Wiring for 2x 3.6kw ovens, & β€œCurrys Team (don’t) Know How”

Wiring for 2x 3.6kw ovens, & β€œCurrys Team (don’t) Know How”

Author
Discussion

Black_S3

1,990 posts

135 months

Tuesday 22nd October
quotequote all
jackofall84 said:
OP - As per usual on these questions I've seen a lot of nonsense replies - I'm not sure why people bother posting an answer when they don't have the faintest idea...anyway, I'd break it down like this:

Firstly work out the max current draw of the 2 ovens...Power = Volts x Amps so (2*3600)/230 = 31.3A, so if you've got both ovens on at the same time warming up from cold its asking a lot from your 32 Amp breaker, get a sparky in to swap that breaker for a 40A or 45A breaker or swap it yourself if you feel confident, will take 5 - 10 minutes to fit and the breaker will cost less than £5.

Secondly, according to the IEE 4E1A table the worst case installed scenario for 6mm cable is 45 Amps. So all wiring and switches can remain as they are perfectly safely.

Simple
If anyone’s tempted to DIY a breaker change, go to bed and reconsider when sober.

MJNewton

457 posts

36 months

Tuesday 22nd October
quotequote all
To the OP: as often needs to be the case with a discussion on the Internet I would recommend you take all the correct bits from our individual postings and discard the rest. Then invite us all round for a roast once you're up and running. I'll bring a takeaway pizza menu with me, just in case. smile

jackofall84

238 posts

6 months

Tuesday 22nd October
quotequote all
Smiler. said:
Table 4E1A is for single-core thermosetting cable with a 90°C insulation.

Domestic cable is still almost all multi-core thermoplastic with 70°C insulation, so the correct table is 4D2A, worst case current carrying capacity being 32A.
Apologies, this is the right table

BaldOldMan

954 posts

11 months

Tuesday 22nd October
quotequote all
jackofall84 said:
Apologies, this is the right table
Still a pointless post......

OP says in his original post that the manufacturers state a dedicated 16A supply for each oven

Therefore why anyone feels the need to validate their maths is kind of interesting & then why you'd conclude that they'd need more than 16A, so just change the MCB yourself is, quite frankly, mind blowing.

Similarly, I guess it's possible that after clearly specifying 16A, that they would over spec the cable & add additional cost to their product - you never know wink

Jambo85

1,610 posts

35 months

Tuesday 22nd October
quotequote all
Initforthemoney said:
fking hell.


rofl
Thought you were watching from the sidelines? biggrin

Ilovejapcrap

2,731 posts

59 months

Tuesday 22nd October
quotequote all
beedj said:
Unfortunately I wasn’t home but my wife just accepted what they said
Edited by beedj on Sunday 20th October 10:16


Edited by beedj on Sunday 20th October 10:16
Why is it whoever is at home during delivery always just goes ok then

Teddy Lop

1,844 posts

14 months

Tuesday 22nd October
quotequote all
jackofall84 said:
OP - As per usual on these questions I've seen a lot of nonsense replies - I'm not sure why people bother posting an answer when they don't have the faintest idea...anyway, I'd break it down like this:

Firstly work out the max current draw of the 2 ovens...Power = Volts x Amps so (2*3600)/230 = 31.3A, so if you've got both ovens on at the same time warming up from cold its asking a lot from your 32 Amp breaker, get a sparky in to swap that breaker for a 40A or 45A breaker or swap it yourself if you feel confident, will take 5 - 10 minutes to fit and the breaker will cost less than £5.

Secondly, according to the IEE 4E1A table the worst case installed scenario for 6mm cable is 45 Amps. So all wiring and switches can remain as they are perfectly safely.

Simple
jesus H.

What is it about electrical advice that brings out so many walts though?

Smiler.

10,276 posts

177 months

Tuesday 22nd October
quotequote all
Teddy Lop said:
jesus H.

What is it about electrical advice that brings out so many walts though?
walts, or volts?

jackofall84

238 posts

6 months

Tuesday 22nd October
quotequote all
BaldOldMan said:
Still a pointless post......

OP says in his original post that the manufacturers state a dedicated 16A supply for each oven

Therefore why anyone feels the need to validate their maths is kind of interesting & then why you'd conclude that they'd need more than 16A, so just change the MCB yourself is, quite frankly, mind blowing.

Similarly, I guess it's possible that after clearly specifying 16A, that they would over spec the cable & add additional cost to their product - you never know wink
That's 16A/oven, not for both ovens, so minimum of 32A is required to run both at full throttle. As smiler said, you'll probably get away with running both at 32A as it's extremely unlikely it'll pull that much and as it was pointed out to me the load carrying capacity of 6mm cable is 32A not 45A so best leaving the breaker as is at 32A to protect the existing cable more than anything.

changing an MCB yourself is not mind blowing...https://www.youtube.com/watch?v=n33S60qmU5w - if you think that looks difficult I'd hate to think how you would have managed 15 - 20 years ago when you had to wire a plug on a device.


