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!

 

[GLENNSPARK]

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

i know Murdoch....thats why i suggested he use the 13A table at post #10...

 

[SirKit Breaker]

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

Keith,

Nothing wrong with wanting to go the extra mile with your testing. as long as the Zs is in spec for your spur, then you wont have any probs with going out of spec for Zs on fuse for your lights, unless the circuit is excessively long.
Whatever fuse is fitted wont blow before the MCB trips at the CU anyway, or it is very unlikely to.

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

 

[sedgy34]

come on guys admit do you sit there with these books :book:

 

[GLENNSPARK]

come on guys admit do you sit there with these books :book:

you should try it sedg....

 

[Octopus]

i know Murdoch....thats why i suggested he use the 13A table at post #10...

Hadn't seen post #10 when I last posted - too many people contributing at the same time. Like these sort of threads.

 

[telectrix]

Whatever fuse is fitted wont blow before the MCB at the CU anyway


​all depends on the current. if it's overload and under 40A , it will be the 5A fuse that goes. last week i had a blown lamp blew 2 3A 1362's and took out the 16A MCB in the CU all together.

 

[Octopus]

Actually guys I found this a while back and I think it covers pretty much everything...


View attachment ZS values - maximums.pdf

Unless anyone wants to disagree!

 

[telectrix]

won't disagree, murdoch, but the max. value you enter on your cert is for the whole circuit, from origin at CU, not from the FCU fuse.

 

[ipf]

Correct Tel.

 

[keniff]

Thanks everyone! So just to clarify you disregard all test results for the output of the fused spur zs wise and record the zs at the supply side of it?

 

[robd]

The value they are looking for is related to the mcb and not the fused spur. Don't waste too much time on it, life's too short!

 

[telectrix]

no. you measure at the extremity of the lights. that is the furthest point of the circuit/spur.

 

[ipf]

Thanks everyone! So just to clarify you disregard all test results for the output of the fused spur zs wise and record the zs at the supply side of it?

Could be feeding a further socket outlet or light rather than an appliance. In such a case, no.

 

[robd]

Sorry assumed he was asking the max permissable value of zs to record on the test sheet and not where to test which is obv furthest point/highest value, but still if the mcb max permissable value was recorded it would be a lower value which would presumably be met anyway

 

[keniff]

Sorry assumed he was asking the max permissable value of zs to record on the test sheet and not where to test which is obv furthest point/highest value, but still if the mcb max permissable value was recorded it would be a lower value which would presumably be met anyway

So furthest point would be the light in this case, max zs would be 1.93 for the fuse and 1.15 for the mcb, iv always had mixed replies on this just thought I would start a debate! I have always tested at the end of the circuit even after a spur if I'm honest