PVWire all the way to the inverter or splice

[Cheese_boy]

What do you do more often?
Run PVWire from the panels to the inverter, or splice/join in a box and then THHN/THWN to go back to the inverter?

I favor PVWire all the way if feasible. More expensive for the wire, but fewer connections to be made and I think fewer potential points of failure.

 

[SolarPro]

Okay. You can do that, and you're not alone. Just be aware that spending more money that is required on hardware doesn't scale very well to larger systems.

Most PV installation companies transition to THWN-2 as close as possible or practical to the array, and use THWN-2 in conduit between the combiner or transition box and the inverter. If you torque your connections properly and put a commissioning program in place, you should't have problems with these mechanical connections.

 

[ggunn]

What do you do more often?
Run PVWire from the panels to the inverter, or splice/join in a box and then THHN/THWN to go back to the inverter?

I favor PVWire all the way if feasible. More expensive for the wire, but fewer connections to be made and I think fewer potential points of failure.

It depends on the architecture of your system. If the inverter(s) is/are right next to your array and you aren't combining strings, then it might be best to run the PV wire all the way, but if the inverter(s) are a long DC run away, then it usually makes sense to transition to THWN-2.

 

[jaggedben]

We always transition.

I've seen it done otherwise but I don't see it saving much time and expense. Especially with more than one circuit. It gets ridiculous to pull more than a couple PV wire conductors through a conduit.

A Buchanan splice is unlikely to fail.

 

[Zee]

What they said.

Also:
Consider wire, sure. However, also consider conduit size in terms of extra work and cost. It' s been a while since I used larger than 1/2" EMT!:roll:

Before, I used to run USE-2 straight thru.

Now, with PV Wire available, I always use it. It is thicker====> Will a circuit fit in 1/2" EMT?
Will 2?
Splicing used to add ugliness too... a big ole box next to a clean modern array. Now, Soladeck boxes hide neatly under arrays, so i have been splicing for years now.

That said...... if array was right above MSP and Inverter..... i would likely drop the PV Wire straight thru.

 

[ggunn]

What they said.

Also:
Consider wire, sure. However, also consider conduit size in terms of extra work and cost. It' s been a while since I used larger than 1/2" EMT!:roll:

Good point; the conduit fill tables don't have numbers for PV wire and PV wire is significantly larger than the same gauge THHN-2.

 

[jtopham26]

PV wire is often classified as RHW-2 as I recall on a datasheet. possibly southwire

 

[Carultch]

PV wire is often classified as RHW-2 as I recall on a datasheet. possibly southwire

PV Wire is a listed standard for the application, although there is no standard diameter for this wire type. PV Wire can be classified dual USE-2 or RHW-2 or both, but the reverse isn't necessarily true.

 

[ggunn]

PV Wire is a listed standard for the application, although there is no standard diameter for this wire type.

Right. For conduit fill you have to look up the specs on the wire you are using and do the calculation by hand. Or of course you could compare the specs to those of other conductors that are in the fill tables and look up the fill rate for a conductor the same size or larger.

 

[Carultch]

Right. For conduit fill you have to look up the specs on the wire you are using and do the calculation by hand. Or of course you could compare the specs to those of other conductors that are in the fill tables and look up the fill rate for a conductor the same size or larger.

I added the data from Encore's datasheets onto my conduit sizer spreadsheet. Encore wire is the most common PV wire that is available in my area.

And in our drawings, I write the note that "PV Wire" refers to Encore products, and the use of other manufacturer's wire may affect conduit size calculations.