BaldOldMan

954 posts

11 months

Wednesday 23rd October
quotequote all
Oh dear, you still don’t get it.

When you open with this you’d better be right or you’re kind of setting yourself up....

jackofall84 said:
OP - As per usual on these questions I've seen a lot of nonsense replies - I'm not sure why people bother posting an answer when they don't have the faintest idea....
2 x 16 = 32

The one thing that absolutely didn’t need touching is that MCB

The mind blowing thing was firstly getting it dangerously wrong and then recommending a DIY swap - not because it’s particularly hard - but it is dangerous which is why you need to be qualified to do it.

Black_S3

1,990 posts

135 months

Wednesday 23rd October
quotequote all
BaldOldMan said:
The mind blowing thing was firstly getting it dangerously wrong and then recommending a DIY swap - not because it’s particularly hard - but it is dangerous which is why you need to be qualified to do it.
Crazy stupid. All for the sake of £60 odd for an electrician who works out the correct breaker and signs it all off properly.

jackofall84

238 posts

6 months

Wednesday 23rd October
quotequote all
BaldOldMan said:
2 x 16 = 32

The one thing that absolutely didn’t need touching is that MCB

The mind blowing thing was firstly getting it dangerously wrong and then recommending a DIY swap - not because it’s particularly hard - but it is dangerous which is why you need to be qualified to do it.
I always design for worst case, in the UK, AC voltage fluctuates between about 220 - 240 with 230 being the nominal voltage. Taking the lower voltage (220V) and putting it into the Formula P = VI we can see that the current draw for both ovens at full capacity could be 32.7A – so it would trip the 32A breaker. Whilst this is unlikely to happen, I would give myself some head room just to air on the side of caution and have a 40A breaker fitted. Most devices have plenty of head room in the fuse, look at the fuse in the plug on your TV, I ‘ll bet it’s a 13A fuse even though the TV probably only draws about 2A at the most when working correctly, so in actual fact they’ve given head room of 11A!

Legally and safely speaking you can over size the breaker for the cabling, I suspect even in your own house the 2.5mm cable from your sockets is connected to a 32A breaker though the cable is only rated to carry 17.5A when enclosed in a wall. This is because if there’s a fault (likely to be a short) the current draw will go infinitely high and trip the breaker (or RCD these days) in a fraction of a second, this is nowhere near enough time for the cable to draw enough power to heat itself up to a dangerous level.

Years ago before everyone had breakers in their consumer units, people actually had to pull a fuse out the consumer unit, thread the correct gauge wire through and re-install it….all without calling out an electrician. It’s really not that different from changing a breaker.

Black_S3

1,990 posts

135 months

Wednesday 23rd October
quotequote all
jackofall84 said:
I suspect even in your own house the 2.5mm cable from your sockets is connected to a 32A breaker though the cable is only rated to carry 17.5A when enclosed in a wall. This is because if there’s a fault (likely to be a short) the current draw will go infinitely high and trip the breaker (or RCD these days) in a fraction of a second, this is nowhere near enough time for the cable to draw enough power to heat itself up to a dangerous level.
Did you skip out ring and radial in whatever qualification you did? I’m not an electrician but I can spot you are talking absolute bullst.

jackofall84

238 posts

6 months

Wednesday 23rd October
quotequote all
Black_S3 said:
Did you skip out ring and radial in whatever qualification you did? I’m not an electrician but I can spot you are talking absolute bullst.
You're always allowed 1 socket on 1 spur (unless you fit an FCU then you can have multiple sockets on 1 spur) that spur will be 1 cable from a socket. It will not have twice the load carrying capacity as the sockets on the ring.


BaldOldMan

954 posts

11 months

Wednesday 23rd October
quotequote all
jackofall84 said:
Years ago before everyone had breakers in their consumer units, people actually had to pull a fuse out the consumer unit, thread the correct gauge wire through and re-install it….all without calling out an electrician. It’s really not that different from changing a breaker.
FFS - take yourself off into a corner and have a serious word with yourself before spouting any more st

An old fuse could be pulled out and re wired - but in doing so was isolated from the live supply. That’s a lot different to taking the cover off a consumer unit. Have a think about it whilst you’re figuring out how a ring works........



Black_S3

1,990 posts

135 months

Wednesday 23rd October
quotequote all
jackofall84 said:
It will not have twice the load carrying capacity as the sockets on the ring.
You googled that quickly. This is why you don’t watch a youtube video and start fking about with breakers.

jackofall84

238 posts

6 months

Wednesday 23rd October
quotequote all
Black_S3 said:
You googled that quickly. This is why you don’t watch a youtube video and start fking about with breakers.
I did only find out about the FCU on a spur a few months back, it was really useful though as I have an old coal shed that I wanted to run several sockets in but the only existing socket in there was already on a spur. I just don't think people should be so afraid of their house electrics, it's all about risk management. New consumer units have an isolator switch. You can ensure further the power has been switched off by putting a meter over the breakers to ensure the power is off and safe to work on.

