What connectors are you using for 240 single phase?

FlyFishn

Registered
Registered
Joined
May 17, 2020
Messages
167
I am making a break-out box for electrical power, just a short run from a dryer outlet (14-30) or generator outlet (L14-30) for now.

The main idea I have is a box on the end of a cord with 3 gangs - 2x 120v duplexes (1 per leg) then 1 gang for 240. That, I believe, limits me to 6-15 or 6-20.

If I go to an L14-30 (4 pin round locking) that requires 2 gangs. I guess that isn't out of the question (bump up to a 4 gang box), but is it worth it?

Where I could see the benefit of any 4 pin connector is the requirement of 120v for controls and 240v for motors - on the same machine. Regardless, both voltages would be at the box so a further rewiring of it would be easy if necessary. Just trying to think ahead.

In all source cases they are 30 amp supplies (30 amp breakers) so 20 amp connectors (5-20 and 6-20) would work.
 
unless you are utilizing the neutral for some reason, i can't see using 4 wire plugs and connectors in a single phase system
 
That is my question - neutral is required for 120v. Is there any reason anyone can see for a machine plug to have it? Or are control circuits + other electronics (DRO's, lights) for 240v machines able to run on 240v? Or do they have 2 cords for wiring to both separately?
 
The main idea I have is a box on the end of a cord with 3 gangs - 2x 120v duplexes (1 per leg)
If I'm not mistaken, that requires 4 wires. 1 each leg, neutral, and ground. If you are going that far, might as well wire in a 4 pin 220 outlet.
 
I use L14-30 socket/plug to power both my mill and lathe (3 Hp), since they are both in the middle of my garage floor. I have a 15A dual breaker at each machine to provide power to a dual gang box on my mill for two duplex 120VAC sockets for the drives and DRO. On my lathe I have a similar setup to provide 120VAC for the DRO and off the back of the lathe I have a 240VAC 20A socket and a duplex 120VAC socket. On the wall I have a dual gang box with two L40-30 sockets for each machine, and another duplex socket with a 240VAC 20A and a 120VAC GFI duplex socket. Each socket at the wall is wired/breaker independently at the main panel.

Issue would be if you have have a 30A and 15/20A socket on the same breaker would not be acceptable.
 
If I'm not mistaken, that requires 4 wires. 1 each leg, neutral, and ground. If you are going that far, might as well wire in a 4 pin 220 outlet.
That is the purpose of the L14-30's - they carry 4 pins/wires. That is what I am using from the supply end, and isn't the question.

The distribution end is the question - the outlets on the box. The pair of duplex outlets will split the 120v legs (L1 + neutral + ground on one duplex, L2 + neutral + ground on the other).

The question is the 240v outlet(s). Should I wire as [L1, L2, ground] or [L1, L2, Neutral, Ground]?

If there is no reason to have 120v on a machine that runs 240v then a 6-20 duplex will be what I want. I can get 2x outlets in 1 gang spot. If there is then I need at least a 14-30 plug (dryer plug), or locking equivalent - L14-30.
 
I use L14-30 socket/plug to power both my mill and lathe (3 Hp), since they are both in the middle of my garage floor. I have a 15A dual breaker at each machine to provide power to a dual gang box on my mill for two duplex 120VAC sockets for the drives and DRO. On my lathe I have a similar setup to provide 120VAC for the DRO and off the back of the lathe I have a 240VAC 20A socket and a duplex 120VAC socket.

Sounds like you are doing the same thing - running both 120 and 240 to your machines then splitting it. So the 120v loads are wired to separate plugs or split in a hardwired box at the machine?
 
It looks like the electrical boxes for a lot of machines use transformers for control voltages etc post-main power switch. So 240v in then everything down-stream takes care of itself in the box.

I suppose that makes sense - only 1 "line voltage" to worry about.

On the other side of the coin, for 120v (like a coolant pump, DRO, what have you) going through another transformation (step down) would be less efficient than running on its own feed - given the option is there.

So I think with that info I'll stick to 5-20's for the 2x duplexes and 6-20 for the 240v duplex. Again, easy enough to change down the road if that is warranted.
 
The breaker on a circuit must match the SMALLEST device.

So if you are plugging into a 240 grounded and with neutral outlet and at the other end you have both a 240 vac outlet and 120 vac outlets then either use twist locks matching the breaker or make a subpanel.

We just ran an additional plug next to the mill with a multiconductor cord with 2 plugs, one 240 vac for VFD and 120 vac for accessories.

On mill we have a 3 phase disconnect, L1 , L2 are for 240 vac and L3 is for 120 vac.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
See schematic below which give a general outline. I use 4 wire power cord to the machine, if everything is 20A you can breakout the L1 and L2 to either a 20A 240VAC socket and/or split each leg with a neutral and use either 1 or 2 120VAC duplex sockets. If you are bringing in 30A to the machine then you need a supplementary breaker or fusing for the rated output of the sockets you are installing.

The reason machines are not wired for 4 wire, because it is not a standard receptacle for machines. Also many machine are 3 phase, they use a transformer off of 2 legs to generate a 120VAC output. You may find it in some appliance that use both 120 and 240VAC, and use a 4 wire socket or hard wire to a box. Typically machines may have a step down transformer to provide a nominal output 120VAC for say a DRO or some sub-system/contactors. This also provides some noise isolation. It is not intended to provide high current 120 VAC for drives, etc. If it is your own shop/machine you can bring in 4 wire and have everything work off of a single power source. You need to be mindful that if you power other electrical devices that this adds to the total circuit current draw and can cause some imbalance if you have say a 120VAC pump that is drawing a lot of current.

I do 4 wire because it means that everything turns on/off with one power switch and it is one less power cord I need to run to my machine. As I mentioned, I do fit two 30A 4 wire twist lock receptacles in a duplex box. It will not work for a dryer type plug.

Machine Sockets.jpg
 
Back
Top