Allowed to run Direct Burial wire in Flex Liquid Tight Conduit

[DIYSolarShed]

Is it generally allowed to run this sort of wire inside Flexible Liquid Tight Conduit? From the PV panels to the Inverter?

https://www.amazon.com/gp/product/B083LC3SCZ/

Once it enters the structure, does it need to transition to metal conduit? https://forum.solar-electric.com/discussion/10267/solar-wiring-and-conduits-inside-the-wall ?

 

[DIYSolarShed]

Also, does the flexible liquid tight conduit meet this requirement:

690.31(A) Wiring Systems.

New Table 690.31(A) provides ambient temperature correction factors for PV source and output circuits.

www.electricallicenserenewal.com

690.31 Where PV source and output circuits operating at voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be guarded or installed in Type MC cable or in raceway.

HYDROMAXX 1 in. Dia x 25 ft. Non Metallic UL Liquid Tight Electrical Conduit Kit with 2 Straight and 2 Angle Fittings Included 4105100025K - The Home Depot

This Flexible, Non-Metallic PVC Liquid Tight conduit, commonly referred to as NM Liquid Tight, flexible conduit, Non-Metallic PVC, Flex PVC and PVC Electrical Conduit is perfect for use in multiple applications

www.homedepot.com

Here is the product.

 

[newbostonconst]

In the electrical component use thing, it some times helps to read the UL listing on the packaging. This will give you insight to what instances it was certified to be used in. Wire in conduit usually needs to be rated for wet conditions.

All of your components are supposed to be UL listed.

I think I would transition to a standard wire that is pulled through conduit like THWN. But even in the building THWN has to remain in conduit where NM-B doesn't.

I know I didn't answer your questions but most electricians wire in a certain way that the inspectors are used to and if you don't they may fail you even though you wired it correctly, just because they are not used to it. Then you may fight with them and that just isn't a good way to go.

I would transition from PV wire to THWN in the disconnect located at the panels, then either stay in conduit all the way to your panel or transition to NM-B if you like once inside the house.

 

[newbostonconst]

I am not an electrician but do have my builders license and have built 2 houses for myself. I am an electrical industrial engineer and we wire everything in conduit with THWN.....It is just easier to do everything the same way.

Good Luck.

 

[DIYSolarShed]

What's the easiest/proper way to transition from MC4 cable coming off the panels to THWN "out in the field" -- this is ground mount.

Edit: I see you said to transition at the disconnect. Can you link me to the product you normally use? Most disconnects I've found seem to only be AC rated. This would be DC for ~150 ft back to the house.

Would I need something like this: https://www.zoro.com/siemens-solar-disconnect-switch-1110-in-h-hnf361rpv/i/G8495864/ ?

Thanks!

 

[newbostonconst]

Can you give more info? Do you know your string voltage (how many panels and their voltage) Just one string or multiple? How big of an array?

 

[DIYSolarShed]

One string is ~270v voc with 12 of these panels: https://www.amazon.com/RICH-SOLAR-Premium-Monocrystalline-Solar/dp/B086ZL9PM8

The other one is ~381v voc 8x of these: https://www.solaris-shop.com/solaria-powerxt-370r-pd-370w-mono-solar-panel/

Distances to the inverter is about 150ft for the 12 smaller panels, and about 65ft for the larger panels.

I was planning to run this in non metal liquid tight conduit from each of the panels to the house, and then metal conduit into the house: https://www.amazon.com/gp/product/B083LC3SCZ/

 

[DIYSolarShed]

The wire is rated RHW-2 or USE-2 if that means anything about the conduit?

 

[BobH]

Assuming you are in the US and your local building codes follow NEC 2017, the wire entering the building is DC and over 30 volts. Therefore, it needs to be in metal. MC cable, separate THWN/XHHW wires inside EMT, FMC, or Liquid Tight FMC.

Wiring inside your attic/building carrying your solar DC would not meet NEC 2017 code if it was inside Non-Metal Conduit. At least not where I live.

