Discussion in 'Electricians' Talk' started by COYR, Dec 30, 2013.
That's interesting to know, thanks for that.
just to let you know that after weighing up all the helpful advice given on this thread I decided to connect up my oven on a like for like basis. After checking the cable from the Consumer Unit it appears the outer sheath has been stripped/plastered as far back as behind the adjacent Kitchen units so doing any further work with this at the back of the oven housing would not have been possible.
I also checked the Junction Box and it is 30 amp. We are planning on getting some extra sockets and an outside light fitted in a few months which I will employ an electrician to do. Whilst he is here doing that I'll get him to run a new cable from the Oven/Hob back to the Consumer Unit (only a few metres away) and tidy up the other fittings.
Thanks again for your help.
Please do not wire your single oven in with out the 13amp fuse. That fuse is there to protect the appliance and the cable that feeds the appliance from if the cooker developed a fault, otherwise why would the manufacturer fit it (most single ovens do not get supplied with a plug as the manufacturer leaves it up to the installer to choose between putting on a plug or fitting it directley into a fused connection unit) and why does every thing else electrical in mine and your house have a 13 or 5 or a 3amp fuse on the end of it. It is unsafe a bad practice to wire your oven in with out that fuse on the end of the cable due to how the manufacturers have designed your oven. Bigger ovens are different, due to how they are designed and the cable that feeds them but yours must have a 13amp fuse. If you are unsure then contact the manufacture and get it confirmed, but I can put money on it that they will back me up. I hope you get that electrician around soon as the rest of the electrics behind your cooker are substandard as I know you are aware from the other post's. Regards Chris.
Excellent post Mad 4
I am amazed at the poor standard of meter fitting in this country. I often see heavy 25mm wires looped around and loose from the main fuse to the meter and from the meter to the CU and all unclipped. Some stick out which is easy for kids to hang off.
I thought British plumbers were generally poor in quality of workmanship and product specification, but electricians are clearly poorer overall. This is not plumber v Spark contest, just that electricians and utility companies have to get better. I have never seen heavy wires hanging off CUs in the USA or Germany.
I find "most" DIYers look at the best way of doing electrical things aim to do things properly and neat and will take the time to get it neat.
The reason we have 13A fuses is to plug into rings. A ring has a 32A mcb at the Consumer Unit. Say it has 10 sockets off that ring. In theory 10 3kW heaters can all be on at the same time before the mcb trips to protect the ring cable. That is about 120A. The 32A mcb will trip of course. They assume that average use will not exceed 32A. You can take about three 3kW kettles off one ring. All plug in appliances. The 13A fuse is to protect the appliance cable and ring, so large appliances greater rhan 3kW are not plugged into a ring. Note there are no plug fuse ratings higher than 13A. On the Continent they do not have fused plugs. They use radial circuits rated at 16A, so fused plugs are not needed. This means they use more circuits while the cheapo Brits use two rings in one house, saving cheap cable and have a tiny Consumer Unit. Note how much bigger Continental CUs are. Saying that there are advantages to use rings.
Note that the lighting circuits in houses are radial circuits not rings.
If the maker determines the appliance needs protection they put in their own fuse, as seen in plug in electronic appliances. White goods appliances do not have internal fuses as they know their appliance can take a lot more than 13A, apart from the elements, so no switches or internal cables, etc, will will burn out. Only the cable is rated at 13A max. But their is leeway on this.
If an oven maker does not have a 13A plug then it is best to read the instructions. Many will state 16A max mcb protection for radial circuit fitting as is common on the Continent. Most appliances are the same for all over the EU, so most are radial circuit fitted. They do not do rings over there. Only the UK and Ireland do rings.
A 3kW oven can plug into a ring and many do, the reason why they keep the oven down to under 3kW - for ease of fitting.
In this case, the oven appears to be off a 40A cooker circuit. The oven will not draw more than 12-13A, so the oven cable is protected in normal operation and will not overheat, and of course is the 2.5 back to the Oven switch and the oven cable back to the CU's mcb. Now, the problem is when the appliance is at fault it may draw more than 13A. The oven flex cable and 2.5mm cable out of the oven switch are not protected. 2.5mm is rated for 27A max, and the oven flex at 13A (usually far more). The oven circuit mcb at the Consumer Unit is rated at 40A. So protection is needed in the line to the oven other than the 40A at the CU.
I have fitted ovens for relatives that came with 13A plugs. On talking to the makers tech dept, they have said it is OK to take of the plug and wired directly into a 16A circuit with a 16A mcb at the CU, as per the norm on the continent. Having a fuse behind a fixed appliance is a pain as if it blows (they do for no apparent reason at times) it is a pain to get the appliance out. On the continent you do not see fuses behind fixed appliance. Only the Brits do because they think their appliances may be plugged into a ring.
