Question on Trenching and Materials

[Mr onetwo]

Good morning all,
I am starting a project on my new 30ac property out in the countryside and I have a couple of questions concerning getting power up to a remote location from my new future shop. A shipping container cabin is going to be set up on top of a fairly steep hill about 350ft feet from the panel in the shop.I am going to plan on a 40amp sub-panel in the cabin.Considering the material and labor cost of using pvc I want to use 1" 100lb black poly water pipe instead.There is no electrical code or inspection in this area... just a building, septic and plumbing permit. Is there any reason why this won't work and what aluminum wires would you use for this purpose? Thanks

 

[Stuart in MN]

While there may not be local inspections, the state of Maine does require you follow the 2020 edition of the National Electric Code. If budget is a driving factor, check pricing on direct bury cable instead of using conduit. You'll also need to consider voltage drop because of the distance.

 

[PCustoms]

It's not code/rated for electric.

It's probably going to **** (black poly is soft and wire can hang up).

35 sticks of 1.5" conduit is only $440. This will fit #1 aluminum wire. Looks like wire is $600-700 depending on if you reduce neutral

 

[Loud Lyle]

Tray cable would probably work for you it’s direct bury rated.

 

[PCustoms]

Tray cable would probably work for you it’s direct bury rated.

They make direct burray cable rated/designed for this application.

Unless the op site is on a gravel deposit, which is possible, I would not recommend direct bury in the state of Maine

 

[Innovate1]

It's not code/rated for electric.

It's probably going to **** (black poly is soft and wire can hang up).

10 sticks of 1.5" conduit is only $440. This will fit #1 aluminum wire. Looks like wire is $600-700 depending on if you reduce neutral

Did you mistype that? 10 sticks is only 100 feet and it shouldn't be $44 a stick. Even if you are figuring 20' "sticks" it doesn't add up. They need 35 pieces of 10' for garage to cabin. And more for meter to garage if that is buried too. I'm totally confused about price. Looks like the local big box stores are about $17 for 10' of 1.5"! Some of the electrical supplies show much less on google but I didn't drill down to check it out.

For voltage drop of 3% they need #1 aluminum. #2 gives 3.6% drop which would work.

 

[Bert_]

If you use direct bury wire the the poly would not break any codes for the underground portion at least.

I often use foam core plumbing PVC to protect direct bury wire. The wire does not require conduit so if it needs to be protected anything can be used.

Direct bury wire does need to be in conduit above ground. So you need to switch back to an actual conduit. That's another reason why I like the foam core PVC. The pipes are the same size so it's easy to change back and forth from conduit.

 

[mm08822]

Have you considered adding sand or stone dust to the open trench?

This could eliminate any conduit and you just lay the conductors into the trench.

 

[PCustoms]

Did you mistype that? 10 sticks is only 100 feet and it shouldn't be $44 a stick.

I did mistype that, I had 35 sticks in my home Depot shopping cart in Augusta Maine. The total was correct

 

[Mr onetwo]

Back in the day (I'm old) everyone in the back country up here used well pipe for buried service because it was cheap

 

[PCustoms]

Back in the day (I'm old) everyone in the back country up here used well pipe for buried service because it was cheap

Where in Maine is "up here"?

By well pipe do you mean black poly?

Everytime I've dealt with direct bury in Maine it's either been a problem or over trenched and buried in so much sand they should have just paid for conduit.

What size poly pipe would you use? Does it come in 350' rolls? How much?

 

[Mr onetwo]

Have you considered adding sand or stone dust to the open trench?

This could eliminate any conduit and you just lay the conductors into the trench.

I am going to have a trench open for water anyway and can't see not using conduit of some kind

 

[tarmy]

I had several 200’-500’ runs. Once the trench was open I buried 3 extra conduit, a 2”water line and propane line. Years went by and I have used all of them. Just a thought OP.

 

[beltfeed]

350 foot is a long run for 1" plastic. It would be a lot easier to pull that through 2".

 

[PCustoms]

350 foot is a long run for 1" plastic. It would be a lot easier to pull that through 2".

Conduit or water pipe?

I asked OP several questions and no replies. But I still think <$500 for the correct conduit probably isn't much more then the roll of black poly

 

[Mr onetwo]

Where in Maine is "up here"?

By well pipe do you mean black poly?

Everytime I've dealt with direct bury in Maine it's either been a problem or over trenched and buried in so much sand they should have just paid for conduit.

What size poly pipe would you use? Does it come in 350' rolls? How much?

Anywhere in "rural" Maine

SDR-11 100lb HDPE poly pipe....300ft,500ft,1000ft

poly or conduit it will be 1 1/2"

 

[beltfeed]

PCustoms, Conduit. I just put in a new 400-amp service that goes 375 feet to a meter pedestal. I had to run 3" for the poco. My system splits at the meter pedestal into two 200-amp feeds, one to my house and one to the shop. I used 3" conduit for the 200-amp feeds also. They are about 175' runs each. Bigger conduit costs more but it sure helps pulling service wire in it.

 

[PCustoms]

Anywhere in "rural" Maine

SDR-11 100lb HDPE poly pipe

poly or conduit it will be 1 1/2"

I spent a lot of my life in Maine.

Good chance my definition of rural is different then your definition of "rural". Unless you're building a secret off grid compound I don't see the harm in mentioning a town...

 

[Mr onetwo]

Sorry, I have been doing my research to properly sus this out.It turns out in this day and age poly is basically the same price ($420)...no savings.I may say screw it and just direct bury MHF. My next question is can I use 2-2-4-6 for this or 2-2-2-4? The only 240v load will be the smallest size mini split I can find and some sort of water heater.This cabin will only be used late spring until late fall.

