Emergency lighting

[thepprentice]

A few questions on emergency lighting,

Is it ok to wire it in standard t/e, as I have seen some in a white fire type stuff and some in normal t/e. I would have thought it would need to be wired in fire retardent stuff???

Also would you wire the emergency lighting into its own MCB or would you wire it into one which the rooms lighting goes to (if thats the case, what if theres two lighting circuits)

Also when talking about maintained emergency lighting, can that mean simply wiring through a test switch?

Cheers

 

[Steve]

A little thought needs to go into it.

For example, a shop with four aisles. Each aisle has two groups of lights, alternating on 2 switches, but the same circuit, all switches on a grid switch. You require two EMLs per aisle. I would wire them so when that aisle circuit looses power, the EMs come on. So the power to the EM test switch must come from the feed side of the switch.

Things get more complex where theres 3 phase available, and you try to alternate the phases on each aisle to make a more pleasant shopping experience But in this scenario, IMO, you're more likely to just loose one phase at a time and therefore if theres at least 2 phases on an aisle, you wont need the EMs to come on.

As for cable, i dont see the need to wire it in any sort of protected cable. In a fire, you want the power to cut and the EMs to come on before the main lights go out.

 

[Lectrician]

Emergency lighting must be on a local lighting circuit providing the main lighting source to that area. The em lighting is meant to come on in the event of local lighting failing - If the MCB trips for a corridoor for example, the corridoor em lighting should come on.

Use T+E to wire to self contained fittings (integral battery).

Use T+E (or conduit, swa etc) to wire the mains into a battery pack, but use firetuff/MI from the battery pack to the EM light.

Think about it - you want the EM light to remain lit during a fire, so need to fire proof the cable between the battery and light if the battery is remote from the light.

There is no requirement at all to use fire tuff to supply the battery pack or self contained fittings.

It was common to wire all em's on their own cable back to the CU, and fit a key switch adjacent the CU, and connect to the correct MCB. These days it is more common to run a 3 core for the lights and EM's, or just pickup the live feed where you want, and fit a key switch adjacent each em light.

 

[baz1968]

Anyone got a link to websites advising on maintence of EM lights and guides/or regs on regular testing and operation?

 

[Lectrician]

Anyone got a link to websites advising on maintence of EM lights and guides/or regs on regular testing and operation?

you need to pay for the BS really, although Emegylight and JSB (or similar) have some generalised litterature.

 

[Lectrician]

If a shop aisle was fed by more than one MCB, it would still be typical to just wire the em's to a single MCB - the one with the most lights if possible, and certainly the one that is used if the lighting is two stage, as it is in many large stores (They alternate each fitting, so 50% on in the day and 100% at night for example - where roof lights are available).

If the lighting is contactor controlled, it is typical to feed the lights from the contactor control MCB/HRC, assuming this MCB/HRC is on the load side of any TP breaker feeding the lighting DB.