Has my oven being wired dangerously?

WhyTheFace

Hi,
I got a new kitchen fitted. The guy who fitted it offered to re-wire a new hob and oven. The only thing is that while the hob is connected to the mains, he simply has the oven plugged into the wall, like you would a kettle. I phoned him and he said that that was the way it said to be done. I phoned an electrician mate and he said he wasn't sure as instruction manual is not clear but that it doesn't sound right.

I've used the oven a few times and it has worked fine but I'm still very paranoid.

Here is the product http://www.hotpoint.ie/appliances_hp/_SHS_53_X_S/pid_F080810IE.do

Any thoughts/opinions much appreciated.

cerastes

WhyTheFace wrote: »

Hi,
I got a new kitchen fitted. The guy who fitted it offered to re-wire a new hob and oven. The only thing is that while the hob is connected to the mains, he simply has the oven plugged into the wall, like you would a kettle. I phoned him and he said that that was the way it said to be done. I phoned an electrician mate and he said he wasn't sure as instruction manual is not clear but that it doesn't sound right.

I've used the oven a few times and it has worked fine but I'm still very paranoid.

Here is the product http://www.hotpoint.ie/appliances_hp/_SHS_53_X_S/pid_F080810IE.do

Any thoughts/opinions much appreciated.

I cant imagine how anyone would think an oven like that should be plugged into a socket? Id have thought the rating on the oven would be a clear indication, but Id be sure an appliance like that would have to have a permanant connection of an appropriate size with an isolation switch.

Im not an electrician myself, Im fairly surprised an electrician doesnt know this off the bat, or that he's relying on the instructions and not the ECTI? (I believe) wiring regulations.
Maybe someone can come along and describe what the wiring regulations state, but Id be stunned to hear that it should be as you have described. Surely it blows fuses in the plug? aside from I didnt think a 13amp plug would stand up to the load without showing signs of overheating.

titlebearer

Electrical Connection:
Voltage Frequency: see data plate
Fuse Section: 16A
Supply cable: 3x1.5mm2
You can connect your oven to the system means of a
terminal board. Refer to above information for the minimal
cable sections and the calibration of the protective elements
according to the connection.
If the appliance is installed with a junction box, an
omnipolar circuit breaker - with a minimum contact
opening of 3mm - should be installed between the appliance
and the mains.
Power cable supply connection to the electrical mains:
We recommend you use a power supply cable which is
long enough to allow you to take the oven out of its recess
in the event of maintenance operations (only use HAR - H
05 - RRF quality cables fitted with a plug conforming to the
regulations in force.
The plug must be accessible at all times.

cerastes

three 1.5 square? for an oven?

titlebearer

Thats the specification that the oven recommend.

It also recommends that you hardwire a connection but at max heat that oven runs at 14 -15 amps. A plug would generally have a 13 amp connection. You would just have to ensure that the oven isnt on max heat for 5-6 hours. That will just heat up the 1.5mm squared cable. The fuse will blow before the cable goes on fire so its ok.
I have seen plugs installed before and they seem to be ok too.

Really the electrician should have ensured that the socket be wired in at least 4mm to the board. If so then there wouldnt be any problem with the 1.5mm cable.

Risteard81

titlebearer wrote: »

Thats the specification that the oven recommend.

It also recommends that you hardwire a connection but at max heat that oven runs at 14 -15 amps. A plug would generally have a 13 amp connection. You would just have to ensure that the oven isnt on max heat for 5-6 hours. That will just heat up the 1.5mm squared cable. The fuse will blow before the cable goes on fire so its ok.
I have seen plugs installed before and they seem to be ok too.

Really the electrician should have ensured that the socket be wired in at least 4mm to the board. If so then there wouldnt be any problem with the 1.5mm cable.

Due to diversity an oven would never, ever, be at full power for extended periods. It cycles on and off. Absolutely nothing at all wrong with an oven being connected via a plug and socket arrangement where it has been designed to be connected in such a way. Although it could alternatively be connected into an unswitched fused connection unit or a flex outlet with 16A protection upstream.

So most of what you have been told is nonsense.

titlebearer

titlebearer wrote: »

that oven runs at 14 -15 amps.

2400W = 10A

Risteard81 wrote: »

Due to diversity an oven would never, ever, be at full power for extended periods.

