Kitchen Electrical Wiring Regulations Advice Please

[DeeBee]

I am in the process of fitting a complete new kitchen, and would like the advice of the experts in this NG regarding some electrical regulations.

I have Googled about a bit and found some answers, but not all the info I need.

So here goes, four topics really.

1.. My understanding is that electrical outlet, 13A sockets, must be at least 300mm from a sink. Is this correct?

2.. I want to put some mains halogen downlighters in a sloping ceiling which will have insulation behind the plasterboard. Am I right in assuming that I should create a box around the downlighters, say 100mm around the light to keep the insulation away from the heat of the lights. The ceiling is yet to be put up, so this would be easy, but the builder wants to plaster the ceiling next week.

3.. Are there any regulations concerning placing junction boxes behind a plastered ceiling? What are the regulations regarding accessibility to the junction box? I have a lighting junction box connecting three external lights to an external PIR.

4.. We are fitting a built under double oven and ceramic halogen hob. My question here is how to wire this in. The Oven is rated at 5.18 kW (22A @

230V) and the hob at 5.4kW (23A @ 230V). Currently the MCB for the slot in cooker is 32A. I will upgrade this to 45A. My idea is to run 10mm cable from the MCB to the Cooker switch above the counter top, and then run two 6mm cables from the cooker switch to cooker outlet plates below the counter top. Is this OK?

Thanks for taking the time to read this, any advice / guidance gratefully received

Duncan

[BigWallop]

It can be directly over the sink if you wish, just as long as it doesn't get splashed with water when your hands are in it doing the dishes. So YES, it is best to keep live electrical outlets away from where you're working with water.

The only thing that you need to watch out for, is that you don't have anything that will combust if it reaches a certain temperature close to the fittings. This includes any timber frame, any combustible paper insulation or linings, Etc.

Any heat building up around the light fittings will also greatly decrease the lamps life expectancy, so try to keep an air flow around the fittings to keep them as cool as possible. The best way to do this, is cut holes through the insulation after it has been laid, then allow the heat from the light fittings to escape into the gap above them. This helps to keep the fittings cool but the rest of the ceiling insulated.

Any electrical fitting with screw terminal (compression type connections) must be allowed access for maintenance reasons. After a short period of time these types of junction boxes work the connections loose through heating and cooling, so if they eventually come loose and break the conenction, you're in the doo doo if have to make repair to them.

Best leave access to the junction box, even if it is sited above a hole for the new light fittings where it can pulled out and worked on.

One 10 millimeter csa' (cross sectional area) cable is the best for total load you're going to take. The diversity rule that says, all the hob rings should not all be on at the same time because of their thermostat controls, and the fact that you're very unlikely to be running both ovens at the same time, all the time, would, I think, come into play here. So you should be able to use just one 10mm cable fused at

45amps for this type of situation. But if you do want to run more than one cable for this, then take into consideration the cable grouping rules as well.

[Christian McArdle]

It's more of a guideline than a rule.

32A would be fine. There is no need to upgrade to 45A. I would keep the 32A for increased short circuit protection, particularly if the cable runs are long.

You may have difficulty getting two lots of 6mm cable into the 45A DP switch. If so, you can probably use 4mm cable for the runs to the cable outlets. Although 4mm can't take the full 45A, I believe you are permitted to take advantage of the fact that a heating device is unlikely to produce an overload situation beyond the total sum of its heating elements as there are no failure modes for a heating element to do this. 4mm (even 2.5mm) cable is quite capable of carrying the 23A that each appliance needs.

This assumes that the runs between the DP switch and cooker outlets are short (they should be, as the outlets must be close to the switch). If not, you may have trouble using the MCB for short circuit and earth fault protection, as the earth loop impedence may be too high.

Christian.

[The Natural Philosopher]

I believe so.

Two points. My sister in law, having just spent 60 quid on new halogen blsb inher kitchen, is now disappinted to find that 50% have gone withong 4 months.

I am delighted that only two of my LV spots have gine in two years.

LV pays for itself quite quickly....AND the bulbs are cheaper too.

Secondly, unless the insulation is flammable don't worry about the lights getting it hot. Plasterboard doesn't burn either. But DO worry about nearby woodwork, and if you use LV, about overheating transformers.

If the insulatin is a wool type you can generally make a void by pushing it back. If its celotex you need to cut around teh area - about a square foot I'd say to mount the lights in a void if LV, a little less for mains.

Junction boxes are supposed to be accessible. strictly, you should use crimps for a 'permanent' buried connection. In practice, if the building inspector doesn't see it, and you feel confident in making a good connection with a box and burying it - who cares?

Pass. Can't remember cable ratings, but it sounds fine to me...