Possible dodgy oven wiring discovered

[James2019]

I've moved house and have had a full re-wire and new kitchen fitted in Nov 2020, incl a new electric oven and gas hob. The oven is a Bosch HBG675BS1B. We only actually moved into the properly on 21st Dec. On 23rd Dec (not good timing!) the oven stopped functioning and would not power on. The electricity didn't trip off and the cooker switch neon still illuminated (electric ignition of gas hob above still worked).

Miraculously I managed to get a Bosch contractor to come out on Christmas Eve to take a look. He and I were very surprised to find that the oven and hob were actually connected to a double socket behind the appliance, so the 45A DP cooker switch must just be controlling the power to the double socket. I thought that the cooker was wired directly to the cooker switch, but I was wrong. The Bosch contractor said that this is dodgy, and showed me that this is a 3.6Kw oven and so I understand that a 16A current is required. Therefore it would be impossible for a 13A plug/socket to be OK.

The Bosch contractor plugged in some diagnostic tool which was in the shape of a plug to the double socket, I'm afraid I do not know much about what it showed but he said it was showing a lot of red instead of green, and if he shook it about it would go green. The Bosch guy thought that perhaps the wiring in the socket had overheated and the wiring was not sound inside the double socket anymore. When he plugged the oven back in (to the same possibly dodgy socket) for testing it started working again. He has given me a piece of paper to say that he's looked and that its not fitted in accordance with regulations, dangerous and I should not use it until an Electrician has rectified the issue.

As further info, the oven is not on a completely dedicated circuit, instead it is on a dedicated circuit shared by all kitchen sockets. On the EIC it says that the rating is 20A for this kitchen circuit, which to a clueless person like me sounds like its too low for fridge, oven, dishwasher, toaster, kettle. However in reality this is a discrepancy as when I checked the CU I understand that there is really a 32A breaker for this circuit (BG CUCRB32).

The kitchen fitting was done by a builder at the same time as the re-wire, the full re-wire was conducted by a combination of builder and electrician. I was given an EIC for the work with no observations/abnormalities.

I'm going to get in touch with the Builder who arranged all the work, so he can get the electrician in to sort it out (not him). I would like to give them the opportunity to rectify this work. However I just need some advice:

• During a full re-wire / new installation should the oven have been put on a dedicated circuit? Or is this just a recommendation and it is acceptable to be on a shared circuit with all kitchen sockets (single electric oven is the only large appliance with high consumption).
• Should the oven have been wired directly to the DP cooker switch? Instead of 13A socket.
• Is it acceptable for the electric ignition of the gas hob to share the cooker switch?
• The NICEIC contractor has signed that reasonable care was taken to design, construct and test the work. Surely this is a lie if it has been wired as above and in the test results table it says 20A rating for kitchen sockets instead of 32A.
• The builder arranged the electric subbie, having seen this should I have some concerns that corners have been cut with the design, construction and testing? I would like to think that no-one would sign something off which wasn't right, as they have nothing to gain from that, but now this issue has put doubts in my mind.

 

[littlespark]

Was it you that ordered the rewire in the first place? This would have brought up the need for a cooker circuit at the time.

How difficult is it for a new dedicated circuit to be run in?

There’s no problem running the ignitor from the same supply as the oven, single socket next to the oven outlet.

 

[telectrix]

if the oven came with a fitted plug, it was meant to be connected to the socket circuit. bear in mind the 3.6kW rating is for all elements addes together. in real life it would never pull 16A for any length of time . it is probable that the double socket, being loaded close to it's rated 20A, has failed , cheap socket perhaps? thereis more than 1 way to sort this out at reasonable cost. if you post your location, one of us may be close.

 

[James2019]

Was it you that ordered the rewire in the first place? This would have brought up the need for a cooker circuit at the time.

How difficult is it for a new dedicated circuit to be run in?

There’s no problem running the ignitor from the same supply as the oven, single socket next to the oven outlet.

Yes I ordered the full rewire in the first place, as it was a 1930s semi with old wiring / fuse wire.

We took the house into renovation condition with complete rewire and replastering throughout as I wanted to bring back up to scratch somewhat.

The CU is on the ground floor down the hall from the kitchen. We have solid floors so wiring would be over the ceiling, but we’ve just finished the renovation and all redecorating now.

 

[James2019]

if the oven came with a fitted plug, it was meant to be connected to the socket circuit. bear in mind the 3.6kW rating is for all elements addes together. in real life it would never pull 16A for any length of time . it is probable that the double socket, being loaded close to it's rated 20A, has failed , cheap socket perhaps? thereis more than 1 way to sort this out at reasonable cost. if you post your location, one of us may be close.

