Multiple cooking appliances.

[Soulsurfer]

Hi all,
Just looking into a kitchen refit where the customer has gone a bit excitable with the cooking side of things !

Have done lots of installs with two appliances on the one circuit but anyone know of any issue with feeding three rather than run a new circuit for say the new hob alone ?

I have an existing 32A rcbo on a 6mm twin for built in oven now and hob but new kit is an oven at 3.45kW
Combi oven / micro at 3.6kW

and finally an induction hob at 5.6kW
24.3A fuse rating on spec sheet so they haven't allowed any diversity.
Anyone fitted them with a diversity applied ? as I haven't fitted any induction before.

I'm making it a shade under 27A for the oven and combi together,

and if allowed on induction 18.7A approximately but I'm thinking likely run a new circuit from cu at the full load rating the manufacturer of the hob has given.

 

[Wilko]

Looking at OSG Appendix A and noting coffee not kicked in yet so hopefully I've understood correctly ...
10+13.5+5(say)=28.5A for domestic and
24.3+12.5+9=45.8A for small shop.
Translation : if the customer likely to go nuts with new kit (ask them?) try to sell them on the idea of a new supply

 

[Midwest]

When I've calculated diversity for domestic ovens, I've applied diversity to each appliance individually, not the total load added together.

I'm not sure if that is the right interpretation, but my thinking is the end user can operate each appliance as they choose to, as opposed a singular appliance preventing them from using all heating elements, if you get my drift. Like a single oven, where you can't use the grill & main oven simultaneously.

 

[Richard Burns]

It would probably be OK on the standard arrangement (subject to Wilko's caveats) but if you have the option to run a new supply for the hob then this means you are very safely covered.
The customer will need to be informed that they are using a lot of power and be sensible!
If you turn everything on and then jump in your 10.5kW electric shower you could get the main 60A fuse to go!

 

[Octopus]

2 appliances - OK, adding a 3rd may push it............ I would probably recommend a 2nd supply OR changing the induction hob for one with a 13A plug!

 

[Wilko]

When I've calculated diversity for domestic ovens, I've applied diversity to each appliance individually, not the total load added together.

I'm not sure if that is the right interpretation, but my thinking is the end user can operate each appliance as they choose to, as opposed a singular appliance preventing them from using all heating elements, if you get my drift. Like a single oven, where you can't use the grill & main oven simultaneously.

It would be interesting to compare the two methods, hopefully it would have the same outcome

 

[buzzlightyear]

and if allowed on induction 18.7A approximately but I'm thinking likely run a new circuit from cu at the full load rating the manufacturer of the hob has given.

looking at that loading you have given .I makes more sense.reg 433.1.103 (111)connecting cookers hobs
exceeding 2kw on own dedicated r/circuit.
how many times we have been around the houses with hobs &cookers on this forum!

 

[buzzlightyear]

I forgot soulsurfer in channel islands .by the time the bong drums start banging. he would be able to hear it!

 

[hightower]

I makes more sense.reg 433.1.103 (111)connecting cookers hobs
exceeding 2kw on own dedicated r/circuit.

My understanding is, using a dedicated radial circuit means not connecting it among other appliances such as on the RFC etc. It doesn't mean a radial for each appliance over 2kW.

You can have a dedicated radial for all three appliances, just so long as that circuit meets design requirements. It's still a dedicated circuit for those appliances.

 

[buzzlightyear]

when I do installs cookers hobs ,on the own dedicated circuit. but that's for me only.
with this day and age you will never know .

 

[Phil Thompson]

After being caught out a few times by being given incorrect (smaller) kw ratings of induction hobs, I now just pull in a seperate feed for them than the oven when I hear induction hob mentioned.

Last time was given a similar rating to the OP, however on day of fitting it was actually 7.8Kw.

I see more and more folks on my Facebook feed doing batch cooking at weekends due to work commitments during the week. So they are using all rings and ovens to be doing as much as they are doing, no longer just a Christmas dinner thing anymore for some households to be using full ratings of cooking appliances as it used to be.

 

[Midwest]

It would be interesting to compare the two methods, hopefully it would have the same outcome

Don't think your following what I'm suggesting Wiko.

For the three appliances of 3450w, 3600w & 5600w, using Table A1 (applying diversity separately) I get a figure of 37.5amps (no sockets).

Or have I got my maths wrong?

 

[telectrix]

all 3 in use are never going to pull >45A, so a single 45A isolator, fed 6mm on a 40A breaker if method C. 10mm cable id insulation correction required.

 

[Soulsurfer]

I forgot soulsurfer in channel islands .by the time the bong drums start banging. he would be able to hear it!

What's the bong drums dare I ask !

 

[buzzlightyear]

What's the bong drums dare I ask !

their you go soul train!

 

[Midwest]

when I do installs cookers hobs ,on the own dedicated circuit. but that's for me only.
with this day and age you will never know .

buzz are you sparksburntout's twin or doppelganger or even his alter ego, as he never seems to bring you to task about your atrocious spelling and grammar

 

[Soulsurfer]

Ha ha loads of them today ! Battle of Flowers on. Bongo bongo time lol, only the other Bong thing you'll find down where I surf but that's nothing to do with electrics

 

[Soulsurfer]

Ha ha loads of them today ! Battle of Flowers on. Bongo bongo time lol, only the other Bong thing you'll find down where I surf but that's nothing to do with electrics

 

[buzzlightyear]

buzz are you sparksburntout's twin or doppelganger or even his alter ego, as he never seems to bring you to task about your atrocious spelling and grammar

sorry sir !

