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?

 

[Rockingit]

By far your easiest and cheapest solution will be to put them on 13A plugs. There's nothing in itself wrong with the 16A solution you suggest (except technically you'd need to have a reducing CPD involved as well down to 16A, so realistically that's a small garage style DB involved too) but it's a lot of work and expense for no real benefit.

 

[mainline]

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?

Just add two sockets to the existing cooker supply using a pair of 2.5 mm or one 4 mm and plug the ovens in with 13amp fused plugs.

 

[mainline]

By far your easiest and cheapest solution will be to put them on 13A plugs. There's nothing in itself wrong with the 16A solution you suggest (except technically you'd need to have a reducing CPD involved as well down to 16A, so realistically that's a small garage style DB involved too) but it's a lot of work and expense for no real benefit.

Why would the cpd need to be reduced to 16amp with it being a fixed load.

 

[Rockingit]

Why would the cpd need to be reduced to 16amp with it being a fixed load.

Because of the 16a rating of the Commando's.

 

[mainline]

Because of the 16a rating of the Commando's.

But they feed a fixed load of less than 16 amps

 

[Deuce]

Because of the 16a rating of the Commando's.

Out of interest why would that be any different to putting a couple of 16a lights on a 32>2x16a 1ph splitter plugged into a distro at an event? (I checked your profile, I work events/TV/film too!)

I've seen that sort of thing done endless times. Surely so long as the device plugged into each 16a is itself rated 16a or less then there should be no issue? Same as plugging two kettles into a single domestic RFC which would have 32a protection.

 

[Deuce]

Thanks both for the replies. Tbh as I was typing the bit about breaking into the existing FCU and adding the 16a sockets I was questioning why exactly I would bother when I could simply plug them in using standard 13a plugs... I know the plugs/sockets are over designed in terms of capacity and I really doubt the actual load will be anything like enough to blow the 13a fuses either.

If it blows the fuse, then that's about the worst that can happen and I'll sort the 16a supplies on the existing cooker circuit.

 

[Rockingit]

But they feed a fixed load of less than 16 amps

Regs state that each and every component of a circuit needs to be able to cope with the maximum demand that may be put upon it under fault conditions - so in this case that would be 40A of the upstream MCB.

Out of interest why would that be any different to putting a couple of 16a lights on a 32>2x16a 1ph splitter plugged into a distro at an event? (I checked your profile, I work events/TV/film too!)

I've seen that sort of thing done endless times. Surely so long as the device plugged into each 16a is itself rated 16a or less then there should be no issue? Same as plugging two kettles into a single domestic RFC which would have 32a protection.

The distro in question will almost certainly have a 16a MCB/RCBO on the source side - so therefore plugging in a 16a ceeform attached to a 17A rated (at least) cable is indeed no issue. What it's feeding is irrelevant because we fault and overload protect the cable, not the device (that's down to the manufacturer to do).

 

[Dustydazzler]

Just whack em on plug tops as a temp measure

 

[Avo Mk8]

I really doubt the actual load will be anything like enough to blow the 13a fuses either.

If it blows the fuse, then that's about the worst that can happen and I'll sort the 16a supplies on the existing cooker circuit.

16A won't blow the 13A fuse. In fact 20A shouldn't blow it if it's made to spec.
Might make the plug (tops?) a bit hot though.

 

[Deuce]

Regs state that e

The distro in question will almost certainly have a 16a MCB/RCBO on the source side - so therefore plugging in a 16a ceeform attached to a 17A rated (at least) cable is indeed no issue. What it's feeding is irrelevant because we fault and overload protect the cable, not the device (that's down to the manufacturer to do).

No I meant plugging a 32a 1ph splitter cable into the distro which then splits down to 2 or more 16a sockets. I've just googled and I see that all such currently sold splitters have the MCB's mounted on the cable now, makes sense.

I still definitely see people using older splitters to go from 32a to multiple 16a without and inline protection though... I work in automation and SFX so I'm not as upto date with power regs as you will be.

 

[Rockingit]

32>2x16a 1ph splitter

Such a thing should never exist and if I see one then my snips are rarely far behind.

 

[Deuce]

Such a thing should never exist and if I see one then my snips are rarely far behind.

They do exist though, Although I appreciate they should not and why.

Like riggers that should never scale truss without at least one safety lanyard hooked on and people on scissor lifts without a hard hat..

 

[mainline]

Regs state that each and every component of a circuit needs to be able to cope with the maximum demand that may be put upon it under fault conditions - so in this case that would be 40A of the upstream MCB.

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 ?

 

[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.