Paul Posted January 30, 2005 Share Posted January 30, 2005 Hi, don't know if any sparkies are on this board or anyone familier with wiring but I need a bit of advice. I'm in the process of ripping out the kitchen and will be installing new built in oven and a combination microwave. I've looked at the tech info for these and the current draw is as follows Single Oven........Max current draw 15 Amps Combi Microwave....... Total connected load 3.6KW (15.65 Amps?) Would there be any problem connecting both to the same dedicated 30 Amp supply using 6mm cable to feed them? As these are Max values and I heard something about 'diversity' being used. BTW. I know about part P..........but I fitted these last year Paul Quote Link to comment Share on other sites More sharing options...
Toytown Posted January 30, 2005 Share Posted January 30, 2005 Hi m8, assuming you have a modern distribution unit, you will be using a 32A mcb & the 6mm will be fine unless it's a rediculous long run (not worked it out but I doubt that will be an issue). IF you have an old fuseboard: 1: get shot & have it replaced so you get RCD protection 2: Still no problem with the above because your 30A fusewire will be protecting a cable that can handle 38A (if I remember correctly) No way would both of them running flat out bust a 30A fuse, well it would take hours (again it could be calculated but i don't have the formulae handy). in a sentence: Yep do it Just as another point, your 15.56A was obviously worked out on the stated 230v, i bet if you meter your suply you get nearer 240v which brings the load down to 15A max Quote Link to comment Share on other sites More sharing options...
merckx Posted January 30, 2005 Share Posted January 30, 2005 Has the kitchen got it's own 30A fused supply already, or are you going to take a new supply from the consumer unit. If so, is it a ring circuit or radial circuit? The power rating of the combi microwave appears to be very high! Quote Link to comment Share on other sites More sharing options...
merckx Posted January 30, 2005 Share Posted January 30, 2005 Just as another point, your 15.56A was obviously worked out on the stated 230v, i bet if you meter your suply you get nearer 240v which brings the load down to 15A max Infact the current draw will be higher, to calculate the current on AC you cannot simply divide the power by the voltage. You have to consider the power factor. Quote Link to comment Share on other sites More sharing options...
Toytown Posted January 30, 2005 Share Posted January 30, 2005 Infact the current draw will be higher, to calculate the current on AC you cannot simply divide the power by the voltage. You have to consider the power factor Not on domestic electrical installation as far as I am aware, although I do admit it was a few years ago I did the course ! Surely this wouldn't apply to a resistive load ? Please enlighten me if I have missed something critical but I can't remember this being a factor on domestic work ?? Quote Link to comment Share on other sites More sharing options...
Paul Posted January 30, 2005 Author Share Posted January 30, 2005 Cheers lads, Right then, yes it's on an old style fuse board, I intend to upgrade it but not before fitting these. So the max fuse is 30amp and yes there is a dedicated supply for the cooker. The Microwave is a combi, grill etc, and a high spec Bosch one, Quantum Speed???????? Maybe that's why the rating is higher than expected? Paul Quote Link to comment Share on other sites More sharing options...
Toytown Posted January 30, 2005 Share Posted January 30, 2005 Hope we helped in some little way Paul FWIW, I would do it & not have any problem with doing it for myself or anybody else. merckx might have a "technical" point but as i said above, in quite a few years of domestic contracting I can't ever remember a problem. Your cable is rated @ 38A & you're protecting it with a 30A wire, the chances of that wire blowing are on the borders of zero - trust me Quote Link to comment Share on other sites More sharing options...
merckx Posted January 30, 2005 Share Posted January 30, 2005 Not on domestic electrical installation as far as I am aware, although I do admit it was a few years ago I did the course ! Surely this wouldn't apply to a resistive load ? Please enlighten me if I have missed something critical but I can't remember this being a factor on domestic work ?? Doesn't matter if it's domestic or industrial, the loads involved are unlikely to be purely resistive. Infact the microwave would have some element of inductance therefore the current draw woud be higher. Saying that, for most domestic installations you would simplify the calculations and use more than sufficient size cables anyway. Quote Link to comment Share on other sites More sharing options...
merckx Posted January 30, 2005 Share Posted January 30, 2005 Your cable is rated @ 38A & you're protecting it with a 30A wire, the chances of that wire blowing are on the borders of zero - trust me I agree, if you're just supplying the oven and microwave you'll be fine. How are you wiring them in to the circuit? Quote Link to comment Share on other sites More sharing options...
Toytown Posted January 30, 2005 Share Posted January 30, 2005 Think we better draw a line under this one m8, before we bore the arse of the other supra bods From what I can see, we are both correct: Your technical observation is correct, I agree it's not 100% resistive load. My advice was correct (PLEASE dispute if I have missed something important, although I'm pretty confident my advice was both safe and usual practice in a domestic situation) Looks like we got a happy customer Quote Link to comment Share on other sites More sharing options...
Toytown Posted January 30, 2005 Share Posted January 30, 2005 How are you wiring them in to the circuit From the initial post, I assumed that a new 6mm was being installed, from an unused 30a fuse. On the other end (again I assume) D/P isolator switches (I would prefer 45A cooker isolators, dunno why would just feel happier with them ?? Quote Link to comment Share on other sites More sharing options...
merckx Posted January 30, 2005 Share Posted January 30, 2005 I just wanted to make sure that the wiring into the isolator switches was ok and the 6mm supply was only being used by these 2 items . Wouldn't want this bloke to have any problems with overloading. Quote Link to comment Share on other sites More sharing options...
