Calcs Check

[LankyWill]

New to the designing part and want to make sure im correct.

Got a 10 t+e that i want to feed a garage submain. I have wired it to an adaptable box which im going to joint with armoured. The armoured will run about 2 meters in a duct buried in the ground to a depth of 0.8m. There is no bunching factor as its run on its own through the ceiling and down block work to exterior hole. It doest pass through insulation as such but the cavity is insulated with polystyrene balls. Here is my calcs so far:

It= 43A
Cg= 1- no grouping factor as its on its own
Ca=1 -30*ambient temperature
Cs=1 -not sure if i need soil res if it runs through a duct?
Cd= 1 -is my run long enough to add derating factor?
Ci= 0.88 - tables a bit confusing length in insulation? or length of cable run in insulation?
Cf= using 60898 so not applicable
Cc= 0.9 as it runs underground for 0.8m

Iz=34.056A

i can therefore use a 32A B type to protect this cable?

What should i do if the install is 80% t+e and 20% 3 core armoured?

 

[telectrix]

way out. 10mm T/E ref method C is Iz = 65A. the little bit of cavity wall insulation can be ignored. 50A MCB is advised. what you need to consider is if it's PME and there are extraneous parts in the garage, then the cpc of that 10mm T/E is too small to serve as a bonding conductor.

 

[LankyWill]

There is no extraneous bonding needed as there is no pipework in garage, Its a tn-c-s installation so the 4mm earth inside the 10mm will be adequate for fault protection. I thought single core was 65A and multicore was 63A?

 

[telectrix]

i stand corrected. 63A is as per table F5(i) in green osg. i read the wrong table.