Need ideas for 240V plug bar

[Tom Jones III]

I've got 4 machines running 240V right in the middle of my shop. Does anyone have suggestions for a building a safe plug bar for 4 240v sockets?

Currently I've got what I call an octopus, a junction box that has short arms coming out of it to individual metal boxes that hold a single 240v socket each. I've never been particularly happy with it and I'd rather come up with a better solution than add another arm to it.

[Jim Becker]

"Technically", each 240v machine outlet should be on a separate circuit from each other. Some folks who are in "one person" operations will split a circuit in a j-box and have two or more outlets available--essentially what you have now with the "octopus". I don't see any other way to safely do what you want to do other duplicating the current setup by mounting multiple boxes on a column with proper conduit or code-acceptable wiring to them. And again...it's not recommended to do this, especially if you have more than one person who might be working in the shop. (Like you on a saw and the LOYL on the new lathe...hint, hint...)

[Doug Jones]

Jim, does this situation sound familar?
Tom, I was asking pretty close to the same question just the other day.

[Russ Massery]

This is what I use. A electrician freind built this for me when I had only one outlet at the time. I still use it for my "mobile machines". It has a 12/3 cable feeding it.

[Jeff Sudmeier]

As Jim said, the only perfect way to do this is to run separate circuits for each for the main. However, in a one man shop you can know your limit and not run two 220v on the same curcuit at once.

Most 220v plugs come in a single gang configuration for a single gang box. You should be able to fit 4 side by side in a 4 gang box.

[Ken Garlock]

Tom, I would handle your problem as follows:

1. Get 4 junctions boxes.

2. Run your supply line to the base of the nearest tool.

3. Install a junction box containing the supply line, a 2 or 3 ft pigtail with a twist lock receptacle(female cable connector,) and lastly a length of the same gauge cable as the supply line - this is the supply line for the next junction box.

4. Connect the three sets of wires paying attention to the colors. Use wire nuts to make the connections. Twist the bare equipment ground wires together. Cram everything in the junction box and screw down the cover plate.

5. Install a twist lock plug on the cable from your machine.

6. Repeat steps 2-5 as necessary until all tools have power.

I have a like setup in the dust collector trench down the middle of my shop. On it currently is 240V 10" cabinet saw, 120V router table, and at the end of the run, a 240V 2hp jointer. Down the road, I will add a planer/sander to the string. Being a single person shop, no two tools will be in operation at one time. Even if two were on at once, a 30 amp. 10 Ga. circuit will handle it.

[Barry O'Mahony]

Even if two were on at once, a 30 amp. 10 Ga. circuit will handle it.Uh, no, you can't do this. The only receptacles allowed on 30 amp circuits are 30 amp receptacles. You cannot use 15 or 20 amp receptacles. NEC 210-21(b)(3) is quite clear on this.

240V tools are usually operated at that voltage because they use alot of power, usually close to the rating of the circuit they operate on. Thus it is usually difficult, if not impossible, to devise a Code-compliant arrangement where multiple 240V tools run on the same circuit. Although there is no generic prohibition against having more than two receptacles on the same branch, many/most inspectors disallow it for that reason. The rationale "but I'll only use them one at a time" tends not to work with thiese guys; they think about the next person you sell the house to. That person may try to use two things at once, get sick of the breaker tripping, and do something stupid like upgrading the breaker without doing the same for the wiring. It's happened before.

[Ken Garlock]

Barry, the circuit breaker at 30 amp will protect 10 ga. wiring. That is what is the only purpose of a circuit breaker, it is not to protect the equipment.

[Barry O'Mahony]

Barry, the circuit breaker at 30 amp will protect 10 ga. wiring. That is what is the only purpose of a circuit breaker, it is not to protect the equipment.That's flat-out wrong. Although it must be the most oft-quoted "internet urban myth" about the NEC that spouted by "amateur electrical engineers".

As I said, Section 210 specfies allowable receptacles on branch circuits. Elsewhere in Chapter 2 it specifies overcurrent protection requirements for flexible cords, and equipment and fixture wiring. Other Chapters specify overcurrent protection requirements for specific types of equipment; e.g., Chapter 4 for motors.

[Dev Emch]

That's flat-out wrong. Although it must be the most oft-quoted "internet urban myth" about the NEC that spouted by "amateur electrical engineers".

As I said, Section 210 specfies allowable receptacles on branch circuits. Elsewhere in Chapter 2 it specifies overcurrent protection requirements for flexible cords, and equipment and fixture wiring. Other Chapters specify overcurrent protection requirements for specific types of equipment; e.g., Chapter 4 for motors.

Barry, your starting to sound like an OWWMer. You sure your not a closet OWWMer? You know, your hiding that 30 inch BUSS 4L-M planer in your garage and you sneak out to your hootch to run a board across your oliver 232 table saw.

Sorry, the only guys I know who talk like that are into old iron.:D:p:D:p

[Barry O'Mahony]

Dev,

No I'm not, at least not that I know of. 'just don't have the time to hunt down and restore old iron.

Not that I don't stand in awe of huge old pieces of industrial "kit", as the Brits say. I had to go to Las Vegas last week on business. 'first time there, not exactly my kind of place -- a tacky, adult corrupt version of Disneyland. The ony fun I had during the trip was the time I managed to "escape" and drive to Hoover Dam. Amazing place. Being in the same room with 2 gigawatts of generating capacity is a humbling experience.

