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We have just bought a Bosch induction hob (Serie 2 PUG61RAA5B) and oven (Serie 2 HHF113BROB), both plug in. They are to replace an old plug in electric oven and a gas hob (that plugged in for ignition), which both used an existing dual socket. Bosch told us that the new oven and hob both have 13 amp fuses in their plugs and work together in ordinary sockets, so we expected the replacement to be relatively simple.
The gas plumber that removed the gas hob and re-sized the hole in the work surface to fit the induction hob said that he thought the wire feeding the dual socket looked a bit narrow and suggested getting an electrician to check it.
An electrician came and has given us a quote that involves using thick cables and 32 amp junction boxes, and costs considerably more than the oven.
Obviously, we want the wiring to be safe, but wonder if this is a case of “using a sledgehammer to crack a nut”. We can’t understand why we would need 32 amp boxes for plug in appliances (that don’t require hard-wiring). In the spec supplied, it says the oven takes up to 2.4kW and the hob takes a maximum of 3.7kW (although it also says 2 rings are 1.4kW and 2 are 1.8kW).
The dual socket has been in use for many years without issue but safety is a major concern for us; we don’t want to risk fire or appliances blowing up! We spoke to Bosch again, who said the worst that would happen if we didn’t change the wiring is that the fuses would trip the circuit breaker.
We are now rather confused as to how necessary this work is and would really appreciate any professional advice. Thank you in anticipation.
2400W + 3700W = 6100W.
6100W / 230V = 27A
Yes the gas hob has been in for years, but will be pulling next to no power for just the ignition.
The hob that you have purchased and said can draw over 3kw will need to be hard wired you should have check the induction hib draws under 3kw then you would have been able to just plug them in and some if the bosch neff Siemens appliance state they need to have a certain size and type breaker
first as K said if ther applaince load exeeds 3Kw then it needs a dedicated cooker main to feed it
some induction hobs can be plugged into a 13A socket as the software inside limits the total power to 3Kw. cant see any reference to this in the model you have listed
if both units are like this then you would need to check if the socket that you are plugging into is on the ring main and not a spur off the ring main
The oven power is nore or less constant when in use but turns on and off to keep temp correct. the hob power is dependant on use. its unlikely you would have all the rings on full as once things start to boil you turn them down. So its very unlikely to draw the maximum power ever.
Dave
kaibart wrote:The hob that you have purchased and said can draw over 3kw will need to be hard wired you should have check the induction hib draws under 3kw then you would have been able to just plug them in and some if the bosch neff Siemens appliance state they need to have a certain size and type breaker
Maybe I misread the spec regarding the power drawn. I have spoken to Bosch themselves and they say the hob just needs to be plugged in to a normal socket, and it comes with a manufacturer fitted 13 amp fused plug to do this. They state that neither the hob nor the oven need to be hard wired.
electrofix wrote:
some induction hobs can be plugged into a 13A socket as the software inside limits the total power to 3Kw. cant see any reference to this in the model you have listed
if both units are like this then you would need to check if the socket that you are plugging into is on the ring main and not a spur off the ring main
Dave
After searching the internet for more information regarding the hob power, I found this on John Lewis’s site:
“Fitted with a conventional plug, simply connect this hob to any standard socket, and it’s ready to use – no wiring required. If you choose to plug it in at the wall, it’ll limit heat levels across your hob to a total of 12, so if you need a bit more oomph, we’d recommend hard-wiring it in”.Unfortunately, it doesn’t say how many kilowatts correspond to heat levels of 12, but presumably it would be less than 3kW. In that case, could both oven and hob be plugged into a dual socket, or would each need to be plugged into a socket on a separate ring main?
no as long as the socket is part of the ring and not a spur of it
if socket has one cable going into it it will be a spare and could do with being uprated
Dave
Excerpt below from the Bosch site.
“Plug & Play induction hobs are easily installed into an existing plug socket. It’s worth noting that as these products are plugged into mains electric, the nominal power is limited to 3.7kW. This means when cooking with more than two pots at the same time, the hob triggers an automatic power management, which may be inconvenient for large households that frequently cook larger meals with many pots at the same time. For higher power output, please select a hob without plug/with fixed wiring.”The factor of 12 I believe to be max setting of three per plate instead of four?
Don
Thanks very much for your replies and help.
Each plate setting is 9, and one plate can use booster setting (which spec seems to say is 3.1kW), so it looks like only one plate on full and one on low can be used at the same time.
As Bosch state that “hobs are easily installed into an existing plug socket…….as these products are plugged into mains electric, the nominal power is limited to 3.7k”, it would seem that the limited power means it’s fine to plug the appliance into a socket on the downstairs socket ring circuit, but wouldn’t approximately 16A current fllow through the plug then and blow the 13A fuse, or does nominal power have a different meaning?
The Product Information for the hob says “- Power management options for 16A, 13A or 10A connection: limit the maximum power if needed (depends on fuse protection of electric installation)” so one would hope that a UK spec version with a 13A plug is limited correctly and would be safe in a 13A socket. However as stated earlier you need to check that the double socket is part of the ring and not a spur as a spur would need the wiring upgraded if you are going to plug the oven and the hob into it.
Following all your useful advice, we asked another electrician to look at the wiring. It appears that the wire feeding the dual socket comes from a junction on top of the wall cabinets and is only 1mm thick. The wire is hidden in the wall behind the cabinets and comes down to the dual socket at the back of the floor cabinet next to the oven. He said he could bring a new wire from the junction on top of the cabinet down the wall through trunking, through the corner of the worktop to the current socket position. His quote was for “installation/resupply of a new cooker/hob point and extractor fan from the existing cable”. It included:
6mm cable
40 x 25 Trunking
50A Junction box
1 x Double socket and surface pattress
1 x Switch fuse spur and surface pattress
1 x 32A RcboThis is a different approach to the first electrician and would cost significantly less, so we would appreciate your opinions on whether this sounds appropriate and safe, and also any comments on the following:
1 – When we asked if the oven, hob and extractor would be on their own ring circuit or on a spur, he said they would be connected together on a 32A radial circuit.
2 – He said the work would be certified but doesn’t need to be Part P notified.
3 – He also said that the hob could be hardwired for minimal cost “if the hob can be upgraded to a 32A”.Thank you very much for all your help.
and what would the hob be hard wired to?
A hard wired cooker circuit must be on its own fuse in the ciruit board and can only feed the cooker. no other sockets are aloowed to be connected to this circuit
Dave
and what would the hob be hard wired to?
Dave/QUOTEi don’t know, but the extra cost would only be £18, which seems to suggest that not much extra work is involved. The electrician said it can be done “if the hob can be upgraded to a 32A”, so could he just run a second cable from the junction box on top of the cabinets and put a second 32A Rcbo in the fuse box?
Does the rest of the work suggested (without hardwiring) sound reasonable, especially point 1 in my last post?
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