VIR Cables Current Carrying Capactiy

graham123 · Dec 23, 2016

Anyone know of any information out their on the current caring capacity of old VIR cables, looks like they are between 16mm-25mm, so any info on the older imperial sizes would be useful

Thanks

graham

Midwest · Dec 23, 2016

Don't think I would worry trying to find out their CCC. I'd be just thinking about replacing them, or advising that?

Octopus · Dec 23, 2016

Are you 100% certain they are suitable for use now?

telectrix · Dec 23, 2016

i'll hazard a guess at 19/.044, which equates to approx. 20mm². to be on safe side treat as 16mm², or interpolate between 16 and 25. assuming state of cables is fit for continued use.

graham123 · Dec 23, 2016

The bigger submains appear in good condition from what we can visually see. the small stuff is in a bad way.
19/0.44 cables are on 63a mcbs

telectrix · Dec 23, 2016

graham123 said:
The bigger submains appear in good condition from what we can visually see. the small stuff is in a bad way.
19/0.44 cables are on 63a mcbs

looks about right to me. 80A is about the max. if in free air .

0.03 19/.044 80A 105A 125A 115A 125A 135A 90A 110A 115A ... VD. 2.4/ 2.1

davesparks · Dec 23, 2016

I've got a few old regs books with ratings tables for this cable at home, if I remember when I get home I'll post up some pictures.

Do you know what type and age of cable it is?

Pete999 · Dec 23, 2016

graham123 said:
Anyone know of any information out their on the current caring capacity of old VIR cables, looks like they are between 16mm-25mm, so any info on the older imperial sizes would be useful

Thanks

graham

file:///C:/Users/Pete/Desktop/Petes%20resources/Electrical%202/cable_sizes.pdf

Taylortwocities · Dec 23, 2016

We cannot view that file Pete, it's internal to your C:drive!

Taylortwocities · Dec 23, 2016

I found this extract in my files, may be of some help...?

The 1955 13th edition IEE Regs is the last one in which I can find a reference to rubber insulated cables (ie Vulcanised general purpose Rubber compound Insulation to BS.7, as distinct from butyl rubber).
Table 13 of those Regs gives ratings for flat twin, and 3-4 core cables, installed "in conduit, troughing or casing" as well as in "free air" - including rubber insulated cables with tough-rubber sheathing or lead sheathing, and pvc or polythene insulated cables with pvc sheathing.

conductor size …. single phase current …. ECC if lead sheath+T&E …. ECC size if pvc
1/.044 (0.0015 sq in) …. 5 amps …. no ECC listed for this …. 1/.044 (0.0015 sq in)
3/.029 (0.002 sq in) …. 10 amps …. 1/.036 (0.001 sq in) …. 1/.044 (0.0015 sq in)
3/.036 (0.003 sq in) …. 15 amps …. 1/.044 (0.0015 sq in) …. 1/.044 (0.0015 sq in)
7/.029 (0.0045 sq in) . 20 amps …. 1/.044 (0.0145 sq in) …. 3/.036 (0.003 sq in)
7/.036 (0.007 sq in) …. 28 amps …. 1/.044 (0.0145 sq in) …. 7/029 (0.0045 sq in)
7/.044 (0.01 sq in) …. 36 amps …. 1/.052 (0.002 sq in) …. 7/.036 (0.007 sq in)

then getting up to more industrial sizes
7/.052 (0.0145 sq in) …. 43 amps …. 1/.064 (0.003 sq in) …. 7/.044 (0.01 sq in)
7/.064 (0.0225 sq in) …. 53 amps …. 1/.072 (0.004 sq in) …. 7/.052 (0.0145 sq in)

How many people remember working with lead sheathed twin cables, going into metal junction boxes with a snap-on metal lid and screw down clamps to secure and earth the cable sheaths?

The cable sizes are the actual diameter of the individual strands in each cable - in inches - (so 3/.029 was 3 strands of 0.029 inch diameter cable), so cable sizes could be readily checked with an imperial micrometer.
I guess my mic is not the only one with a burned up anvil where a cable was carelessly checked live and the rest of the mic touched to earth (my shoes or the flooring must have been good insulators in those days! )