My voltage is too high

[Elec_1]

I have a older building my medium voltage comes in on the left compartment stepdown transformer in the center compartment and the mdp in the right compartment.I am suppose to have 12470 in and 480 out(no tap adjustments on the 480 side) my measured 3 phase voltage is 505 phase to ground I believe I measured 291. My receptacles are like 121ac. I have had the hvac shop install a new unit for a students computer lab. The HVAC compressor unit aparently has pt on it so when it sees the voltage hit say 506 the pt cut the compressor out.I need a economical way to cut my power back just on this one air handling unit Iis rated 16.8 ampr rla and the fan.8amps fla. my They are using a 3 phase disconnect with 30 amp fuses in it. I need a economical way to get my voltage cut back to 480 volts on this piece of equipment, and when I ask my supply houses for help they are bewildered.

 

[bob]

I have a older building my medium voltage comes in on the left compartment stepdown transformer in the center compartment and the mdp in the right compartment.I am suppose to have 12470 in and 480 out(no tap adjustments on the 480 side) my measured 3 phase voltage is 505 phase to ground I believe I measured 291

1. If this service is from the utility, it is a little high. You can speak to them and see if the substation regulator can be lowered.
They may also have a large capacitor on this circuit that would cause the primary voltage to be high.
Before you do anything else. try this an see if you can solve the problem.

 

[steve66]

505 volts is only about 5% high. I doubt if the utility will do anything to lower it.

I would be surprised if a compressor has a PT on it that cuts out on voltage that is a little too high. Possible, especially if its a really big compressor. But why do you think its cutting out due to the voltage?

My money would be on some other problem, unless its a really large compressor.

 

[iwire]

I would be surprised if a compressor has a PT on it that cuts out on voltage that is a little too high.

It seems that once companies add processors to equipment they add all kinds of features like this. I am sure with good intentions but often become problematic.

 

[Elec_1]

505 volts is only about 5% high. I doubt if the utility will do anything to lower it.

I would be surprised if a compressor has a PT on it that cuts out on voltage that is a little too high. Possible, especially if its a really big compressor. But why do you think its cutting out due to the voltage?

My money would be on some other problem, unless its a really large compressor.

We have pretty stable voltage as this is on a small college campus with 2 separate feeds into the system 12470. with me having a output of 505 the HVAC compressor is rated for 460 volts so even taking in the 10% rule I am at the upper limits and yes I have been told by the HVAC technicials this has pt's on it . I have been having problems finding a buck boost set up and am looking at things like condtioners to try to clip the power back about 10% to the 480

 

[steve66]

It seems that once companies add processors to equipment they add all kinds of features like this. I am sure with good intentions but often become problematic.

That I can believe. And now that we know its a college campus, it makes more sense. They seem to spec. everything under the sun for the most mundane items.

Is there any adjustment for the high voltage cutout? Adjusting that would be the easiest solution.

 

[zog]

I have a older building my medium voltage comes in on the left compartment stepdown transformer in the center compartment and the mdp in the right compartment.I am suppose to have 12470 in and 480 out(no tap adjustments on the 480 side) my measured 3 phase voltage is 505 phase to ground I believe I measured 291. My receptacles are like 121ac. I have had the hvac shop install a new unit for a students computer lab. The HVAC compressor unit aparently has pt on it so when it sees the voltage hit say 506 the pt cut the compressor out.I need a economical way to cut my power back just on this one air handling unit Iis rated 16.8 ampr rla and the fan.8amps fla. my They are using a 3 phase disconnect with 30 amp fuses in it. I need a economical way to get my voltage cut back to 480 volts on this piece of equipment, and when I ask my supply houses for help they are bewildered.

The taps will be on the MV side, you should match the tap setting to the actual primary voltage, if it is set at 12,470 and the measured voltage is actaully 12,470 you may have a transfromer problem (TTR test would confirm that). Is this a utility owned transfromer or the campus?