side note, it might be interesting to note that the DNO generally work on a basis of 10A per house average to size their kit (averaged over half an hour roughly), but this works because their stuff can tolerate gross overloads (ie. at dinner time) for a short while due to the thermal capacity of all that metal and oil of the local distribution transformer. Obviously in a house things are averaged over much shorter periods, but 60A is pretty fair as it goes