Zs

[keniff]

Hi, when Installing a fused down spur off a rfc, do you record the max zs for the 32a mcb or the bs1362 fuse? Had different opinions on this!

 

[sedgy34]

the highest zs i record on circuit

 

[Octopus]

Ah ha, a very good question indeed. Presumably its a MWC you are completing.

I would record the protective device as the fuse value in the FCU and the Zs is taken at the end of the fused down spur.

 

[SirKit Breaker]

Can I assume you mean a Fused Connection unit / Fused spur, for a boiler or an alarm etc?

Then your Zs will be measured at the supply side not the load side connections, and as post above states (the one before murdoch got in!) you record the highest measured Zs, which if you have spurred off a ring will be at your spur unless you have more than one spur.

The maximum allowed Zs will be that for the circuit protective device protecting the ring including your spur as per the table in the on site guide. The output side of the spur has no relevance as the fuse fitted is only there to protect the flex to whatever you are supplying, which is the same as if you were to plug an appliance into a socket.

Cheers...........Howard

 

[keniff]

Ah ha, a very good question indeed. Presumably its a MWC you are completing.

I would record the protective device as the fuse value in the FCU and the Zs is taken at the end of the fused down spur.

Correct that's exactly what I'm doing, I can't seem to find a max zs for a 5 amp bs1362 fuse?!

 

[keniff]

Can I assume you mean a Fused Connection unit / Fused spur, for a boiler or an alarm etc?

Then your Zs will be measured at the supply side not the load side connections, and as post above states you record the highest measured Zs, which if you have spurred off a ring will be at your spur unless you have more than one spur.

The maximum allowed Zs will be that for the circuit protective device protecting the ring including your spur as per the table in the on site guide. The output side of the spur has no relevance as the fuse fitted is only there to protect the flex to whatever you are supplying, which is the same as if you were to plug an appliance into a socket.

Cheers...........Howard

Yes fused connection unit, taking lights from it as cant disturb floor or ceiling, I will take r1+r2 at furthest light and ir test , but wondered whether to record zs at furthest light or at spur and like I said can't find a max zs for fuse bs1362 but I have been told both ways

 

[GLENNSPARK]

(P48)...BRB Keith..

 

[sedgy34]

Correct that's exactly what I'm doing, I can't seem to find a max zs for a 5 amp bs1362 fuse?!

we know!! so do as me/sirkit breaker suggests

 

[GLENNSPARK]

(p55) bgb

 

[GLENNSPARK]

use the 13A...

 

[GLENNSPARK]

table that is..

 

[SirKit Breaker]

(p55) bgb

This needs the x0.8 correction factor though, thats why i referred to the OSG. The regs are not my favourite publication!

Cheers..........Howard

 

[telectrix]

sir kit is correct. record R1+R2 and Zs at furthest light, but the max. Zs is that for the 32A MCB at the origin of the circuit. 1.44 for a B type ( less temp. correction if you use the osg figures)

 

[Octopus]

(p55) bgb

but not the value for the 5A or 10A varieties!

 

[GLENNSPARK]

This needs the x0.8 correction factor though, thats why i referred to the OSG. The regs are not my favourite publication!

Cheers..........Howard

yes indeed Howard.....the OSG is a quicker reference isn`t it...