Attachments​

 

[PCustoms]

Anywhere in "rural" Maine

SDR-11 100lb HDPE poly pipe

poly or conduit it will be 1 1/2"

Looks like that pipe is over $1/ft, so there goes at least $400 (assuming you buy in 100' rolls). Not sure how you would join the lengths and still pull wire either...

 

[acer66]

Conduit or water pipe?

I asked OP several questions and no replies. But I still think <$500 for the correct conduit probably isn't much more then the roll of black poly

I also think running the wire in pvc is cheap insurance.

 

[Mr onetwo]

I spent a lot of my life in Maine.

Good chance my definition of rural is different then your definition of "rural". Unless you're building a secret off grid compound I don't see the harm in mentioning a town...

If I tell yah, I'll have tah kill yah

 

[PCustoms]

Sorry, I have been doing my research to properly sus this out.It turns out in this day and age poly is basically the same price...no savings.I may say screw it and just direct bury MHF. My next question is can I use 2-2-4-6 for this or 2-2-2-4? The only 240v load will be the smallest size mini split I can find and some sort of water heater.This cabin will only be used late spring until late fall.

I think the smallest size 240v mini split I saw last year was 18k btu, the 12k were 120v.

My gut says 2/2/4/6 is OK but technically you're supposed to run the calc.

 

[mm08822]

If I tell yah, I'll have tah kill yah

He's close to Waterville. Stake it out that HD and follow the next guy buying 36 lengths of 1.5" pvc conduit.

 

[mm08822]

Plan on a pull box mid run.

 

[Bert_]

I get 1 1/2" foam core PVC for about 50 cents a foot. 2" is what I use the most, 65 cents a foot.

20' sticks go together quick. Can glue an electrical 90* right to it and easy to change the electrical PVC to go above ground.

 

[Mr onetwo]

I get 1 1/2" foam core PVC for about 50 cents a foot. 2" is what I use the most, 65 cents a foot.

20' sticks go together quick. Can glue an electrical 90* right to it and easy to change the electrical PVC to go above ground.

Technically not code worthy and foam core is very prone to punctures from rock. It is forbidden underground in the plumbing code for that reason.Also I don't think you could use a blanket on it to bend a sweep.

 

[PCustoms]

Technically not code worthy

And black poly is?

 

[Bert_]

Technically not code worthy and foam core is very prone to punctures from rock. It is forbidden underground in the plumbing code for that reason.Also I don't think you could use a blanket on it to bend a sweep.

There is nothing in the electrical code that prohibits it when you run a direct bury rated wire.

Direct bury cable does not require conduit. So if you choose to protect it you can you use whatever you want.

 

[Mr onetwo]

I think the smallest size 240v mini split I saw last year was 18k btu, the 12k were 120v.

My gut says 2/2/4/6 is OK but technically you're supposed to run the calc.

There's a bunch of 208/240V 9K units out there with a SEER of over 20. They draw around 7.5 amps typically.

 

[Mr onetwo]

There is nothing in the electrical code that prohibits it when you run a direct bury rated wire.

Direct bury cable does not require conduit. So if you choose to protect it you can you use whatever you want.

I was not aware...thank you. Foam core can be had in 20ft sticks...I am going to check it out next week.

 

[Mr onetwo]

And black poly is?

No it is not.However the original premise of saving money and no couplings is moot...same price basically. I will investigate price and availability of 1 1/2" x 20ft foam core...maybe I can save a few bucks.Can fiber be run safely in the same conduit?

 

[Norcal]

There is nothing in the electrical code that prohibits it when you run a direct bury rated wire.

Direct bury cable does not require conduit. So if you choose to protect it you can you use whatever you want.

Due to a incident many years ago, I get real pissy about electrical cables in white PVC. There is P&C duct that would work quite well & is gray.

 

[Mr onetwo]

Are you referring to DB60?

 

[wyliesdiesels]

Sorry, I have been doing my research to properly sus this out.It turns out in this day and age poly is basically the same price ($420)...no savings.I may say screw it and just direct bury MHF. My next question is can I use 2-2-4-6 for this or 2-2-2-4? The only 240v load will be the smallest size mini split I can find and some sort of water heater.This cabin will only be used late spring until late fall.

Attachments​

when i do the calcs by hand for #2 AL 40a @ 350' i get 8.4v or 3.5% drop

 

[PCustoms]

when i do the calcs by hand for #2 AL 40a @ 350' i get 8.4v or 3.5% drop

So with that calc, what would you run?

 

[wyliesdiesels]

So with that calc, what would you run?

If the anticipated load will never be more than 40-50a should be fine with #2.

Otherwise, id run #1 or 1/0 if theres a possibility of larger loads

 

[PCustoms]

If the anticipated load will never be more than 40-50a should be fine with #2.

Otherwise, id run #1 or 1/0 if theres a possibility of larger loads

Kind of where I was thinking, cheap to do now

 

[Mr onetwo]

There will be a 2 burner Empava induction cooktop which draws 1800 watts @120v, a small Vissani fridge that draws less than 1 amp,split draws less than 8 amps,lighting is negligible, fan on composting toilet. Perhaps a GE Profile heat pump washer/dryer combination unit (11 amps@120v). The water heater is all that is left to figure out.Is anyone aware of a small heat pump water heater? 40 gallon way too big.

 

[Mr onetwo]

Is it ok to run 2-2-4-6 instead of 2-2-2-4?