3 phase panel with single phase 240 v appliance

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Strombea

Strombea

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Prescott, Arizona, USA
I'm confused about hooking up a single phase 240v appliance (washer or dryer) to a 3 phase panel. A single phase system is 180 degrees phase offset and 3 phase is 120 degrees. So when hooking up a single phase 240v double pole (120 and 120) appliance to a 3 phase panel the phase shift is not that of single phase. Does the phase offset matter and will it affect the single phase motor?

It would seem that out of 60 hz at 120 offset but only using 2 phases, it would be missing power for 1/3 of the 60 hz?
 
Strombea said:
I'm confused about hooking up a single phase 240v appliance (washer or dryer) to a 3 phase panel. A single phase system is 180 degrees phase offset and 3 phase is 120 degrees. So when hooking up a single phase 240v double pole (120 and 120) appliance to a 3 phase panel the phase shift is not that of single phase. Does the phase offset matter and will it affect the single phase motor?

It would seem that out of 60 hz at 120 offset but only using 2 phases, it would be missing power for 1/3 of the 60 hz?
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You are making it way, way to complicated.
Phase angle etc has nothing to do with it.
You didn't say what type of supply that you had other than 240v 3ph.
If that's what you actually have and you appliance requires 120/240v you are out of luck as you don't have 120v available according to your post. I'm not going to put words in your mouth but suggesting what your supply would be in order for the stove to work.
What I would like for you to do is to look at you panel that you intend to feed your appliance with an tell me what the voltage is. If it's just 240v 3ph3w your up a creek without a paddle. If it's something other than that please advise what it actually is. If it is what I hope it is may me you won't have any issues and it will be a piece of cake.
 
Strombea said:
I'm confused about hooking up a single phase 240v appliance (washer or dryer) to a 3 phase panel. A single phase system is 180 degrees phase offset and 3 phase is 120 degrees. So when hooking up a single phase 240v double pole (120 and 120) appliance to a 3 phase panel the phase shift is not that of single phase. Does the phase offset matter and will it affect the single phase motor?

It would seem that out of 60 hz at 120 offset but only using 2 phases, it would be missing power for 1/3 of the 60 hz?
Click to expand...

Are you sure it is a 240 3 phase panel or is it a 208Y/120 panel?

If it is straight 240 three phase you will not be able to supply a typical American electric dryer from it.

On the other hand if it is a 208Y/120 panel you are all set and it is done 100s of thousands of times across the US.
 
Keep in mind that if the appliance is rated 240 only it may not run as intended on 208. If this is a standard residential washer and dryer it will have no problem running on 208 instead of 240. It will take a longer to dry due to only 2/3 power, however that usually isn't even perceived. There must also be a neutral since residential dryers have 120 volt parts in them.



Now if these are commercial units check the name plate voltage as well as the panel voltage. Commercial units rated 208 can not always be run on 240 and vis versa. Some can and are rated 208/240 or have a minimal and maximum voltage like 198 to 253, which in this case would be ok for either 208 or 240. If the units have a slash rating such as 120/208, they will then require a neutral, something not all 3 phase panels have though most do.



Also, make sure the panel isn't a high leg delta. Any appliance requiring a neutral can NOT be connected to the B phase. Only across A and C, since 208 volts could end up on the 120 volt parts.
 
The panel is 208y/ 120 4 wire.
I understand how to hook it up and to be sure A & C phase only, but I was just curious if the phase angle mattered since a single phase transformer offsets at 180 and 3 phase is 120, basically curious if appliances etc can run off 120 offset or 180 offset with no difference.

As far as installing and hooking it up, it all done and working. Just curious that giving it only 2 out of 3 phases isn't any different than giving it 2 out of 2 phases(single phase).

Thank you for all the explanations.
 
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Strombea said:
The panel is 208y/ 120 4 wire.
I understand how to hook it up and to be sure A & C phase only, but I was just curious if the phase angle mattered since a single phase transformer offsets at 180 and 3 phase is 120, basically curious if appliances etc can run off 120 offset or 180 offset with no difference.

As far as installing and hooking it up, it all done and working. Just curious that giving it only 2 out of 3 phases isn't any different than giving it 2 out of 2 phases(single phase).

Thank you for all the explanations.
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With 3? systems the voltage between any two different connection points is 1?. You cannot measure and equipment does not realize any "phase shift" until utilizing three connection points. While utilization equipment such as a dryer do have a supply connection to three points ? two different Lines and a Neutral ? the internal components only utilize voltage between two connection points.

The difference exhibited by the internal components will simply be that of 240V vs. 208V.
 
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FWIW, there are many multiplexes (read multifamily dwelling units in NEC speak) that have 208/120V 3? 4W services but then distributed to the apartments as 120/208V 1? 3W ? which is two Lines and a Neutral.

PS: Welcome to the forum... :thumbsup:
 
Okay that makes sense that the appliance doesn't care about phase angle until it is connected to all 3 points.


This is what I was visualizing is happening.
imagejpeg
 
Strombea said:
The panel is 208y/ 120 4 wire.
I understand how to hook it up and to be sure A & C phase only, but I was just curious if the phase angle mattered since a single phase transformer offsets at 180 and 3 phase is 120, basically curious if appliances etc can run off 120 offset or 180 offset with no difference.

As far as installing and hooking it up, it all done and working. Just curious that giving it only 2 out of 3 phases isn't any different than giving it 2 out of 2 phases(single phase).

Thank you for all the explanations.
Click to expand...

If its 120/208Y then you can use any phase. Just land a double pole breaker anywhere and you are fine.

Avoiding B phase is only for delta systems, not Y, all Y systems will have 120 to ground where as delta will have 208 to ground. I think your over thinking this, just start putting in 2 poles one after the other and youll be fine.
 
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