Running Sub Panel and Looking for Advice

[Dwain Lambrigger]

All,

I am going to run a sub panel in my garage to run my power tools. I have the following

1) Shop Fox 3 HP 220v table saw
2) Delta 2 HP 220v RAS
3) Jet 1 HP dust collector
4) Rigid jointer (don't know hp, but can't be over 1 HP)
5) Rigid CMS
6) Jet 1.5 HP 110V Bandsaw

I know the only things I will run simultaneously are the DC and any of the power tools. I will also be running a bunch of hand power tools (routers, biscuit jointer, sanders, etc.

Is a 60 amp subpanel enough to get this done? My FIL is an electrician, and he has stated this will work. I don't want to wish I had more later, but I don't want to break the bank with a larger sub panel, wire, etc.

I am not an electrician, so any advice is greatly appreciated.

Thanks,

Dwain

[Maurice Ungaro]

Go for 100 amp if you can swing it.

[Rod Sheridan]

Hi, my shop runs from a 30 ampere feeder, except for the lights.

Here are my loads;

- 1.5 HP cyclone

- 3 HP General saw, 3HP General shaper, 4HP planer/jointer

- smaller machines such as 2HP bandsaw, drill press, lathe etc.

My Cyclone draws 8.5 Amperes continuously, my tablesaw 12.5 amperes at maximum load, normally probably half that.

So 30 amperes meets my needs.

For your shop lets use the following

3 HP Machines (Tablesaw at present) (20A 240V circuit)

2HP Cyclone (future dust collector) (15A 240 Circuit)

2 X 15A lighting circuits

All your machines would use the same 20A 240V circuit, in addition if run as a split circuit, it will also provide two 20A 120V circuits for portable power tools, all from a single 20 2P breaker.

So you would need a 6 space panel for the above, and the load above wouldn't exceed 40 amperes if you fully utilized the above circuits to 80% load.

Unless you want to add heat or air conditioning a 60 ampere panel would more than cover all your needs, one with 10 spaces would be fine.

The above is based upon a 2HP dust collector, and 3 HP machines with only the dust collector and one 3 HP machine running. Note that a 5HP machine wouldn't change the requirement for a maximum 60 ampere feeder.

Regards, Rod.

[Greg Narozniak]

I have a 100amp sub right next to my main 200 amp service. If your going to do it the inital cost may be a little higher (Feeder cable price, etc.) but I would not hesitate in going for 100. You never know what you may add down the road and it's better to have more power than not enough.

[Jason Beam]

60a at 240v is a LOT of juice for a shop. I'll venture to say nearly none of us hobby woodworkers use nearly that much juice on our best day with friends over. Unless you had three 5hp motors all going at the same time, plus lights, a radio, fridge, air cleaner and disco ball, I doubt you'd ever hit the ceiling of a 60a feed.

Since a 100a panel is not much more expensive than a 60a one, but copper ain't near cheap, I would weigh my options based on distance from the main panel. If you've only got a dozen or so feet between the main and the sub, then springing for the 100a is good advice. The blanket advice is always to go bigger but not every situation fits within the limitations that kind of advice pushes. If you've got 60ft between your main and your sub and you're never going to need all 100a, it's foolish to spend so much more money on the wire to feed it. The situation you're in dictates certain things you must consider.

I personally think you'd be more than fine with 60a unless you've got factors we aren't aware of (welding, central air, electric heat, etc etc). If you only have a short distance to go, sure, throw the 100a panel in - but be prepared for quite a jump in wire price.

[Bill Arnold]

I estimated my worst-case load at 60 amps or so, but installed 100 amp service to a 30-position panel. I wanted to be able to have a lot of seperate circuits for protection. Currently, I have it configured with eight 220V breakers and 14 110V breakers. It may sound like overkill, but the overall cost wasn't much higher than a smaller 60 amp panel.

[Scott Wigginton]

Is your garage attached or deatched? If it is attached then go for 100 amp.

If detached consider the cost of the cable (and increase the size as necessary for voltage drop). In my area for my distance, I could get two 8/3 (40 amp) cables for just the same price as 4/3 (60 amp). I already have a 30amp fusebox for lights & outlets so only adding 8/3 for my 240V tools was easily the best value. Also consider whether you'll eventually need heating/cooling.

[Jack Briggs]

The price of a higher load center isn't much more. I installed a 125 amp sub panel from a 100 amp breaker feed off of the main panel with 2/2/2/4 Al feed wire of 35 ft. Even in my one-man operation, I could have the DC (15A), pin router (20A) and compressor (30A) simultaneously drawing on the sub feed. This totals 65A, so it's not a bad idea to have 100A service or better.

Oh, this doesn't take into account the lights and spray booth (exhaust fan can be on for days).


