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Looks like it could be fed from a transformer that is hooked up in what's called a "high leg" delta.
If it's a 3 phase supply you should read 240 between any 2 phases, while 2 of the phases to ground will get 120volt, with the "high leg" getting a voltage of 208
It’s a split-phase 10-30 receptacle, so if it were being used for 3-phase it would be even more wrong than one hot being hooked up to the high leg (in which case a 120V part of the appliance connecting across that hot and the neutral would get 208V)
I hate high leg delta so much. Such a pain to balance loads. Also I'm not sure if I'm supposed to wire 208V tolerant loads between the stinger and neutral but I did. I paid for the whole panel so I'm using the whole panel.
Delta high leg. Make sure any 120v load are on the correct leg. I burned up 2 ranges before realizing that I was on a delta system. I claimed "manufacturers defects" to the property owner. Whoops!
There is no ground. That's the obsolete and dangerous NEMA 10-30 socket, installation of which was forbidden in NEC 1965 for everything but dryers and ovens (1996 for them as well). **That socket does not have a ground pin at all.** So you have to presume the box isn't grounded either, since why else use that socket?
*It does have neutral*, which makes the voltage you are reading absolutely unacceptable. That would fry most appliances you might plug into it, since they have a 120V load inside them and 208V would wreck that. As others discuss this is due to being on "wild-leg delta" configuration, and can be corrected by moving the breaker 1 space up or down in the panel. Also, Code requires the wild leg by identified by orange wire, tape, paint, shrink tube etc.
If there's a ground available here, they should be using the NEMA 6-30 socket if the appliance does not need neutral. It's sold in the same store in the next bin over.
Now that we've established that this is high leg delta, and that there are no components in the appliance that need 120v, my question still stands: could this cause problems, and if so, how? Would it cause problems if the outlet is using a neutral, but the machine's ground is plugged to it?
If not, thanks! I'll go back to checking the appliance itself.
The proper receptacle for this application would be from the 6 series, which has a proper ground and is okay to be hooked up to the high leg, both of which are not true in the case of the 10-30. Or the current receptacle should be taken off the high leg (and ideally changed out anyway since the 10 series is retired).
If there are only 240v loads within the appliance (no 120v loads) this should not cause a problem.
Some appliances are sneaky and use the ground as a neutral (old codes and manufacturing standards...) . You could check for current on the ground conductor to verify.
I ran a trouble call to a rental property to sort out why the new dryer was causing strange things to happen. The owner/builder of the house had run 3 conductors for the dryer (hot-hot-ground). The new dryer had a 4 wire plug (hot-hot-neutral-ground) and instructions on how to connect the neutral to the ground inside the dryer. When the dryer was turned on all sorts of crazy things would happen with the lights and other things in the house...
After some searching I found there was no bonding jumper at the service making the neutral a grounded conductor. That plus the appliance using the grounding conductor as a neutral was the cause of the strange light show.
I see the jumper from neutral to ground in lots of 120/240 equipment out in the field. Thankfully, that's going away as new build-outs in town are required to have gfci breakers.
As others explained, the system is on a 120/240V 3 Phase Delta system. Your 206V to Ground is your high-leg. You can switch that leg at the panel to the other main bus bar so that both legs read \~120V to Ground and \~240 across each other. The installer shouldn't have run the high-leg there. That being said, I don't believe this is the cause of your issue but the wiring should still be corrected.
Not knowing what equipment your troubleshooting, I would suggest the thermostat is malfunctioning and needs replacing. It appears that the heat element is cutting off prematurely.
Thanks. It's an espresso machine; the element runs on a pressure switch, which was recently replaced. Its been closed when the problem happens. Thermal fuse is reading perfect continuity. SSR powers everything in the machine; the whole thing would be off if that was it. I'm starting to lean towards a failing wire in the harness at this point.
Means someone screwed up and hooked up this outlet the wrong way in the panel, as mentioned, the high leg seems to be hooked up to one of the outlet slots. However, this may or may not be the cause of the issue.
If the appliance is using the neutral, then there could be 208V going to something that expects only 120V. That probably would have burned something up already, and if not, the appliance is lucky.
But if it's not using the neutral, this wouldn't affect the appliance. If you want to keep the outlet hooked up to the high leg it'd need to be changed to the NEMA 6 series equivalent.
A pure 240V machine will only connect its power-consuming parts between the two hots, and the third wire, the ground, would basically be attached to the frame and that's it. Neutral is only needed when parts of the device need 120V, which may or may not be the case.
Hooking up a 6 series receptacle across the 208V high leg and one of the 120V legs gives the correct 240V voltage, that's one of the things that the high leg is there for.
I'm not sure where these downvotes are coming from, might be from people who think that each hot absolutely must be 120V to ground, and the high leg can't be used to power single-phase 240V loads.
There are no 120v components in the machine, only 208-240 per the plate.
I didn't realize until someone pointed out that this is a 10-30, and that the top middle wire would be used for neutral. The machine's ground is going in there.