The oven didn’t come with a fitted plug, in the product specifications it says plug type: no plug. I never saw it as the kitchen was brand new ordered through Howdens / the builder.

Perhaps it is a cheap double socket which has failed due to the relatively high load. As you suggest as I’m pretty sure the cheapest have been used, as I did not supply these. However it would not have gotten close to 20A I don’t think, as the fuse has not gone on the oven’s plug being used.

Im near Croydon thanks for the suggestion, however I’m just trying to work out what’s right and wrong, before contacting the original electrician to come and fix it, if it is a reasonable request for me to make to them. Otherwise I’ll pay someone else to resolve.

 

[telectrix]

if it's a question of just replacing the double socket. £60 inc. labour up here. maybe a bit more down in bandit land.

 

[Lucien Nunes]

What do the manufacturer's instructions say about the supply requirement? That should be the first point of reference. If no plug was supplied it is likely they stipulate 16A minimum, in which case 13A socket is incorrect although might work for a while. If the load is actually <13A then a plug is acceptable although not best practice, as sustained high load on a plug that is never unplugged and replugged can lead to tarnished contact surfaces and heating due to increased resistance.

Sharing a circuit with other appliances is OK, the circuit does not need to be dedicated to just the oven (although it is conventional to have a dedicated cooker circuit to allow for higher load appliances if fitted). However, the point is that it should be on a circuit on which sufficient capacity has been reserved for those appliances, rather than taking a chunk out of the available capacity on your general-purpose socket-outlet circuit which should be available for portable appliances etc.

 

[littlespark]

The make and model of the oven is in the OP. If you google the specs, it does say its 3.65kW, 16A, so it is not designed to be simply plugged into a socket.

The builder or electrician should have known the size of the oven if they were supplying it, and designed the installation to suit.

I would get onto the builder first if they were the main contractor. Its his responsibility to do it right first time... if hes got to strip out half the kitchen, and put right afterwards, that will be at his cost.

Good luck

 

[Lucien Nunes]

The make and model of the oven is in the OP

Oops, sorry I missed that. Then the installation is clearly wrong in a couple of ways.

 

[DefyG]

Is the point of 45A DP isolator to deceive the occupier that a cooker circuit has actually been installed?

 

[FatAlan]

What was the specification agreed for the rewire and in particular for the kitchen? It may be the case that the oven you have purchased is over rated for the wiring that you have specified.

 

[Baddegg]

Sounds like a cooker circuit has been run in hence the 45a isolator but someone forgot to add a point for the hob and decided to just put a double socket in as a quick solution...

Edit just looked at the pics and no cooker circuit??...strange set up indeed,I’d be calling the spark back to clarify I think mate..

 

[DPG]

Sounds like a cooker circuit has been run in hence the 45a isolator but someone forgot to add a point for the hob and decided to just put a double socket in as a quick solution...

Edit just looked at the pics and no cooker circuit??...strange set up indeed,I’d be calling the spark back to clarify I think mate..

No cooker circuit RCBO in the picture. I think someone realised they hadn't got space in the consumer unit that they've fitted, and so they connected the cooker to the socket ring.

 

[James2019]

The make and model of the oven is in the OP. If you google the specs, it does say its 3.65kW, 16A, so it is not designed to be simply plugged into a socket.

The builder or electrician should have known the size of the oven if they were supplying it, and designed the installation to suit.

I would get onto the builder first if they were the main contractor. Its his responsibility to do it right first time... if hes got to strip out half the kitchen, and put right afterwards, that will be at his cost.

Good luck

Thanks a lot, will give him a try!

 

[James2019]

What was the specification agreed for the rewire and in particular for the kitchen? It may be the case that the oven you have purchased is over rated for the wiring that you have specified.

I'm afraid there was no clearly agreed specification, I only went through the requirements and approx points with him at the start. I decided to use one main contractor to oversee everything to try to avoid issues. This same contractor was used for some small building works, replastering, supply of kitchen (and appliances), fitting of kitchen, replacement boiler, full re-wire.

So the requirements should have been known if paying close attention to detail. I had expected as I was conducting a full re-wire, it would automatically be designed and built to the average requirements of a 3bd home and up to date to the latest safety regulations etc. As I only have very limited knowledge myself!

 

[James2019]

No cooker circuit RCBO in the picture. I think someone realised they hadn't got space in the consumer unit that they've fitted, and so they connected the cooker to the socket ring.

