What is the rating of the cable as installed? I'm thinking a multicore in conduit is Method B which from table 4D2A (4D5 doesn't have a column for method B) has a rating of 38A which therefore not suitable for a 40A MCB.
Is a 45A circuit suitable for a 17.1kw electric cooker?
- Thread starter xdave
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Is that size cable rated for the load that will be on it, given its installation method?
That might be more than the cable rating.
But the biggest problem is that the installation instructions for the cooker tell you to provide a 45A supply, not a 40A one, so your proposal will not comply with the instructions and therefore will not comply with the wiring regulations, so if your electrician signs an EIC for it it will be false, and therefore so will his declaration that the work complies with the Building Regulations.
The difference in price between 6mm² and 10m² is small, and when looked at in the context of the overall cost for the work and the new appliances it's non-existent. There is absolutely no excuse for not doing it properly.
Do not use a 40A breaker, and do not use 6mm² cable.
Earthed conduit?
Over its entire length?
No socket on the CCU?
I can't answer that, but you have suggested that it isn't so I will query it.
The manual is here. I can't find any numbers in there but the company I bought it through provided instructions that showed positions, ratings, and so on and it did show a 45A DP switch. However over the phone the manufacturer said that a 45A circuit would be fine. I will query with the electrician if they meant 'up to' or 'minimum'. I was present when he called them but I didn't hear the whole conversation.
That's why I'm asking.
I understand the reasons why from these replies and I will pass those on. If the cable is changed to 10mm/2 would the breaker not still need to be less than 45A because the isolator switch in the kitchen is rated at 45A? Or is that wrong as well?
Yes to all three. Fortunately that much I do understand. It's when numbers and ratings come along that my eyes glaze over.
Completely OT, what do you have against sheds?
I mean this:
not this:
not this:
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Screwfix is the online shed offering from the company that owns B&Q sheds.
TP have grown their business by buying up small independent companies and assimilating them into their green and yellow sheds.
Jewsons have probably done the same - I wonder how many independent timber merchants owned and run by people with a stake and a pride in their business and proper product knowledge are left?
Isn't PlumbCentre a plumbing shed?
TP have grown their business by buying up small independent companies and assimilating them into their green and yellow sheds.
Jewsons have probably done the same - I wonder how many independent timber merchants owned and run by people with a stake and a pride in their business and proper product knowledge are left?
Isn't PlumbCentre a plumbing shed?
Hi bas, sorry for the delay, I wasn't able to reach the electrician yesterday. He has said that he calculated that 6mm cable would be ok but is happy to install 10mm if I want. I said 'I want', so that is sorted I think. Even if it turns out not to be needed for this cooker I guess it gives flexibility in the future should I find the cooker is unbearable and want to change it. I am paying his material costs + 30% so he said it would only be about £15 more which is well within the 20% extra I allowed for the unforseen problems you don't find until the day of installation.
I queried whether the manufacturer specified 'up to' or 'at least' a 45A circuit for the cooker and he said it doesn't make any difference. As they specified 45A that is what he has designed it for... and I agree it was a silly question for me to ask. I was not thinking very logically there!
I asked whether a 40A MCB was still suitable and he said that a 45A MCB was not available for my CU, but that the one I already have (not used) would not trip until at least three times that amount was being drawn. Cooker isolation switches are only available in 45A in the range I've asked for so the MCB cannot be rated greater than that. As the manufacturer wants a 45A circuit that is ok and the MCB would protect the cooker and the switch from overload damage.
Does this sound reasonable? Is it true that circuit breakers only trip at over three times the rated current? That sounds a bit dangeous to me (120A needed to trip a 40A breaker?)
I queried whether the manufacturer specified 'up to' or 'at least' a 45A circuit for the cooker and he said it doesn't make any difference. As they specified 45A that is what he has designed it for... and I agree it was a silly question for me to ask.
I was not thinking very logically there!I asked whether a 40A MCB was still suitable and he said that a 45A MCB was not available for my CU, but that the one I already have (not used) would not trip until at least three times that amount was being drawn. Cooker isolation switches are only available in 45A in the range I've asked for so the MCB cannot be rated greater than that. As the manufacturer wants a 45A circuit that is ok and the MCB would protect the cooker and the switch from overload damage.
Does this sound reasonable? Is it true that circuit breakers only trip at over three times the rated current? That sounds a bit dangeous to me (120A needed to trip a 40A breaker?)
Seriously - if you've got an electrician who thinks that 6mm² cable is OK for a 45A circuit then it's time for you to get a new one.
//www.diynot.com/forums/viewtopic.php?p=76467#76467Does this sound reasonable? Is it true that circuit breakers only trip at over three times the rated current? That sounds a bit dangeous to me (120A needed to trip a 40A breaker?)
I would have preferred to have used the firm that fitted my new consumer unit, but unfortunately given that they relied on work from one of the main house builders they went out of business before xmas (and were honest enough to admit they would probably not be able to carry out the work so I wouldn't lose my deposit).
When I went out for quotes last year I approached five firms/individuals; only two bothered to turn up to talk through my requirements in person, and the guy I am using now was the only one who took the time to look in detail at what I currently had (as mentioned earlier, the consumer unit was recently changed and some circuits added, such as electrical cable already run through to the new extension ready to be connected). He quoted a little bit more but gave me more confidence in him than the other guy did who seemed very dismissive about things I think are quite important. (eg. "oh that doesn't matter as you won't see it" and taking it on word that the prep work was done correctly without actually checking.) I've used people like that before when forced to and the unforseen costs come installation build up quickly - or they take shortcuts - neither of which are acceptable to me.
