Underground service longevity

[bluedog225]

I’ve been resigned to not having electric service at my cabin/shop for a while. But I’m putting in a waterline and the guy who’s doing it is an electrician. Waterline is a side gig.

I’ve got a pole and transformer at the front of the property. He’s going to give me a price on running an underground feeder to my cabin. About 800 feet. I’d be fine with 100 amps at 120 volts.

I realize aluminum is gonna be cheaper. My real question is what’s the expected service life of copper versus aluminum?

It’s not going to be cheap to do this once. I really don’t want to do it twice.

Thanks

 

[mike93lx]

Longer than you will be alive. Physical damage is the only real concern, so conduit is never a bad decision

There is no way I would even be remotely considering copper at 800 ft.

50a at 240v is the same power as 100a at 120v but uses much thinner wire. Why would you only want 120v service?

 

[bluedog225]

I don’t need much power. Small place. I was thinking fewer watts needed, less ampacity, smaller/cheaper wire.

Sounds like alu is the smart move.

 

[bluedog225]

Edit-I do understand the 240 volt advantage. Was just trying to indicate the modest need for power.

 

[mike93lx]

Edit-I do understand the 240 volt advantage. Was just trying to indicate the modest need for power.

Understood.

Is there a meter at this pole already?

 

[bluedog225]

There was. The meter loop(?) is shot. A line, transformer, and pole.

 

[bluedog225]

When 240 volt is run a distance like this, is it run on 2 lines? Instead of phase A and phase B?

And then needs a transformer at the shop?

I ask because the buzz of a transformer might be a problem 24/7.

 

[wyliesdiesels]

what are your intended loads? 800' of wire gonna be pricey

 

[wyliesdiesels]

When 240 volt is run a distance like this, is it run on 2 lines? Instead of phase A and phase B?

And then needs a transformer at the shop?

I ask because the buzz of a transformer might be a problem 24/7.

240v is achieved with 2 phase legs 180* opposite each other. phase a and phase b can describe them. no you dont need a transformer. you would however need to run a ground wire as well. if you want 120v also, you would need to run a 4th wire which would be the neutral conductor.

look at the diagrams in post #3 on the electrical FAQs in the link below. it will show you the feeder needed for a detached building

Electrical FAQs

Welcome All I have started this sticky as an FAQ thread for info on the basics that are encountered countless times every week on here. Hopefully this will help some. If u have a topic request, go ahead and post it. And if you have an FAQ you would like covered let me know.... Or if you...

www.garagejournal.com

 

[bluedog225]

Air conditioning is main load, 2-3 mini splits at 1000 watts (?) each, then lighting, and misc household loads.

 

[wyliesdiesels]

so you need a 4-wire feeder.

2-3 mini splits is gonna be more than 1000w. those are usually 10-15a each and @ 240v.

 

[bluedog225]

I’m surprised at those numbers. Thought they were more efficient.

 

[wyliesdiesels]

I’m surprised at those numbers. Thought they were more efficient.

pull up the manual for a mini-split. they pull more than 4a @ 240v (1000w)

 

[bluedog225]

Checked a couple of random websites. Got numbers like this. I was thinking 12,000 btu units.

 

[wyliesdiesels]

how about pulling up the specs on the actual mini-split you have or are buying? thats an avg over 272 units and i dont think its accurate

 

[mm08822]

The minimum service size permitted by NEC is 100A. If the meter is kept at the pole you may be able to get away with running a smaller feeder to the cabin.

At 800' you may want to consider running two transformers at 600v between pole and cabin. Step back down to 120/240v. Transformers won't be cheap but they will offset the cost off wire. For 100a service, using transformers is ~$12k vs. ~$20k just to get wire up to the cabin.

Can the POCO do anything for you and at what price?

At 800ft, you need to be concerned with motor start-up inrush, not just the full load amps.

 

[BillK]

I realize aluminum is gonna be cheaper. My real question is what’s the expected service life of copper versus aluminum?

