voltage drop

[puckman]

i should know this problem but i don't . there is this service 208volt 3 phase,
the highest reading i get is 200v lowest is 198v. i have an ac unit 175' away
and the voltage at unit when running is 187v., the unit has been in service for years and just started to tripout. ac unit is wired with #10 solid in a 3/4 " emt with 8 # 12 in conduit and i plan on changing to #8 mc. my question is do i have power co. problem
or is 200volts reading standard? the ac uses 197v to 240v .
thanks for your replys.

 

[ron]

I think the 230V AC unit has been applied in the wrong application. 200V motors are made for 208V nominal systems. The utility can supply +-10%, so a unit rated down to 197V doesn't have a chance when the utility voltage swings low.

 

[kingpb]

You can always use a small boost transformer at the a/c unit.

Do the calcs, I think the unit is fried.

 

[bob]

i should know this problem but i don't . there is this service 208volt 3 phase,
the highest reading i get is 200v lowest is 198v. i have an ac unit 175' away
and the voltage at unit when running is 187v., the unit has been in service for years and just started to tripout. ac unit is wired with #10 solid in a 3/4 " emt with 8 # 12 in conduit and i plan on changing to #8 mc. my question is do i have power co. problem
or is 200volts reading standard? the ac uses 197v to 240v .
thanks for your replys.

You will be wasting your time and material to install #8 conductor. The problem is 1. The unit appears to be a 240 volt unit and 2. The voltage at the source is too low to begin with. Changing out the #10 won't increase the supply voltage. Verify what the unit voltage should be. Have it checked to see if it is still ok. You can install 10% boosters to increase the voltage if the unit still works.