The electrician is on www.competentperson.co.uk, and was recommended by my LABC BCO when I submitted the building notice last year and said who I was using. He seems very thorough and takes the time to explain to me why he is doing things one way over another. When I had the new boiler put in over xmas the 'major central heating/energy provider with a blue flame as their logo' electrician just wired it in to the old fuse box immersion heater circuit, even though the old fuse box had a label on it saying it only provided circuits for the kitchen and our existing 13A oven (on the old cooker circuit), and would be disconnected soon. There was a new MCB installed in the new consumer unit marked 'boiler' when we had it installed. The guy I am using now for my extension/kitchen had to wire it in properly and give me a form for it... even though the 'blue flame' electrician had sited the FCU for the boiler right next to the new consumer unit and ran flex from that down the wall to the old fuse box. The 'blue flame' guy also didn't use our existing thermostat despite it having woked with the old boiler so now we have two thermostats and timers to control heating in the same parts of the house (radiators and underfloor heating). That is unecessary because we paid extra to have a thermostat put in that was able to monitor and control both systems from the same control panel.
I work in an IT engineering field, so I know that two equally educated professionals can disagree on all sorts of things relating to their profession, even fundamental things, which is why I'm asking here to gather more answers on the questions I've asked. I assumed that when it comes to cables and ratings - the base units that electricians work in - there should be little disagreement, but I don't believe the electrician I am using is necessarily bad. No one can know everything, but he must have passed the relevant exams to become a member of NICEIC and get on that website so I am prepared to give him a chance. If those exams mean nothing then how can I, Joe Public, ever hope to choose a qualified tradesperson to carry out work for me?
Thanks for the link bas, I read it, thought about it then read it again and I think I know what he meant about tripping current. Being piggy in the middle sometimes I misinterpret what I've been told or just plain don't understand it which makes it awkward to relay, but it makes sense now.
When I went out for quotes last year I approached five firms/individuals; only two bothered to turn up to talk through my requirements in person, and the guy I am using now was the only one who took the time to look in detail at what I currently had (as mentioned earlier, the consumer unit was recently changed and some circuits added, such as electrical cable already run through to the new extension ready to be connected). He quoted a little bit more but gave me more confidence in him than the other guy did who seemed very dismissive about things I think are quite important. (eg. "oh that doesn't matter as you won't see it" and taking it on word that the prep work was done correctly without actually checking.) I've used people like that before when forced to and the unforseen costs come installation build up quickly - or they take shortcuts - neither of which are acceptable to me.
The electrician is on www.competentperson.co.uk, and was recommended by my LABC BCO when I submitted the building notice last year and said who I was using. He seems very thorough and takes the time to explain to me why he is doing things one way over another. When I had the new boiler put in over xmas the 'major central heating/energy provider with a blue flame as their logo' electrician just wired it in to the old fuse box immersion heater circuit, even though the old fuse box had a label on it saying it only provided circuits for the kitchen and our existing 13A oven (on the old cooker circuit), and would be disconnected soon. There was a new MCB installed in the new consumer unit marked 'boiler' when we had it installed. The guy I am using now for my extension/kitchen had to wire it in properly and give me a form for it... even though the 'blue flame' electrician had sited the FCU for the boiler right next to the new consumer unit and ran flex from that down the wall to the old fuse box. The 'blue flame' guy also didn't use our existing thermostat despite it having woked with the old boiler so now we have two thermostats and timers to control heating in the same parts of the house (radiators and underfloor heating). That is unecessary because we paid extra to have a thermostat put in that was able to monitor and control both systems from the same control panel.
I work in an IT engineering field, so I know that two equally educated professionals can disagree on all sorts of things relating to their profession, even fundamental things, which is why I'm asking here to gather more answers on the questions I've asked. I assumed that when it comes to cables and ratings - the base units that electricians work in - there should be little disagreement, but I don't believe the electrician I am using is necessarily bad. No one can know everything, but he must have passed the relevant exams to become a member of NICEIC and get on that website so I am prepared to give him a chance. If those exams mean nothing then how can I, Joe Public, ever hope to choose a qualified tradesperson to carry out work for me?
Thanks for the link bas, I read it, thought about it then read it again and I think I know what he meant about tripping current. Being piggy in the middle sometimes I misinterpret what I've been told or just plain don't understand it which makes it awkward to relay, but it makes sense now.
I was just about to reply to all that when you got rid of most of it.
So I'll just reply to what's left.
Why 3 x 10mm²?
So I'll just reply to what's left.
Why 3 x 10mm²?
because the manual says it can have a 3 phase input or 3 x live + 3 x neutral ( does specify 6mm max cable size if not using the jumper which has a 10mm capacity )
you'd need a 3 pole switch though...
EDIT: must use spell checker...
you'd need a 3 pole switch though...
EDIT: must use spell checker...
You may not have seen the original post - it was much longer and full of all sorts of interesting claims.
One of which was that the beast would require serious earthing, and that the cpc should be 10mm²...
One of which was that the beast would require serious earthing, and that the cpc should be 10mm²...
3x10mm2= L+N+PE.
Had some great claims, but they didn't look so great on screen, so yeah I had to delete them! (At least Mr Shed got to enjoy it) Still I think it is a monster of a cooker. Maybe 3-phase/400V wouldn't be so stupid mm2 wise! (that's a joke)
ps. earthing fixtures and your home properly is nothing to be ashame of! ds.
Had some great claims, but they didn't look so great on screen, so yeah I had to delete them! (At least Mr Shed got to enjoy it) Still I think it is a monster of a cooker. Maybe 3-phase/400V wouldn't be so stupid mm2 wise!
(that's a joke)ps. earthing fixtures and your home properly is nothing to be ashame of! ds.
So are you expecting very high protective conductor currents from this cooker? To the extent that the cpc normally considered adequate in 10mm² T/E would not be sufficient?
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