# Thread: Trane CVHF Over voltage issue

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Originally Posted by R123
A low voltage potential transformer has a ratio of 20. So if you have 480 volts going in, you have 480 / 20 = 24 going out. The Starter module has a 0 - 30 volt input. The transformer ratio (20) is set in the controls parameters so the controls displays the proper voltage. If the input voltage is 460, then 460 / 20 = 23. The module sees 23 volts and knows its 460 volts. If you have a medium voltage chiller, then the ratio is 140. So 4160 volts / 140 = 29.7 volts input to the starter module.
Thanks for the clarification.

2. Originally Posted by R123
As far as chillers are concerned, anything over 600 volts. Typically 2300 volts or 4160 volts. In the electrical power distribution industry, there can be many ranges but generally 600 to 35000 volts.
Im still a little confused by this. The chillers actually see this voltage and use it to do work?

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Originally Posted by Core_d
Im still a little confused by this. The chillers actually see this voltage and use it to do work?
Yes, a medium voltage chiller compressor motor actually has 2300 or 4160 volts coming into the starter and into the motor. You don't open up the line voltage section of the starter or peckerhead of the motor while its energized unless you have proper PPE!!!

4. Oh, cool.

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Just to chime in, what the electrical distribution industry calls high and low voltage is quite different from just about everybody else. They work with such a vast (and high) range of voltages that they even have a medium voltage. Just about the only people in our industry who are aware of that are large tonnage chiller techs, at least that is my experience. It is also my belief that that is why you will sometimes here the term "line voltage" used instead or "high voltage" when discussing voltage supplied to the motor and motor starter. One is always correct (line), the other (high)- not always, in fact, usually not. R123 did an as usual great job of explaining, I just thought I would point out how, and why, the terminology can be confusing.

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Originally Posted by Nuclrchiller
Just to chime in, what the electrical distribution industry calls high and low voltage is quite different from just about everybody else. They work with such a vast (and high) range of voltages that they even have a medium voltage. Just about the only people in our industry who are aware of that are large tonnage chiller techs, at least that is my experience. It is also my belief that that is why you will sometimes here the term "line voltage" used instead or "high voltage" when discussing voltage supplied to the motor and motor starter. One is always correct (line), the other (high)- not always, in fact, usually not. R123 did an as usual great job of explaining, I just thought I would point out how, and why, the terminology can be confusing.
Great explanation. I am so used to doing large tonnage chiller work I sometimes forget not everybody understands the termonolgy.

As a side note, the higher voltage chillers pull less amps which means smaller copper wire size but thicker insulation. For expample, a 1200 ton chiller at 460 volts will pull about 1000 amps at full load where a 1200 ton 4160 volt chiller will pull about 110 amps.

7. Both Trane and York offer chiller motors with up to 13,200 volts now. I am unsure about other manufacturers but I am sure they probably do as well.

8. This is practical because you dont need a transformer and can use smaller conductors? Anything else? Seems to me Kw would remain the same and the chance of arc flash and shorts would greatly increase.

9. Originally Posted by Core_d
This is practical because you dont need a transformer and can use smaller conductors? Anything else? Seems to me Kw would remain the same and the chance of arc flash and shorts would greatly increase.
You aren't likely to find medium voltage on anything unless it draws a lot of power. The kW is the same, however you will go through fewer transformers to step the voltage down. Each transformer step is going to cost you a few percentage points of efficiency (or more) and on large motors, that savings can add up. The arc flash and shorting potential CAN be greater, yes, but you tend to get fewer yahoos working on them so the safety factor is racheted up quite a bit more. You will also save on purchase, install and maintenance of those transformer and conduit as well. But you pay higher labor rates to get anything worked on as there are fewer people qualified and willing to work on them.

10. Originally Posted by R123
A low voltage potential transformer has a ratio of 20. So if you have 480 volts going in, you have 480 / 20 = 24 going out. The Starter module has a 0 - 30 volt input. The transformer ratio (20) is set in the controls parameters so the controls displays the proper voltage. If the input voltage is 460, then 460 / 20 = 23. The module sees 23 volts and knows its 460 volts. If you have a medium voltage chiller, then the ratio is 140. So 4160 volts / 140 = 29.7 volts input to the starter module.
Have to agree with the others. Text book explanation! Beat my little one sentence answer to death! Good job!

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nucrlchilller, that explanation was awesome. Thanks so much, but I have a afd on the machine. I will copy and paste your explanation in my good reader folder under trane chillers thouigh!! I did not get any trips after that one incident. I did however try and contact trane bas guys to question why the tracer summit took an hour to reset! no reply yet!!

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You're welcome 000, but are you sure you don't have me confused with somebody else? R123, maybe? Which explanation are you referring too? Sounds like I may want to read it.

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also going to need help with getting my foot out of my mouth!!!

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