Type D MCB for lighting circuit?

[cadspark]

I've just installed a big chandelier fitting with twenty 12 volt halogen capsule lamps. It has a toroidal transfomer built into the fitting. It's in a chapel conversion and fed on a dedicated radial in 1.5mm. It's currently on a 6 amp Hager type B which trips frequently. The instructions that came with the fitting actually recommend a type D. Has anyone come across anything like this before as I know type C is recommended where halogen spots are used but I've not used type D on a domestic before?

 

[Sidewinder]

Prob not for the halos mate prob for the torroidal inrush current!

 

[springcrocus]

A thermistor in series with the torroidal may help somewhat.

 

[steptoe]

done a few that required a D to prevent the inrush tripping,

if you are in a jam perhaps a C 10 may do the job, sometimes works.

 

[springcrocus]

How will a thermistor stop a B breaker from tripping on inrush surge ?

Higher resistance at low temperature, should slow down the surge.

But I'm probably wrong... ray

 

[Evans Electric]

You need to check the Zs chart before fitting C or D types . If that were a problem and as its a Hager, you could fit a HRC fuse carrier in place of the MCB . Hager are about the only ones who make those.

I did it at a small print works last year, the summer heat pushed the thermal limits of the MCBs up , plus they were all touching each other on a dinrail, so replaced them with some Hager 10A HRC flip out carriers.

I'm guessing the problem is the transformer inrush current.

 

[Sidewinder]

Deke,

Not "right", but, if the cct is on a 30mA RCD, then nae bother really.

Not that this is correct "really"!

 

[SLIPSHOD & SLAPDASH]

Deke,Not "right", but, if the cct is on a 30mA RCD, then nae bother really.

Not that this is correct "really"!

Mmmmmm

 

[Riggy]

Deke,Not "right", but, if the cct is on a 30mA RCD, then nae bother really.

Not that this is correct "really"!

Bang on, no problem with touch voltages if there's an RCD. Absolutely fail safe! :innocent

 

[Sidewinder]

:innocent O)

 

[springcrocus]

Can anybody explain why an NTC thermistor would NOT work in this situation? I would have thought that one would have been fitted by the manufacturer automatically.

I must be missing something here?

 

[Sidewinder]

[No message]

 

[cadspark]

I've ordered up a type D and the circuit is within limits with regards to the Zs. I was just suprised to see a manufacturer suggesting it. The chandelier in question looks stunning but required a scaffold tower to install. Don't know how the client will get on when the bulbs start to blow.

 

[loonytoon]

Pics?

 

[SLIPSHOD & SLAPDASH]

Must be a short cable run ?

 

[Chr!s]

Can anybody explain why an NTC thermistor would NOT work in this situation? I would have thought that one would have been fitted by the manufacturer automatically.I must be missing something here?

A ntc would limit the inrush, though its probably easier to just select a breaker suitable for the level of inrush

 

[Andy™]

Deke,Not "right", but, if the cct is on a 30mA RCD, then nae bother really.

Not that this is correct "really"!

but what if L-N loop is too high.

 

[Sidewinder]

Not an issue mate as curve is for L-E fault as far as Zs is concerned.

L-N fault is overload, curve not involved for this as far as 7671 is concerned.

My quotes are a hint!

BTW then, what is the disconnection time required under 7671 for an overload fault, NOT any L-E faults of ANY description.

ONLY true overcurrent faults, i.e as Andy says L-N "faults".

Anyone?

 

[Chr!s]

BTW then, what is the disconnection time required under 7671 for an overload fault, NOT any L-E faults of ANY description.ONLY true overcurrent faults, i.e as Andy says L-N "faults".

Anyone?

BS 7671 places no time on over current, other than to say it needs to be interrupted within a time so that the cable max temp is not exceeded, saying that the k factors in the regs are for upto 5 secs disconnection, so this tends to set a upper limit of 5 secs, though other k values may be used beyond 5 secs.

 

[Sidewinder]

Chris,

I forgot you were around tonight!

Perhaps you could have kept your trap shut for a few minutes! ; )