Outside Lights - Part P

[dk1uk]

Hi, I have an outdoor light with an inbuilt PIR. The house is opposite a field so at night it’s pitch black and one light is not adequate.

I can see the cable in the garage that passes through the external wall to feed the light.

What I want to do is basically remove the existing light and replace it with three lights and one PIR. I’ll need to check the existing load of course, but if I took a feed from the existing feed to power two more outdoor lights and the PIR is it Part P? I’m a DIY’er.

I read on another post that it’s only Part P if installing a new circuit (which I don’t think is what I’ve tried to decribe above?).

Many thanks.

 

[DetlefSchmitz]

Part P merely states that you must do electrical wiring in a safe manner. You are asking if you have to notify to Building Control. No, you don't.

 

[dk1uk]

Great thank you. A perhaps silly question, but the lights will be installed on wood cladding. The house builder already installed the existing one on the cladding, so I presume there’s no safety issue with that?

The lights will be something like this: https://www.juiceelectricalsupplies...ainless-steel-ip44-wall-lightsaxby-palin.html

 

[DetlefSchmitz]

Well, not so silly.

Very much a matter of judgement though...

422.1.2 Electrical equipment shall be so selected and erected that its normal temperature rise and foreseeable
temperature rise during a fault cannot cause a fire. This shall be achieved by the construction of the equipment or by
additional protective measures taken during erection.

I'm sure many would consider it ok. This may be one of the cases where you should ask the manufacturer.

 

[dk1uk]

Hi, so the existing outdoor light is on the Hager MCB that’s in the off position on the pic (Ground Floor Lighting).

Which I think is rated at 10amp?

I need to work out what the current load is on that circuit.

Am I right that the maximum load would be 230v x 10 * 66% = 1,518?

And that I basically total up the wattage of the lights? If the extra lights bring me below 1,518 then all good, and if not, I need a plan B?

I have done the count yet but I think every bulb is LED so I presume the total will be a lot lower than 1,518, but is there anything else to think about? Like maximum number of lights on a single circuit?

Many thanks.

 

[flameport]

the maximum load would be 230v x 10 * 66% = 1,518?

The maximum load for that circuit breaker is 230x10 = 2300W.
It is a 10 amp and also a type C which is an unusual choice for a house.

And that I basically total up the wattage of the lights?

Yes.
If you have more than 2300W of lights on the ground floor of your house, you are throwing money away and need new lights.

 

[dk1uk]

Thank you. Why is type C an unusual choice for a house?

 

[EFLImpudence]

Which I think is rated at 10amp?

According to the picture, yes.
This is most unusal as normally it would be 6A.

I need to work out what the current load is on that circuit.

In practice, you don't really in a normal domestic situation.

Am I right that the maximum load would be 230v x 10 * 66% = 1,518?

The maximum load on a 10A MCB is 230 x 10 = 2300W.
The 66% is a figure based on the premise that only 66% of the lights are likely to be on at the same time, so -
2300W / 0.66 = 3485W is allowed - in that 66% of 3485 = 2300W.

And that I basically total up the wattage of the lights? If the extra lights bring me below 1,518 then all good, and if not, I need a plan B?

Theoretically - using the correct numbers.
So, 348 x 10W LEDs, even 34 x 100W - not likely.

Fluorescent lights have a power factor of ~1.8 so the wattage for them must be multiplied by 1.8.

I have done the count yet but I think every bulb is LED so I presume the total will be a lot lower than 1,518, but is there anything else to think about? Like maximum number of lights on a single circuit?

Only that they don't add up to more than 3485W

 

[dk1uk]

Super thanks. I have:

- 22 internal downlights
- 6 pendants (total 78w)
- 4 outside lights (total 18w)

Annoying I can’t see the bulb rating on the downlights as I can’t get the bulb out! See pic, should I unscrew those 3 little screws? Or can I safely assume that as LEDs they’re unlikely to be greater than 10w each?

 

[EFLImpudence]

Yes, they won't be more than 10W.

 

[ban-all-sheds]

- 22 internal downlights

IMO you should, at least once, think about whether needing that many lights to light up rooms might indicate that they aren't actually very good at doing the job of lighting up rooms..

 

[dk1uk]

Yes, I don’t even like downlights. They were put in by the house builder, we hardly ever use them as we prefer to use table/floor lamps to light rooms.