quick response please, wire sizes, need to figure out by Monday

heynow999 · March 2009

Hi

My problem is I have to run a wire for a solar array on Monday. The house is under construction and the drywall is going up on monday so I basically have to figure out what wire I need and install it first thing monday morning.

It is a 3 story house and we want to put a 2 kw solar array on the roof. It will be 10 x Evergreen 190's or similar. It will be grid tied with a Fronius or Sunny boy inverter. A quick check on the Fronius website gives me this

Optimal Configuration!
Number of Strings: 1
Number of Modules per String: 10
Maximum String Current: 7.2 A
Maximum PV Current: 7.2 A
Maximum Voc according to NEC: 383.8 V

So what size and type of wire would I need to run from the array on the roof to the inverter 50 feet away on the side of the house? I guess we need to run a ground wire as well? Is solid copper wire ok? We had a peice of #10 we were going to use but it says 300 volts on it. Can we run the wire through the house like typical AC wireing? Should we run the ground through it's own hole?

We are just trying to get into the business so we want to be cautious. We have gotten some opinions from other solar guys and an electrician, but the industry here in Canada is not mature yet, and it is hard to find solid answers

All input is appreciated

Thanks

Peter

mike95490 · March 2009

Re: quick response please, wire sizes, need to figure out by Monday

10 gauge would be fine, but I my grid-tie case, it needed to be 600V rated, and in condouit, so nobody would think it was 120VAC.

Your local codes should spell out what's needed.

From what I recall, it needs to be:
600V insulation
Waterproof
UV rated

Gauge depends on your amps & distance.

homerramirez · March 2009

Re: quick response please, wire sizes, need to figure out by Monday

Check the approved plans of the installation, it will give you details about voltage and ampacity, schematics for wiring and location, use the NEC for wire size , remember to make up for voltage drop and if run with more than 3 conductors, adjust or correct, if you never been in class for journeyman or master electrician, it could be a little hard to interpret the NEC...

good luck.:cool:

n3qik · March 2009

Re: quick response please, wire sizes, need to figure out by Monday

Another potential problem would be if a roof penetration is allowed before to the first disconnect/fuse.

If you do, do it, run the wires inside a metal conduit.

heynow999 · March 2009

Re: quick response please, wire sizes, need to figure out by Monday

thanks

There are no plans, at this point it is just roughing in the wire so they can do it later if they choose to.

About the fuse/disconnect, what we understand is that the inspectors want all of the equipement/switches where they can see them without having to climb on a roof, so I guess that means the disconnect will go on the wall beside the inverter and the meter. That makes good sense about running it in a pipe. We originally planned to run a pvc conduit when we gave a quote, then the builder calls us today and says we need the wire run for Monday. No proper roof penetrations are in place, they want us to run it out an attic vent. Frankly I think we should pass on it. Please keep the ideas coming.

How about the ground wire?

Solar Guppy · March 2009

Re: quick response please, wire sizes, need to figure out by Monday

Wire has to be in metal conduit from the roof penetration to the inverter input, you can't just put wires for PV behind the drywall.

Also, any electrical requires permits, if new construction, then the PV must be on the plans so the inspector knows its there and what it is for.

halfcrazy · March 2009

Re: quick response please, wire sizes, need to figure out by Monday

First if code allows pvc then go for it it is a lot easier to run then metal. Our code here requires metal conduit.
Second dont let the builder push you around do this right the first time and make the proper roof penetrations. Dont give your self a bad name doing a cutrate job just to passify the builder

PS Solar Guppy he is in Canada so i dont know what there code is? They may be exempt from John Wiles

niel · March 2009

Re: quick response please, wire sizes, need to figure out by Monday

this is after the fact, but why just size it for a 2kw array when you should always run more than you would need for possible future expansions? it is easier to run it now than later and is why i assume you are doing it now in the first place. as far as losses go, there is a voltage drop calculator here on the forum that would tell you by plugging in values just what wire you might wish to go for. it is in the sticky in the general solar topics section of the forum and has been there for a long time. the question would be what voltage drop percentage are you after? at the time of the calculator's creation 3% was the goal for pv to batteries. outback specifies 2% and you can go even lower if you can afford the extra cost in thick copper wire. though the calculator is setup for battery systems, it can calculate losses in high voltage systems and you'd still want to stay within those percentages up to the inverter and is easier to do with smaller wire sizes in hv systems.

quick response please, wire sizes, need to figure out by Monday

Comments

Categories