Cheers,

[Rollie Meyers]

The price of a higher load center isn't much more. I installed a 125 amp sub panel from a 100 amp breaker feed off of the main panel with 2/2/2/4 Al feed wire of 35 ft. Even in my one-man operation, I could have the DC (15A), pin router (20A) and compressor (30A) simultaneously drawing on the sub feed. This totals 65A, so it's not a bad idea to have 100A service or better.

Oh, this doesn't take into account the lights and spray booth (exhaust fan can be on for days).


Cheers,

If you use #2 AL you CANNOT use a 100 ampere circuit breaker ,use a 90 A or use the proper size wire which would be 1 AWG.

[Jack Briggs]

#4 Cu or #2 Al for 100 amps.



Cheers,

[Rob Russell]

Jack,

Table 310.15(B)(6) does not apply here. You did not run a "3-wire, single phase" cable - you ran a 4-wire cable.

You need to use the ampacities from the normal table - 310.16, which is what Rollie is referring to.

Rob

[Rollie Meyers]

Jack,

Table 310.15(B)(6) does not apply here. You did not run a "3-wire, single phase" cable - you ran a 4-wire cable.

You need to use the ampacities from the normal table - 310.16, which is what Rollie is referring to.

Rob


The reason you cannot use that table is a shop subpanel is not a DWELLING service or feeder & it has to serve as the MAIN feeder or service, so if you run a feed off your main panel #2 AL is rated @ 90A @ 75°C & #4 CU is rated at 85A @ 75°C also.

[Jack Briggs]

After consulting with 3 or 4 licensed electricians (who all agreed that I was "okay" to use 2/2/2/4 Al feed from a 100 amp breaker in MP), I figured I was good to go. But if it's as simple as changing the breaker to 90 amp to adhere to code, then that's what I'll do.

Thanks for the input, guys.



Cheers,

[Rick Christopherson]

Go for 100 amp if you can swing it.Sorry to single you out Maurice, but being the first response to the question, it seems appropriate to use this as a lead-in.

It is so easy to spend someone else's money without forethought, and it drives me nuts when such a large number of people make similar statements without regard to the realities of the situation or without fully informing other readers for the basis of such statements.

This is a garage woodworking shop, and the poster has made no indication of ever getting into metalworking. As such, blindly suggesting a 100 amp subpanel is nothing more than spending someone else's money without justification.

Just to put this into perspective, my workshop is 1800 square feet and was at one time a full production shop with 2 to 3 workers. The only time my power consumption would exceed 60 amps would be if the widebelt sander was running at maximum load, with the dust collector running, and having my compressor kick in simultaneously. Even though this is actually a common occurence in my shop, it is not a common occurance in a garage workshop (you wouldn't have the floor space to have machines of this size).

Without metalworking equipment that have a high power consumption for their small physical footprint, it is almost impossible to exceed 60 amps of power consumption in a garage woodworking shop. And certainly not for the type of loading that the original poster has already listed.

If the original poster turned on every piece of equipment he owns (including lights) and operated them at their maximum load, he would still be sitting below 40 amps.

The original poster may want more circuit breaker positions in his load center, but that is not the same as saying that he needs a 100 amp subpanel. Frankly, a properly designed electrical system for a garage wood shop does not need that many breaker positions either, but I do agree that it is easier to work with and add unexpected circuits in the future.
Is a 60 amp subpanel enough to get this done? My FIL is an electrician, and he has stated this will work. I don't want to wish I had more later, but I don't want to break the bank with a larger sub panel, wire, etc.Your father in-law was correct. This would work for you, and you do not need to break the bank in the process. Make sure all of your 120 volt outlets are on 20 amp circuits. Your 240 volt outlets could be 15 amp, but using all 20 amp circuits is preferred for flexibility. The need for 30 amp circuits is rare, and is typically needed only for 5 hp compressors or dust collectors.

[Rollie Meyers]

The one thing not touched on here is don't cheap out on the size of the panel, if a 12 or 16 circuit panel is enough ATM buy a 24 circuit one & avoid the use of twin breakers whenever you can (IMO they are like trying to stuff 10 Lbs. of stuff into a 5 Lb. bag but they do have their place in a pinch). My own small shop for example has a 42 circuit GE A-Series panelboard useing Bolt-On type circuit breakers (GE THQB) because of my preferance of bolt-on's. In all the years only one circuit has been added because decided to spend some dough & buy a MillerMatic 251 MIG welder but the only limit a is because only 100 amperes are avail., wanted to install a 400A resi service so could have a 200A panel in the shop but it really could not be justified.

[William Hutchinson]

I use a 55amp feed to subpanel located in a detached building. Our shop equipment and simultaneous usage are similar. I have not been in a situation of where power supply was ever a problem.

What I will suggest is using a standard household service panel. It's easier to wire and expand if needs change.

I did add heat and AC to my shop. Lighting will require a separate circuit(s). Your outlets (20amp) will also require a couple of circuits or three.

