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Which cable for TRS?


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Hello all,


I've got some anorak questions about mains cable... :(


I know its common practice to use 1.5mm2 H07RN-F rubber cable for 15Amp extensions, as its the toughest rubber cable. However, is this a requirement or are other options (rubber H05RN-F or H05RR-F) or even PVC cables also acceptable? (All the mains multicores I've ever seen have been PVC jacketed).


One reason for asking is I've seen a lot of blue artic cable in venues recently. As I understand it, 1.5mm2 artic is rated at 15A so should be OK for 15A extensions. However, one venue had used 2.5mm2 with 15A connectors and discovered the cord grips don't fit - so just stripped the outer jacket further back...


The other reason for asking, is that I'm looking to aquire some more extension cable. Everything we use is 15A, but I want to make sure its possible to convert to 16A in the future without having to replace the cable (ie make sure the conductor size is large enough).


To summarise, what (if any) are the cable requirements for 15A extensions? How about 16A extensions? (is 2.5mm2 required?)





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Just a note, if you are looking to build extension cables always go for HO7 cable and not HO5. HO5 cable is not self Extinguishing and some local authorities don't like you using it.




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HO7-RNF is the standard cable for extension leads in theatres etc., as there is a risk of them getting near hot things. PVC isn't suitable for extension leads as it melts easily and isn't very flexible. Arctic cable is good outdoors in the real cold, but usually isn't necessary in UK weather for temporary rigging. Also it's usually blue - this isn't normally desired in theatres, but can be useful (e.g. our workshop 13A extensions are blue arctic, which stops people 'borrowing' them to use on stage; stage has its own 13A HO7 extension leads).


1.5mm2 should be fine for 16A current however considering voltage drop, 1.5mm2 @16A will give a 25% greater drop (0.24V/m loss compared to 0.2V/m) than for 2.5mm2 @16A (iirc). i.e. you need to consider how long your cables are going to be and what current you are going to pull down them.


1.5mm2 is the maximum you can normally terminate in the terminals of a 15A plug and get under the cord crip, however a 16A ceeform will allow 2.5mm2 no problem.

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to follow up to Rob's last post.


HO7RN-F is not designed for contact with hot objects, in fact many data sheets make that point. HO7 is made with a Neoprene outer jacket as opposed to HO5 which is Rubber. This means you have an operating temp of 60 deg C for HO5 and 85 deg C for HO7. PVC is good for 70 deg C, though you can get 90 deg C PVC.


The difference of 15 deg C or so will make very little difference in it's ability to stand contact with hot objects.


Where HO7RN-F scores is it's 'toughness', it's ability to resist attack from oils etc and it's fire retardance. You can also get fire retardent PVC.


You should not use HO7 to rewire lanterns thinking that it is heat resisting, for that you need silicone based outers, good to 180 deg C.


Oh, and thanks for the heads up on artic colours, I'd seen yellow about but not the other. Anyone know where to get black at a good price.



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Thanks to everyone who replied. :D


Based on what's been said, I think I'll get some more HO7 for front of house and use artic for the less visible runs.


I wasn't aware that HO5 is not self extinguishing - so thanks for pointing that out!


To follow up on Brian's question - anyone know where to get black artic and what it costs, and/or a good source of HO7?





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Harmonised Cable Coding


Identification of design

H Harmonised Standards

A Authorised National standards


Nominal voltages

03 300/300V

05 300/500V

07 450/750V


Insulating Material


R Rubber

S Silicon


Sheathing Material


R Rubber

N Polychloroprene (PCP)

J Glassfibre braid (GFB)

T Textile

T2 Textile with flame resistance


Special construction

H Flat, divisible cords

H2 Flat, Non-divisible cords

D5 Central core (non-supported element)


Conductor form

U Solid wire

R Stranded wire

K Fine wire (for permanent installation)

F Fine wire (for flexible cables)

H Super-fine wire

Y Tinsel


Number of cores

2 2 Core

3 3 Core






Harmonised, 300/500V, PVC, PVC, Fine wire flexible cable, 3 core




I don't know where the "self extinguishing" ideas have come from, they don't seem to be part of the standard.


An aside on Arctic colours:- Blue should only be used for 230v and yellow for 115v

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The "self extinguishing" bit should actually be "Flame Retardant" which is a feature of the PCP outer sheath (and also oil resistant).


But as I pointed out it isn't good enough to stand contact with a hot lamp.

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