Service Feed to Detached Garage

[BigTicket]

I am pulling permits (Building/Electrical) for a 24 x 36 detached garage next week. I am trying to figure out the best/most effective way to get power to it because I have some limitations. My house has 200 amp service with a 200A main service disconnect outside the house next to the meter. My main panel is inside my house about 40' from the service entrance. My house was wired in 1983. So, here are my limitations. My backyard is essentially my leech field. I have 3 septic drain lines curved throughout, so an 18" burial is out of the question. I'm considering three options.

1. Bury rigid conduit at 12" through the backyard (Approximately 80' run). RMC is about $239 per ft. That's about $1900 in conduit.

2. Have a second meter installed by Duke Energy (easiest), but that will also be an approximately 80' run (have to go around the septic tank and huge oak). Duke charges trenching costs at $25 per ft. That is $2000. They will bill the garage meter at commercial rates and a flat $35 per month. Way upside is having full service at the garage which would afford options later (welder, mini splits, etc.)

3. Run an overhead service from the house to the garage. My electrician seemed very nervous about this one. Maybe because it's so rare these days. I have 12" of clearance at the house under my eave, so I wouldn't have to mount the service mast on the roof.

As far as my planned loads initially, I'm looking at a 15amp compressor, a 20 amp lift and some LED light and garage door openers.

I know everyone has their own ideas but I would love to get some thoughts. I think that having a meter installed is the answer.

Chris

 

[dcg9381]

I've never heard of RMC being buried, not sure why you think it's OK at 12". I may be missing something on that.
Can you "go around" the septic system, even if that's a much longer path? Here, depending on type of septic, it'd be possible to hand dig it.... For a 20x36 garage, I'd plan on 60A.

 

[mm08822]

I assume the 80' maximizes the use of the basement/crawl space.
2" GRC conduit is about $8/ft = $80/length. What have you priced out at $23.9/ft??

Start with what size service you need in the garage. Then figure the conduit size based upon conductor size..

 

[mm08822]

I've never heard of RMC being buried, not sure why you think it's OK at 12". I may be missing something on that.
Can you "go around" the septic system, even if that's a much longer path? Here, depending on type of septic, it'd be possible to hand dig it.... For a 20x36 garage, I'd plan on 60A.

grc can be buried and has been done for years. It only requires a 6" depth in residential. I would be more worried about the conduit path being in the way of future plans.

 

[dcg9381]

grc can be buried and has been done for years. It only requires a 6" depth in residential. I would be more worried about the conduit path being in the way of future plans.

Thanks.. I found the cite. Learned something new:

 

[BigTicket]

I assume the 80' maximizes the use of the basement/crawl space.
2" GRC conduit is about $8/ft = $80/length. What have you priced out at $23.9/ft??

Start with what size service you need in the garage. Then figure the conduit size based upon conductor size..

Clearly I haven't researched the rmc universe very well! It was a site online. I see that grc is very reasonable.

 

[wyliesdiesels]

I am pulling permits (Building/Electrical) for a 24 x 36 detached garage next week. I am trying to figure out the best/most effective way to get power to it because I have some limitations. My house has 200 amp service with a 200A main service disconnect outside the house next to the meter. My main panel is inside my house about 40' from the service entrance. My house was wired in 1983. So, here are my limitations. My backyard is essentially my leech field. I have 3 septic drain lines curved throughout, so an 18" burial is out of the question. I'm considering three options.

what youre calling "main panel" is actually a subpanel since you have a disconnect at the meter.

1. Bury rigid conduit at 12" through the backyard (Approximately 80' run). RMC is about $239 per ft. That's about $1900 in conduit.

2. Have a second meter installed by Duke Energy (easiest), but that will also be an approximately 80' run (have to go around the septic tank and huge oak). Duke charges trenching costs at $25 per ft. That is $2000. They will bill the garage meter at commercial rates and a flat $35 per month. Way upside is having full service at the garage which would afford options later (welder, mini splits, etc.)

will be cheaper in the long run to run a feeder from your house. you could even size it to run a welder and mini split

3. Run an overhead service from the house to the garage. My electrician seemed very nervous about this one. Maybe because it's so rare these days. I have 12" of clearance at the house under my eave, so I wouldn't have to mount the service mast on the roof.

yeah i wouldnt do that

As far as my planned loads initially, I'm looking at a 15amp compressor, a 20 amp lift and some LED light and garage door openers.

I know everyone has their own ideas but I would love to get some thoughts. I think that having a meter installed is the answer.

Chris

very minimal loads...

