New kitchen planning underway. Looks like we're going to replace a gas hob with an induction hob requiring a 32A connection back to the CU (photo here:
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The CU is pretty old (1995 when the house was built). There is a spare position but on the non-RCD protected side. I assume using this slot would not be acceptable practice?
I've noticed that the current cooker is also on the non protected side of the CU, and given there is a combined isolation switch/13A outlet next to the cooker I was wondering if regardless of the need to add the induction hob this alone should be a reason to update the CU, as that socket isn't protected by the RCD? Ignore the water heater note - the immersion heater is no longer connected.
A final question. Any reason not to use 10mm on the 10m run to the kitchen? Hob and oven won't be sharing a circuit.
There are RCBOs available for that board. Probably secondhand, but they are available. You have one/two CB's there that arent a good fit, maybe look to get them changed, they arent expensive.
Like for like change, so you could use the existing arrangement. You need to take into account the Manufacturers (of the hob) instructions, if they call for a RCD, then it is prudent to fit one.
No reason not to, but no reason to fit 10mm really, unless you are expecting to upgrade to 50 amps or so in the future, or, it is run in insulation.
4mm T&E may be enough, it can hold 37A clipped direct or buried in a masonry wall.
It may be old(ish) but its a decent brand and appears to be in good order. (although that non Mem/Eaton water heater MCB does not fit that well, and leaves a larger than desirable gap in the facia)
You appear to already have a cooker circuit there with a 32A MCB on it. Any reason why you are not using that?
If you use that then its a like for like swap of appliance, and you don't need to meet new requirements for cable protection.
If you want a completely new circuit, then looking to see if there is a RCBO that will fit that CU might be a more pragmatic answer. (especially with the space afforded by removing the water heater MCB - so even a double module RCBO would be ok).
(Another option for more RCD space would be to get a longer bus bar for the RCD side, and shorted the non RCD side, so you move the split to the right a bit - but the RCBO would be a better choice IMHO).
With a single RCD "split load" installation like that, its quite common to want the cooker on the non RCD side. Cookers (and anything else with a mineral insulated heating elements in close proximity to moisture) are a common source of higher earth leakage currents that are prone to "sensitising" RCDs or even nuisance tripping them. Also there are not many likely electric shock scenarios with a bit of fixed equipment like a cooker.
Its a reason to get shot of the combined "cooker point". Since the socket really would benefit from RCD protection, and it also reduces the nominal capacity of the circuit by 5A [1]
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Nothing inherently wrong with it, although it would likely be overkill unless you have many de-rating factors to contend with. 6mm^2 is more commonly used, and has the benefit of being easier to work with.
I would say a good move. Easy to control and keep clean. Although I grew up with a gas cooker I now find them quite alarming to use. There was one running on Calor gas in a holiday home we quite often stayed at.
The four ring Bosch Induction hob I bought a couple of years ago has three max current settings, 20A, 16A and 13A. The seller gave me £30 for the old hob, so the net cost was £300. I bought a similar Bosch hob
15 years ago. It cost me well over £400 and Mr Bosch had to come and change the circuit boards after a couple of weeks.
We're keeping a built in cooker which is on the other side of the kitchen. I thought that and the hob would be asking too much. I've not checked to see what cable is used for the existing cooker. I'll check this and the rating for the cooker. That said today for example I was using two fan ovens and three gas rings when cooking sunday lunch.
As Alan has pointed out, looks like MCBOs are still available, but at £30-40 each. Two of these would not be far off a new CU.
A new kitchen is looking like 8k (units, couple of appliances, plastering, lighting and flooring). Spending a couple of hundred upgrading the CU to be future proof for another 20 years would seem like a sensible investment.
Any recommendations for which CU to choose? Also, you can't do a job like this without buying some new kit. Would there be one thing that would make the CU swap easier for a mostly competent DIYer?
Just a Fluke DMM. I need to do some more homework but this sort of thing is likely to take me to the edge of my comfort zone. Might be worth getting it done by a Pro...
I've often wondered something about these hobs, do they have any inductive effects, ie when switched off is there a pulse from the coil or whatever it is? Brian
We ended up with three 32A runs : Induction Hob, Main Fan Oven, Combi Microwave/fan oven. While the last one could, perhaps, have just plugged into a socket on the ring main, the numbers were very close.
The extra cost of a new CU and a couple of cable runs (there was one in place) was trivial in the overall price.
Personally, I'd not feel comfortable without having an immersion heater as a back up. While we've not had many issues with our heating, not having hot water for showers etc is a big issue.
Its one of those jobs, that is not that difficult, if you are methodical and take your time. You can manage basic tests with a DMM along the way, although you won't be able to capture a full set of tests as you go (e.g. you could do circuit impedance tests, but not insulation resistance or RCD tests). Ultimately that would leave you with an installation no worse than current, so long as you are not bothered by lack of paperwork etc.
Post a photo of the inside of your CU. It will help me decide which new CU has the layout that would be most suitable as a replacement without extending the cables.
Could you make the non-RCD side into RCDed? Might need to put 2 circuits into one MCB to make that work - I've not looked at your circuit layout but that's often entirely doable.
I'd expect a hob + oven to be ok on 32A due to diversity.
The very reason I have resisted changing to a combi-boiler.
Even if power failed and we had neither boiler nor immersion, we'd still have 40 gallons of hot water and with care could eke that out for a couple of days before it became freezing cold to shower.
The house still has the option of using the gas fire and/or portable electric heaters in the cold months.
We have had our boiler fail a couple of times over the years - just fan bearings siezing and the backup has proved itself useful until bearing could be obtained.
I should have made it clear that, whilst I do have an immersion heater in the hot water tank, it is not permanently connected. I have had to use it twice in the last 10 years when the gas valve on the boiler failed. When it has been needed, I've, shall we say, made temporary arrangements to power it.
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