2.5m T&E on a 3.9KW system?

[Easters]

Seen an install on a 3.9KW system with 2.5mm T&E but I have always used 6mm cable for a system that size and never gone below 4mm on any system. But the sparky said he was right and 2.5mm cable was right and if any one thought different they cant be a real sparky. I really want to clear this up as I would not use 2.5mm cable even for 1meter of cable.
Any help weather I am right or wrong would be really great!!

 

[steve Leese]

lots of threads on this already, the sparky is not being very wise in his choice of cable, he will be very lucky if he dos`nt get alot of drop out problems, and conplaints from the customer.

 

[BruceB]

Two avenues to explore if you want reassurance:
- the manufacturers instructions on the quality inverters will tell you to use 4mm2 or 6mm2 (or more) giving maximum circuit lengths for each.
- the 1% calculation will rarely be satisfield with 2.5mm2 unless the inverter is right next to the consumer unit.
Regards
Bruce

 

[mmorse60]

I wouldnt put a 2.5mm on a 3.9 system either

 

[SolarCity]

To be fair, 2.5mm cable on a 3.9kWp system MAY be ok and probably will be on a short system on some inverters. Exactly why anyone would scrimp on a few metres of cable, however, is anyone's guess.

 

[Easters]

Also the fact of running 2 DC strings in 1 isolator and taking the links out I have seen as well. Or running them parallel the same isolator I have seen allot of.

 

[grandfortune]

i sort of agree with the spark, 2.5mm is fine, if your all concerned why dont you all use 16.0mm T&E ??

 

[solartecpv]

Just had a quick run through on Amtech and for a 16A SP&N supply with 2.5 T&E clipped direct, the max length for vd came back at 14.44m.

 

[BruceB]

Is that for 1% V drop?

 

[solartecpv]

Is that for 1% V drop?

Well spotted, I calculated it with the default settings. It should read 8.72m for 1% but I cant edit my post now. Just shows how tight things can be if you dont calculate things properly. I'll put a few more lengths through later and see what cable sizes come back.

 

[cal]

Just to add a little, do those calcs take into consideration the cable going through insulation in the attic (roof or attic floor or cav wall insulation) they all drop the cable value by a fair bit