Wire type and size-need to get this right

[Bluedog225]

Good evening everyone,

I really need to get this right. Any help appreciated.

I’ve got a conex with the inverter and batteries 200 feet from the cabin. Between the two, I have 2” schedule 80 pvc conduit buried at 30 inches. A gentle curve with two 90 degree turns-one at the conex and one at the cabin.

My ultimate plan is two Victron Quattro 48/5000 inverters for split phase to the cabin.

1. Is it 5000 watts divided by 120 volts? Therefore 41.67 amps per line? The spec sheet for the Quattro says “5000 VA.” Then it de-rates to watts. I’m not sure how to translate VA into real world wire size needed.

2. Should I calculate a 3% voltage drop? Or would more conservative be better? 2% or 1%? And do I increase the line length to account for the farthest run in the actual cabin? About 225’. I’m ok planning a lower voltage drop, and spending the extra cash, if it’s going to make a difference.

3. I’m guessing aluminum is fine, ok, good enough? Or is copper going to give me a longer service life? Any other considerations on aluminum versus copper?

4. Line one, line two, neutral, and ground. So 4 wires, right? And I’m reading that THWN separate strands is preferable for ease of pulling. Is this the right call? Or is there an advantage to going with 4 conductor direct burial underground feeder even though it will be inside the conduit?

5. What temperature rating should I look for on the wire?

6. The wire size calculator is asking me “raceway, cable, buried in earth, or open air.” I’m not sure which one to pick as I’m using conduit.

If I can get these pinned down, I can make a decision on the actual wire.

Happy to provide any other information that may be helpful.

Many thanks

 

[Bluedog225]

Edit to add that running high voltage DC to the cabin at this point isn’t really an option.

I’ll have to take my lumps on wire expense. Still cheaper than the $25,000 the utility wanted.

 

[Sennen]

Personally, I'd run for 200a so you never have to risk redoing it all. 2/0 copper 4/0 aluminum

https://up.codes/viewer/texas/nfpa-70-2023/chapter/3/wiring-methods-and-materials#310.12

Your current plan is just under 100a and if you're sure you'll never expand on that or never sell the property, you can eke by on 2ga copper or 1ga aluminum. Now the chart says 4/2, I'd up that for the distance.

 

[Sennen]

Only problem with 4/0 aluminum is you can only stuff 3 of those in 2" conduit

 

[AZ Solar Junkie]

Personally, I'd run for 200a so you never have to risk redoing it all. 2/0 copper 4/0 aluminum

https://up.codes/viewer/texas/nfpa-70-2023/chapter/3/wiring-methods-and-materials#310.12

Your current plan is just under 100a and if you're sure you'll never expand on that or never sell the property, you can eke by on 2ga copper or 1ga aluminum. Now the chart says 4/2, I'd up that for the distance.

Confused because his current plan seem to be 2 hots that are less than 50 amps each. I wouldn’t think he would need to size for 100 amps let alone 200 amps. He could size the wires for 100 amps - 1 AWG copper - and still have room to double the system size if needed.

 

[Sennen]

Confused because his current plan seem to be 2 hots that are less than 50 amps each. I wouldn’t think he would need to size for 100 amps let alone 200 amps. He could size the wires for 100 amps - 1 AWG copper - and still have room to double the system size if needed.

I understood that, and called that out in the latter half of the post. My recommendation of 200a capacity was for future proofing as it's a long, underground run. (In conduit, so easier to rework should the pipes not leak, but that still wastes the original wire cost and time)

 

[Supervstech]

Confused because his current plan seem to be 2 hots that are less than 50 amps each. I wouldn’t think he would need to size for 100 amps let alone 200 amps. He could size the wires for 100 amps - 1 AWG copper - and still have room to double the system size if needed.

True, but a 200A panel is easier to buy, cheaper in many cases, and has room for individual circuits. But that 200A breaker means ya gotta feed it with 200A calculated wire… (no way 4/0 aluminum can handle 200A for long!)
Sure, 125A panels are available and cheap often, but limit the number of circuits you can run.

 

[Supervstech]

Good evening everyone,

I really need to get this right. Any help appreciated.

I’ve got a conex with the inverter and batteries 200 feet from the cabin. Between the two, I have 2” schedule 80 pvc conduit buried at 30 inches. A gentle curve with two 90 degree turns-one at the conex and one at the cabin.

My ultimate plan is two Victron Quattro 48/5000 inverters for split phase to the cabin.

1. Is it 5000 watts divided by 120 volts? Therefore 41.67 amps per line? The spec sheet for the Quattro says “5000 VA.” Then it de-rates to watts. I’m not sure how to translate VA into real world wire size needed.

2. Should I calculate a 3% voltage drop? Or would more conservative be better? 2% or 1%? And do I increase the line length to account for the farthest run in the actual cabin? About 225’. I’m ok planning a lower voltage drop, and spending the extra cash, if it’s going to make a difference.

3. I’m guessing aluminum is fine, ok, good enough? Or is copper going to give me a longer service life? Any other considerations on aluminum versus copper?

