Temp hooking up a pair of 16a ovens for Christmas day..

[Deuce]

Hi all,

Our kitchen is going to be ripped out and replaced in the new year, and currently has just one small oven in it - I have 10 guests for Christmas dinner and it ain't going to be up to the job!

However, I already have two new built in single ovens delivered but uninstalled and a carcass from the new kitchen that I can put them in temporarily to make them usable.

My thinking is that there whilst not at all acceptable as a permanent solution, there should be no problem with me pulling the front of the existing FSU (40a cable and 32a MCB protection in place back to CU), and putting in a couple of cables on the load side with 16a commando sockets on them, and then 16a plugs on the ovens. I know the ovens will not exceed 16a and will be unlikely to even exceed 13a as I won't be using the grill element, I assume there is also a reasonable headway included in the 16a rating.

Or... Am I overthinking this and could make it even simpler by just plugging them into standard 13a sockets on two seperate RFC's using a 13a plug on each? If it doesn't blow the fuse... and I really doubt it would, is there an technical reason this would not be safe?

It goes without saying that whatever the temp solution, I'll be with the ovens the entire time they're used and would give them a test run ahead of the day.

Thoughts?

 

[loz2754]

It could be argued that, because the load is supplied via a 16 amp socket outlet, then it is not a fixed load, as anyone could plug anything into that socket.
In this particular case though, it's unlikely that would happen.

 

[Deuce]

The circuit from the 32amp mcb is fed in to a load which cannot draw more than about 26 amps, that's not allowing for diversity, so how can it be overloaded ?

I assume he meant in my original example of using 2 x 16a plugs/sockets onto the existing cooker circuit which has 32a protection. In theory either oven could develop a fault and draw enough current to exceed what the plugs/sockets can handle but not enough to trip the 32a mcb..

A problem avoided entirely with the 13a plugs as they have the fuse protection in the plug.

 

[Rockingit]

The circuit from the 32amp mcb is fed in to a load which cannot draw more than about 26 amps, that's not allowing for diversity, so how can it be overloaded ?

See 512.1.2 (ii)

 

[mainline]

It could be argued that, because the load is supplied via a socket outlet, then it is not a fixed load, as anyone could plug anything into that socket.
In this particular case though, it's unlikely that would happen.

They can still only draw 16amps from each

If the load is fed from socket outlets, then they each will be fused down so can't be overloaded.
If fed from 16amp commando sockets, they still can't be overloaded.
If hard-wired in, they still can't be overloaded.

 

[loz2754]

If fed from 16amp commando sockets, they still can't be overloaded.

As I said, anyone could plug anything into such a socket, so it could in theory be overloaded.
And also as I said, it's very unlikely to happen though in this case.

 

[mainline]

As I said, anyone could plug anything into such a socket, so it could in theory be overloaded.
And also as I said, it's very unlikely to happen though in this case.

Agreed, but that could be said for anything if someone's willing to wire in something to which the socket isn't rated for.

 

[timhoward]

Swap the commando sockets for wiska boxes with 41A Wagos.
Obviously with appropriate cable restraining glands, and loads of gaffer tape around everything in sight to complete the look.

Or just plug the damned things in!

 

[Lucien Nunes]

What hasn't been mentioned so far is that some oven manufacturers stipulate maximum 20A upstream protection and are not intended to be connected to a 32A MCB, regardless of any plugs and sockets.

 

[mainline]

I assume he meant in my original example of using 2 x 16a plugs/sockets onto the existing cooker circuit which has 32a protection. In theory either oven could develop a fault and draw enough current to exceed what the plugs/sockets can handle but not enough to trip the 32a mcb..

A problem avoided entirely with the 13a plugs as they have the fuse protection in the plug.

Can you think of a fault scenario in a oven circuit which could cause a high enough current to be drawn, but not enough to cause the mcb to disconnect ?

 

[Deuce]

What hasn't been mentioned so far is that some oven manufacturers stipulate maximum 20A upstream protection and are not intended to be connected to a 32A MCB, regardless of any plugs and sockets.

True and I haven't even checked what protection they stipulate. No point until

It's hardly a concern for this instance though, given they'll be used for a single day with me present the entire time.

 

[Deuce]

Can you think of a fault scenario in a oven circuit which could cause a high enough current to be drawn, but not enough to cause the mcb to disconnect

I suppose failed insulation/component somewhere in the cooker could cause it to pull more current than it's internal wiring can handle, enough to cause a fire but not quite enough to trip the MCB. There must be a reason some manufacturers request lower amp than typical protection on the cooker circuit - I can't think of anything else other than a freak internal electrical fault.

Seems more likely I'll suffer a wine related falling over incident than anything else on the day though

Safety first though, should either of the ovens somehow manage to burst into flames, there is a suitable fire extinguisher in the utility room right next to the kitchen.

 

[mainline]

I suppose failed insulation/component somewhere in the cooker could cause it to pull more current than it's supply wiring can handle, enough to cause a fire but not quite enough to trip the MCB.

Very doubtful of that, but the same could also be said for any decent current carrying circuit.

Heating elements usually go open or fail to ground, causing the rcd to trip.

There must be a reason some manufacturers request lower amp than typical protection on the cooker circuit - I can't think of anything else other than a freak internal electrical fault.

Because diversity can be taken into account.