Running a 230 Volt single phase motor on 208 3 phase

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Strathead

Senior Member
Location
Ocala, Florida, USA
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Electrician/Estimator/Project Manager/Superintendent
kingpb said:
Reading the posts in this thread, and many others on this forum; there is a lot of time and effort spent on finding ways around a particular problem. In most cases, including this one, I think one only has to ask themselves:

Is the equipment rated for the installed use and conditions.

In this case, and often times, no. Therefore, you have two options here. Provide the properly rated motor, or provide the proper voltage to the motor you have. From a good engineering perspective, these are the only choices.
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No sarcasm or offense meant, but there is a third option. It is often done. That is do nothing. And frankly, knowing what I know about 208/230 rated motors, I am not uncomfortable with that decision in this type of scenario.
 
R

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
No offense should be taken.

Fewer Permits or Plans are seen with industrial & commercial maintenance, where supervision of qualified persons are possible.

Without permits, plans, or engineering, voiding warranties is not always considered a problem.

And, if equipment fails under 110.3(b) violations, any Warranty is void.
 
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Besoeker

Besoeker

Senior Member
Location
UK
ptonsparky said:
Think about what is entailed in replacing a single phase motor with a three phase.
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Not sure that anyone suggested a three phase replacement.
But, that said, I don't discount that possibility and that I missed it.
It's a forte of mine.
 
kwired

kwired

Electron manager
Location
NE Nebraska
ptonsparky said:
Well, I kind of assumed (I know, I know) when talking about a 208v replacement motor that 3 phase was inferred. My motor guy tells me most of what he sells of single phase motors are rated 208-230v. Live and learn again and again and again...
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I think most NEMA motors will be 208-230 volt. It is OEM motors that may only have a single voltage rating marked on them.
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I think it is probably better to either change the voltage or change the motor for a new install.

In an existing system if I discovered this kind of thing had been installed years ago and was still running, I might just be inclined to leave it be and make a note that if/when the motor fails to do something about it then. I might well be retired before anything needs doing and then someone else can worry about it.
 
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Hv&Lv

Senior Member
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-
Occupation
Engineer/Technician
I thought we were discussing three phase 208 to three phase 240, not three phase to single phase.

Three phase 208 to single phase 240???
 
mivey

mivey

Senior Member
Besoeker said:
Indeed it could and I apologise for my gaffe.
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Gaffe? I don't see it.

The title: "Running ... single phase ... on 3 phase". Also:

Boiler79 said:
...The motor on the equipment is ... single phase. He wants to leave the motor as is...
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FWIW, a buck/boost transformer would have been my first thought. Maybe the cost would drive me to get a rated motor but who knows?
 
mivey

mivey

Senior Member
Hv&Lv said:
I thought we were discussing three phase 208 to three phase 240, not three phase to single phase.

Three phase 208 to single phase 240???
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End user wants to use a single-phase circuit from the 3-phase 208 volt service to run a single-phase 230 volt motor.
 
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Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
mivey said:
End user wants to use a single-phase circuit from the 3-phase 208 volt service to run a single-phase 230 volt motor.
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I had to go back to the OP to see what the original question was. I still say do nothing if delivered voltage is around 215...
 
H

hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
The only problem I have ever had is OEM motors on air compressors like a 7.5hp with a 230 volt rating running on 208, in two cases it only lasted a month or two, then they replaced it With a 200 volt rated motor, I think the problem is the load on the motor is sized for the 7.5 HP and on 208 you don't get 7.5 HP anymore.:happysad:

I should also say that these were both truck repair garages that ran large impacts 1" drives, and the compressors were rated for 175psi so sure if they lowered the pressure it would have worked
 
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kwired

kwired

Electron manager
Location
NE Nebraska
hurk27 said:
The only problem I have ever had is OEM motors on air compressors like a 7.5hp with a 230 volt rating running on 208, in two cases it only lasted a month or two, then they replaced it With a 200 volt rated motor, I think the problem is the load on the motor is sized for the 7.5 HP and on 208 you don't get 7.5 HP anymore.:happysad:

I should also say that these were both truck repair garages that ran large impacts 1" drives, and the compressors were rated for 175psi so sure if they lowered the pressure it would have worked
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In a place like that nobody knows why they don't spend more on the compressor in first place. The one you describe still won't last long with heavy daily use even if it is supplied with 240 volts. Couple years later you are called back to fix/repair motor, or even run a circuit to a 3 phase unit with better build.
 
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hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
kwired said:
In a place like that nobody knows why they don't spend more on the compressor in first place. The one you describe still won't last long with heavy daily use even if it is supplied with 240 volts. Couple years later you are called back to fix/repair motor, or even run a circuit to a 3 phase unit with better build.
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Its called wearing blinders economy, all they see is the price right in front of them, kind of like the people who will spend $60.00 for a set of tires that they only get 20k miles out of when a set of $120.00 can last 80k miles now which is cheaper? as you can see I opted for the latter:

NewGoodYearDuraTrac016.jpg
of course these are a little more then $120.00 more like $246.00 but they have the rating for the weight of my van and are 4 sizes over
 
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