It would when it's heating up.

coylemj

The manual says power rating is 2250-2400 W so in theory (as it's below 3 kW) would be suitable for a 13A plug and socket.

Cerco

Electric kettles will have a similar power rating as this oven as will some oil filled radiators.

aido79

WhyTheFace wrote: »

Hi,
I got a new kitchen fitted. The guy who fitted it offered to re-wire a new hob and oven. The only thing is that while the hob is connected to the mains, he simply has the oven plugged into the wall, like you would a kettle. I phoned him and he said that that was the way it said to be done. I phoned an electrician mate and he said he wasn't sure as instruction manual is not clear but that it doesn't sound right.

I've used the oven a few times and it has worked fine but I'm still very paranoid.

Here is the product http://www.hotpoint.ie/appliances_hp/_SHS_53_X_S/pid_F080810IE.do

Any thoughts/opinions much appreciated.

It uses about the same as an electric kettle. Would you worry about plugging that into a socket? There's nothing wrong with the way it's been done.

Bruthal

coylemj wrote: »

The manual says power rating is 2250-2400 W so in theory (as it's below 3 kW) would be suitable for a 13A plug and socket.

Plugging it in is fine.

Bruthal

Risteard81 wrote: »

Due to diversity an oven would never, ever, be at full power for extended periods. It cycles on and off. Absolutely nothing at all wrong with an oven being connected via a plug and socket arrangement where it has been designed to be connected in such a way. Although it could alternatively be connected into an unswitched fused connection unit or a flex outlet with 16A protection upstream.

So most of what you have been told is nonsense.

Diversity is to do with the fact items are unlikely to be on together in an installation, or machine etc. As in, all connected loads are unlikely to be on at any one time, so a 63 amp main fuse does for a house, even though all items would add up to far in excess of that.

It doesnt really mean an item will only be on some of the time due to a stat cycling it on and off. The supply still needs to fully be adequate for the load as if it was on continuously.

It would apply alright to a 2 part oven if only one part can be, or would normally be used.

Bruthal

Bruthal wrote: »

Diversity is to do with the fact items are unlikely to be on together in an installation, or machine etc.

I always thought that was a crazy way to do things.
Relying on the consumer's lack of imagination to not overload their supply.

I know it works because the supply has overcurrent but doing the sums at the DB I tend to be "Cowboys!"
Does that also happen in industrial installations or is max. load max. draw?

Bruthal

Sir Liamalot wrote: »

I always thought that was a crazy way to do things.
Relying on the consumer's lack of imagination to not overload their supply.

I know it works because the supply has overcurrent but doing the sums at the DB I tend to be "Cowboys!"
Does that also happen in industrial installations or is max. load max. draw?

Its not really the consumers lack of imagination imo, its just the way everything wont be on together.

If you add up shower, electric hob/oven, immersion, kettle, washing machine and dishwasher, dryer etc (elements), they will exceed the 12kva standard supply.

The entire country connected load would certainly exceed the generated kva at any given time.

I understand but it just looks funny, I wouldn't do it but then again I'm not qualified. :pac:

Is it the same craic with industry though or is it more a case of there's your three phase get your own distro?

Bruthal

Sir Liamalot wrote: »

I understand but it just looks funny, I wouldn't do it but then again I'm not qualified. :pac:

Is it the same craic with industry though or is it more a case of there's your three phase get your own distro?

Industrial is likely to have a lower diversity factor, as in a higher percentage of the connected load is likely to be on compared to domestic.

But an industrial installation is likely to add up the required max load during design, and get a connection to suit. Where as a domestic one tends to be a standard 12kva connection, unless a larger one is requested.

The 12kva only adds up to 52 amps or so, interestingly enough. A 63 amp main fuse could supply an overload up to 70-80 amps for a while.

Is diversity factor in the regulations bible?

• Joe Public recommended 3:1 diversity.
• Acme concrete 1:0.95.

Bruthal

Sir Liamalot wrote: »

Is diversity factor in the regulations bible?

Not that I know of anyway. The connected loads in houses could vary very widely. One house could have 2 electric showers, and cooker, while another might have a mixer shower and gas cooker. Them items alone can widely sway the diversity factor.

So a house could have a smaller connected load than the supply capacity.

2011

WhyTheFace wrote: »

The guy who fitted it offered to re-wire a new hob and oven.