 

[sparky 1971]

Depends on the garage location, but what about replacing the meter and disconnect with a 200 amp meter main that has feed through lugs for the house and additional breaker spaces to feed the garage?

 

[PCustoms]

Depends on the garage location, but what about replacing the meter and disconnect with a 200 amp meter main that has feed through lugs for the house and additional breaker spaces to feed the garage?

Not sure how doing that fixes the minefield in the backyard?

OP, post proposed site layout so we can see what you're dealing with

 

[BigTicket]

Depends on the garage location, but what about replacing the meter and disconnect with a 200 amp meter main that has feed through lugs for the house and additional breaker spaces to feed the garage?

That's possible I suppose. I would have to bore under a sidewalk twice.

 

[RPH]

Does the site have a secondary septic field location planned already. Most places with septic fields nowadays, require the second location to be planned. Once planned that area is out for developing. Check with the health department as they may have the rules.

 

[BigTicket]

Not sure how doing that fixes the minefield in the backyard?

OP, post proposed site layout so we can see what you're dealing with

 

[BigTicket]

Does the site have a secondary septic field location planned already. Most places with septic fields nowadays, require the second location to be planned. Once planned that area is out for developing. Check with the health department as they may have the rules.

Yes. It is in front of the house.

 

[sparky 1971]

Not sure how doing that fixes the minefield in the backyard?

OP, post proposed site layout so we can see what you're dealing with

Like I said, it depends on where the garage is. Since I don't see a location given, for all I know it's on the side of the house 20 feet away from the service, which might eliminate going out the back of the house and across the septic field.

 

[sparky 1971]

That's possible I suppose. I would have to bore under a sidewalk twice.

Going under a sidewalk isn't bad. Just pound a piece of pipe under it with a sledgehammer, when it pops out the other side, pull it back out. But, if the septic field still needs to be crossed, nevermind.

 

[BigTicket]

Going under a sidewalk isn't bad. Just pound a piece of pipe under it with a sledgehammer, when it pops out the other side, pull it back out. But, if the septic field still needs to be crossed, nevermind.

It's not an ideal situation. If I bury it myself, I will cross the septic lines from either the main disconnect or from the sub-panel in the house. Since rigid conduit can be buried at 6", your suggestion would be a shorter burial run. I am hesitant to put anything over the septic lines.

 

[PCustoms]

I still don't know where everything is from your pic.

Pdf won't open

 

[BigTicket]

You can't open the pdf? I'll show it on the picture

 

[P0234]

If it were me I would do whatever it took to get out of another $35 money grab.

 

[PCustoms]

You can't open the pdf? I'll show it on the picture

Works now, I think it was a site issue earlier



IMHO you're overcomplicating it going the 76' you have marked in red. Come right off your meter/disconnect (have a pic?) And go under the sidewalk.

I also assume you have 1 pipe coming from the tank, and then a distribution box prior to splitting out to the laterals. You should be able to cross this if needed.

Edit: super weird spot for your DB, and having the laterals that close initially, are you sure that's correct?

 

[mike93lx]

Go tight to the house so you are minimizing the distance crossing the field

 

[dave*99]

In my old house the utility undersized the direct burial feeder. I had low voltage problems.

They ran a new larger underground feeder. They didn’t follow the old path and their contractor ran a ditch witch through 2 of my laterals in the septic system. They were repairing them when I got home. That was over 30 years ago.

The cable still crosses those laterals.

 

[BigTicket]

Works now, I think it was a site issue earlier



IMHO you're overcomplicating it going the 76' you have marked in red. Come right off your meter/disconnect (have a pic?) And go under the sidewalk.

I also assume you have 1 pipe coming from the tank, and then a distribution box prior to splitting out to the laterals. You should be able to cross this if needed.

Edit: super weird spot for your DB, and having the laterals that close initially, are you sure that's correct?

I agree. I could shorten the run some, but not a whole lot. I measured about 4 feet off the house/deck. The picture is exaggerated a little. Actually, the tank is up closer to the Metal Carport. D box is about 10' from the tank. I just had the tank pumped 2 weeks ago. This drawing was where I thought the tank was.

 

[BigTicket]

The electrician came over today, and we discussed all the options. We initially planned to come off the sub-panel in the house and trench to the garage with a rigid conduit. We ended up planning to do a change of service at my current 200amp main disconnect panel and install a 200amp disconnect with breakers. We will run off that to the sub-panel in the garage. It's a shorter run and will give me some options for any future outside power needs. We decided to go this route due to the shorter run to the garage and the fact that I would end up with only one spot left in my house's sub-panel if we pulled from that.