Issue with power to separate hob and oven

[morzackle]

Hello, I hope someone might be able to help me. We recently removed our old standalone hob/oven and replaced it for a separate integrated oven and an induction hob fitted into the worktop.

We had the original 45a switch with plug socket, which is still in place, and I replaced the cooker connector unit with a dual connector unit behind the oven to accommodate the two appliances.

I have 6mm wire running from switch to connector unit and then to the oven. I am using the wire built into the hob connected to connector unit. (Black wire in photo)

The fuse being provided from MCP is 45amp. The oven is 2.2kw and the hob is 7.2kw.

When I use the hob alone, it works fine. When I use the oven alone, it works fine. Together though, it’s clear there is not enough power being provided and so neither applications can reach their desired temperature.

From what I have explained and also the pictures provided, I’m hoping that someone might be able to see what I’m doing wrong.

Ps, please don’t judge the paint stained switch too hard, it will be replaced with a chrome one soon!!

 

[morzackle]

Just to stay, the picture of the connector unit shows the wires disconnected. This was to accommodate being able to use the hob temporarily on its own

 

[EFLImpudence]

Power is not provided. The appliances will draw whatever they need regardless. They will not be limited by the 45A MCB (miniature circuit breaker).

What is the black wire connected with the brown?

 

[morzackle]

The black with the brown is from the hob. I believe these are both live.

 

[EFLImpudence]

Ok. Five core with Brown and Black Live and Grey and Blue Neutral if that is how it is supposed to be.

I can see nothing which would cause the problem you have.


Nothing to do with the problem but I have just noticed that the supply cable earth terminal has no screw. Put the wire in the other terminal with the other earth wires if you do not have another screw.

Just to stay, the picture of the connector unit shows the wires disconnected. This was to accommodate being able to use the hob temporarily on its own

Right - so - is it the case that the problem occurs when the oven is connected even if it is not switched on?

 

[morzackle]

Ok. I can see nothing which would cause the problem you have.

Nothing to do with the problem but I have just noticed that the supply cable earth terminal has no screw. Put the wire in the other terminal with the other earth wires if you do not have another screw.




Right - so - is it the case that the problem occurs when the oven is connected even if it is not switched on?

Thank you. In the case of 'the problem occurring when the oven is not switched on' - the problem does not occur when it is not switched on, but does occur if the oven is running the fans to cool down from previous cooking. I just removed the connection entirely to prevent this. As soon as I did this the hob was able to boil water as normal.

 

[ericmark]

Nothing shown or said makes any sense to me as to why the hob has reduced output.

So looking at other reasons, like hob having an over temperature device which lowers output should the hob get too hot, or RF from the oven's fan affecting the hob.

In general the whole idea of separate hob and oven is so oven can be fitted at a higher level to reduce bending. Can't off hand remember distance hob to any item along side, but likely some thing like 100 mm so any oven not really that close to the hob.

However have seen it where a kitchen is done as stages, when we moved into this house the oven was under the hob, we up graded to our stand alone cooker, with a stand alone cooker the oven has a 32 amp supply, so the elements can be used together, we have side, top and fan back, allowing door closed grilling, which works well, but mothers over also had door closed grilling, but used a time share between the elements so as not to exceed 13 amp, so result was it did not work anywhere near as good as with the stand alone cooker. So in real terms no point having a built in oven under the hob, may as well be stand alone.

So my first thing is suggest you read the hob installation manual, the electronics of the hob need keeping cool, so how the oven cools is very important, in the main air is drawn from front bottom and blown out front top, it is important that warm air does not heat up the hob. There should be some thing to divide the oven from hob. Seem to remember mothers hob giving a distance between it and oven which could not be done due to low counter her being in a wheel chair, so oven had to be eye level, in fact to be able to miss wheel chair yet allow mother to see items in the grill, there was around ½ inch lee way. Even then they forgot the temperature was written on the top of the knobs, so unreadable in a wheel chair.

Please do say if I am right, it is a guess with over heating of hob, would be nice to see if right.

 

[morzackle]

I really appreciate the time taken to respond to my query, thanks everyone! I'm happy to know its nothing i have done wrong but frustrating it's not obvious at the same time. Oven is directly under the hob and so it could well be an issue. I just find it bizarre that if the hob is boiling water for example, the oven drops temperature (power related) and if the oven is first to be preheated then I cant get the hob to make it to boiling point.
I will be sure to let you know if and when I find a solution.

