High zs on low bay lighting circuits

[Dannyg8810]

just been looking through an EICR we've had done and there's x4 circuits on D type mcbs which have been given c2's as the zs is higher than the maximum permitted......

Iv looked c type would bring this within the maximum permitted

I don't see why these need to be on D's

2.5 t and e on 20a dtype

Woud this be as simple as swapping the mcbs for c's

One of the circuits is 1.5mm so I'd be lowering this to a 10a !

 

[westward10]

Swap them see what happens.

 

[Toneyz]

How many and what type of lamp?. It may be worth a call to the MCB manufacturer if a table is not in their technical information. I thought that lighting circuits were only allowed up to 16A.

 

[Dannyg8810]

Swap them see what happens.

How many and what type of lamp?. It may be worth a call to the MCB manufacturer if a table is not in their technical information. I thought that lighting circuits were only allowed up to 16A.

iv not been to check the ins and outs yet just know the situation with the zs and mcbs types

 

[Krispy_88]

How many lights are on each circuit? I'm assuming this is Discharge Lighting? Been a while since I looked at the regs but it's something like 1.8x normal load to alow for discharge lighting isn't it? They may have just been trying to cover themselves by sticking a D type on so it doesn't trip on start up. You could probably get a rough idea of startup by adding all the lighting loads and working it out but like westward10 said it might just be easier to suck it and see.

 

[Dannyg8810]

How many lights are on each circuit? I'm assuming this is Discharge Lighting? Been a while since I looked at the regs but it's something like 1.8x normal load to alow for discharge lighting isn't it? They may have just been trying to cover themselves by sticking a D type on so it doesn't trip on start up. You could probably get a rough idea of startup by adding all the lighting loads and working it out but like westward10 said it might just be easier to suck it and see.

I'm guessing there going to be either 250w or 400w metal halide

 

[Ian1981]

I've never come across any lighting circuit protected by a D type mcb before, sounds like poor design if too many lights on start up actually requires the mcb to be D type.

 

[Krispy_88]

I'm guessing there going to be either 250w or 400w metal halide

I'm guessing there going to be either 250w or 400w metal halide

Do you know how many are on each circuit roughly?

 

[Dannyg8810]

Do you know how many are on each circuit roughly?

Very limited EICR n/a in points served

TBH I don't think it's been done very well 5 3phase boards in the day

 

[Krispy_88]

Very limited EICR n/a in points served

TBH I don't think it's been done very well 5 3phase boards in the day

Feel for you mate, had a look at one a few days ago and they stated 'Not enough RCD protection' on a site with 5-6 large three phase boards...no more specific than that. They also thought a missing 'Mixed Colour Warning Label' was classed as C2 as well.

 

[Dannyg8810]

Feel for you mate, had a look at one a few days ago and they stated 'Not enough RCD protection' on a site with 5-6 large three phase boards...no more specific than that. They also thought a missing 'Mixed Colour Warning Label' was classed as C2 as well.

I don't understand how they have got a zs for every circuit ,going to be a nightmare this one hahah

 

[westward10]

I've never come across any lighting circuit protected by a D type mcb before, sounds like poor design if too many lights on start up actually requires the mcb to be D type.

See plenty of type 4 and D on this type of lighting.

 

[Krispy_88]

I don't understand how they have got a zs for every circuit ,going to be a nightmare this one hahah

A Zs for every circuit... on an EICR on a site that big? Smells a bit fishy to me. How much did the loops fail by?

 

[Dannyg8810]

A Zs for every circuit... on an EICR on a site that big? Smells a bit fishy to me. How much did the loops fail by?

0.73
0.62
0.92
0.67
0.81

Maximum permitted is 0.44

Maximum permitted for the c type is 0.92 so that was my thinking of swapping these out

 

[Ian1981]

And that's why type D aren't the best idea when type C is available.

 

[Krispy_88]

And that's why type D aren't the best idea when type C is available.

Isn't a C type 0.87? I might be wrong I've just done it on my calculator rather that check the regs. But it would mean a C type wouldn't work for one of them results. Could always drop to a 16A type c maybe if they are 2.5mm's...that'll give you 1.09. D types are awful, avoid like the plague. All depends on the load you have on the circuit really, shame they didn't record it.

 

[Ian1981]

Max zs on a 20 amp type c is 1.09 or 0.87 80% rule of thumb

 

[Octopus]

Think we need far more accurate information before we can give advice .....

 

[Ian1981]

Other options for high zs would be rcbos tho may have problems with nuisance tripping or localised supplementary bonding of the lighting circuits

 

[Dannyg8810]

Isn't a C type 0.87? I might be wrong I've just done it on my calculator rather that check the regs. But it would mean a C type wouldn't work for one of them results. Could always drop to a 16A type c maybe if they are 2.5mm's...that'll give you 1.09. D types are awful, avoid like the plague. All depends on the load you have on the circuit really, shame they didn't record it.

Yes sorry your correct ,so one of the circuits would still be over