In this case a normal single unswitched socket is best to be fitted and the oven plugged in. The 13A fuse in the plug will protect the oven flex cable and the 2.5mm cable.
Ideally a new cable back to the Consumer unit and the oven then has its own mcb - a radial circuit feeding its own heavy current appliance. Then the oven plug can be cut off and the oven wired in directly, as per the Continent and no inaccessible fuse behind an appliance. Also, mcb's are more accurate and reliable than cartridge fuses.
Hi Walt! Good to see you .
I agree - DIYers tend to fall into one of two camps; one is chancer, rough and ready. Basically, if it works and sparks don't fly, then 'it's obviously ok'. The other is the type that takes often a huge amount of time over every task - they are driven to doing things as neatly and perfectly as possible. Provided they technically know what they are doing, the standard of their work often exceeds that of many tradespeeps.
COYR, what is in the unit either side of the oven housing? It is surely no more effort to run a 2.5mmT&E cable from the existing back plate to that unit, install a surface-mounted single socket high up, and then take your oven plug/cable through to that?
But, I guess if you are genuinely going to get a sparkie in in a few months time and will genuinely ask them to look at this wiring, then I guess no-one is going to die meanwhile.
By the way, is that your girlfriend/wife? Punching above our weight, aren't we...
I see that mad4kitchens is posting quite a lot of advice that could be misconstrued. What tends to be misunderstood amongst those who think they know is that fixed loads cannot present overload faults in to the flex feeding them. A fixed load will only use the current it is designed for. So, whilst in essence the advice to not fit the appliance without a 13A fused plug is common, it is not as dangerous as mad4 is making out. There would be nothing wrong in connecting the oven directly on to the outlet plate. The mcb on the fuse board will take care of short circuits and the RCD will take care of earth faults, provided that the circuit is healthy. Worrying over the lack of a plug and 13A fuse in this instance is misguided.
unphased, what if the oven is drawing more than 13A because of an appliance fault? It will only have the 40A mcb protection which is too high.
I disagree. An appliance fault will trip out either an mcb or an RCD. It is not likley to have a 'fault' which generates so little margin of over current as you suggest. It cannot draw more current than it is designed to do. A fault would generate a large current. The only current being used in the flex is 13A. The circuit wiring is sized to cope with 40A.
Would it not be fair to say that under normal working conditions an oven would indeed draw it's stated fixed load in accordance with the manufacturers instructions. However..... Let say a fault developed which "isn't supposed to" and draws more load. I would have said that as appliances get older they tend to draw that bit more and over a period of time to perhaps overload in the unlikely event. Just saying it's not impossible
You just need to understand the difference between "fault protection" and "overload protection" !
Well Walter System that's a very long winded and technical way of pretty much agreeing with what I originally posted for COYER, christ what's the poor guy supposed to do with all that technical waffle, he's only trying to wire his cooker in safely on the cooker circuit.
Point 1. The 13amp fuse is only there to protect the appliance/cable NOT the ring main, protection for the ring main is back at the CU by the 32amp mcb.
Point 2. It seems you are saying that white goods in the UK do not have a fuse in the plug, I hope I have read this wrong as if that is what you are saying then you must be living abroad somewhere ?
point 3. Why does the oven appear to be of a 40amp circuit ? its more likely to be a 32amp Circuit if this is what mcb is at the CU.
Point 4. Most single ovens are on 13amp protection, but there are more single ovens today than ever before asking for 16amp protection due to the higher loads required, these being the more expensive pyrolitic single ovens, which then a 2.5mm radial will be installed covered by a 16amp mcb back at the board
Point 4. "Fuses blow for no apparent reason" I would say in my experience 9 out of 10 times it will be due to a fault has occured in the appliance and in fact I have never come across a fuse just blowing for no reason. So therefore fuses behind appliances will be fine as the appliance will need to be removed to be fixed or replaced anyway.
Point 5. Running a new 2.5mm radial circuit back to the board is well OTT for COYR's situation.
Point 1. We all know that 2.5mm cable rating is around 27amp, so why are you asking COYR to come off his cooker circuit which is rated at the board with 32amp mcb which COYR has already posted that a new board was fitted, with a 30amp mcb "which we all know is 32amp in any new board". The correct advice would be for it to be wired in in 4mm or the prefered 6mm as the rest of the cooker circuit is, also this is bad practice spurring off the cooker circuit with sockets. The plug is for it to be plugged into a socket on the ring main and if wired into the cooker circuit it should be on a fused spur.
