induction hob - 16A with a plug!?

[mrklawuk]

replacing gas with induction hob. 32A fuse at consumer unit, isolator switch in kitchen. Dedicated circuit for 'cooker'. Already have a 2.6kw oven hooked up and there is a second cable being used for the ignition of the gas hob.

confirmed 6mm2 from consumer unit to isolator switch, but only 2x 2.5mm2 runs down to behind the oven. So I'm limited on power and I don't think we can replace the wire with 6mm without a lot of mess.

Bosch have what I thought is a good compromise - a 3.7kw induction hob - so well within the limits of 2.5mm2 but it has a plug on it 'for easy plug and play, no electrician needed'. Reading the instructions it seems you can set it to 10/13/16A as required. But the instructions also say

• Power management options for 16A, 13A or 10A connection: limit the maximum power if needed (depends on fuse protection of electric installation).
• Power cord 1.1 m UK 3 pin plug: plug and play, no electrician required for installation.
• This hob is equipped with a UK 3 pin plug for an easy plug & play installation. The plug limits the maximum power output to 3.7 KW. For higher power output, please select a hob without plug and ensure installation is carried out by a qualified electrician.

so I'm confused. The obvious answer is 'chop the plug off and hard wire it' - there is already a faceplate for a hard wired connection. But AO say they won't cut off the plug as it'll invalidate the warranty. I rang Bosch and they said you can cut the plug no worries as long as its installed by an electrician the warranty is valid.

I just find it confusing they ship with a plug but also 16A capable. Wouldn't it be easier to ship without a plug and give you the option to wire a plug on if you want to just stick in a socket?

Anyone come across one of these 'plug in but also 16A' hobs?

 

[JohnD]

The obvious answer is 'chop the plug off and hard wire it' -

Correct.

Also write a letter of complaint to AO

Or

please select a hob without plug

 

[JohnD]

please select a hob without plug

 

[JohnW2]

The statement ...

Power management options for 16A, 13A or 10A connection: limit the maximum power if needed (depends on fuse protection of electric installation).

... seems to imply tht the hob can be configured to draw a maximum of 16A,13A or 10A. If that is the case, configuring it for 13A maximum would presumably (just about) make it OK with a 13A plug.

Kind Regards, John

 

[ericmark]

3.7 kW = 14.56693 to 17.8744 depending on the voltage which can be 207 - 254 in the UK, since not simple resistive the current may go up not down as the voltage drops, it depends if it uses some form of switch mode control or not, but in any case a 3.7 kW device can't really be supplied from a 13 amp plug, 10 amp = 2300 watt, 13 amp = 2990 watts, and 16 amp = 3680 watt at 230 volt.

One heat area alone on my cooker is 3.7 kW, when boost is selected, but in the main max is half of that, boost can only be used to boil water, and food would stick to the pan and burn. I had a stand alone ring and default was 1 kW and it would turn up to 2 kW but most cooking was at around the 750 kW mark, so 4 rings would only hit 13 amp at that, but to use 4 rings you do really need the full 3.7 kW to gain the advantage of the induction hob which is speed.

My daughter demonstrated filling an electric kettle to mark and pouring in a pan, then refilling and switching on gas and kettle on together, gas ring rated 5 kW and the kettle won, so I repeated it at home, 2.7 kW kettle and 3 kW induction and they took the same time. So with the induction with a 3 kW ring no need to boiler water in a kettle first.

OK other advantages like does not heat the kitchen as much, and you can melt chocolate direct without using a bowl in boiling water. But my cooker is rated 220 - 240V - 50Hz 10466 - 12455 W so around 52 amp, it is on a 32 amp RCBO which has never tripped, it has 1 x 2200 watt, 2 x 3000 and 1 x 3700 but can only use two at that output, normal output is 1 x 1400 watt, 2 x 1850 watt and 1 x 2300 watt made by British Belling.

Knobs marked 1 - 9 and often with the 2200 ring use 7 to 8 for a fry up. Would guess that means around 2 kW on one ring, if output only 3 kW then no real point in 4 rings, three would likely be most you could use together.

 

[JohnW2]

3.7 kW = 14.56693 to 17.8744 depending on the voltage which can be 207 - 254 in the UK, since not simple resistive the current may go up not down as the voltage drops, it depends if it uses some form of switch mode control or not, but in any case a 3.7 kW device can't really be supplied from a 13 amp plug, 10 amp = 2300 watt, 13 amp = 2990 watts, and 16 amp = 3680 watt at 230 volt.

All true. However, as I said, the material quoted seemed to be saying that there was a 'power management system' that could be configured to limit it to (roughly) 2.3, 3.0 or 3.7 kW.

Kind Regards, John

 

[Rodders53]

I'm sure lots of this has been covered before I believe in earlier threads wrt induction hobs and cooker circuits

Induction hobs have diversity as any cooker does so they do not draw excessive current long term. Even if one is daft enough to try having pans of cold water on all and attempting to put all on boost at the same time (often difficult with touch-controls anyway).

The hob makers limit what the user might attempt. My Bosch has 4 'burner rings' in two groups: only one in each group can be 'boost' at any time.