Since the 1st of October 2013 it has been illegal for a non-Registered Electrical Contractor to carry out most electrical work in domestic premises. Refer to the Restricted Works Decision Paper published by the Commission of Energy Regulation (CER). As detailed in the above document “Minor electrical works” are exempt from this legislation.

The work that you have described would be considered as “Minor electrical works”. However it should be stressed that this work should only be carried out by a competent person.

Is the hob electric or gas?
The reason that I ask is that electrical hobs can draw quite a large current. When a large current passes through a substandard electrical connection generate a lot of heat (potential fire hazard).

The only thing is that while the hob is connected to the mains, he simply has the oven plugged into the wall, like you would a kettle. I phoned him and he said that that was the way it said to be done. I phoned an electrician mate and he said he wasn't sure as instruction manual is not clear but that it doesn't sound right.

The chances are that this arrangement will never cause a problem.

However that is not the way that I would do it. An oven such as this is not a portable appliance such as a vacuum cleaner, kettle, laptop etc. As such in my opinion it should be permanently connected, not connected by a plug socket arrangement such as this.

Where is the socket located in relation to the oven?
If the socket feeding the oven is hidden away then it may not be clear how to electrically isolate the oven which is not really ideal (although many would say that this is being am being pedantic). If the socket is visible and a lead can clearly be seen trailing to the oven I would imagine that it is not the most aesthetically pleasing

I've used the oven a few times and it has worked fine but I'm still very paranoid.

Getting something electrical to "work" is generally very straight forward. Most appliances will work if they are wired backwards in the wrong cable, with the fuses bridged out, no earth and every known safety devices bypassed / disabled or removed. The trick is to get electrical devices to work safely within a budget whilst complying with the regulations.

Any thoughts/opinions much appreciated.

Theoretically the socket circuit that this oven is plugged into could be close to the limit that it is designed to take already. The addition of the oven could overload the circuit. If this circuit is wired/installed correctly it will simply trip the MCB which could be inconvenient.

When heating up from cold the full load of 2.4kW will be drawn. Once the oven reaches temperature the thermostat will switch it off. Form then on the oven will switch on and off as required to maintain the desired temperature, so the load will very much reduced. However if the oven is constantly being opened cooling it down during use (such as when making pizzas) the load will increase dramatically. This can cause some sockets and or plugs to fail. I have seen this many times will things like oil filled radiators.

Remember: Although this is a smaller load than most kettles (3kW) a kettle is generally only on for a few minutes at a time.

Bruthal

2011 wrote: »

Remember: Although this is a smaller load than most kettles (3kW) a kettle is generally only on for a few minutes at a time.

True in some respects, but if that is reason enough that a 2.4kw oven shouldnt be plugged in, then sockets are not fit for purpose. Plenty of electric heaters might be plugged in all day.

Dishwashers, washing machines, fridges etc are not all that portable either.

I think some ovens were coming with plugs on them, or still do. I could have imagined it though, with my memory these days.

2011

Bruthal wrote: »

True in some respects, but if that is reason enough that a 2.4kw oven shouldnt be plugged in

I gave more than one reason and also made the most important statement in bold.

then sockets are not fit for purpose.

Some are poor quality.

Plenty of electric heaters might be plugged in all day.

Yup, and sometimes the sockets melt / or end up with burn marks.

I think some ovens were coming with plugs on them, or still do. I could have imagined it though, with my memory these days.

I have seen this with small ovens on the continent, but I still don't like it

WhyTheFace

Hi Guys,

Thanks a million for all your input. A fair whack was over my head tbh.

One thing I should have added is that the socket is behind the fridge. He then has a short extension chord plugged into it, and plugged into that are the fridge and oven.

I get the impression if it overloads the trip will switch so I'm not too worried about the place burning down.

I will get an electrician out if needs be but I'd just rather not have to fork out if it can be avoided. I'm already skint!

Thanks again

CJ Haughey

It complies with the rules and the manufactures instructions. One can argue over where he plugged the socket into for aesthetics reasons but he had to obey manufactures instructions and comply with rules that the plug has to be accessible at all times, unless it has isolation up stream which in that case it may be a hidden socket.

2011

WhyTheFace wrote: »

One thing I should have added is that the socket is behind the fridge. He then has a short extension chord plugged into it, and plugged into that are the fridge and oven.

This arrangement should not be used as a long term solution.
It would be considered very bad practice.

2011

2011 wrote: »

This arrangement should not be used as a long term solution.
It would be considered very bad practice.