Point 2. "I guess no-one is going to die in the meantime" that's alright for you to say as it won't be you or anyone close to you that would get hurt or die from a unforseen incident that may happen from a brand new appliance having a fualt with it and I wouldn't laugh to quick as it can happen as very rare that it is.
Ponit 1. "It is not as dangerous as mad4 is making out" So you are saying that it is slightly dangerous but not as dangerous as I am making it out to be. WTF ?
Point 2. "worrying over the lack of a plug and a 13amp fuse in this instance is misguided" Bloody hell so the manufacturer has put it on there for a laugh. It is there incase the cooker develops a fault at any time in its life as the 32mcb at the CU is way over for that appliance to be used safely.
Mr R, Well said, you seem to know what your talking about.
Ooh, get you, Mad4It
Point 1: I am asking COYR to come his cooker circuit in 2.5T&E simply because that cable will only supply a single 13A socket. Ooh-er, how dangerous is that?
Point 2: What are the chances - no, really, what are the chances - of anyone dying from my suggestion in the few months it takes for COYR to have a sparky look at it? Answer - infinitesimally small. Less than the chance of being run over by an 05-reg'd car in metallic blue being driven by a septuagenarian couple named Frank and Bill as a cat carrying a mouse crosses the road. For no apparent reason.
LoL. Mad4. You made me chuckle. No hard feelings mate. What you say is okay by me. I accept I may be wrong in this case, but there again, I may be right.
Hello, I see that my initial post seems to have opened up a case of electrical handbags at 40 paces!! To say i am confused is an understatement but it appears the cooker should either be powered by a 13amp socket off the ring main if plugged in or a fused spur off the cooker circuit if taken from the cooker connection point. There is a cupboard next to the oven so i suppose either could be fitted reasonably easily. The reason that i required i new oven is that the element of the old oven went and when this happened it did trip the mcb and the rcd so the consumer unit did its job! btw devils advocate the young lady with me is my 10 year old daughter but glad to know you think she has inherited her fathers good looks
Now my next question is black, really black or just a really dark shade of brown?
And black is a very very dark white.
Well DA what do you expect when I've got you 3 having a pop at me, then again I kind a like the name Mad4It, LOL. Ok so,
Point 1, With what you are advising COYR to do is a half hearted way of getting around the problem and does not comply with the 17th Edition it also has a very small element of danger due to the earthing in 2.5mm being undersized for this requirment, and I will agree with you that the chances of anything going wrong is proberly the same as winning the lottery but some lucky people do win, let's hope COYR dosn't win or you'll be a very sorry man. Why don't you tell COYR how to do the job properly so that it follows the 17th Edition, it's real easy if you know what your doing, tell you what, I'll tell you how it should be done.
COYR will need a 35mm dual back box Screwfix part no 48234 and a unswitched fused connection plate Screwfix part no 64816. Recess the back box into the wall behind the cooker insert the cores of the 6mm cable that have been stripped back buy some Numpty and bury these into the wall "some capping over the bare wires would be nice" this will then sort the problem of the stripped back cable. Bring the 6mm cables into the dual box and connect to the cooker connection plate that he has already got which then in turn feeds the electric hob. In the back of the dual box come off the cooker connection plate with 2.5mm into the fused connection plate to feed the oven with a 13amp fuse and before you start shouting at me again the 2.5mm is allowed as it is incased in a noncumbustible unit, so if a problem exsisted with that tiny length of 2.5 circuit, it would be contained within the dual box so no harm done to life or property, cut the plug off the cooker and wire in to the fused connection plate.
There all done and it follows the regs, the only thing that I'm not sure on is the amps on both appliances when added together could pull more than the 32amp breaker, as COYR has not told us what appliances are fitted, so not unsafe just a nuisance on christmas day when loading up both appliances cooking the turkey and trimmings and finding out the mcb pops off ! oh well not great but safe as house's
Oh just have to put this last one in for you, You said and I quote " Infinitely small " (at least I think that was what you were trying to spell) So what your saying is there is a small chance that something could happen with what you have suggested even though it is a very very small chance, well that just don't make sense in my head that you are prepared to very very slightly risk COYR and his family's lifes with your wiring idea, well shame on you, this is exactly why Part P has come about and that's interesting, you ever Googled why was Part P introduced ? Did you know about the MP Jenny Tonge's daughter was killed in 2004, You'll find the read interesting !
Mad4It (Yeah I kind of do like the new name. LOL)
Definitely no hard feelings, you made me chuckle too. LOL
Separate names with a comma.