240v equipment to 208v

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texnwis

Member
I have a120v/240v single phase 3 h.p. fan and only have 208v available. What ramifications can I expect with this installation.
 

360Youth

Senior Member
Location
Newport, NC
You are probaby going to see requests for more info. I am assuming you are running this fan single-phase 240v and want to hook up to your 208v system. I would say you have about 60/40 chance in your favor of it working ok. It depends on the exact voltage of your system. Most 208s that I see are putting out bout 214v, and I have seen 240v motors un just fine. Voltage is nominal, but it depends on what type of range the manufacturer has "allowed" for their equipment to run.
 

growler

Senior Member
Location
Atlanta,GA
I have a120v/240v single phase 3 h.p. fan and only have 208v available. What ramifications can I expect with this installation.

There are all kinds of things to consider. The ambiant temperature where the motor is located ( heat is a factor when running at lower voltage ). The distance of the motor from the panel ( voltage drop under load). If you really have 208V when running there isn't much of a problem but if you start with 208V and add in a 10% voltage drop because of distance and conductors size then that's another thing.

The best place to go for advise when useing a piece of equipment is back to the people that built it. Call the manufacturer and see how they feel about it. They all have an engineering staff so let them earn their money and give out some answers.
 

cpal

Senior Member
Location
MA
what is the wattage at 240v?
That question could use some defining, what is the wattage of what at 240V?
The motor? That would depend on the applied load(maybe) if the question is regarding the motor are you asking about the input or output??

:-?
 

ty

Senior Member
Given that the OP states that the motor is 3HP that would make it around 2.2kW output. For a small, single-phase motor that might equate to about 3kW input.

maybe. somewhere in that area.

I know this is not a resitance load.
But, I was going to do a calculation for theory in seeing what it's connected wattage and full load current would be at 208v.
 

ty

Senior Member
so,
for calculation sake, let's say it is 3000watts at 240v.

R=E(E/P)
R=240(240/3000)
R=19.2

I=E/R
I=208/19.2
I=10.83

10.83x208= 2252.64

so,
connected watts = 2253
F.L.A. = 10.83
edit: at 208v.
 

Mgraw

Senior Member
Location
Opelousas, Louisiana
Occupation
Electrician
All the calculations are great but the bottom line is it may work for a while and it may not. Depends on how close to full load amps it runs and how long it has to run.
 

mcclary's electrical

Senior Member
Location
VA
All the calculations are great but the bottom line is it may work for a while and it may not. Depends on how close to full load amps it runs and how long it has to run.



I agree, if the motor is lightly loaded, it will most likely work just fine, if it's on a compressor,,,,,I will bet money you'll need a buck boost (especiallly when it'd cold starting)
 

Besoeker

Senior Member
Location
UK
so,
for calculation sake, let's say it is 3000watts at 240v.

R=E(E/P)
R=240(240/3000)
R=19.2

I=E/R
I=208/19.2
I=10.83

10.83x208= 2252.64

so,
connected watts = 2253
F.L.A. = 10.83
edit: at 208v.

A bit convoluted and valid just for a constant resistance load.

This a motor on a fan so you can't really make the same assumptions.
 

Goroon

Member
Brings to mind

Brings to mind

:-?
Brings to mind:

95% of the time an electrician says: ? It Should Work?
100% of the time a Lawyer says: ?Was it ?Listed? for that and ?Installed? per it?s listing?
 

ty

Senior Member
A bit convoluted and valid just for a constant resistance load.

This a motor on a fan so you can't really make the same assumptions.

Ummm, didn't I state that in post #7?? Before I even showed the calculation?

But, for a resistance load, I would bet alot of folks could use the calc., and some had no idea how to do it. It was just an exercise with the numbers, as stated. Not for the OP's use on his motor.
 

Besoeker

Senior Member
Location
UK
Ummm, didn't I state that in post #7?? Before I even showed the calculation?

But, for a resistance load, I would bet alot of folks could use the calc., and some had no idea how to do it. It was just an exercise with the numbers, as stated. Not for the OP's use on his motor.
Well, I'm sorry I seem to have ruffled your feathers a bit and I apologise if I did.

Anyway, here's an easier way for your resistive load calculation.
Power at 208V = 3000*(208/240)^2 = 2253W
Current at 208V = 2253/208 = 10.83A
 
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