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Discuss fused connection unit or not? in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

M

marshr02

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Can anyone settle an argument?

45A cct with 10/4mm cable to 45A cooker switch. Switch supplies 7kW hob and 9kW oven via 10/4mm cables to connection units adjacent to each fitting.

The manufacturers cable for the hob is rated at 32A, my training would suggest the reduced cable size needs a fuse in the connection unit yet I never see this. The hob doesn't have an inlet fuse. Same argument goes for the oven.

Thanks for any enlightenment..
 
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R

randyrat

  • Thread Starter Thread Starter
  • #2
Total 16000W equals 69.57 A. Using diversity this reduces to 27.87A. Protection via 32A fuse/mcb/rcd in CU. Thre you go.
Randyrat
 
J

JulesHurley

  • Thread Starter Thread Starter
  • #3
Had a simalar kitchen installation - I treated each unit as seperate applainces and cabled two circuits, and presented at a dual back box, two isolators, onto two cooker outlets. Each was fused at the CU to suit, and labelled.

My reasoning for this - as explained to the client, is that two showers would never be doubled.

Jules
 
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M

marshr02

  • Thread Starter Thread Starter
  • #4
Thanks for the replies. Looking for the simple solution, hence prefer Randyrats.

Still interested in this scenario. Pre-existing cooker cct, 45A. New cooker/hob unit bought that has lower wattage than original with a cable that clearly can't take 45A. Should the connection unit have a fuse fitted to reduce down to 32A (or the mcb/rcbo swapped to 32A) or is the cooker just connected up.
 
W

WarrenG

  • Thread Starter Thread Starter
  • #5
Thanks for the replies. Looking for the simple solution, hence prefer Randyrats.

Still interested in this scenario. Pre-existing cooker cct, 45A. New cooker/hob unit bought that has lower wattage than original with a cable that clearly can't take 45A. Should the connection unit have a fuse fitted to reduce down to 32A (or the mcb/rcbo swapped to 32A) or is the cooker just connected up.
If I have read you right, the loading has changed and the protective device can be reduced down to 32A based on the loading of 27.86A

16000W / 230V = 69.56A

Diversity 1st 10A + 30% of remainder 10A + 17.86A = 27.86A

Yes the cable can be protected by a larger fuse but the closest fuse to you load is a 32A.

In terms of wiring you could use a cooker control switch feeding two seperate cooker connection units (max 2 meters from cooker control SW) for hob and oven...

or

a cooker control switch feeding one cooker connection unit for the hob and a second feed from the cooker control switch to a FCU and to your oven. If oven is wired in flex this can be directly connected to the FCU

Hope this helps!

Warren
 
Thanks for the replies. Looking for the simple solution, hence prefer Randyrats.

Still interested in this scenario. Pre-existing cooker cct, 45A. New cooker/hob unit bought that has lower wattage than original with a cable that clearly can't take 45A. Should the connection unit have a fuse fitted to reduce down to 32A (or the mcb/rcbo swapped to 32A) or is the cooker just connected up.

I think the cable will only draw what the cooker uses.........?
It shouldn't have to pull 45A,but I understand where you are coming from.Quite often new ovens come with a heat resistant 2.5 flex,don't
have my regs handy but I'm pretty sure it would carry 30A no prob.
I recon you would be safe enough connecting both tails into your ccu
as a million before you have done.
 
S

Spudnik

  • Thread Starter Thread Starter
  • #7
Gotta be careful with these new hobs.

If its an induction hob, some have a superheat setting than can draw a lot more than diversity.

Had this recently on a Kitchen Aid induction hob.

As always, check the manual and if necessary contact the manufacturers.
 
M

marshr02

  • Thread Starter Thread Starter
  • #8
Cheers Guys, excellent posts.

The best use of this site for me is to draw on your experience. I'm a recently qualified but not practicing electrician.
e.g.
<I recon you would be safe enough connecting both tails into your ccu
as a million before you have done. >


The hob is an induction hob, with flex connection. I'm a little wary of using diversity too much, purely because I'm keen to avoid nuisance tripping.