Most installers use a pass through box like a Soladeck or Roof_Tech REB (w/ an interior attic junction box) to transition from the PV (USE-2) wires to THNW-2 or similar. They then continue the run inside the attic with EMT, FMC or MC (or a combination of them) to the inverter.

 

[newbostonconst]

BobH he is doing a ground mount. I do agree with what you said though....thanks for typing it out and clear.

Can you mount the inverters under the panels (are they nema rated)?. This way you can use cheap home depot disconnects as a junction box and to convert between wire types. You can get disconnects with fuses also which is the most simple way to go because technically energy can flow in both directions in solar.

 

[BobH]

Watch some Engineer775 & Gains Solar youtube videos. They install ground mounts & roof mounts all the time and go over most of the best practices. They have a couple of good videos on "what not to do" as well, based on the rework they were hired to fix.

 

[DIYSolarShed]

Assuming you are in the US and your local building codes follow NEC 2017, the wire entering the building is DC and over 30 volts. Therefore, it needs to be in metal. MC cable, separate THWN/XHHW wires inside EMT, FMC, or Liquid Tight FMC.

Wiring inside your attic/building carrying your solar DC would not meet NEC 2017 code if it was inside Non-Metal Conduit. At least not where I live.

Most installers use a pass through box like a Soladeck or Roof_Tech REB (w/ an interior attic junction box) to transition from the PV (USE-2) wires to THNW-2 or similar. They then continue the run inside the attic with EMT, FMC or MC (or a combination of them) to the inverter.

Thanks BobH that is helpful. If the wire I want to use is dual USE-2 and RHW-2, would it be possible to simply transition into metal conduit as I enter the house without using the Soladeck box/bus bar? Or does it have to be THNW-2 specifically in the house/garage?

 

[newbostonconst]

Yes, you can transition that way. Most use a "LB connector"

Your panels are about $1 per watt....I can usually get them for $.50 per watt plus shipping. FYI.... Depending on your location.

 

[DIYSolarShed]

I had very specific aesthetic/size requirements for the panels... I know they are expensive

Thanks again -- this was all very helpful!

 

[newbostonconst]

They aren't that bad, I have seen a lot worse.

 

[BobH]

The best practices I have seen would use an IMO DC Disconnect box - https://www.industrialcontroldirect.com/solar-energy-solutions-267/solar-dc-power-disconnect-268/ (or similar) mounted at the ground mount for each string. The USE-2 PV wire goes into the DC disconnect and then THNW-2 wire comes out into a PVC conduit and going through buried pvc conduit to a PVC LB or junction box on the outside of the house. Then a short section of EMT conduit or Liq. Tight FMC through the house wall using a rain tight fitting out of the LB/Junction Box. Once in the house, EMT connects into a wiring trough and then goes from the wiring trough to the inverter. The wiring trough makes a great cable management system for the A/C disconnect(s), Critical Loads panel(s), generator feed lines, Main panel lines to the sol-ark/inverter, battery cables, etc. The troughs aren't cheap, but they sure make all the wire management easy & even simpler for future mods or upgrades.\

Some jurisdictions might require disconnect switches at both the ground mount and the house entry if it's not inline of sight from each other or more than a certain distance. I think it might be 50 ft, but I don't remember.

 

[newbostonconst]

Ours requires a disconnect by the meter.

 

[DIYSolarShed]

The best practices I have seen would use an IMO DC Disconnect box - https://www.industrialcontroldirect.com/solar-energy-solutions-267/solar-dc-power-disconnect-268/ (or similar) mounted at the ground mount for each string. The USE-2 PV wire goes into the DC disconnect and then THNW-2 wire comes out into a PVC conduit and going through buried pvc conduit to a PVC LB or junction box on the outside of the house. Then a short section of EMT conduit or Liq. Tight FMC through the house wall using a rain tight fitting out of the LB/Junction Box. Once in the house, EMT connects into a wiring trough and then goes from the wiring trough to the inverter. The wiring trough makes a great cable management system for the A/C disconnect(s), Critical Loads panel(s), generator feed lines, Main panel lines to the sol-ark/inverter, battery cables, etc. The troughs aren't cheap, but they sure make all the wire management easy & even simpler for future mods or upgrades.\

Some jurisdictions might require disconnect switches at both the ground mount and the house entry if it's not inline of sight from each other or more than a certain distance. I think it might be 50 ft, but I don't remember.