Power management is commonplace and works by sharing the energy to the burners on a time/ need basis. It almost certainly will disallow boost if more than one ring is in use at lowest input current setting(s)... and be a tad slower to heat all the pans.

I find with mine (dedicated 32A mcb) if I use a decent saucepan pan with a reasonably close-fitting lid that vegetables and rice are simmering away on the low settings 2-3 once up to temperature. I have fry pans from Ikea and Schulte Ufer (free with the hob) that I can't use above 7.5 if I don't want to cremate stuff. Other induction pans are not so 'efficiently coupled' (looking at you Hairy Bikers and need 8 - 8.5 for the same cooking 'heat' level).

My youngest son manages with a 13A plug in 4 burner induction hob and his family of 4 (plus us two occasionally) with all rings in use. Spuds take longer than the different veg etc.,. so no need for all rings at highest powers at same time

Only caveat is I've read reports that some over-cheap inductions don't have good electronic variable control and simply switch on/off the full power rating. (Eldest son's rental. His Landlord C****ys own brand cheap replacement for a condemned gas hob). He says it burns food on the pans bases due to that process when 'simmering'. It could, perhaps, be faulty?

 

[markyd1]

So the circuit starts as a 6mm and ends as a 2.5mm on a 32a mcb.......mcb needs derating to a 20a

 

[JohnW2]

So the circuit starts as a 6mm and ends as a 2.5mm on a 32a mcb.......mcb needs derating to a 20a

True, but only if one didn't consider it 'unlikley' that the oven and/or hob would/could result in an overload (as opposed to fault) current - and, even then, a 25A MCB would probably be OK, if one were available for the CU.

However, there would be no problem in reducing the MCB to 20A if one so wished since, allowing for diversity, a 20A MCB would be OK for total domestic cooking appliance loads up to about 10 kW - far more than the OP's oven and hob combined. Indeed, even a 16A MCB would (with diversity) be OK for the OP's appliances.

Kind Regards, John

 

[hovertoast]

I’ve had a 2.5mm radial circuit protected by a 20A MCB feeding my 6kw hob for 3+ years now and it’s never tripped. Even with all 4 rings on full.

 

[JohnW2]

I’ve had a 2.5mm radial circuit protected by a 20A MCB feeding my 6kw hob for 3+ years now and it’s never tripped. Even with all 4 rings on full.

Quite. Even if the 6 kW referred to 230V (which is probably doesn't, they usually quote at 240V, to make their product s sound more powerful!), that 6 kW only represents about 14.8A 'after diversity' - and, even with all rings on full, they are very unlikely to ever draw enough current for long enough to trip a 20A MCB (or probably even a 16A one).

Kind Regards, John

 

[mrklaw]

so AO came, the installer lopped the plug off no problem. Its in and working. However.. its wired into a fused spur (not with a switch just a hole in the faceplate). Im assuming thats 13A as I’ve never heard of 16A ones, so for now I’ve derated the hob to 13A in the settings.

Is there a way to increase to 16A to give me the 3700W powerboost? (I assume the power limit also helps with multiple rings in use). Can you put a 16A fuse in the spur? or remove the fuse and wire direct to the isolator? Thinking if I did that, reduce the MCB to 20A and perhaps leave the oven one as a fused 13A as extra layer of proteciton?

hoping diversity as discussed would allow 20A MCB to cover both hob at 16A and oven at 10/13A? (can’t remember if its 2.6kw but it was a plug in type until I chopped the plug off)

 

[JohnW2]

so AO came, the installer lopped the plug off no problem. Its in and working. However.. its wired into a fused spur (not with a switch just a hole in the faceplate). Im assuming thats 13A as I’ve never heard of 16A ones, so for now I’ve derated the hob to 13A in the settings.

There are (should be!) no fuses for FCUs/plugs greater than 13A - so, for the time being, limitingthe hob to 13A is theoretically a good idea.

Is there a way to increase to 16A to give me the 3700W powerboost? (I assume the power limit also helps with multiple rings in use). Can you put a 16A fuse in the spur? or remove the fuse and wire direct to the isolator?

It could be wired direct to the isolator. Not having a fuse would be OK if it were felt (as I probably would feel) that the hob was (very!)( unlikely to result in an 'overload current' (taking considerably more than 16A, due to some fault) - but if one did not feel that was the case, then, unless the MCB were reduced to 20A, there would have to be a fuse, somewhere, adequate to protect the final bit of cable going to the hob.

hoping diversity as discussed would allow 20A MCB to cover both hob at 16A and oven...

Indeed, as I said, if one invokes diversity, then a 20A MCB would be more than adequate in the supply to both.

Kind Regards, John

 

[mrklaw]

so plan of attack (thanks!) get an electrician in and if those spurs are fused, consider replacing with unfused ones or a dual outlet and rewire both into the isolator, and reduce the MCB to 20A - that should allow me to increase the hob back to 3700W (which is its max anyway)

If I used a dual outlet plate, that’d feed back on a single 2.5mm2 cable - would that be ok for that load?