I'm about to install a gas hob and built-under gas oven (will get a Corgi guy to do the gas stuff) and a plinth fan heater under the oven. The oven and hob require 3A electrical feeds for their ignition, and of course the plinth heater requires a 10A feed. I was planning to install just one 20A DP switch (accessible) to control the whole shooting match, and unswitched FCUs behind the oven to make the actual conections.
It would be simplest if I could find a single FCU that has multiple independently-fused output circuits. But so far I've drawn a blank at Screwfix, RS and Maplin. Anyone know if such a beast actually exists? (Alternatively, if anyone can explain why what I'm planning is a no-no from safety grounds, please do so).
If you're using a 20A switch to take an unfused spur from a 32A ring, then that switch may only supply *one* FCU - the critical point is the fuse, as this limits the amount of current that can be taken by the spur.
You have to consider what might happen if someone changed the plinth heater to a 3kW one in future, or tried to change the gas oven for electric off the FCU.
No, because they would be non-compliant in most situations.
If you really wanted to you could make your own up from a 20A switch and
2 fuse carriers on a gridswitch system.
However it would be far better to put the heater FCU directly on the ring rather than as a spur, and you can then use the FCU as a point to spur to a second FCU for the hob/oven.
If you are using a radial circuit rather than a ring then you can do what you propose (using a 20A switch on a 20A radial, or a 30A switch on a 30A radial, of course).
On 22 Mar 2006 04:32:03 -0800 someone who may be snipped-for-privacy@delback.co.uk wrote this:-
And what will this switch be fed by?
I doubt whether such a thing exists, at least in standard sizes.
An unfused spur should feed one item of fixed equipment.
If the intended the 20A switch is to be fed by a ring main I would probably do the following:
1) install a box to take two single accessories on the ring. These boxes can be metal or plastic depending on whether it is to be flush or surface mounted.
2) install in this box two switched fused connection units, one for the heater and one for the cooking appliances. This has the advantage of meaning you can get to the fuses easily and isolate cookers or heater independently.
3) behind the kitchen units install two suitable cord outlets for the cookers and one for the heater, on the appropriate sub-circuits.
If the intended 20A switch is to be fed by an unfused spur then I would probably do the following:
1) convert it into a fused spur with a 13A fuse at the origin, or a suitable place. The maximum loading of the hob and oven together should be less than 3A and anyway there will be a lot of diversity.
2) near the cookers fit a box to take two single accessories.
3) install into this a 20A switch and (fed from the out terminals of this) a fused connection unit with 3A fuse.
4) from the former a cable would go to a suitable cord outlet for the heater. From the latter a cable would go to two suitable cord outlets for the cookers.
If the intended 20A switch is to be fed by a radial circuit then I would modify the second option slightly as it would not need a 13A fuse at the origin.
However, you are the one who has seen the kitchen.
OK, thanks for confirming. Guess I'll just have to use two individual ones.
I see. What is the rationale behind this, if the multiple items are individually fused (or does that effectively make the spur "fused")?
Anyhow, I could substitute the 20A switch for a 13A switched FCU, and install two unswitched FCUs (10A for the heater, 3A for the oven & hob) behind the oven. I don't envisage any need to individually isolate heater or cooker. That'll do the trick, right?
You may find that a ordinary plug and socket could be simpler for some of these - since it will make removing bits for maintenance easier in the future.
I think it is called a consumer unit! not really ideal for what you want. I suppose you could use a small three way DIN rail mounting box and some HRC fuse carriers. Alternatively, you could mount a twin single back box (i.e. one of the double sized ones that have a central divider and take two single face plates) that would give you two FCUs in a small ish space)
Nothing obviously wrong with it from what you have told us. Where is the feed for the circuit coming from?
An unfused spur should only feed one item (a single FCU, one single socket, or one double socket) as it's the fuse in the downstream item that protects the spur itself from overload.
If you had a spur feeding 3 FCUs and each FCU had a 3kW heater, then the total current on the spur would be limited by the circuit fuse/MCB at
30/32A. This is a problem because the single cable feeding the spur is usually rated at 20A max.
substitute the 20A switch *with* a 13A FCU, you could, but I don't think you'd get much discrimination between the 10A and the 13A fuses. You might as well supply the heater from the first FCU, and fuse down only for the hob/oven.
Using gridswitch components you could make a very neat unit wired as:
Here the 13A fuse both limits the max current on the spur, protecting the upstream spur cable, and protects the heater.
Using one switch for both hob and oven would allow a 4-grid unit to be used. Industrial engravers can engrave and paint infill the characters to give you nice neat labelling.
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