4 Core 1.5Mm Power To & Back From Thermostat. Amp Rating?

[bignose2]

Hi,

I have mounted a thermostat 3 meters from the mains junction box & junction box where the power it then distributed to the heat source, Infra red lamps.

It has a remote probe so I can control the temperature from a different place from where it is measured.

Probe -----------------------------------------

240v ====================== Thermostat  (All in same 4 core 1.5mm SWA)

Heating =================== <<< back to 

I assume the 19AMP rating is for the current passing along one way.

I wondered what the effect of the current going to the stat & coming back along inside the same insulation.

I am guessing it more than halves the safe Amps as the 19 amps is because no heat from external influences whereas if 2 lots in same cable but I did wonder if this situation warrants a slightly different understanding.

I have two of the same but with different power, one with drawn max 6 amps, I figured would be OK, 6x2 = 12amp leaves plenty spare.

But the other could be up to 9 Amps & not so sure of this, I am not going to take any risks of course but more interested than anything else.

Need stranded cable at thermostat & pref keep cable size down as need some flexibility as tricky to connect to stat without stress.

I could use 2 separate 1.5mm but have the 4 core & just think neater.

Thanks I/A

 

[Andy™]

the current would normally return as neutral, so i cant see any problem

 

[Lurch]

You would just de-rate it with the standard bunching factors.

 

[Andy™]

You would just de-rate it with the standard bunching factors.

why? he is extending a switch wire. do you de-rate a light switch wire because it has L & SL in it?

 

[Lurch]

why? he is extending a switch wire. do you de-rate a light switch wire because it has L & SL in it?

No, maybe I misread the OP. I thought he was trying to run 2 circuits down the same SWA? Not entirely sure what he is doing now TBH.

 

[Andy™]

No, maybe I misread the OP. I thought he was trying to run 2 circuits down the same SWA? Not entirely sure what he is doing now TBH.

youve got me thinking that now

 

[kerching]

Not entirely sure what he is doing now TBH.

I fear that you are not on your own in your confusion.....I do not have a clue either

 

[apprentice87]

Hello! I think the same, what he means is he has decided that 1.5 SWA is ok for 19A, but he is running two circuits through the four core because as he says "it is neater" so he has 4 current carrying cores there..

john..

 

[Andy™]

i guess that makes more sense, but dont forget the current rating is for all conductors within the cable being used

 

[bignose2]

Sorry not made it very clear and slightly tricky to explain as I guess not that normal setup because the thermostat control is at a remote location separate from the probe & the Live Feed & Load.

The thermostat requires both L & N 240v feed & the Load with L & N also (not a shared N as I normally see on stats)

So instead of having one cable T&E going to the stat & another T&E coming back & off to the load, it comes back using the other pair in the 4 core.

So the 4 core is made up of a pair feeding L & N to the stat & another pair L & N returning.

Perhaps ignore the thermostat as I guess the same principle

4 core 1.5mm rated 19amps. Red, Black & Brown, Grey.

End (A) Red Live, Black N,

End (B) 3 meters away, join Red & Brown (L) & join Black & Grey (N)

Back to End (A) connect Brown to the Live & Grey N on the heating Load of e.g. 17amps.

Is this OK? I a thinking this can't be rated at the full 19amps

Not quite the same & I know you would not use in such a way but I assume it is not rated 19amp on each pair, e.g. having 19amps Red & Black & same again on Brown and Grey and so this is sort of what I am getting at,

Not sure I have made it any clearer??

 

[Andy™]

itll be fine. if youre that paranoid, use a larger CSA cable

 

[steptoe]

And use a 5 core, 

You need an earth, even if it's not terminated. 

 

[Lurch]

Is the stat DP switching? Sounds like you could do away with the 4th core and common the neutrals at the source. 3c SWA could be used then, or the 4th core could be used for an earth as Steps suggested.