Something odd has gone on. They've put in:

• circuit for downstaris sockets
• circuit for upstatairs sockets
• circuit for kitchen sockets only (inc oven)

I'm personally "OK" with that as long as it is not unsafe. It is just now what I was expecting as I had thought the oven would be put on its own circuit, in hindsight I should have paid closer attention to this but there was a lot going on.

There are two spare places in the consumer unit which are not being used, however the transformer for the Ring doorbell has been put in the spare space of the unused breakers. The doorbell itself is on the outside lights circuit.

 

[FatAlan]

Would be interesting to see how the kitchen socket circuit has actually been wired, is it a ring final circuit or a radial and what size cable has been used between the cooker isolator and the sockets?

 

[Baddegg]

Are you saying they supplied and fitted the oven?

 

[James2019]

Are you saying they supplied and fitted the oven?

Yes that's right.

 

[James2019]

Would be interesting to see how the kitchen socket circuit has actually been wired, is it a ring final circuit or a radial and what size cable has been used between the cooker isolator and the sockets?

Hi there, not sure how it has been wired. Apparently it is a ring final circuit going by the installation report, not sure if that is a good thing or a bad thing. See attached from the report. In the report it says it is 20A rating.... but there is actually a 32A breaker in the CU. I need to clarify whether that is a typo, some funny business or what. I will ask them to come and clarify what gauge of wire has been used etc, when I try to get them to come back and fix this oven wiring.

 

[Baddegg]

Yes that's right.

In that case it’s on them mate, they can hardly say the oven spec wasn’t discussed if they supplied it, you need to speak to whoever did the works and get an explanation.....do keep us updated we like that ?

 

[Baddegg]

Hi there, not sure how it has been wired. Apparently it is a ring final circuit going by the installation report, not sure if that is a good thing or a bad thing. See attached from the report. In the report it says it is 20A rating.... but there is actually a 32A breaker in the CU. I need to clarify whether that is a typo, some funny business or what. I will ask them to come and clarify what gauge of wire has been used etc, when I try to get them to come back and fix this oven wiring.

The RFC circuit is fine for supplying the kitchen sockets but not an oven that stipulated 16a supply, as a rule anything over 2kw should be on its own circuit, not advocating you doing this obviously but it would be interesting to see cable sizing for that 45a isolator and where it’s fed from....

 

[James2019]

I’ve sent the builder a message and will give him a call tomorrow afternoon. It will be interesting to see what they come back with, will try to keep you updated!

Have I got a couple of different options out of this spot of bother? Losing a bit of sleep here. I attached a screenshot earlier from the EIC, if I understand correctly the kitchen sockets are on a RFC, 2.5mm cable with 32A breaker. In the test results it says 20A breaker, but in reality they’ve put 32A.

I understand that option 1 will be to put in a new radial circuit for the oven. I believe this would involve chasing up the wall, running cable over the ceiling about 10m to the CU. Benefit of a small house... but upstairs would have to lift floor in bathroom, hall and guest bedroom to pull it through and down to the CU.

Is there a less invasive but still above board option 2 available to me? Involving updating some localised wiring from the oven to a cooker switch, while keeping it on this existing kitchen sockets circuit? Or is that a non starter due to the spec of the circuit.

I’m pretty peeved about this, as the house was unoccupied in renovation condition for 5-6 weeks, with floorboards up etc for all the works. The rewire was over £5k excl fixtures and fittings, kitchen fitting £2k etc. And now there is the prospect of getting the carpets up again.

I have visions of me selling this expensive posh oven at a loss and swapping it for a boggo spec <13A oven...

 

[littlespark]

It’s going to be a battle.

First, you have to get the builder to accept responsibility. His electrician, his problem.

Then he will try to convince you to have a sub standard repair job done.... either bodge it off the ring somehow, or run a new radial, but run it in surface trunking.

The least disruptive solution is, as you say, to buy an oven that comes with a 13A plug fitted.... but make sure HE pays for it.

My last post asked if there was an old cooker circuit in the kitchen. Maybe this could be reused? Jointed or rerouted to suit where the oven is

 

[James]

Stick to your guns, the builder employed the spark to design, install and test the electrical installation to supply the kitchen that he installed.
Any issues with communication of specifics or layout is between the builder and spark.

 

[Baddegg]

depending on wether you have a written contract will very much decide the outcome here really, assuming you have then ultimately you could demand the builder install what you’ve paid for and make good afterwards, obviously this will involve living in a building site for a while, without trying to sound condescending there may be cable routes the spark could use that you havnt thought off so may not be as disruptive as you’re imagining, as above have the conversation and stick to your guns ?

