Was in a property today and witnessed a gas engineer running 2x 1mm 3 core flex cable to a gas boiler from a wiring centre. This covered some 9 meters including running over an attic. I was always under the impression that flex was limited to 6 foot. On nearly every installation i come across the cables are usually twin and earth or 3 core and earth if over 6 foot. If under 6 foot it's usually just flex. So the question is does this 6 foot rule exist ? Cheers.
No rule as far as I am aware, but that's just rough. Should be done in "fixed" wiring ,i.e. T+E. flex is for final connections.
If you want to wire yer whole house in flex, go ahead. It'll cost you, but I can't see any other reason not to. Should this plumber really have started his run in T&E and then have to fit a JB or summat to convert to flex? I don't think so either.
Why not? It lasts just as long. It's just the same ratings. It'll cope with movement. It's more roundy which is nicer than flatty.
Concur DA - run properly this is no problem using flex whatsoever - by this I do mean control wiring flex (you know 5 core etc) Obviously to supply power to boiler it would be T and E to socket/fcu as per the norm, and then whatever onward at boiler position.
There is no wiring regulation to stop you wiring your entire house in 3-core flex, like this: providing you use the appropriate csa for the circuit.
If fact the regs state you must use flexible cable in Mobile or Transportable Units. T&E is not always the answer. You need to look at the Table VII.3 (Code of Practice for In-Service Inspection and Testing of Electrical Equipment) for maximum lengths of extension leads.
If using flex isn't restricted in length then why do some sparks run t&e to near boiler then do the final connection in flex via a junction box. Also sometimes from the wiring centre to the hot water cylinder the cable is t&e, then flex into the cylinder stat via a junction box. I'm just curious to know why? Is it good practice?
That's the way it is done and how you are taught in college (anybody remember colleges?) Also T&E is much cheaper than flex. Also sparks have loads of T&E on the van with clips to match.
So does anyone know how I've got this six foot rule in my head? Would it be good practice to stick to this? Over the years I've never seen excessive lengths of flex used especially under floors. That's why I thought this 6 foot rule made sense and was correct. But if it's basically from a cost perspective well that makes sense also.
Fixed wiring is usually carried out in the flat T+E type cables. There is no "rule" as such but has been by convention for years. Other options are conduit and SWA. Connections from the fixed wiring to appliances tends to be flexible cable. You can move the appliance, or move the cable out of the way in say an airing cupboard. Also you can use heat resisting flexibles between the fixed wirning and the appliance. Standard practice developed of many years. Kind regards
Once again the thread started with "The plumber wired it" or words to that effect. While plumbers may have the ability to safely connect stuff, they do not seem to have the same finesse as sparkies. It wold have been better to use 3 core and T&E to get the 5 cores but plumbers don't carry the stuff in their van, we don't carry pipe! So really this is the product of allowing other trades to do other trades jobs, no further comment.
This is an old argument... 1.5mm2 cable as standard wired to a 3 pin plug, voltage drop over distance of this conductor is limited. Yes there is a limit but the limit as we all know is determined by the installation and the size of the conductor. If the extension lead is plugged into a RCD protected socket then 25 metres could be ok but if not then you can't really exceed 10 metres or even 5 metres if no RCD is applicable. Most flex is actually 1mm2 or even 0.75mm2 and has a 5-10Amp fuse fitted so 25 metres is well beyond the capability of the cable. So yes for a very high quality 1.5mm2 cable or larger then 25 metres or higher can be achieved but one must note if you run a welder or some very high current device plugged into it you may find it not perform quite the way it should due to power loss. 25 metres powered over as 4mm2 cable would show considerable difference over a 1.5mm2 extension cable if powering a welder. Voltage and Current is directly proportional while resistance terrorises both.
I used some 150 mm² flex to power a concrete pump, and also 120mm² flex for a crane, the latter was reeled out and in as the tower crane moved and was something like 60 meters long. The problem with flex is protection, the crane was inside barriers, outside the barriers it was SWA. However be it a lamp, boiler, welder or whole house nothing to stop you using flex, except if you have ever tried soldering 150 mm² flex into the pins of a 125 amp plug you would definitely hide the next time the job came up. It may be called flex but not very flexible.
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