My house was built in 1978. That means the underground feeder is 45 years old and it is aluminum. I cannot think of anyone I know that has had a feeder fail in our area and everything is underground. I would stop worrying

 

[bluedog225]

Thanks for the wire estimate. That’s up there.

The POCO estimated about $25,000 and a 30’ cleared easement around the overhead line. Not going that way due to cost and aesthetics.

I’ve got a pretty good solar setup working with 20,000 watts of LiFePO4 battery. Good surge capacity in the inverter.

Some supplementary juice would be nice to keep everything topped up and chugging along on cloudy days. That’s why I was toying with the idea of a small feed.

 

[ArcReactorKC]

$25K buys a lot of solar, and even some wind plus batteries.

 

[bluedog225]

$25K buys a lot of solar, and even some wind plus batteries.

Yeah. That’s been the direction so far.

 

[rooster59]

Talk to the power company about running the wire and putting the xformer and meter close to the cabin

 

[gleman]

If you're already trenching, I'd drop some conduit in for future use.

My electric co-op wouldn't let me trench my service to my barn and that came out to 10 bucks a foot from them. I thought it was reasonable.

I wanted to install wind and batteries out there because of snow and clouds but that's a back burner project that I'm not sure I'd get to. I be interested in seeing your battery setup.

 

[mike93lx]

My electric co-op wouldn't let me trench my service to my barn and that came out to 10 bucks a foot from them. I thought it was reasonable.

10 bucks including pipe and wire? That's cheap

 

[gleman]

Yeppers, I was planning on renting a DitchWitch and doing it myself but I'm sure it would have cost me more. This was 3 years ago so prices may have changed.

 

[bluedog225]

If you're already trenching, I'd drop some conduit in for future use.

My electric co-op wouldn't let me trench my service to my barn and that came out to 10 bucks a foot from them. I thought it was reasonable.

I wanted to install wind and batteries out there because of snow and clouds but that's a back burner project that I'm not sure I'd get to. I be interested in seeing your battery setup.

Mosty of my stuff is Victron from currentconnected.com

These are the batteries. Not the cheapest around but user serviceable BMS and cells.

 

[bluedog225]

Talk to the power company about running the wire and putting the xformer and meter close to the cabin

That was the $25,000 the quoted me.

 

[bluedog225]

I don’t understand enough about electricity to know if there is some clever unconventional smaller wire solution to provide some trickle charge to the battery bank 24/7. Higher voltage and lower amps.

Even 2000 watts delivered 24/7 would be useful. If it were cheap enough.

 

[mike93lx]

I don’t understand enough about electricity to know if there is some clever unconventional smaller wire solution to provide some trickle charge to the battery bank 24/7. Higher voltage and lower amps.

Even 2000 watts delivered 24/7 would be useful. If it were cheap enough.

At 800 ft, you could get about 20a at 240v with #2 MHF.

2-2-2-4 Aluminum Mobile Home Feeder Cable

2-2-2-4 Aluminum Mobile Home Feeder Cable. Sold by the foot.

www.wireandcableyourway.com

2k into wire, need conduit where it comes out of the ground, but you can direct bury for the rest of it.

Just need the meter at the pole, then a panel off that with a 20a two pole breaker

 

[rooster59]

That was the $25,000 the quoted me.

Sorry, missed that. How about a generator? Nothing wrong with wire, just an idea.

https://powerequipment.honda.com/generators/models/eu3000is

 

[gleman]

Mosty of my stuff is Victron from currentconnected.com

These are the batteries. Not the cheapest around but user serviceable BMS and cells.

I'm use to seeing marine or deepcycle batteries in a box, are yours in a server rack? It sounds like a pretty nice setup.

I don't know much about life batteries but Im interested. I have an old 36v golf cart with dump bed that needs to be repowered and there's a life kit that looks intriguing.

 

[bluedog225]

You bet. I’ve got a champion dual fuel for charging when needed.

