long flex for boiler thermostat under floors

[stevie2011]

On a domestic install a plumber has hooked up his boiler to the mains and then run a flex probably longer than 8 meters underneath floorboards to his thermostat. I'm doing the rewire, but this had happened while i was away on other things, i'd told him this wasnt good practice and needs to be a 3 core and earth flat. As far as I've been looking the regs are vague about flex to fixed appliances, but through my experience (which has been mostly lighting systems install) we'd never used flex in lengths more than a meter, has anyone got any answers? because i can't actually think of a logical safety reason why we'd never do this.

 

[KAS1]

Would 8Mts of flex be classed as fixed wiring?

 

[kingeri]

Nothing in the regs about using flex instead of T&E. As far as I can see, you could wire a whole circuit in it, might be a bit expensive though! It should still be clipped or otherwise secured though.

 

[High Tower]

It's no different to wiring a Splan or YPlan in flex,as long as its used correctly, it's still double insulated so its fine.

 

[monkeyelectric]

No problem i can see with that

 

[Midwest]

Current carrying capacities & volt drop are different for cables with flexible conducters (Table 4F3A). That would have to be considered.

 

[telectrix]

as long as he's got enough cores and uses the green/yellow as cpc...........

 

[stevie2011]

thanks guys, yeah makes sense, its no more than 3 amps anyway, I can't remember if he said 0.75 or 1 mm but i'm sure it will be alright. I guess i'm just over thinking (which i'm trying not to do) because this is the first job im solely responsible for and i think this one will be inspected by the NIC. The plumber probably lashed it in, so I'd better make sure its picked up off the ground. Panic over!

 

[Elmer BeFuddled]

as long as he's got enough cores and uses the green/yellow as cpc...........

Surely that should be over-sleeved for line??

 

[Geordie Spark]

On a domestic install a plumber has hooked up his boiler to the mains and then run a flex probably longer than 8 meters underneath floorboards to his thermostat. I'm doing the rewire, but this had happened while i was away on other things, i'd told him this wasnt good practice and needs to be a 3 core and earth flat. As far as I've been looking the regs are vague about flex to fixed appliances, but through my experience (which has been mostly lighting systems install) we'd never used flex in lengths more than a meter, has anyone got any answers? because i can't actually think of a logical safety reason why we'd never do this.

How many cores are in the flex and is one of them being used as earth / CPC?

 

[stevie2011]

3 core and earth, earth is being used as the cpc

 

[telectrix]

sounds OK then. even if the stat does not require earthing, you need a cpc in the cable.

 

[Risteard]

sounds OK then. even if the stat does not require earthing, you need a cpc in the cable.

At the accessory rather than in the cable.

 

[High Tower]

At the accessory rather than in the cable.

No as tel said even cables supplying equipment that doesn't require a earth should have a cpc helps with the whole ADS thing when someone nails through it

 

[stevie2011]

when i was training i was always told, as electricians we protect our cables, so yeah, it definitely needs an earth cable connected to earth so if a hungry mouse gets at it or something we get automatic disconnection of supply.

makes me think of the old school boy error of not joining the earths at double insulated light fittings, which means the continuity of cpc gets lost. Funny how common that is, i saw that again recently on a maintenance job, anyway I'm trailing off topic here!

Thanks for your help guys.