Correct MCB for 3.6kW oven please ....

[r6deano]

Afternoon guys.

I'm prepping my kitchen ready for my spark. I can't get through to him ATM. I love all aspects of building and have been lucky to be hands on with most of my project. I'm just arranging the CU for his visit next week - my question is I have X2 built in ovens each with their dedicated 2.5mm feed and 20a DP iso.
Each rated at 3.6kw. I work it out at just over 15A. Would a 16A (each) MCB be safe or should I be adding a buffer to the load, therefore protect with a 20A MCB?
Or does diversity apply here, meaning the 16a more than sufficient? Cables clipped direct to blockwork and approx 6m total length.

Tia

 

[EFLImpudence]

I'm prepping my kitchen ready for my spark. I can't get through to him ATM.

Try again.

I love all aspects of building and have been lucky to be hands on with most of my project. I'm just arranging the CU for his visit next week -

Ok. Has he told you what to get?

my question is I have X2 built in ovens each with their dedicated 2.5mm feed and 20a DP iso.
Each rated at 3.6kw. I work it out at just over 15A. Would a 16A MCB be safe(each)

The OPD (MCB) is worked out so that it protects the cable - not the appliance.

The cable' rating depends on it size and installation method.
2.5mm² has a maximum current carrying capacity of 27A (clipped direct or buried in masonry) so any MCB up to 25A would do.

So, 16A is alright for the oven and cable ratings.

or should I be adding a buffer to the load, therefore protect with a 20A MCB?

No, no need but it doesn't matter if you do.

Or does diversity apply here, meaning the 16a more than sufficient? Cables clipped direct to blockwork and approx 6m total length.

It does apply but there's not much scope at 15A - down to 12.5A.
Can all elements be switched on at the same time, anyway?

 

[r6deano]

No can do- he's too busy on the golf course on fridays!

One of the manuals I've found hidden in braille, specs the device with a 16a plug(!) or fuse. The other manual, also bosch, is near identical but doesn't have the UK& Australia paragraph like the other that stated the 16a. But it's 500W less powerful.

However, one of the ovens was going to spur to a fcu for a warming drawer .... It's just under 500W, so total load 3.7kw.

Thank you

 

[EFLImpudence]

No can do- he's too busy on the golf course on fridays!

It's not Friday for very long.

One of the manuals I've found hidden in braille, specs the device with a 16a plug(!) or fuse. The other manual, also bosch, is near identical but doesn't have the UK& Australia paragraph like the other that stated the 16a. But it's 500W less powerful.

I'm not sure what you are asking.
Bosch is German, where they have 16A plugs.

However, one of the ovens was going to spur to a fcu for a warming drawer .... It's just under 500W, so total load 3.7kw.

I presume you mean one of the circuits. Ok.

Are these ovens near each other?
Did your electrician not suggest one 32A circuit in 6mm² (4mm² would do) cable, as 99% of homes have, to which you can connect all the cooking appliances you will ever need in a usual domestic kitchen?

 

[r6deano]

It's not Friday for very long

I needed some advice today rather than wait the weekend, thus the post to the forum my man!

I'm not sure what you are asking.
Bosch is German, where they have 16A plugs.

The instruction manual under installation, was broken down into sub-paragraphs, and under 'UK&Australia' all it said was have 16a fuse/d plug, but strangely only for one appliance (the other manual was absent that paragraph, same Series Bosch range)

Are these ovens near each other?
Did your electrician not suggest one 32A circuit in 6mm² (4mm² would do) cable, as 99% of homes have, to which you can connect all the cooking appliances you will ever need in a usual domestic kitchen?

They are in adjacent towers. At the same height as each other.
My electrician suggested one 40a circuit which we ran 10mm because at the original 1st fix a range was planned, but ended up being induction hob plus 2 built in ovens. My neighbour popped in yesterday who was a spark until last year, and he threw the spanner in the works RE one circuit for all appliances, suggesting that of it can be done, run a circuit for each appliance, as all under one circuit wouldn't offer individual protection. Ie if just one oven was on and overheated, then the 40a breaker wouldn't pick it up for some time.

 

[EFLImpudence]

The instruction manual under installation, was broken down into sub-paragraphs, and under 'UK&Australia' all it said was have 16a fuse/d plug, but strangely only for one appliance (the other manual was absent that paragraph, same Series Bosch range)

They may state a 16A supply which is what they have in Europe in order for it to work.

They are in adjacent towers. At the same height as each other.
My electrician suggested one 40a circuit which we ran 10mm because at the original 1st fix a range was planned,

10mm² is used as the supply cable for whole flats.
As above the cable and MCB ratings are what matters.
Clipped direct -
32A 4mm²
40A 6mm²
63A 10mm²

as all under one circuit wouldn't offer individual protection. Ie if just one oven was on and overheated, then the 40a breaker wouldn't pick it up for some time.

It wouldn't notice overheating, MCBs notice overloading of the cable but cooking appliances don't do that.

Sup to you.

 

[flameport]

My electrician suggested one 40a circuit

They were correct. (although a 32A and smaller cable would probably do just as well)

as all under one circuit wouldn't offer individual protection.