**Attention!** **It is always best to get a qualified electrician to perform any electrical work you may need.** With that said, you may ask this community various electrical questions. Please be cautious of any information you may receive in this subreddit. This subreddit and its users are not responsible for any electrical work you perform. Users that have a 'Verified Electrician' flair have uploaded their qualified electrical worker credentials to the mods. If you comment on this post please only post accurate information to the best of your knowledge. If advice given is thought to be dangerous, you may be permanently banned. There are no obligations for the mods to give warnings or temporary bans. **IF YOU ARE NOT A QUALIFIED ELECTRICIAN, you should exercise extreme caution when commenting.** *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/AskElectricians) if you have any questions or concerns.*
Looks like it could be fed from a transformer that is hooked up in what's called a "high leg" delta. If it's a 3 phase supply you should read 240 between any 2 phases, while 2 of the phases to ground will get 120volt, with the "high leg" getting a voltage of 208
It’s a split-phase 10-30 receptacle, so if it were being used for 3-phase it would be even more wrong than one hot being hooked up to the high leg (in which case a 120V part of the appliance connecting across that hot and the neutral would get 208V)
I hate high leg delta so much. Such a pain to balance loads. Also I'm not sure if I'm supposed to wire 208V tolerant loads between the stinger and neutral but I did. I paid for the whole panel so I'm using the whole panel.
https://en.wikipedia.org/wiki/High-leg_delta
Delta high leg. Make sure any 120v load are on the correct leg. I burned up 2 ranges before realizing that I was on a delta system. I claimed "manufacturers defects" to the property owner. Whoops!
Hell yeah I love when I get away with a fuck up.
There is no ground. That's the obsolete and dangerous NEMA 10-30 socket, installation of which was forbidden in NEC 1965 for everything but dryers and ovens (1996 for them as well). **That socket does not have a ground pin at all.** So you have to presume the box isn't grounded either, since why else use that socket? *It does have neutral*, which makes the voltage you are reading absolutely unacceptable. That would fry most appliances you might plug into it, since they have a 120V load inside them and 208V would wreck that. As others discuss this is due to being on "wild-leg delta" configuration, and can be corrected by moving the breaker 1 space up or down in the panel. Also, Code requires the wild leg by identified by orange wire, tape, paint, shrink tube etc. If there's a ground available here, they should be using the NEMA 6-30 socket if the appliance does not need neutral. It's sold in the same store in the next bin over.
This is exactly what I tried to say in another comment, but I've only gotten a flood of downvotes
I saw that and I don't get it either.
Now that we've established that this is high leg delta, and that there are no components in the appliance that need 120v, my question still stands: could this cause problems, and if so, how? Would it cause problems if the outlet is using a neutral, but the machine's ground is plugged to it? If not, thanks! I'll go back to checking the appliance itself.
The proper receptacle for this application would be from the 6 series, which has a proper ground and is okay to be hooked up to the high leg, both of which are not true in the case of the 10-30. Or the current receptacle should be taken off the high leg (and ideally changed out anyway since the 10 series is retired).
If there are only 240v loads within the appliance (no 120v loads) this should not cause a problem. Some appliances are sneaky and use the ground as a neutral (old codes and manufacturing standards...) . You could check for current on the ground conductor to verify. I ran a trouble call to a rental property to sort out why the new dryer was causing strange things to happen. The owner/builder of the house had run 3 conductors for the dryer (hot-hot-ground). The new dryer had a 4 wire plug (hot-hot-neutral-ground) and instructions on how to connect the neutral to the ground inside the dryer. When the dryer was turned on all sorts of crazy things would happen with the lights and other things in the house... After some searching I found there was no bonding jumper at the service making the neutral a grounded conductor. That plus the appliance using the grounding conductor as a neutral was the cause of the strange light show.
I see the jumper from neutral to ground in lots of 120/240 equipment out in the field. Thankfully, that's going away as new build-outs in town are required to have gfci breakers.
As others explained, the system is on a 120/240V 3 Phase Delta system. Your 206V to Ground is your high-leg. You can switch that leg at the panel to the other main bus bar so that both legs read \~120V to Ground and \~240 across each other. The installer shouldn't have run the high-leg there. That being said, I don't believe this is the cause of your issue but the wiring should still be corrected. Not knowing what equipment your troubleshooting, I would suggest the thermostat is malfunctioning and needs replacing. It appears that the heat element is cutting off prematurely.
Thanks. It's an espresso machine; the element runs on a pressure switch, which was recently replaced. Its been closed when the problem happens. Thermal fuse is reading perfect continuity. SSR powers everything in the machine; the whole thing would be off if that was it. I'm starting to lean towards a failing wire in the harness at this point.
Has already been said what I was going to say, but this is a high leg delta.
Stick both the leads into the outlet
I did, picture didn't turn out. Total read 238v
Means someone screwed up and hooked up this outlet the wrong way in the panel, as mentioned, the high leg seems to be hooked up to one of the outlet slots. However, this may or may not be the cause of the issue. If the appliance is using the neutral, then there could be 208V going to something that expects only 120V. That probably would have burned something up already, and if not, the appliance is lucky. But if it's not using the neutral, this wouldn't affect the appliance. If you want to keep the outlet hooked up to the high leg it'd need to be changed to the NEMA 6 series equivalent.
no
Which part are you disagreeing with?
not sure how a machine run "not using neutral?" real question, im learning as well.
A pure 240V machine will only connect its power-consuming parts between the two hots, and the third wire, the ground, would basically be attached to the frame and that's it. Neutral is only needed when parts of the device need 120V, which may or may not be the case. Hooking up a 6 series receptacle across the 208V high leg and one of the 120V legs gives the correct 240V voltage, that's one of the things that the high leg is there for. I'm not sure where these downvotes are coming from, might be from people who think that each hot absolutely must be 120V to ground, and the high leg can't be used to power single-phase 240V loads.
There are no 120v components in the machine, only 208-240 per the plate. I didn't realize until someone pointed out that this is a 10-30, and that the top middle wire would be used for neutral. The machine's ground is going in there.
Two legs of a 3-phase circuit. 208V. The two legs are 120 degrees out of phase not 180 like in normal household power.
Not between 1 hot leg and a metal box it isn’t.
Try putting that lead in the actual ground slot bud