4. Line one, line two, neutral, and ground. So 4 wires, right? And I’m reading that THWN separate strands is preferable for ease of pulling. Is this the right call? Or is there an advantage to going with 4 conductor direct burial underground feeder even though it will be inside the conduit?

5. What temperature rating should I look for on the wire?

6. The wire size calculator is asking me “raceway, cable, buried in earth, or open air.” I’m not sure which one to pick as I’m using conduit.

If I can get these pinned down, I can make a decision on the actual wire.

Happy to provide any other information that may be helpful.

Many thanks

In conduit means raceway.
With AC “watts” mean a lot of math and variables based on load types, VA is precisely what the inverter is rated for.
Interchangeable for watts in the basic calculations.

 

[hwy17]

1. Yes, 43 amps.

2. I would make this a 50 amp breaker on the house side, and use 3% drop for 4 CU or 2 AL and then upsize from there based on economy (how cheap it is to get bigger wire). Identify what breakers will be used first so you can check what wire type and size they accept. If I oversized it would be to accommodate potential future inverter size expansion, not cause I'm worried about 3%.

3. I bet the victron calls for CU only so AL will require transitioning in a junction box through probably Polaris taps but you could use split bolts. Compare cost of AL with the Polaris taps to CU only, and weigh your own preference value for having that junctions or not.

4. 4 wires. THHN for sure if pulling in conduit.

5. 90 cause that's what THHN is but your terminations will probably be 75.

6. Use the Southwire calculator it has a non metal conduit option.

 

[hwy17]

4/0 AL is allowed for 200 amp service based on the 83% feeder rule. Probably better not to use the 83% rule in off grid, but if it's the sole service to the house the logic would seem to apply. But we don't have inverters that big anyway.

 

[Bluedog225]

Thanks hwy17. A couple of follow up questions to make sure I understand what you are saying.

1. Got it.

2. Not sure what you mean by “4 CU or 2 AL”

3. Good point on the Victron. I’ve got a 200 amp Siemens main panel in the conex (cheap restore purchase). I’m guessing I can go copper from the Victron to the Siemens, then to the aluminum for the long run. Sound right?

4. #2 mobile home feeder has been suggested. Because it is cheap and readily available. Sounds like you think that would be a bad idea?

5. Got it.

6. Got it.

 

[Sennen]

4CU = 4ga Copper
2AL = 2ga Aluminum

Thanks hwy17. A couple of follow up questions to make sure I understand what you are saying.

2. Not sure what you mean by “4 CU or 2 AL”

 

[Sennen]

You can also get the wire in bundles (4-3, 2/0-3) from your preferred electrical supply company. Given your conduit run, this may be preferred to running individual wires (as a bundle) through the conduit. And remember: There's always time for lube.

 

[AZ Solar Junkie]

You can also get the wire in bundles (4-3, 2/0-3) from your preferred electrical supply company. Given your conduit run, this may be preferred to running individual wires (as a bundle) through the conduit. And remember: There's always time for lube.

BTW what kind of lubricant is safe to not damage the insulation on THHN?

 

[hwy17]

Thanks hwy17. A couple of follow up questions to make sure I understand what you are saying.

1. Got it.

2. Not sure what you mean by “4 CU or 2 AL”

3. Good point on the Victron. I’ve got a 200 amp Siemens main panel in the conex (cheap restore purchase). I’m guessing I can go copper from the Victron to the Siemens, then to the aluminum for the long run. Sound right?

4. #2 mobile home feeder has been suggested. Because it is cheap and readily available. Sounds like you think that would be a bad idea?

5. Got it.

6. Got it.

2. 4awg copper or 2 awg aluminum.

3. Yes good idea. In my opinion get real regular brand aluminum thhn if you use it, Southwire or Cerrowire, and not some off brand online stuff. It's going to be a hard pull and you want the proven stuff. Edit: Oh wait, but check if your Siemens 40 or 50 amp load breaker there is going to accept 2awg aluminum first. It might not.

4. I have adopted the electricians attitude of not considering pulling anything but thhn in conduit myself. So idk, but I think it will end with you hooking the pull string to a truck bumper if you do that. Maybe it will be that way for THHN anyway though.

 

[Sennen]

BTW what kind of lubricant is safe to not damage the insulation on THHN?

https://www.polywater.com/wp-content/uploads/2022/01/Polywater_J_TDS.pdf

 

[Bluedog225]

Does something like Klein damage insulation? I thought it was safe for all wire.

 

[Bluedog225]

I must be doing something wrong here. Why is it recommending 1/0 wire?

 

[Sennen]

Aluminum wire. Switching to Copper puts you in 2 gauge.

 

[hwy17]

I must be doing something wrong here. Why is it recommending 1/0 wire?

You have it set to 120 and I have it set to 240 but it's sort of doing my head in right now to justify why or if we get to use the 240v calculation for feeder voltage drop even though they can carry 120v currents at full amperage. Maybe we just don't typically expect that much of an imbalance so we tolerate higher potential voltage drop in that scenario.

Wait for @timselectric or another expert to clarify here.