Leaning towards a 45A cct with 10/4 cable. Yes the hob should only draw what it needs, but what about any fault condition? I would prefer a local fcu for the hob only.

This raises one last question, a 32A fcu? surely I need to fit a one module CU to actually fit a 32A fuse/mcb. I'm always wary when the solution starts getting complicated...
 
Cheers Guys, excellent posts.

The best use of this site for me is to draw on your experience. I'm a recently qualified but not practicing electrician.
e.g.
<I recon you would be safe enough connecting both tails into your ccu
as a million before you have done. >


The hob is an induction hob, with flex connection. I'm a little wary of using diversity too much, purely because I'm keen to avoid nuisance tripping.

Leaning towards a 45A cct with 10/4 cable. Yes the hob should only draw what it needs, but what about any fault condition? I would prefer a local fcu for the hob only.

This raises one last question, a 32A fcu? surely I need to fit a one module CU to actually fit a 32A fuse/mcb. I'm always wary when the solution starts getting complicated...
It should give the load on the information plate on the appliance or with the paperwork/manual .I think you will find it will be below 18A,Fan assisted units need less heating elements. .......But if you really really want to provide additional protection I suppose you could install an inline fusecarrier such as found on streetlamps inside the appliance,or indeed an mcb in an area not exposed to the heat,mounted on a dinrail.But you might find that this will invalidate any warranty. I doubt you would have enough room behind the oven to surface mount your mcb,I haven't come accross a flush mounted box and cover plate that you could use and fits inside a standard size backbox. Maybe you are ripping the arse out of this and the greycells are needing further lubrication;)
 
W

WarrenG

  • Thread Starter Thread Starter
  • #10
I think I would take your feed to a cooker control switch feed out of that to two seperate FCU's - one for hob, one for cooker and put a 32A in the CU.

Flex's from cooker and Hob straight into individual FCU's.

Either can be isolated and if the hob goes and takes the FCU fuse the cooker can stay on and vice versa etc
 
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M

marshr02

  • Thread Starter Thread Starter
  • #11
Mrloy99, thank you for a new catchphrase that made me laugh <ripping the arse out of it> this is so true, you can think to hard about something...

For me the induction hob has flex that can handle 32A. Yet if I'm feeding the combined induction hob/oven then I want to use a 45A at the CU. This means that without a 32A MCB at some point the hob flex isn't protected.

If the solution involves inline fuses, fixing DIN rails & MCBs to the wall - then for me this is too complicated (and no one else does this). I'm thinking 2 ccts; a 32A MCB at the CU to the hob. A separate cct for the oven based on it's rating. All switched via two separate 1G switches fixed alongside each other for cosmetics.

WarrenG - if the induction hob is rated at 32A, and experience of others suggest it can't be subject to too much diversity allowance, then a 13A FCU would be too small?

Cheers Guys.
 
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W

WarrenG

  • Thread Starter Thread Starter
  • #12
marshr02 quite right, getting a little thrown with diversity here.....how ever you could still rip the arse out of it!
 
Can anyone settle an argument?

45A cct with 10/4mm cable to 45A cooker switch. Switch supplies 7kW hob and 9kW oven via 10/4mm cables to connection units adjacent to each fitting.

The manufacturers cable for the hob is rated at 32A, my training would suggest the reduced cable size needs a fuse in the connection unit yet I never see this. The hob doesn't have an inlet fuse. Same argument goes for the oven.

Thanks for any enlightenment..
How about fitting a heavier flex,or even fit a plug and socket arrangement,eg comando socket suitably rated,then,it no longer is part of the fixed installation.But then again,who is paying for it?If you are going to get paid to put in a new circuit,then if you are gonna get a few quid in the skyrocket,who are we to tell you not to "rip the arse";)
 
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