 

[bluedog225]

Yes. Server rack batteries. They sell a 5 rack unit. 25,000 watts. The 90-100% discharge of these things gives them much more useable capacity than traditional lead acid. EG4 also sells a semi-reputable product cheaper. Though I don’t think they are serviceable without a spot welder.

 

[LiketoFix]

If you're already trenching, I'd drop some conduit in for future use.

My electric co-op wouldn't let me trench my service to my barn and that came out to 10 bucks a foot from them. I thought it was reasonable.

I wanted to install wind and batteries out there because of snow and clouds but that's a back burner project that I'm not sure I'd get to. I be interested in seeing your battery setup.

I know that the code doesn't allow the two utilities to be installed underground closer the 3 feet apart that's why it makes it harder to put them both in the same trench. These codes and regs. are for Safety reasons as water and Electric don't really mix!

LTF

 

[bluedog225]

At 800 ft, you could get about 20a at 240v with #2 MHF.

2-2-2-4 Aluminum Mobile Home Feeder Cable

2-2-2-4 Aluminum Mobile Home Feeder Cable. Sold by the foot.

www.wireandcableyourway.com

2k into wire, need conduit where it comes out of the ground, but you can direct bury for the rest of it.

Just need the meter at the pole, then a panel off that with a 20a two pole breaker

That’s the info I needed. Thanks Mike!

Gives me something to discuss with the electrician that’s in the realm of possible.

And I’d be pretty comfortable with 4800 watts. That would meet most of my needs. It’s been pretty informal out there till now….

 

[bluedog225]

I know that the code doesn't allow the two utilities to be installed underground closer the 3 feet apart that's why it makes it harder to put them both in the same trench. These codes and regs. are for Safety reasons as water and Electric don't really mix!

LTF

Understood. No code out in my parts. But want to be safe.

If I recall, he wanted to put the electricity at 4’ and the water at 18”. 18” is more than enough for freeze around here. No frost line.

 

[gleman]

I don’t understand enough about electricity to know if there is some clever unconventional smaller wire solution to provide some trickle charge to the battery bank 24/7. Higher voltage and lower amps.

Even 2000 watts delivered 24/7 would be useful. If it were cheap enough.

Which inverter do you have? Does it have multiple inputs. A small wind turbine should keep the batteries topped up.

 

[gleman]

I know that the code doesn't allow the two utilities to be installed underground closer the 3 feet apart that's why it makes it harder to put them both in the same trench. These codes and regs. are for Safety reasons as water and Electric don't really mix!

LTF

I'm well aware but if the trencher is right there better to take advantage of it

 

[bluedog225]

Victron Quattro 48/5000. I believe it does have multiple inputs. No wind though.

Hate to be dense. What does 2-2-2-4 exactly stand for? Google not much help.

Thanks

 

[mike93lx]

Victron Quattro 48/5000. I believe it does have multiple inputs. No wind though.

Hate to be dense. What does 2-2-2-4 exactly stand for? Google not much help.

Thanks

Three two gauge conductors and one 4 gauge. All insulated.

Also coded exist everywhere and you are subject to them, you may just not have an inspection

Power doesn't need to be anywhere near 48" deep. 2' is what you need for direct burial

 

[Packard V8]

I know that the code doesn't allow the two utilities to be installed underground closer the 3 feet apart that's why it makes it harder to put them both in the same trench. These codes and regs. are for Safety reasons as water and Electric don't really mix!

LTF

It's pretty wet underground in many areas. The electrical cable is by necessity waterproof. Those codes are for years later when either of the lines must be exposed for repair. They don't want to have to worry about hitting the other utility's junk.

FWIW, when I was having a new waste line connected to our sewer, the water, gas and sewer guys came by with the wheel counter and spray can to mark the lines in the area. The water guy missed the line going to the mother-in-law house behind big house up front. When a backhoe hits a 1" water supply line under full pressure, a river ensues until the entire block can be shut off.

jack vines