240v question

[Paul F Mills]

When I check the voltage in the panel on a double pole breaker, I get 120 on each pole (hot on one side of the breaker to the neutral). When I check the voltage at the receptacle I only get 120 between both hots. Am I doing something wrong here?

[Malcolm McLeod]

Check voltage between both hot lugs at the breaker; L1<>L2. Should read 240V. If CB is not inserted properly or is damaged, you may not be energizing one of the wires. Or, a long shot, but both lugs could be on the same 'phase' (bus bar in panel).

Hopefully, the receptacle has a ground. Check voltage from each hot to the ground. Both should read 120V; L1<>GND and L2<>GND. If you get 240V between a hot and the ground you have a wire swapped....GND should be bare or green, so really hard to mess this up. He said.

[Charles Lent]

What kind of breaker is it? Some of the 2 pole breakers are designed to only occupy one slot in the breaker panel, and thus only connect to one buss in the panel. They are great for their ability to add another 120 volt circuit when the panel is already full, but will not supply 240 volts between the two poles, only 120 volts from either pole to neutral.

For a 240 volt circuit, you need a 2 pole breaker that connects to two adjacent buss points in the panel. It should also have a mechanical tie between the handles, so that both handles must operate together.

Charley

[Paul F Mills]

Thanks for the reply Malcolm.

I should have given more info last night about the issue. I have wired up lots of 120v circuits successfully, but have never tried a 240v. I did this for a new jointer. When I plug it in, the green power light comes on but it will not start. The magnetic switch is in place.

I checked it again this morning when I was fresh. L1<>L2 is giving 120v, but L1 or L2 to the ground is also 120. So I am hoping it is a bad breaker, I will pick up another today.

At the receptacle, I am getting 120v from each hot to the ground, and hot to hot.

I also have a call into my electrician but am worried he may not be able to get to it the day before a holiday, and naturally I want to use the jointer this weekend.

Thanks

[Paul F Mills]

Charles, it is a double pole breaker, the one on the bottom right (ugly wiring job, I know). I am not sure what you mean but a mechanical tie between the handles.

And the white wire from that line goes to the neutral but nothing at the receptacle. The article I read said to connect it, but it does not make sense to me.

581FA678-3420-4E42-8E09-4949F1F142DD.jpg

[John Lanciani]

Have you confirmed that you have 240 volts at the breaker? Measure between the two hot legs there and let us know what you find.

[Bill Dufour]

Use your meter and check voltage between the two output screws on the breaker.
If the receptacle is only for 240 it will have no neutral connection. If it is for both 240 and 120 it will need a neutral wire connected.
Bill D.

[Paul F Mills]

Have you confirmed that you have 240 volts at the breaker? Measure between the two hot legs there and let us know what you find.

I have not checked that. The electrician that installed it quoted it as a 240, so hopefully it is. He passed away two years ago so I will be out of luck if it is only a 120 panel. I will check when I get home.

[Robert Engel]

You may already know this but thought I'd mention it.

Be sure the double pole breaker is spanning both sides of the phases in the panel. I made that mistake once when I replaced a hot water heater my panel had several knockouts missing and I didn't get it plugged in correctly. There is a split in the breaker which needs to correlate to the divider in the panel.

I had 120 on each leg but wasn't getting 240.

[Billy Merrill]

If you do not have 240VAC across a double pole breaker then the breaker is not on a buss location in the panel to supply 240. Check the label inside the panel or on the door for which spaces will supply 240.

At the panel for a 240 breaker you should have approximately the following readings.
L1 to neutral = 120
L2 to neutral = 120
L1 to L2 = 240

If you measure 120 across a double pole breaker then the breaker contacts are both on the same buss bar or phase.
If you look at the picture of the panel in the above post you can see the copper buss bars (L1 and L2) are interweaved like a zipper.
Some panels only do this for specific spaces limiting the number of usable 240 volt spaces.

[Malcolm McLeod]

Charles, it is a double pole breaker, the one on the bottom right (ugly wiring job, I know). I am not sure what you mean but a mechanical tie between the handles.

And the white wire from that line goes to the neutral but nothing at the receptacle. The article I read said to connect it, but it does not make sense to me.

581FA678-3420-4E42-8E09-4949F1F142DD.jpg

So since you've got it open, first I'd check before investing another minute - or breaker ... Check across the main lugs where your feed wires land on the bus bars (Black (big) & Red w/ Black stripe). If that is not 240V, all else is futile.

I'll assume this is a subpanel, so if feed here is not 240, you've got to work your way back in the main system until you find 240V - and the problem?

That you get 120V on L1<>L2 has me head-scratching... one of them has to be seeing 120V and the other a neutral or ground. A bad breaker should leave one of them open (disconnected)...???

- - - In a rush and clicked submit early. A faulty CB, or improper insertion of it, should either: 1) leave both legs open and 0V on everything downstream; or 2) leave one leg hot and one leg open, so you'd again read 0V on L1<>L2, or 3) both legs would be on the same buss (bar) and still you'd read 0V on L1<>L2 (::they have the same potential). Thus, the ONLY way to get 120V on L1<>L2 is a hot and neutral, or hot and ground.
...Something just doesn't add up???

[Andrew Seemann]

Charles, it is a double pole breaker, the one on the bottom right (ugly wiring job, I know). I am not sure what you mean but a mechanical tie between the handles.

And the white wire from that line goes to the neutral but nothing at the receptacle. The article I read said to connect it, but it does not make sense to me.

581FA678-3420-4E42-8E09-4949F1F142DD.jpg

That style box with that style breaker should be giving you 240V across the hots if it is wired correctly. It shouldn't be possible for both hots to be on the same bus on a double breaker in that particular box. As said above, check the across the main black and main black/red wire feeding the box (the ones connected to the copper bus bars). You should be getting 240V there, just like you should be getting 240V across the hots on your 20A double breaker.

[Tom M King]

I'm hoping that it's just an issue with the way it's hooked up in the main panel that feeds that panel.

[Paul F Mills]

The electrician came by today, apparently my multimeter is bad. There is 240v to the receptacle.

So that means there is an issue with the brand new Powermatic jointer. I have a call into Woodcraft so they can troubleshoot it. I have checked the power buttons in the cabinet and the magnetic switch is in place. The green light is powered, the jointer just will not start.

[Tom M King]

As much as I like digital multimeters, I keep an analog one too. Betting on a loose connection in the jointer motor.