Circuit breakers are there to protect cables, not appliances.

if just one oven was on and overheated, then the 40a breaker wouldn't pick it up for some time.

A circuit breaker would never trip due to an overheated oven.
Ovens already include overheat protection, in the form of a device which disconnects the element if the temperature exceeds a set level. They are not resettable and must be replaced if such an event occurs - usually along with the thermostat which caused the overheating in the first place.

Elements fail in one of two ways - they either melt through and stop working, or they deform and contact the outer metal casing, causing a short circuit, a big bang and and a tripped circuit breaker.
They cannot magically draw more current than they are designed for, and will never trip any circuit breaker due to overload.

A range cooker with two ovens and a hob on top is electrically identical to two separate ovens and a separate hob.

Your neighbour should refrain from offering advice on things they apparently know nothing about.

 

[JohnW2]

The instruction manual under installation, was broken down into sub-paragraphs, and under 'UK&Australia' all it said was have 16a fuse/d plug ....

They don't seem to know what they're talking about then. The UK (and a few remnants of past bits of 'the Empire') is the only place that has fused plugs, and 13A is the most you can have (Germany uses unfused ones rated at 16A).

My electrician suggested one 40a circuit which we ran 10mm because at the original 1st fix a range was planned, but ended up being induction hob plus 2 built in ovens.

That would have been way OTT, even for a range cooker - by virtue of diversity, a 32A 6mm² (or even 4mm² in most cases) circuit is OK for a total 'rated' cooking appliance load of about 19kW.

Kind Regards, John

 

[ban-all-sheds]

I needed some advice today rather than wait the weekend, thus the post to the forum my man!

And when you ask him to sign this:

I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2015 except for the departures, if any, detailed as follows:​

and he (rightly) refuses because it would be a lie, what will you do?

Also, what did you do about Building Regulations approval? Did you notify in advance?

 

[r6deano]

And when you ask him to sign this:

I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2015 except for the departures, if any, detailed as follows:​

and he (rightly) refuses because it would be a lie, what will you do?

Also, what did you do about Building Regulations approval? Did you notify in advance?

Hi B-A-S!
Yes mate it'll be no probs, because I'm probably the most anal belt and braces self builder /renovator out there, everything is done above and beyond building regs . This is my own home so no corners cut. I've obviously over worried about appliance protection and others have kindly offered their opinions, reminding me it's about cable protection, which, overkill or not, we've gone with 10mm on the hefty hob .

And each oven has its own dedicated circuit to which I'm sure my spark will agree that's not a bad thing with spare ways on the board. Next week, he will come and check ALL my work, ALL connections and certify my work. Because he recognises I dont do things myself to save money, in fact I'll be paying him to go over my work so I'm only losing my own time, I do it for the buzz and satisfaction. Excuse the pun. Or don't.

May I remind you this is a DIY forum with electrical sub category, I've been reading this site for many years on and off and it seems there's a lot of p*ssed off tradesmen that feel put out that people want to attempt things thereselves, perhaps they feel like their work is being taken from them. I advise they perhaps stick to trade only forums to discuss secret trade talk, so not to be offended buy DIY enthusiastic people that like the satisfaction DIY can give. I appreciate qualifications thus i employ skilled workers too.

Thanks for the certification comment all stemming from my question of making sure I had the right sized breaker!

Be lucky (and happy!)

 

[EFLImpudence]

overkill or not, we've gone with 10mm on the hefty hob .

That's ridiculous.
Are you going to use 6mm² for the sockets?

May I remind you this is a DIY forum with electrical sub category,

May I remind you that not all work may be DIYed.
Try asking a gas question on the plumbing forum.

I've been reading this site for many years on and off and it seems there's a lot of p*ssed off tradesmen that feel put out that people want to attempt things thereselves, perhaps they feel like their work is being taken from them.

Why do you think they are here, then?
It makes no difference to me.
Advice also includes being advised NOT to do things which you may not do because of legal implications.
Is your electrician registered to self-certify (which actually means self-notify)?
If not then YOU should have notified the Local Authority before the work commences.

I advise they perhaps stick to trade only forums to discuss secret trade talk, so not to be offended buy DIY enthusiastic people that like the satisfaction DIY can give. I appreciate qualifications thus i employ skilled workers too.

They do not need your misplaced advice.
No qualifications are required to do electrical work but the legal requirements must be followed and may not be ignored because you want a buzz.

 

[r6deano]

That's ridiculous.
Are you going to use 6mm² for the sockets?


May I remind you that not all work may be DIYed.
Try asking a gas question on the plumbing forum.


Why do you think they are here, then?
It makes no difference to me.
Advice also includes being advised NOT to do things which you may not do because of legal implications.
Is your electrician registered to self-certify (which actually means self-notify)?
If not then YOU should have notified the Local Authority before the work commences.


They do not need your misplaced advice.
No qualifications are required to do electrical work but the legal requirements must be followed and may not be ignored because you want a buzz.

Hey, whatever pal.

I've seen too many of your replies in the past to recognise sarcastic know it all advice.