Probably trip every time your fridge compressor starts up with the oven pilot light on.

Cerco

WhyTheFace wrote: »

Hi Guys,

Thanks a million for all your input. A fair whack was over my head tbh.

One thing I should have added is that the socket is behind the fridge. He then has a short extension chord plugged into it, and plugged into that are the fridge and oven.

I get the impression if it overloads the trip will switch so I'm not too worried about the place burning down.P

I will get an electrician out if needs be but I'd just rather not have to fork out if it can be avoided. I'm already skint!

Thanks again

Extension leads again :eek:

WhyTheFace

What are his options thou if it has to be plugged in?

There is one socket and that is for the fridge. The other is for washing machine.

Am I right in thinking I could still get it wired up to mains to remove all risk/doubt?

Thanks

Risteard81

Sir Liamalot wrote: »

2400W = 10A




It would when it's heating up.

Heating up is not for an extended period.

Risteard81

Bruthal wrote: »

Diversity is to do with the fact items are unlikely to be on together in an installation, or machine etc. As in, all connected loads are unlikely to be on at any one time, so a 63 amp main fuse does for a house, even though all items would add up to far in excess of that.

It doesnt really mean an item will only be on some of the time due to a stat cycling it on and off. The supply still needs to fully be adequate for the load as if it was on continuously.

It would apply alright to a 2 part oven if only one part can be, or would normally be used.

Cooker diversity takes into account that even where all rings are energised at the same time, once they heat up they will cycle on and off at different times. So yes there is diversity for an installation (to ensure an adequate ESB etc. supply), but there is also diversity within an installation e.g. within final circuits. As an example, in a domestic premises, all luminaires will not be lit at the same time. In reality, whichever rooms are being used will be.

2011

Risteard81 wrote: »

Cooker diversity takes into account that even where all rings are energised at the same time, once they heat up they will cycle on and off at different times

....except in this case it is a single oven with no rings.

MrWatt

With the load on this oven it's fine. That said, the socket should be accessible to allow for easy disconnection when needed and the cable coming from the oven is heat resistant.

Confusion arises from what is good practice in a domestic situation and normal practice is to wire for a 45 Amp double pole cooker switch because of the max assumed load of electric cookers available which is much much higher than your oven's load.

The only issue you may see is nuisance tripping of that socket's breaker but it's very unlikely. Although it does depend on the general wiring ie. way it was installed, age of installation etc.

Risteard81

2011 wrote: »

....except in this case it is a single oven with no rings.

Sorry about that. So it is.

However we are often quoted a "total connected load" with these appliances which cannot be simultaneously energised. So the manufacturer might add the grill element to the oven element and quote this as the power even though it is not possible to do this.

In reality 15kW of cooking appliances can generally be fed from a single 30/32A domestic cooker circuit.

2011

Utilization factor is a the ratio of the amount of energy used divided by the maximum possible to be used.

MrWatt

WhyTheFace wrote: »

Hi Guys,

Thanks a million for all your input. A fair whack was over my head tbh.

One thing I should have added is that the socket is behind the fridge. He then has a short extension chord plugged into it, and plugged into that are the fridge and oven.

I get the impression if it overloads the trip will switch so I'm not too worried about the place burning down.

I will get an electrician out if needs be but I'd just rather not have to fork out if it can be avoided. I'm already skint!

Thanks again

Only saw this part now.

I wouldn't leave it like that. Not with the trailing lead. If the hob is wired to the mains and the cooker is nearby then hooking the oven up inline with the regs should be quick and cheap. And don't just get a registered electrician, get a good registered electrician. There's a difference.

MrWatt

Risteard81 wrote: »

In reality 15kW of cooking appliances can generally be fed from a single 30/32A domestic cooker circuit.

Potentially close to a 70 amp draw on a 30/32 amp circuit??

Risteard81

MrWatt wrote: »

Potentially close to a 70 amp draw on a 30/32 amp circuit??

The point is that it isn't potentially a 70A draw. It is actually impossible to achieve anything like that, and in reality it has been shown over many years that a 30A supply is perfectly adequate for it.

IEE guidance (notwithstanding the fact that ETCI Rules and not IEE Wiring Regulations are what is relevant in this case) suggests that domestic cooker diversity can be assumed to be the first 10A of the load plus 30% of the remainder.

This formula has worked for decades without any issue.