[John Eaton]

I did a large panel at 100 amps. My thinking was that at some point I will want to run a welder off it so I wanted the extra capacity. Something to think about is to put your sub-panel feeder breaker on a side that balances with your largest existing breaker - for instance if you're in the shop mostly in the summer put it opposite the side with the breaker for the AC unit and furnace. The idea is to balance the load on each side of your main that might be pulling juice at the same time.

You can buy a whole SquareD 125 panel with 10 20amp single ple breakers for around $40-50 at Home Depot.

-- John

[Tom Veatch]

... The idea is to balance the load on each side of your main that might be pulling juice at the same time...

Assuming that we're talking about single phase service, I've always been under the impression that it doesn't matter in which side of the box double pole breakers were installed as far as load balancing was concerned. They bridge across both mains in either case. I also assume the breaker feeding the subpanel would be a double pole breaker as would be the other referenced loads, i.e., 240v circuits.

Single pole breakers (120v) only pick up one main, so balancing the load between mains by positioning simultaneous 120v loads on opposite mains makes some sense. But with 240v circuits, I don't see where it could make any difference since the breaker connects to both mains simultaneously regardless of the position in the box. If it didn't connect to both mains, it couldn't supply 240v.

I certainly don't claim to "know-all, see-all" with electrical wiring, and I'm posting this only because I'm trying to resolve, in my own mind, an apparent discrepancy between what was stated and what I've always understood to be true.

[Anthony Smaldone]

I just ran a 100 amp sub in my basement. The best advise I can give, is get a 12/24 pannel.(that's the amount of circuits it will handle) You will be surprised how fast you fill it up. It doesn't cost much more and will save you a ton of problems in the future.

Good Luck
Anthony

[Rick Christopherson]

Something to think about is to put your sub-panel feeder breaker on a side that balances with your largest existing breaker - for instance if you're in the shop mostly in the summer put it opposite the side with the breaker for the AC unit and furnace. As Tom already suggested, there is no balancing required or available for 240 volt circuits/breakers.

However, what I really wanted to point out is that phases alternate vertically down the panel, not from side to side. Even though you see the main lugs being on the right and left above the bus bar system, the busses alternate vertically. For example, the top-left and top-right breakers would be on phase-A, and the second-left and second-right breakers would be on phase-B.

[John Eaton]

Didn't think of that but now that you point it out it makes sense. Someone suggested it to me and I just ran with it. Guess I overthought that in my own panel.

-- John

[Duncan Horner]

If detached consider the cost of the cable (and increase the size as necessary for voltage drop). In my area for my distance, I could get two 8/3 (40 amp) cables for just the same price as 4/3 (60 amp). I already have a 30amp fusebox for lights & outlets so only adding 8/3 for my 240V tools was easily the best value. Also consider whether you'll eventually need heating/cooling.

I seem to recall a code prohibition on running more than one multiwire branch circuit to a detached building, am I mistaken? Can an electrician confirm?

[Joel Earl]

Holy Cracker Jacks guys - I live in a 3500 s/f house built in 1965. I have a 50a sub in my 3 car garage shop - shop only about 600 s/f of it. Car won.

I run 220 8a saw, 220 7.5a DC, electric baseboard heaters in adjacent room and a Reznor natural gas w/ blower in garage,A/c in summer, lights, stereo, compressor kicks in, sometimes a planer might be running at the same time too (110) - that'd likely be my peak load. Never had a flinch yet.

Back to the house and the main itself. It's only a 100 amp service in TOTAL. Never had a blackout, multi A/C's run in summer, a big pumps draws 17a that feeds a huge water pond/falls.....and all the usual things like 2-3 50" plasmas on at once, computers and printers everywhere.

I don't see why you see the need for a 100a subpanel.:o

[Anthony Smaldone]

The reason for the 100 amp is size. My sub is a main lug, with a 50 amp breaker to it. A smaller box only has 8/16 circuits in it, and if you need a few 220 breakers it will fill up fast.

[Dwain Lambrigger]

Thanks for all of the advice. I admit I got lost about half way down the list, but I can answer some of the questions asked:

1) This is an attached garage. The panel will be inside my garage, no more than 30 feet from the exterior panel. I will be running conduit.

2) I will not be running heat or air, I may be buying a very large shop fan however. I am not sure of the amps it takes.

3) What kind of difference will it be between 60A or 100A panel, and is there an option in between (90A?) that may be a good idea?

What kind of price difference would it be to run wire for 60A vs. 90A or 100A?

Thanks again for all of the advice.

Dwain

[Charles P. Wright]

3) What kind of difference will it be between 60A or 100A panel, and is there an option in between (90A?) that may be a good idea?

You can get the 100A panel and feed it with a 90A breaker. That gives you space for breakers, but you can use the smaller wire. I have a Murray 100A main breaker panel fed from SER 2/2/2/4 with a 90A breaker. The cost for the wire was $1.25/ft (it isn't designed for conduit, so you'll need something else) and the panel was $130. The other thing to consider aside from cost is that bigger wires are harder to pull.