oven isolation??

[scrag]

Hi Guys. Got a job on tuesday to supply two separate Miele ovens. Each oven is 3.6KW and because of the logistics of the kitchen I am going to use the existing 32 amp (6mm cable) supply which originally supplied the previous oven. The job was prepared before the ovens arrived with the information I had been given. The manufactorers instructions are to fit a fused connection unit or a double pole isolator. The connected flex from the ovens is 2.5mm.

The max load of the ovens is nearly 16A each. Therefore 13A fcu's would be insufficient and the 32A MCB at the c/unit would not protect the ovens. Your advice and thoughts would be most appreciated. I know that manufactorers spec supercedes the red book.

I

 

[ian932]

I see no problem with 32A mcb covering the circuit and a 45A DP Isolator feeding a 2 way cooker outlet with the ovens connected to that.

Has the manufacturer specified the oven should be protected by a certain trip rated device?

The only other thing that springs to mind if you want each oven covered is a 2 way enclosure fitted with 2x16A mcbs in a local cupboard and fed from your 45A isolator above.

 

[scrag]

Thanks for the reply. The answer is No, the manufacturer does not insist on any kind of protection, except that a FCU is the preffered method but a double pole isolator would be sufficient. It just seems odd to me that in this country you can only fit 13A Max 1361 fuses in a FCU and they do not know this.

 

[ian932]

Thanks for the reply. The answer is No, the manufacturer does not insist on any kind of protection, except that a FCU is the preffered method but a double pole isolator would be sufficient. It just seems odd to me that in this country you can only fit 13A Max 1361 fuses in a FCU and they do not know this.

I know what u mean, its 1362 fuse though.

A 1362 has a fuse factor of 1.6 to 1.9 so it could handle 16A but not recommended.

 

[scrag]

Sorry!! I stand corrected. Yes 1362. Not a good idea so looks like I will just fit an isolator and hope appliance has internal fuse. It does also state that isolator can be installed but I dont like it as per The manufacturers specifications. So I am covered.

 

[batty]

I would have them both on the 32a circuit as long as your earth fault loop is ok there will be no problem. In an ideal world you would have two 20a circuits but you have to do what you have with whats there.

Batty

 

[Evans Electric]

Just wondering where it is stated that manufacturer's instructions override the BRB.

As you say , a spur unit would be no good at 13 amps. The flexes would be rated at , what, 20 A, so really the MCB is not protecting the flexes.

 

[Andy™]

Hi Guys. Got a job on tuesday to supply two separate Miele ovens. Each oven is 3.6KW and because of the logistics of the kitchen I am going to use the existing 32 amp (6mm cable) supply which originally supplied the previous oven. The job was prepared before the ovens arrived with the information I had been given. The manufactorers instructions are to fit a fused connection unit or a double pole isolator. The connected flex from the ovens is 2.5mm.The max load of the ovens is nearly 16A each. Therefore 13A fcu's would be insufficient and the 32A MCB at the c/unit would not protect the ovens. Your advice and thoughts would be most appreciated. I know that manufactorers spec supercedes the red book.

I

nothing wrong with 2.5 feeding the ovens from cooker outlet. the max load of oven is less than that of the 2.5. also, the 32A MCB is there to protect the fixed wiring. its not there to protect the appliance. although in most cases, it often does this at same time as protecting the fixed wiring.

 

[tom1]

16A oven is that not 12a per oven then

16-10*30%+10 =11.8

you can run 2 ovens from the same cooker switch so long as they are in 2 meters of the switch

 

[Andy™]

if using a cable without overload protection, you should work on max load

 

[tom1]

so 13A fcu be ok then?

 

[Andy™]

so 13A fcu be ok then?

possibly. may blow the odd fuse though. if it was me, id just stick both ovens into the same cooker outlet and leave on 32A MCB

 

[tom1]

[quote name='Andy

 

[Andy™]

i concur,says in osg 3 ovens off i switch, would u add the max load for all and appliy diversity to give you your mcb and cable rating?

yes, but if your working with a cable rated smaller than MCB (like the 2.5), dont apply diversity to it since there is no overload protection and cable can overheat

 

[Badger]

i have a suggestion, why dont you mount a 2 way C/u with 2 x 20 amp mcbs in the c/u either in a cupboard or at ceiling height where the 32 amp feed comes into kitchen ??

 

[tom1]

[quote name='Andy

 

[Andy™]

yer i would always put cable bigger than mcb, i have read on here discusions about fixed appliences like showers and cookers not needing overload protection, but still, cable higher than mcb every time (exceptions ring main spurs)

but there is still 2.5 between oven and outlet.

 

[batty]

i have a suggestion, why dont you mount a 2 way C/u with 2 x 20 amp mcbs in the c/u either in a cupboard or at ceiling height where the 32 amp feed comes into kitchen ??

You are making a lot of work for yourself. You have two ovens at 3.6 kw each which is no more than 15 amps each. Connect them to the 32 amp circuit via a piece of 2.5 flex x 2. The maximum oven is going to use is 15 amp when switched on and as long as the earth fault loop is high enough to trip circuit breaker if there is a short circuit everything will be fine. I know work maybe short at the moment but I cannot see the possible need for a consumer unit to protect this circuit.

Batty

 

[Andy™]

exactly what ive been trying to say!

 

[scrag]

Just got back so here we go. I have to try to use the existing circuit to keep costs down. Fix it and bodge it did the barn conversion 5 years ago. The building works are crap but the electrics appeared to be done proffesionally. Theres underfloor heating and some horrendous routes, the elderly couple are very pleasant and we are trying to keep costs down. There is another builder there putting things right also. Idealy it would be nice to run some more circuits. As far as I am aware and I have checked it out with the NICEIC that manufacturers specification overides the red comic. Any suggestion on the last point.