Advice required re: newly installed chandelier

[333rocky333]

If the cable is not up to carrying 10amps then it is not wise to fit one.
certain factors dictate what the cable can safely carry.

Bigger breakers may sometimes solve problems like yours.
But can sometimes create other potential hazards,unless the circuit is checked first.
These checks may have been done by the electrician ,hopefully, so dont worry

Without checking the book, I am not sure whether a B10 is any better than a C6 regarding your tripping case

B breakers are more common in domestic as they trip faster,
As you say the board is sensitive.
C breakers are more commercial use as they trip slower, but as said by others , the Earth Loop Impedance needs to be lower for them to operate.

To jump from B to C the max limit for the ELI is reduced,

To jump from 6 to10 the max limit for the ELI may be further reduced.
The cable size will also need consideration

That is why they are asking for the ELI to the light.
The ELI readings you gave are for other things.

 

[JohnD]

As a rule of thumb (if I'm wrong I hope someone will correct me ) a B10 trips on the same start-up surge as a C5 (if you could get one) so a C6 would be just a tiny bit slower than a B10 but unlikely to make any practical difference I would have thought.

 

[333rocky333]

chloe

How big is the base of this light,an option is to get the electrician , to change the transformer for a electronic one , these start without a surge. and fit it either in the base or possibly above in the ceiling.

When you brought it did you notice a very heavy round coil of wire in the base bit, before it was fitted, if so that is a wire wound transformer.

For 15 X 20w lamps it would need to be 300VA the same rating as the existing one.

If you changed to 10watt then 150va could replace it
If you changed to 5watt then 75va could replace it
But you would then have to stick to that lamp size to prevent damage to the transformer.

I wonder if keeping the existing transformer and reducing to 15 X 10 watt lamps may help,this might however reduce the lamp life though

you could try reducing the load by removing 8 lamps temporary to see.
Mind they are not hot if you do, and do not touch the glass with your bare hands either.

Another option is contact the maker for a SUITABLE dimmer, preferably with soft start, this will absorb the initial start surge.
You might be able to refit the B6 mcb then as well.
Do not just fit any old dimmer though.

Also get the mcb change,checked with the electrician if possible.
To make sure it was ok

 

[Adam_151]

As a rule of thumb (if I'm wrong I hope someone will correct me ) a B10 trips on the same start-up surge as a C5 (if you could get one) so a C6 would be just a tiny bit slower than a B10 but unlikely to make any practical difference I would have thought.

Amost the same, aye

6A type C, won't trip instantly at less than 6x5=30A, but must trip instantly at 6x10=60A

10A type B won't trip instantly at less than 10x3 = 30A but must trip instantly at 10x5 = 50A

for course the exact value will vary a little, but I'd expect it to probably be in the lower half of the range for modern breakers

B = 3-5xIn
C = 5-10In
D = 10-20In

 

[333rocky333]

Well done adam
for chloe then
What mcb would you pick providing ELI , cable size etc was all ok
Are you saying a 6C would be better than a 10B ,in regards to the tripping
I read it as a 6C.

Dont suppose you have the max ELI for a 6C and a 10B handy

 

[plugwash]

If it is tripping a B10 it will probablly trip a C6 as well.

The next step up would be a D6 or C10 but other circuit characteristics absoloutely need to be checked before making such a change.

 

[kixchloe]

Hi guys,

Thanks very much for trying to help me (although I must admit I am a bit lost by all the tech speak!). In answer to some of your questions/comments:

I don't have a certificate for the CU. It is fairly new (RCD split board), but still before part P became standard.

The electrician said the lighting circuit wire is thick enough to cope with a 10A breaker (and said you could not go any higher).

The light has a fairly large base and I am pretty sure judging by your descriptions that it is has a wire wound transformer.

Thanks,
KixChloe

 

[JohnD]

contact the maker...

 

[kixchloe]

Hiya,

I don't know if this helps at all ... but I just found another part P of some work I had done on the kitchen ages ago and those electricians tested the lighting circuit and put down a "Maximum measured earth fault loop impedence" of 0.91 ohms down.

Since the kitchen I have had lights installed upstairs, but do not have a certificate.

Then recently, this electrician installed the downstairs lights (which includes this chandelier).

Would you expect this value to have changed because of the new installations? Or could you use this as the basis of a breaker calculation?.

Thanks,
KixChloe

 

[333rocky333]

if the kitchen light is on the same mcb as the chand . that is the ELI, and new lights will not affect it unless extra wiring was installed also.
It may be the max allowed for the circuit, to conform though, rather than what they measured

Ie any tests carried out must be lower


This max allowed for the circuit is wrong now as the mcb has been changed

Does it say the cable size also
ie 1.0mm or 1.5mm, it may be called L, N or R1 or Rn or similar
It may also have a size for the earth or CPC which may be different

 

[kixchloe]

Hiya,

The Kitchen light is on the same MCB as the chandelier. Here are all of the details in the "LIGHTS" row of the old Kitchen Part P certificate ...

Type of wiring = A
Number of points served = 11

Circuit conductors (csa):
Live mm sq. = 1.5
cpc mm sq. = 1

Max. disconnection time permitted = 0.4? (writing not clear)

Overcurrent protective devices:
BS (EN) = 60898
Type No = B
Rating = 6
(I guess this is my old B6 breaker?)

RCD:
Operating current = N/A

Circuit impedances:
Ring final circuits only:
r1 (Phase) = N/A
rn (Neutral) = N/A
r2 (cpc) = N/A

All circuits:
r1 + r2 = 0.67
r2 = not filled in

Insulation resistance:
Phase/Neutral = 100
Phase/Earth = 100
Neutral/Earth = 100

Polarity = tick
Maximum measured earth fault loop impedence Zs = 0.91

RCD operating times:
at I delta n = N/A
at 5 I delta n = N/A

I know you probably don't need all this info, but hopefully some of it will be useful!.

Cheers,
kixChloe

 

[Qedelec]

A D10 will allow up to 1.2 ohms ELI so .91 is .75% of maximum allowed (less than the 80% guide).
1.5 mm conductor is rated at 19.5amps.

 

[333rocky333]

The Zs 0.91 reading then ,may have been done at the end of the circuit, or it may be they just wrote the highest reading ,they got at the kitchen, switch or light if that is where they were working.

In the book it looks like the maximums must be no greater than

B6 is 6.40 max
C6 is 3.20 max
B10 is 3.84 max
C10 is 1.92 max
So whatever breaker your ELI appears well lower which appears good.

The only thing in dispute is whether a 10 amp mcb is overrated for a 1.5 cable, this would depend on the length and volt drop

 

[Qedelec]

Personally I'd fit a C6.

 

[333rocky333]

Also It may be doubtfull if G9 lampholders are allowed on the 10amp mcb.
ses and sbc are not allowed but G9

I personally would go for a C6 mcb and contact light maker for a compatible soft start dimmer