 

[Midwest]

No cooker circuit RCBO in the picture. I think someone realised they hadn't got space in the consumer unit that they've fitted, and so they connected the cooker to the socket ring.

Would be interesting to see how the kitchen socket circuit has actually been wired, is it a ring final circuit or a radial and what size cable has been used between the cooker isolator and the sockets?

I might be clutching at straws here, but I'm wondering if a cooker radial has been installed, but just not connected? Did the inclusion of the 'Ring Doorbell' supply, meant there wasn't sufficient space in the CU?

What RCBO isolates the 45A DP Cooker Switch? I suppose the only way to tell from afar, is what cable(s) are behind said switch (and inside CU). Not suggesting you investigate OP.

Have you a pic of the cables entering the CU, on the outside OP (i.e. don't take off CU cover) ?

 

[telectrix]

i'm sure OP is intelligent enough to switch off the main switch, remove the CU cover, and take a pic. obviously observing relevant safety precautions.

 

[brianmoooore]

i'm sure OP is intelligent enough to switch off the main switch, remove the CU cover, and take a pic. obviously observing relevant safety precautions.

A close up pic. of the inside of the CU, showing the brown wires going into the breakers would certainly help.

 

[James2019]

It’s going to be a battle.

First, you have to get the builder to accept responsibility. His electrician, his problem.

Then he will try to convince you to have a sub standard repair job done.... either bodge it off the ring somehow, or run a new radial, but run it in surface trunking.

The least disruptive solution is, as you say, to buy an oven that comes with a 13A plug fitted.... but make sure HE pays for it.

My last post asked if there was an old cooker circuit in the kitchen. Maybe this could be reused? Jointed or rerouted to suit where the oven is

Cheers, thought as much! Oh dear.

Before the re-wire the house had wiring from approx 70s/80s without a dedicated cooker circuit (kitchen shared the downstairs circuit). The previous owners had a gas oven.

 

[Strima]

Looking at the manufacturers instructions the oven should be on it's own dedicated circuit.

The previous owners had a gas oven.

TBH this would be your best option as you already have gas for the hob.

 

[James2019]

This is a picture of the cables entering the CU. The right hand side is where the kitchen breaker is.

I will see if I can turn off the power and remove the cover later, to provide a better view. I’m worried I’ll mess something up.

The builder has responded to ask if they (I believe him and spark) can come tomorrow at 9am to “sort out the problem”. As last night I had said I would like him to arrange for him and spark to attend, resolve the issue and spark to provide a written report explaining how the 16A oven is now wired correctly. I am not sure what they currently have in mind.

 

[James2019]

Here is a photo of the wiring inside the unit. You can see the first post photo for the labels but the far right breaker is the kitchen sockets one.

 

[littlespark]

Just clarify that when the kitchen ring is turned off, the socket that the oven is plugged into goes off. (Ignitor for hob won’t fire)

All you need to say is the oven is too high a rating to be simply plugged into a 13A socket.
The builder and spark can then argue amongst themselves whose fault it is.

Dont take anything else apart, there’s no need to.
Bottom line, they designed it, they supplied the oven. The circuit for the oven should be there.

 

[Strima]

When the spark turns up tell him to leave the half starve rat in his van that he used to trim the cables with.

 

[James2019]

Just clarify that when the kitchen ring is turned off, the socket that the oven is plugged into goes off. (Ignitor for hob won’t fire)

All you need to say is the oven is too high a rating to be simply plugged into a 13A socket.
The builder and spark can then argue amongst themselves whose fault it is.

Dont take anything else apart, there’s no need to.
Bottom line, they designed it, they supplied the oven. The circuit for the oven should be there.

Yes that’s right, when the kitchen ring is turned off all the sockets in the kitchen go off. Including the neon for the cooker switch and the electric ignition for the hob won’t work. If the kitchen ring is on, the neon for the cooker switch illuminates.

I will see what they can suggest for me.

 

[westward10]

If a so called electrician connected that consumer unit I fear the quality of the rest of the installation. I would be wary of them doing anymore works in your property.

 

[Strima]

It is a recommendation in BS7671 (appendix 15 note (iii)) cookers and hobs with a rating exceeding 2kW be connected on their own dedicated radial circuit.

