Detached Garage Sub Panel Feeder and Load Questions

[jmvar]

I have a 750 sq ft detached garage that I had big plans for but I have hit a bit of a hiccup financially so I need to use as it sits right now with out any upgrades for a while.

The original owner that had the garage built and wired used a 60A breaker off the 200A panel in the house. They ran what looks like 8 awg copper wire to the garage to a small panel. It is run in PVC conduit underground and the distance is about 40 ft from the main panel to the sub panel in the garage.

I am trying to figure out what load this can support and see if I can get by for a while before I upgrade it.

Questions:

- I am looking for the gauge on the wire but can't seem to find it. I measured it to have .228" diameter with my calipers and the only identifier I can see on it says " oil and gasoline resistant". My assumption is that it is 8 awg THHW wire from AWG diameter charts I have found and descriptions. Does this sound about right?

- Assuming it is 8 awg THHN wire, it looks like max ampacity is 55 amps. At 80% this would be cut down to 44 amps. Does this sound right?

- I want to run the normal garage tools and some wood working equipment while having the 220 v electric heater (17A) or window AC (5A) unit running. I have a delta dust collector (220v, 6A or 120V, 12A) dewalt planner (15 amps), Miller 211 welder I want to run off 220V, small delta jointer (12A), craftsman 113.** table saw (14A). Assuming the biggest draw would be while the heater is running, dust collector, and the planner, adds up to 44 amps. Lights are 4 8' CFL fixtures but not sure what wattage the bulbs are. Am I cutting it close?

 

[klassenl]

My wood shop runs on 30 amps. For a time I had some electric heat but no welder. If you're a one man shop a 60a service will do you 99% of the time - unless of course your welder is huge, then you're screwed.

 

[dcg9381]

> 80% this would be cut down to 44 amps. Does this sound right?

That's "full draw" continuous - yes. As it's on a 60, you're looking at 80% of that, 48 amps continuous draw before something flips.


60A, in my experience, is more than enough for a 750 sqft garage. I have a 2400 sqft garage, it's running on a 90A circuit. Hot tub, refrigerator, 50A RV outlets, 4 tons of AC, all sorts of stuff.

What will get you is electric heat - that might kick you over if you're up north and running a big electric heater to keep the place warm. I avoided that by using propane on any appliance that needs to heat things fast (tankless hot water, dryer, etc).

 

[jmvar]

What will get you is electric heat - that might kick you over if you're up north and running a big electric heater to keep the place warm. I avoided that by using propane on any appliance that needs to heat things fast (tankless hot water, dryer, etc).

I will climb up and check the label on the electric heater.

What about my assumption that I have 8awg THHW wire? I measured it to have .228" diameter with my calipers and the only identifier I can see on it says " oil and gasoline resistant". My assumption is that it is 8 awg THHW wire from AWG diameter charts I have found and descriptions. Does this sound about right?

 

[nafterclifen]

What about my assumption that I have 8awg THHW wire? I measured it to have .228" diameter with my calipers and the only identifier I can see on it says " oil and gasoline resistant". My assumption is that it is 8 awg THHW wire from AWG diameter charts I have found and descriptions. Does this sound about right?

You can use this table as a guide to size your wire. Count the number of wires in the strand and measure it.

http://www.nehringwire.com/stranded-wire-gauge-table/

 

[pattenp]

#8 Cu THHN/THWN is 50A, not 55A. The max temp you can use is 75 deg C.

The .228 is about right for #8 THHN.

 

[jmvar]

#8 Cu THHN/THWN is 50A, not 55A. The max temp you can use is 75 deg C.

The .228 is about right for #8 THHN.

Thanks, good to know.

So looking at the wiring in the panel it looks like the ground and the neutral are not bonded. From what I read, this is a good thing. However, I don't see a ground rod anywhere like I do by the panel for the house.

Can you guys look at this setup and see anything I need to address?

 

[kest874]

Double tapped neutral, top right of your picture, each white neutral should be under it's own lug.

 

[Norcal]

In addition to the comments in post number eight the neutral has white tape on it, that is only allowed with 4 AWG and larger conductors, with 6 AWG and smaller the marking must be continuous it’s minor but still a code violation.

 

[cyclic]

Also one of the 15a breakers is double tapped. Move a white wire over and add another 15a breaker.

 

[Norcal]

Also one of the 15a breakers is double tapped. Move a white wire over and add another 15a breaker.

Not a problem with SQ D QO or HOM breakers they are listed for two conductors.

 

[alfredeneuman]

There's no main breaker so the panel is limited to 6 "handle throws".
(Edit) If there isn't 2 ground rods wired to the equipment ground bus in the panel, there should be

 

[teamextreme]

In addition to the comments in post number eight the neutral has white tape on it, that is only allowed with 4 AWG and larger conductors, with 6 AWG and smaller the marking must be continuous it’s minor but still a code violation.

Based on the look of that panel, it's installation likely preceeded the code change limiting taping to #4 and larger. I'm pretty sure it was allowed to tape any size neutral back in the 80's, maybe 90's. If that's not the case, it was at least a rule that nobody I worked with ever followed back then.

 

[sberry]

Continuous is 3 hrs or more. It should have the breaker changed to 50. Having a small welder is an asset here, you may never need more than that or changing heater to gas may be cheaper than changing electric?