[Bill Lewis]

Being in the same room with 2 gigawatts of generating capacity is a humbling experience.And... you can go back in time and still have .8 gigawatts to spare.:)

Ok, so it's early here...

[Dev Emch]

Dev,

No I'm not, at least not that I know of. 'just don't have the time to hunt down and restore old iron.

Not that I don't stand in awe of huge old pieces of industrial "kit", as the Brits say. I had to go to Las Vegas last week on business. 'first time there, not exactly my kind of place -- a tacky, adult corrupt version of Disneyland. The ony fun I had during the trip was the time I managed to "escape" and drive to Hoover Dam. Amazing place. Being in the same room with 2 gigawatts of generating capacity is a humbling experience.

Ah the city of lost wages. I was there two summers or so ago. I drove past the strip on the interstate but have no memory of the attractions. I had a front disc brake failure, fading trailer brakes, a blown out (as in explosion) trailer tire, a beeping trailer brake controller, a dog who was suffering from the excessive heat and about 20,000 pounds of Oliver and Yates American iron on the trailer. I took a white bathroom towel and dipped it into the cooler water and tied it onto my dogs head like a woman's scarf to keep him cool. Something about a black lab wearing the latest in scarf fashions. Why you ask? Dont ask. It was a stupid deal I was involved in and in the process I lost out on both a yates Y-20 snowflake that my buddy Russ restored and the only Oliver 20-C Lima Drive patternmaker's lathe I have come into contact with. I wound up with a tenoner with a broken coping motor and bearings that were on their last legs. I only recently got the tenoner running right and its still not totally to my liking. But I can now say that I too have been to Sin City.

[Brian Hale]

Not wanting to hijack the thread but.......

I've got a 30 amp breaker feeding (3) 30 amp twist lock receptacles via 10ga wire. I normally run 1 machine and the DC at the same time.

This is temp wiring for the next year or so till the shop building gets built but i planned on following the same wiring setup in the new shop.

Brian :)

[Jeff Sudmeier]

The sum of your amps on the line is what your wiring needs to be. If your machine pulls 20 amps and so does your DC you are overloading that line, risking a fire.

[Tom Jones III]

"Technically", each 240v machine outlet should be on a separate circuit from each other. .... And again...it's not recommended to do this, especially if you have more than one person who might be working in the shop. (Like you on a saw and the LOYL on the new lathe...hint, hint...)

What a memory for piecing together separate threads ... we'll have to start calling you the elephant.

Are you saying that each 240v machine in your shop needs to be on a separate set of romex back to it's own circuit breaker? Unfortunately those Code Check booklets aren't real helpful when it comes to 240v power, I thought I just needed to meet the same % of capacity rules as I would for 120v circuits.

[Ken Garlock]

That's flat-out wrong. Although it must be the most oft-quoted "internet urban myth" about the NEC that spouted by "amateur electrical engineers".

It is unfortunate that you find my statement so egregious. It is based upon reading, and making a conclusion from, Ray C. Mullin's book "House Wiring with the National Electrical Code." Mr Mullin, in one form or another, goes through the process of 1) sizing the load, 2) sizing the wire to the load, and 3) sizing the breaker to not exceed the current capacity of the wire. Yes, there are special considerations for motor applications like air conditioning compressors. No doubt you will want to contact Mr. Mullin, and discuss with him the error of his ways: info@delmar.com.

"Amateur electrical engineers," yes I plead guilty to having been an amateur radio operator for 50 years, and currently hold an Extra Class license. Electrical Engineer, no; however I have had 2 courses in AC circuits, one in field theory, and graduated with a BS in math.

At this point, I think the prudent thing to do is to agree to disagree.

[Dev Emch]

The sum of your amps on the line is what your wiring needs to be. If your machine pulls 20 amps and so does your DC you are overloading that line, risking a fire.

The issue with this statment is that you need to size *ALL* components on the maxium sum of current. In this case, you will need to size your branch circuit on at least a 40 amp breaker and then wire this branch circuit with at least 8 gage wire. Now you cannot get into each machine with 8 gage wire. Furthermore, the largest hubble like plugs are rated at at 30 amps. There are some plugs that can go to 50 amps. After 50 amps your moving into pin and sleeve territory and your going to need a second mortage to pay for these.

The solution is to use a quick disconnect fuse box for each machine. Then you install slow blow fuses sized to protect each machine in these boxes. Thus, I can run 8 gage into the box. But from the fuses outbound to the machine, I can drop down to either 12 or 10 gage depending on the machines nameplate current requirements.

Here the breaker is sized to protect the buss which is way more massive than any device attached to it. Once again, this scheme can be made to work but I dont recommend it. In principle, you could end up with shop full of quick disconnect fuse boxes with a buss made using massive copper wiring and a branch circuit fed by a 100 amp breaker. This is not a good idea. For small limited use, it can work. But for the record, I dont use this system on a permanent basis.

By the way, under industrial codes, its often required to have one of these disconnect boxes regardless of how you feed the machine. The large disconnect switch can take a machine offline in a jiffy should you need to do so... (i.e. when you need to restrieve your finger(s) from the dust chute).

[Dev Emch]

.....

"Amateur electrical engineers," yes I plead guilty to having been an amateur radio operator for 50 years, and currently hold an Extra Class license. Electrical Engineer, no; however I have had 2 courses in AC circuits, one in field theory, and graduated with a BS in math.

At this point, I think the prudent thing to do is to agree to disagree.

So, ahhh Ken, is it safe to assume you stayed at a Holiday Inn last night?:D