Another Detached Shop Wire Size Question

[snowdust2]

I have been reading for awhile, but I can't figure out what I should do. Currently I have a 200a panel at the house with a 100a subpanel off of it. In the subpanel there is a 50a breaker that runs about 125' to my detached shop in conduit. Wire is THHN #8 and #10 for the ground. Shop has a small panel with a 40a breaker. The shop started as a detached garage that just needed power for lights and outlets. I now added onto it and will need more power out there. Just a hobby shop with 6hp compressor small welder and the usual other stuff.

I'm going to trench water this summer so I'll add another run of electrical then. Does it make sense to have a second panel out there for the second run? If I were to use the same size wire as the current run, could I just use a single panel and maybe a 60a breaker? To make it a little complicated, the next run will be more like 200' as I need to trench around the septic field lines for the water.

This isn't my area of expertise so any feedback is appreciated!

 

[Bert_]

One feeder to a building is the rule.

How big is the conduit? Could maybe re pull some bigger wire.

 

[wyliesdiesels]

Your plan does not work.

As said above, you can only have one feed to a building.

you would need to abandoned the current feed and run a new one. Then run another subpanel off the first subpanel

 

[snowdust2]

Ahh that's not good. I don't remember the size of the conduit, but I know it wasn't big enough for larger wire. Maybe I'll just have to run a complete new line then. Looks like I would need 2-2-2-4 MHF wire for about a 70a circuit. That seems like the cheapest option. Thoughts? I'd run it in conduit the entire way.

 

[jeepxj]

trench in a new line and abandon the old one.

 

[teamextreme]

You say you need "more power". Do you need more circuits, or more than the 50A you have now? For a small 1-man operation, a lot of guys get away with a 60A service with no issues. Do a real load calc and my guess is you may be just fine with the 50A. What you likely need are more circuits, which can be solved by installing a new subpanel with more circuits and using the same feed wires.

Or, another option, verify the conduit size you have and see if you can get away with upsizing to #6, which will get you to 60A.

 

[snowdust2]

That's fair. I probably should do a load calc. I just figured I'm going to have a trench open so might as well future proof it. That was before I knew I couldn't have two lines though. I'll check that conduit today.

 

[snowdust2]

Conduit is 3/4" so it looks like I technically could get #6 in there. I re-measured and the total run is more like 165' including inside the buildings. For that distance it looks like 6 wouldn't be enough for 60a.
I'm thinking since I'll have an open trench, I might as well incur the cost and run the MHF. It's not that much work and I know it'll be somewhat future proof. I appreciate the replies.

 

[Jagmandave]

The point of load question is a good one, if it's just you working out there how many things can you run at once? Are you adding a big A/C unit for summer use or something?

My whole house has a 100 amp panel, and even tho I've added a lot of electrical equipment, since it's just me I can only use one thing at a time, so it's no issue, even if the house A/C is on and the wife has the electric oven on (rare circumstance).

 

[snowdust2]

Off the top of my head, here is why I am thinking I need more capacity.

Lights - 10a (20 fixtures @ 1/2 each)
Air Compressor - 20a (Quincy QT54)
Hot water heater - 20a
Hobart 140 welder - 20a

There are a few other items but not that would all be run concurrently. It is entirely possible all of the above are running at the same time though. Again, I am not an expert so pick my thoughts apart. I realize that some of these will not pull those amps all the time so maybe I'd still be ok?

 

[mike93lx]

Do you have a generator? The existing wire could be reconfigured to allow it to be the feed, locating the generator at the shop instead of your house. This is what I plan to do so that the noise can be reduced and I can keep it in a heated space

Have you ever tripped the existing breaker?

It it was me, and it was going through the trouble of another trench, I would run new wire. 2awg aluminum, either xhhw in conduit or MHF direct burial

 

[snowdust2]

I don't have a generator so that's not an option.

I'm just building this out now so haven't tripped breakers or anything. I am just working on the electrical inside now and planning out the line to the shop for early this summer. Like you said... I'm just going to make a new run since the trench will be open. It's not that much money and I know I'll regret it if I don't.

 

[sberry]

The water heater may be a factor. What voltage is it and what is the air comp? I bet the existing would run it. I am so use to air on demand forget it could be switched on or its really simple not to weld while the air is running.

 

[Innovate1]

Put in at least a larger conduit while you have a trench open. You can always upgrade later that way and not that expensive. If you go ahead with the larger feed you can use the existing wire for runs in the garage and use the small conduit for low voltage - internet, security system, phone...