Bob, that link is very helpful.

Can you tell me if one of those boxes can support multiple independent (not parallel or series) strings?

My Sol-Ark has two MPPT controllers. Or would I need two separate boxes for that scenario?

 

[BobH]

You'll have to consult your inverter PV input specs. for the allowed string Voc & Isc. If it was me, I would want the capability to shutdown each string individually for maintenance or troubleshooting at each array. The IMO's come in 2 pole, 4 pole, and all kinds of string combinations for amperage (16, 25, 32 & more) Click on the IMO link and select one of the listed disconnects. Scroll down to the bottom of the product page and there is a table with all the pole/string combo's along with the available amperage & DC voltage ratings.

Based on a quick glance at your panel specs, 2 of the the IMO SI16-PEL64R-2 would work. The smaller wattage string (100)W has a amperage of ~6A if connected in series and the other larger panels (370W) have ~10A if connected in series. Each string falls well under the 16A disconnect amperage & the 800V DC max rating of the IMO IMO SI16-PEL64R-2. If your local code requires the disconnects be mounted outside the house near your power panel, then you might want 4 in total (2 disconnects at the outside of the house & 1 at each array.)

Here are the allowed connections specifics for the Sol-Ark 12based on their manual (page 9)...

10. Solar Panel Install

1. Sol-Ark 12K has 2 separate pairs of solar panel inputs. (Dual MPPT)
3. Max PV input: 13,000W(+/- 5%) per system (6,500W per MPPT) PV = 500Voc Max
Max Isc input per MPPT: 25A (self-limiting to 20A @450Voc/300Vmp or 18A @ 500Voc/400Vmp)
Note: Damage will occur if PV Voc > 550V.
4. Connect the strings of solar panels to the system as shown on pages 9/10.

As for the hydromaxx non-metal liquid tight (in your original post) as the conduit from the array mount to the house, I would seriously look at Sched 40 pvc electrical conduit if buried in open ground or Sch 80 if it goes under a driveway or other path that would see vehicles driving over it. The 1" Hydromaxx is $51 for 25 ft. Sched 40 Electrical PVC 1-1/2" dia would be less than $20 for the same 25ft length. There would only be 2 conductors & a ground wire from each array, so there's plenty of room in a 1-1/2" pvc conduit. Most installers use 2" pvc, since pvc is cheap and there's always room for expansion or pulling cables for other purposes (security cameras, yard lights, etc). Digging the trenches costs more than the pipe, by far, so over sizing the pipe is a no brainer.

I guess it all comes down to conduit costs vs. wire costs vs dc disconnect hardware location. 10 AWG THWN-2 can be found for .22 cents per foot, while 10 awg PV wire is .28 cents per foot. Not much of price difference really for a 500 ft spool. (www.wireandcableyourway.com)

 

[Hedges]

What's the easiest/proper way to transition from MC4 cable coming off the panels to THWN "out in the field" -- this is ground mount.

Edit: I see you said to transition at the disconnect. Can you link me to the product you normally use? Most disconnects I've found seem to only be AC rated. This would be DC for ~150 ft back to the house.

Would I need something like this: https://www.zoro.com/siemens-solar-disconnect-switch-1110-in-h-hnf361rpv/i/G8495864/ ?

Thanks!

I have rigid conduit from combiner box at house fanning out to multiple ground mount arrays. There is a waterproof box at each array and MC pigtail wires coming out of them to connect PV strings. Inside the box, MC joins to 12 awg THHN with wire nuts or "Ideal" setscrew type nuts. I run each strings separately back to the combiner box.

You can probably use PVC conduit (or flexible) if buried deep enough, like 18" vs. 12" for rigid. I originally had PVC surface-mounted for part of the length and inspector didn't like that, so changed to rigid.