You commented on my thread purely to have a dig at someone doing work (and following regs and advice) themselves that had gone on a DIY forum to check something. There was no
'hi r6, here's something useful for you....'

I'm very professional and courteous in my day job, as I am outside of work. Sick and tired of keyboard warriors that have too much time to try and bring someone down.

I asked for advice, got some great feedback (especially after two sparkies at my site have different opinions which is why I came on here), then you pipe up with nothing useful other than to criticise me working on my own house. And my ridiculous 10mm wire. Which, yes, is ridiculous. Fitted after yet another electricians advice, not my guess work.

You're part of the D&G movement, doom and gloom my man, doom and gloom.

Anyways, have a great weekend ripping apart more people on the internet.

 

[EFLImpudence]

Hey, whatever pal.
I've seen too many of your replies in the past to recognise sarcastic know it all advice.

You seem to be forgetting who has given you the most replies.
You thanked me twice.


What you may not realise is the number of electricians who are reportly unavailable to their customers and information that cannot possibly wait is instantly required.
Whilst we can obviously never have any proof, we suspect that many, if not all, do not exist and we are being taken for a ride.

 

[r6deano]

You seem to be forgetting who has given you the most replies.
You thanked me twice.

Apologies here - I didn't look I thought it was still BAS replying. I appreciate your replies.

But it feels like you made assumptions based on other threads that perhaps I'm impatient and need to know urgent advice and made up the fact I'm using a spark....as a DIYer I must say, when I've posted on this /and other forums, you do sort of hold your breath and wait for the sarcasm/someone tearing you a new one because you've missed out a small detail. Or being belittled because how dare a non professional attempt work...I put as much info into the original post of install method, lengths, location and cable size. I just needed to know how close to a breakers limit a breaker would cover!

Your replies consisted of-
1) 'Well just keep trying your spark, I don't believe you have one, don't dare come on a forum for help'

2) "has he told you what to get?" -'im calling you out I don't believe you have a spark'

3) I give the reason I cant ask him, and you basically say well just wait, "it's not Friday for very long"

4) Sarc-y remark about me using 6mm for sockets

Please don't mistake my enthusiasm for some cheapskate that doesn't want to pay the money out. My BO visits and chuckles how OTT I have been going beyond regs for insulation/fire rating etc, this is my forever home and I've been fortunate enough to bend my self employment to allow me to be part of this project start to finish.

If a guy wants to OCD all the cables and clip them neatly to the board before they enter the CU and then leave everything neat and tidy ready for the spark to tighten all connections, or chase and run all the cables, metal trunk them all in and let the spark check everything - just because he enjoys being part of it all - i don't see what's wrong with that! I hope this clarifys I'm not ignoring legal requirements just looking for a buzz!

 

[ban-all-sheds]

Hi B-A-S!
Yes mate it'll be no probs, because I'm probably the most anal belt and braces self builder /renovator out there, everything is done above and beyond building regs .

But who is going to officially certify that the work has been done to that standard, and how?

This is my own home so no corners cut. I've obviously over worried about appliance protection and others have kindly offered their opinions, reminding me it's about cable protection,

That's not an opinion, it's a fact.

which, overkill or not, we've gone with 10mm on the hefty hob .

And that complies, just like fitting Y rated tyres to a G-Wiz would do.

And each oven has its own dedicated circuit to which I'm sure my spark will agree that's not a bad thing with spare ways on the board.

Whether he agrees or not is irrelevant. It's a design decision which he did not make, and therefore he may not sign a declaration to say that he did.

Next week, he will come and check ALL my work, ALL connections and certify my work.

When you say "certify", what do you mean? Does his definition of the word align with yours? If to both of you "certify" means "issue an Electrical Installation Condition Report", and Building Control are happy with that because when you applied for permission to do the work you told them that's how you'd be going about it, then all will be well.

If that's not the situation then don't be surprised if things go wrong.

May I remind you this is a DIY forum with electrical sub category, I've been reading this site for many years on and off and it seems there's a lot of p*ssed off tradesmen that feel put out that people want to attempt things thereselves, perhaps they feel like their work is being taken from them.

Well I'm not a tradesman, so that concern can be ignored, but even if I were it's not about that.

Of course you may DIY the electrics, just as you may, if physically able, build an entire house using your own hands, but it should not be done unlawfully. It should not be done via getting a professional to falsify documentation to disguise the fact that you DIYed.

If you had answered this

what did you do about Building Regulations approval? Did you notify in advance?

along the lines of "I notified the work in advance, paid their fee, told them I'd be DIYing and getting it inspected by an electrician, and they approved that" then you wouldn't be having this conversation with me, or EFLI.

But the bluster we've had instead does make a reasonable person wonder if you do have an electrician. Even if you do, even if we all say "Fine, I accept that you have an electrician" there remains the question of what is his legal status in this project.

Be lucky (and happy!)

You too, Because if, when you applied for Building Regulations approval, you told Building Control, or by default allowed them to assume, that your route to compliance with Part P would be to have the work done by an electrician, you'll be neither of those things when it comes time for the completion certificate from them.