What spec cable for a long DC run?

[Grinnders]

About to have a roof installation done for some SANYO HIT235SE PANELS and a SUNNYBOY inverter.

I want the inverter to be located next to the consumer unit in the integral garage. The gable end of my house is almost directly in line.

I had assumed the cable would run down the outside of the house and because of the length of the run (2 stories) know I need a higher spec cable than if the inverter was in the loft. What would you recommend?

The installer is suggesting 4mm and has made the assumption that the cable will run through floors on the inside of the house.

1. Is 4mm enough?
2. Is there a technical reason for running the DC cable inside the house rather than the outside?

Many thanks

 

[BruceB]

Put the setup into sunny design and see what it says. 4mm on the dc side will normally do quite a long way.
Outside or inside - whatever is the best combination of short, protected from damage and aesthetically pleasing. You can always run it in SWA if it needs a bit more protection.
Regards
Bruce

 

[Grinnders]

Thanks... what is SWA in this context. I did google it and found that Products sell all sorts of electrical components. I'm not doing the install myself, I'm the customer. However I've had a bash at 20ft of 4mm on two strings and it says my rel. power loss is 0.08% and 0.07% (8W and 9E panels respectively) which according to the green ticks may suggest that's okay. Regards

 

[flamefix]

yeah anything under 1% is fine.

 

[powervan]

out of intrest y not in loft? always best to keep dc cables short as poss! sunny beam in kitchen! never have to go in loft to touch inverta! sma sunny boy loves lofts!

 

[Grinnders]

I've read on here that having good acess to the inverter can be quite useful and I plan to use sunny explorer (bluetooth) software on my PC (rather than the hand held monitor) so I can regularly download data wirelessly.

 

[moggy1968]

I am always reluctant to run DC under floors, in fact I never have, because of the lack of fuses ir MCBs if the cable is damaged, especially given the voltages involved and the tendancy for DC to arc. my preference is always to run outside in conduit unless it is in the loft

 

[BruceB]

SWA is steel wire armoured cable.

 

[Grinnders]

Thanks for the explanation Bruce and as the obvious wall to run the cable to the garage is a side wall which is dead space to me and my immediate neighbour (and it's got my massive 1.1m satellite dish hanging off it) I'm not too precious about it being aesthetically discreet.

 

[Noshocks]

I wouldent run DC cables through house, your first thought is correct, get installer to run in conduit down gable wall, quick and safe and looks tidy.