 

[telectrix]

Here is a photo of the wiring inside the unit. You can see the first post photo for the labels but the far right breaker is the kitchen sockets one.

can't believe an "electrician" fitted that abortion. more like a builder using a spade to dress the cables.

it shouldlook more like this:

 

[loz2754]

Not the neatest consumer unit install I've ever seen.
As an aside, I can't see any main bonding cables. Could be that they aren't needed, or connected to a main earthing terminal elsewhere...

 

[Midwest]

Might be my eyes deceiving me, but the wires for circuit 4 (central heating) seem slightly larger gauge, than the wires for the RFC‘s.

Where is the FCU for the CH located OP?

 

[brianmoooore]

Might be my eyes deceiving me, but the wires for circuit 4 (central heating) seem slightly larger gauge, than the wires for the RFC‘s

I thought that as well. Doncaster cable for that circuit only?
Also wondering why the heating needs a 16A MCB all of its own. All the CH systems I've ever wired have been through a 3A fuse, except for a few larger systems where the fuse was 5A.
I also subscribe to the theory that a smoke detector feed should be incorporated into a circuit whose failure would be obvious, such as the downstairs or upstairs lights, although I know there are those on here who disagree.

 

[James2019]

Might be my eyes deceiving me, but the wires for circuit 4 (central heating) seem slightly larger gauge, than the wires for the RFC‘s.

Where is the FCU for the CH located OP?

Hi there, if I I understand the question correctly the boiler is located upstairs in the wiring cupboard on the landing. The fused spur for it is located there.

 

[James2019]

I thought that as well. Doncaster cable for that circuit only?
Also wondering why the heating needs a 16A MCB all of its own. All the CH systems I've ever wired have been through a 3A fuse, except for a few larger systems where the fuse was 5A.
I also subscribe to the theory that a smoke detector feed should be incorporated into a circuit whose failure would be obvious, such as the downstairs or upstairs lights, although I know there are those on here who disagree.

Boiler is a new mid-range combi boiler, separate circuit wasn’t any special request from me! No water tank or immersion heater.

 

[James2019]

Development is they will come tomorrow to discuss and take a look. Builder speaking with the spark in the morning.

He said he was thinking they will just wire the oven to the cooker switch, however I have said you can’t put a 16A appliance on an RFC... thanks to your advice on here! Then he talked about it being straightforward to convert an RFC to a radial. However I said if 2.5mm cable has been used (unconfirmed) then you can’t use a 32A breaker and suggested it will be a problem as 4mm will be needed. Otherwise the cables could overheat and not be protected by the breaker. So he said he will check with the spark in the morning and let me know the plan.

I’ll see what options he’s willing to offer me... at this rate I’m still strongly leaning if you just getting a 13A oven below 3kW to save me any more stress over this.

 

[littlespark]

It was quite common to utilise an old immersion supply to supply a new boiler, and it just stuck that a 16A radial was needed for a new circuit for the same thing.

I wouldn’t bother bringing that issue up as well as the oven. The boiler will (should) have a 3A fuse in the fused spur

One other thing I’d like to bring up would be fire detection. How many smoke detectors were actually fitted as part of the rewire?

 

[brianmoooore]

post removed! Getting confused between threads.

 

[James2019]

It was quite common to utilise an old immersion supply to supply a new boiler, and it just stuck that a 16A radial was needed for a new circuit for the same thing.

I wouldn’t bother bringing that issue up as well as the oven. The boiler will (should) have a 3A fuse in the fused spur

One other thing I’d like to bring up would be fire detection. How many smoke detectors were actually fitted as part of the rewire?

Yes won’t bother mentioning the boiler, otherwise he’ll start to think I’m being funny with him.

Smoke detectors are fitted on upstairs and downstairs landing as part of the rewire, plus a heat detector in the kitchen.

 

[Midwest]

Yes won’t bother mentioning the boiler, otherwise he’ll start to think I’m being funny with him.

Smoke detectors are fitted on upstairs and downstairs landing as part of the rewire, plus a heat detector in the kitchen.

I was just thinking perhaps your electrician had installed a cooker supply, possibly 4mm in your case. Perhaps he used it to supply the CH instead.

Long shot, but does seem a bit strange to use a larger cable for such a radial circuit.

 

[James2019]

I was just thinking perhaps your electrician had installed a cooker supply, possibly 4mm in your case. Perhaps he used it to supply the CH instead.

Long shot, but does seem a bit strange to use a larger cable for such a radial circuit.

There did used to be an immersion heater there, before we replaced the boiler and conducted the rewire. In the test results of the installation report it says 2.5mm wire though, so maybe it is just the photo?