People will soon be buying explosives to light in their back gardens but are terrified to have a go at domestic electrics. Personally I'd feel safer changing a breaker than lighting a firework.

Anyway enough already!

Black_S3

1,990 posts

135 months

Wednesday 23rd October
quotequote all
jackofall84 said:
I did only find out about the FCU on a spur a few months back, it was really useful though as I have an old coal shed that I wanted to run several sockets in but the only existing socket in there was already on a spur. I just don't think people should be so afraid of their house electrics, it's all about risk management. New consumer units have an isolator switch. You can ensure further the power has been switched off by putting a meter over the breakers to ensure the power is off and safe to work on.

People will soon be buying explosives to light in their back gardens but are terrified to have a go at domestic electrics. Personally I'd feel safer changing a breaker than lighting a firework.

Anyway enough already!
Congratulations. By the sounds of it you probably have a single 2.5 between the back of a socket and a spur/FCU feeding a whole outbuilding that someone could run likely run electric heaters and god knows what else in.

Many CUs don’t have isolators and require the whole house fuse pulling to isolate, which is another level of stupid for a DIYer - even electricians should be calling out the electricity supplier for this.

All so crazy you must be trolling.

Jambo85

1,610 posts

35 months

Wednesday 23rd October
quotequote all
Black_S3 said:
jackofall84 said:
I suspect even in your own house the 2.5mm cable from your sockets is connected to a 32A breaker though the cable is only rated to carry 17.5A when enclosed in a wall. This is because if there’s a fault (likely to be a short) the current draw will go infinitely high and trip the breaker (or RCD these days) in a fraction of a second, this is nowhere near enough time for the cable to draw enough power to heat itself up to a dangerous level.
Did you skip out ring and radial in whatever qualification you did? I’m not an electrician but I can spot you are talking absolute bullst.
+1, absolute ste being spouted by this chap.

jackofall84 said:
look at the fuse in the plug on your TV, I‘ll bet it’s a 13A fuse
Assuming it's the factory fitted one and hasn't had the plug replaced by a moron, I'll bet it fking isn't.

Jackofall - you need to understand that MCBs and fuses are there primarily to stop cables going on fire. Once you appreciate that you'll realise that everything of yours I've quoted above is wrong, and dangerous.

Also worth reading about fault currents and EFLI etc. If fault currents were infinitely high as you suggest, then none of this would be difficult and hypothetically your main 60/80/100A fuse would be adequate for over current protection of your entire house. Trouble is, they ain't.

A minor point given the other stupidity surrounding it, but also be aware that RCDs don't have overcurrent protection, in my experience at least.

Mr Pointy

4,399 posts

106 months

Wednesday 23rd October
quotequote all
jackofall84 said:
I always design for worst case, in the UK, AC voltage fluctuates between about 220 - 240 with 230 being the nominal voltage. Taking the lower voltage (220V) and putting it into the Formula P = VI we can see that the current draw for both ovens at full capacity could be 32.7A – so it would trip the 32A breaker. Whilst this is unlikely to happen, I would give myself some head room just to air on the side of caution and have a 40A breaker fitted. Most devices have plenty of head room in the fuse, look at the fuse in the plug on your TV, I ‘ll bet it’s a 13A fuse even though the TV probably only draws about 2A at the most when working correctly, so in actual fact they’ve given head room of 11A!

Legally and safely speaking you can over size the breaker for the cabling, I suspect even in your own house the 2.5mm cable from your sockets is connected to a 32A breaker though the cable is only rated to carry 17.5A when enclosed in a wall. This is because if there’s a fault (likely to be a short) the current draw will go infinitely high and trip the breaker (or RCD these days) in a fraction of a second, this is nowhere near enough time for the cable to draw enough power to heat itself up to a dangerous level.

Years ago before everyone had breakers in their consumer units, people actually had to pull a fuse out the consumer unit, thread the correct gauge wire through and re-install it….all without calling out an electrician. It’s really not that different from changing a breaker.
Please, please tell us you're not a qualified electrician who does this & gets paid for it.

Why would you think an oven is a constant power device? It's almost certainly not - it's a constant resistance device (within the temperature/resistance characteristics of the elements). The current draw at 220V is lower than at 240V & given we don't know the nominal voltage the OP's oven are rated at we can't speculate on the current draw at 220V or 240V.

Your view that the current is greatest when the voltage is lowest is so wrong it brings into question everything you say. Please confirm that you're not a qualified electrician?