 

[ericmark]

I did an internet hunt for "induction hob installation instructions" don't know the make of yours, so just selected the first one which was Bosch,

It says it should not be mounted over the fridge or washing machine or similar items, I would guess that is because of the heat from them, as to if an oven is considered as a similar item not sure, but main difference is a fridge or washing machine normally stands on the floor, so you can't get the ventilation shown.

So what does your installation instructions say?

 

[opps]

I did an internet hunt for "induction hob installation instructions" don't know the make of yours, so just selected the first one which was Bosch, View attachment 278128View attachment 278129It says it should not be mounted over the fridge or washing machine or similar items, I would guess that is because of the heat from them, as to if an oven is considered as a similar item not sure, but main difference is a fridge or washing machine normally stands on the floor, so you can't get the ventilation shown.

So what does your installation instructions say?

Tnx, I wasn't aware that induction hobs need airflow.

Our ongoing "new" kitchen saga has been going on for over 3 years now. The company's fitter(s) clearly don't believe in reading fitting instructions. They didn't fit a vent for the condensing tumble drier or microwave combi steam oven. And now it looks like our hob may need a vent as well.

 

[ericmark]

The company's fitter(s) clearly don't believe in reading fitting instructions.

To be frank don't blame them, I have read so many when bored, and they have so many daft bits in them. Even seen instructions on how to fit a plug with battery operated equipment.

Some manufacturers do a separate installation and users instructions, but many combine them. And it's not only electrical instructions.

Bored waiting for wife in then reasonably new Vauxhall Agila one of the originals, I started to read the hand book, which said do not use a mobile phone in the car without using an external aerial, I know why, some Vauxhall cars had problems with RF upsetting the ABS brakes, but the Vauxhall Agila did not have ABS brakes.

So we have a gas boiler which says "Type A RCD's

must be employed where additional protection is required" it may as well say when there is a C in the month, as it does not say when additional protection is required. Either the boiler can cause DC to be superimposed on the supply, or it can't, so your plumber is suppose to know when to swap the RCD, and do it safely?

I did note with mothers kitchen how the oven carcase had to comply with set parameters, and reading the instructions it was near impossible to see if it complied with what was required, including the cooling on the 13 amp plug. Normally we say a 13 amp plug should be in free air, but where the oven cooling fans are forcing the air past the plug that's not really a problem, neither was the food stored above the oven, as long as the fan ran, then they were kept cool.

The problem was when the social services sent a woman to teach my mother in her 80's with dementia how to use the oven, and she told my mother to turn off the oven at the wall when not being used. Which stopped fan working, and it then required to clock to be reset. When I pointed out the error, was told the woman giving instructions used gas, asked if she turned the gas isolator off, the woman turned her back and walked away. I had a problem getting my mother to believe me, I am only an electrical engineer, the woman from council knows best.

Hence why I read the instructions which clearly said do not switch off as it will stop cooling fan.

 

[opps]

To be frank don't blame them, I have read so many when bored, and they have so many daft bits in them.

With respect, I disagree.

My mum's £1300 microwave combi oven kept tripping the RCB. The Siemens' engineer turned up and showed her the rust holes in the top of the inner lining. The manual clearly stated that it needs airflow. The convention Siemens oven below it doesn't require free air flow and had no rust.

Without airflow our steam combi oven is a complete PITA. You have to use a towel to dry it.

Bizarrely, the 4th(?) kitchen fitter that turned up to fix the bodges created by fitters 1 to 3, insisted that that the condensing tumble drier didn't need a grill, even though the condensing grill was obscured by the plinth. He then went on to insist that our combi boiler housing needed a grill though. I had to explain the concept of balanced flues.

Moments later he fecked up our conventional oven. He tugged on the slide under door and pulled it off. Then wasted 10 minutes trying to refit it, in the meantime failing and shredding the seal. We were without the oven for a over 3 months. Sure, we had the combi oven, but if we wanted to cook a pizza, we could only do one at a time.

He too should have RTFM.

 

[JohnW2]

With respect, I disagree.

That may be valid in this particular instance, but I have to say that it is (unfortunately) only too true that ..

..... they have so many daft bits in them.

So, I'm afraid that, like many, I usually only move to 'RTFM' as a last resort

Kind Regards, John