 

[Wilko]

Don't think your following what I'm suggesting Wiko.
For the three appliances of 3450w, 3600w & 5600w, using Table A1 (applying diversity separately) I get a figure of 37.5amps (no sockets).
Or have I got my maths wrong?

You're right, but I've got it now. Your maths are correct, or I make the same mistake
The answer is quite different using Table A1 method, as its got 3 lots of 10A, vs only one lot when using Table A2. I think A2 is the one to use for this, just going by its name (?).

 

[Soulsurfer]

You're right, but I've got it now. Your maths are correct, or I make the same mistake
The answer is quite different using Table A1 method, as its got 3 lots of 10A, vs only one lot when using Table A2. I think A2 is the one to use for this, just going by its name (?).

So table A2 by using the total loads, I'm getting 41.5 A after diversity ?

 

[Dave OCD]

buzz are you sparksburntout's twin or doppelganger or even his alter ego, as he never seems to bring you to task about your atrocious spelling and grammar

Hmmm you could be on to something here, another little known fact is that Tel and Pete are actually twins.

 

[telectrix]

Hmmm you could be on to something here, another little known fact is that Tel and Pete are actually twins.

not treue. pete is 4 months older than me. that,s 18 weeks to correct the minor defects and create perfection.

 

[Midwest]

You're right, but I've got it now. Your maths are correct, or I make the same mistake
The answer is quite different using Table A1 method, as its got 3 lots of 10A, vs only one lot when using Table A2. I think A2 is the one to use for this, just going by its name (?).

According to the introduction on Appendix A, Table A1 is used to calculate the current demand for a final circuit, making an allowance for diversity. Table A2 is used for calculating the current demand of an installation consisting of a number of final circuits, also making an allowance for diversity.

The 'definition' used in both (for cooking appliances) is the same (IMO), although they are written differently.

Appendix H, and H4 advises the use of Table A1 for cooker circuits in household premises. It states that a 30 or 32 A circuit is usually appropriate for household or similar cookers of a rating up to 15kW. It also advises about the connection of two or more appliances on one circuit.

Mind you, these diversity tables were composed 'hundreds' of years ago, before induction hobs, steam ovens etc were introduced. Down to the designer.

 

[telectrix]

steam ovens? are we now regressing back to the age of steam, when things were designed and engineered to perform, regardless of accountants going for cheapest option,, broken within weeks instead of decades?

 

[Midwest]

No not steam engines, steam ovens bit like this;

 

[Rpa07]

not treue. pete is 4 months older than me. that,s 18 weeks to correct the minor defects and create perfection.

18 week wonder well that's another whole topic on the forum - out with the old Electrical Trainee in with the new!

 

[Wilko]

According to the introduction on Appendix A, Table A1 is used to calculate the current demand for a final circuit, making an allowance for diversity. Table A2 is used for calculating the current demand of an installation consisting of a number of final circuits, also making an allowance for diversity ...

Re reading the docs, I see what you mean and I'm seeing the wisdom. Table A1 title has "points of utilisation or current using equipment" and in this case there are 3 of them, so apply it 3 times

Learning everyday, cheers !

 

[Soulsurfer]

Re reading the docs, I see what you mean and I'm seeing the wisdom. Table A1 title has "points of utilisation or current using equipment" and in this case there are 3 of them, so apply it 3 times

Learning everyday, cheers !

So in your opinion Wilko would you go by 3 different applications of the 10A +30% calc and cover all (15kW) on one 50A control switch or seperate radial say for one appliance and seperate isolator of course ?

 

[Midwest]

I think if you have one existing 32A radial, I'd be inclined to drag in another. If you have a butchers at H4 OSG (described by some, as a storybook with pictures), it makes reference to isolation, and refers to reg 536.2, which I can't make sense of, but think says refer to manufacturer?

 

[Wilko]

Isn't the problem that you've only got 6mm and a 32A mcb? Now I've smelt the cooking I def would not add this new hob to that circuit, a change from what I implied at 6:30 this morning ...(darn, too late to edit?). If circuit was at least 40A then it's a maybe but we are back to actual useage vs OSG advice. A 2nd 6mm and it can be Christmas every day

 

[Soulsurfer]

I think if you have one existing 32A radial, I'd be inclined to drag in another. If you have a butchers at H4 OSG (described by some, as a storybook with pictures), it makes reference to isolation, and refers to reg 536.2, which I can't make sense of, but think says refer to manufacturer?

Yes mate, I did read that and the reg which is another quite flouncy sentence and in my mind is taken as add an isolation switch to switch the appliances conveniently rather than one switch to shut off 3 different appliances for instance. Either way thanks for input from all I'm nearly off to the airport as Mallorca soon !

 

[Midwest]

I'm nearly off to the airport as Mallorca soon !

Lucky ****

 

[Rpa07]

At least take the OSG with you for lying by the pool reading material - you'll be clued up by the time you return!
Happy holiday!

Yes mate, I did read that and the reg which is another quite flouncy sentence and in my mind is taken as add an isolation switch to switch the appliances conveniently rather than one switch to shut off 3 different appliances for instance. Either way thanks for input from all I'm nearly off to the airport as Mallorca soon !

 

[Soulsurfer]

Got to get through Gatwick & out to Stansted & away first !
It's all a struggle really
Enjoy your summer chaps

 

[Soulsurfer]

Just need a postcard wall here now