Inspection and Testing Question

[mickmdt]

Hi
I am studying for my 2392 and need to ask how or if you test beyond a FCU. For example, if a lighting circuit is being fed from a FCU how do you test that particular lighting circuit and how do you fill in the test certificate.
Hope this makes sense.
Many thanks
Mick

 

[JUD]

Test the lighting circuit as you normally would, the only difference being that the FCU is the Overcurrent device for the circuit i.e. R1 + R2 would be measured from the FCU to the end of the circuit.

When filling in the certificate you would put BS1362 as your overcurrent device and your maximum Zs would become 16.4Ω (based on 3A fuse).

Don't forget though, any voltage drop calcs would still need to be worked out from the origin of the supply i.e. the Consumer Unit or Distribution Board.

Hope that helps.

P.S. Welcome to the forums

 

[mickmdt]

Hi JUD, and thanks for welcoming me to the forums.

In response, I just have a couple more things to ask:

• When you fill in the certificate and put BS1362 as your overcurrent device, what would you put down as the overcurrent device, short-circuit capacity. Will you still leave it, for example as 6kA for MCB type B? Or do you fill in a separate sheet for this?

•*Where in the Big Red Book/OSG is the maximum Zs for a BS1362?

•*When Calculating voltage drop from the CU, how do you work this out when you have one part of the circuit up to the FCU in 2.5mm and the next part in 1.5mm?

Hope this all makes sense!

 

[JUD]

Hi JUD, and thanks for welcoming me to the forums.

In response, I just have a couple more things to ask:

• When you fill in the certificate and put BS1362 as your overcurrent device, what would you put down as the overcurrent device, short-circuit capacity. Will you still leave it, for example as 6kA for MCB type B? Or do you fill in a separate sheet for this?
As far as I know the breaking capacity of BS 1362 is 6kA although I can't seem to find the tables at the moment.


•*Where in the Big Red Book/OSG is the maximum Zs for a BS1362?
Page 48 BRB Table 41.2

•*When Calculating voltage drop from the CU, how do you work this out when you have one part of the circuit up to the FCU in 2.5mm and the next part in 1.5mm?
Work it out in 2 stages. VD from CU to FCU and VD from FCU to end of circuit and then add them together.

Hope this all makes sense!

My GREEN

 

[Amp David]

On previous jobs I have recorded the test results for the FCU part as a seperate circuit on the schedule of tests.

Another spark I work with treat the FCU part asseperate and does a completely seperate cert, which seems to me to be OTT.

 

[mickmdt]

Many thanks for your replies, but there is still one thing that I need to ask. To calculate the Zs for the lighting circuit, would you test your R1 + R2 from FCU to end of circuit then add the highest reading taken from the circuit you have spurred off? i.e:

Zs = Ze + (R1 + R2) Ring or Radial + R1 + R2 Lighting Circuit?

Cheers Mick

 

[pushrod]

Many thanks for your replies, but there is still one thing that I need to ask. To calculate the Zs for the lighting circuit, would you test your R1 + R2 from FCU to end of circuit then add the highest reading taken from the circuit you have spurred off? i.e:

Zs = Ze + (R1 + R2) Ring or Radial + R1 + R2 Lighting Circuit?

Cheers Mick

You could do it that way but probably it is best to just test it - at least that way you are also checking the resistance of the mcb.

 

[Risteard]

would you test your R1 + R2 from FCU to end of circuit then add the highest reading taken from the circuit you have spurred off?

I wouldn't add the highest reading for the circuit but the reading at the point of connection of the FCU.