400BHP Posted January 30, 2005 Share Posted January 30, 2005 I don't want to pour cold water on this but are you aware that undertaking any electrical work in your home unless you are an NIC electrician is against the law? Also, does your oven have a plug top on it or just a connection on the back for an incoming cable (ie to go to a cooker panel) Quote Link to comment Share on other sites More sharing options...
Toytown Posted January 30, 2005 Share Posted January 30, 2005 Wouldn't want this bloke to have any problems with overloading absolutley agree 100% m8. I don't want to pour cold water on this but are you aware that undertaking any electrical work in your home unless you are an NIC electrician is against the law? He said the work was "previously done Yes the installer should be Part P reg'd which means belonging to an official body like NIC / ECa or many others by now i don't dount Also, does your oven have a plug top on it or just a connection on the back for an incoming cable (ie to go to a cooker panel) I assumed the are not, simply for the loading @ 15A. Doubtful any manufacturer would produce an appliance capable of pulling 15A & then pop a 13A plug on the end of it Quote Link to comment Share on other sites More sharing options...
merckx Posted January 30, 2005 Share Posted January 30, 2005 I don't want to pour cold water on this but are you aware that undertaking any electrical work in your home unless you are an NIC electrician is against the law? I think you can do the work yourself but you have to get it inspected by the council. Saying that, If you're not confident then get someone else to do it. Quote Link to comment Share on other sites More sharing options...
Toytown Posted January 30, 2005 Share Posted January 30, 2005 I think you can do the work yourself but you have to get it inspected by the council. Dunno about the council but certainly by a Part P auth sparks or the building inspector bods. Part P is another useless piece of red tape, the cowboys will still do cash jobbies, no receipt not warrnaty & the only ones that will suffer are the one man band (good) spraks that can't afford the time & costs of belonging to ECA/NIC etc. Bloody glad I got out of the game a few years ago Quote Link to comment Share on other sites More sharing options...
Whitelightning Posted January 30, 2005 Share Posted January 30, 2005 Hmmm electricity is VERY dangerous. If in doubt - lick it and see Quote Link to comment Share on other sites More sharing options...
Terminator Posted January 30, 2005 Share Posted January 30, 2005 Dont hold your breath waiting for someone to come and check, most electricians have better things to do than to come a check some cables. Quote Link to comment Share on other sites More sharing options...
Paul Posted January 30, 2005 Author Share Posted January 30, 2005 Thanks all, Yes I'm looking at running a fresh supply from a spare 30 amp out using 6mm cable. This will be the only thing off this, ie the oven and microwave. I'm also looking at putting individual isolator switches for each (45 amp) mounted to the side of the unit they are fitted in. As I see the new part P, it's OK to install all this as long as the building inspector for the council or someone else qualified checks it out. I can assure you though that any doubt I will contact a spark and let them tuck me up , I mean sort it. Anyway, I did this last year, remember? As mentioned earlier, this might be a good time to change the consumer unit. I know the cost of these but any idea of the sort of charge for changing one or the rough time it should take? Thanks again all for in depth answers, really has helped me. Paul Quote Link to comment Share on other sites More sharing options...
Rob Posted January 31, 2005 Share Posted January 31, 2005 I don't want to pour cold water on this but are you aware that undertaking any electrical work in your home unless you are an NIC electrician is against the law? It's illegal to exceed the speed limit as well, even if no-one sees you. Quote Link to comment Share on other sites More sharing options...
Jake Posted January 31, 2005 Share Posted January 31, 2005 ...and the nominations for "Dullest Thread Of The Year" are...... :D Quote Link to comment Share on other sites More sharing options...
Whitelightning Posted January 31, 2005 Share Posted January 31, 2005 ...and the nominations for "Dullest Thread Of The Year" are...... :D Ok, who is for dancing Mexican Llamas ? Perish the thought we get voted the most boring thread. I say bring on the Llamas and to hell with it !! (OK, if you squint - they COULD be Llamas. Hey ! No icons - comprendez !) Quote Link to comment Share on other sites More sharing options...
400BHP Posted January 31, 2005 Share Posted January 31, 2005 in all honesty you'd be better off just running the oven off the 45 amp breaker you suggested and the microwave off the kitchen ring main, a 45 amp double pole switch wont have a fuse in it and in order to run your microwave you'd need to run a radial off of the 6mm circuit into the back of either a switched spur or 13a outlet, in order to connect the microwave, which will need to be fused at 13amps. If you do run this radial off of the 45amp switch, either do it in 2x 2.5t&e or the 6mm. Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 31, 2005 Share Posted January 31, 2005 Just a slight thread hijack: Please can someone who knows clarify this new "illegality" of doing your own electrical DIY? I heard about it a couple of weeks back and couldn't believe my ears! I've always done my own electrical work and I'm buggered if I'm going to pay a bazzillion quid for a sparky to come out every time I want a new wall socket putting in. Does this mean that B&Q won't be selling wall sockets and switches anymore? Quote Link to comment Share on other sites More sharing options...
Supragal Posted January 31, 2005 Share Posted January 31, 2005 Although some people are capable of this kind of thing, many aren't... I happen to agree with the new law in general and the idea of buying a house that some muppet with no clue has messed about with worries me somewhat. Quote Link to comment Share on other sites More sharing options...
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