Liebert AC UNIT

[don_resqcapt19]

We installed a 75 k but phase a under load only puts out 198 volts not 208 . trace it out further the 277 primary from street only has 274 on phase a. is it worth up sizing this thing again at the expense of the H V A C guy. without a load we run only 201 one a 205 on b and c the primary run is less than 110 feet and the wire is over sized . Looking for help

What is the voltage on the primary side of the transformer when it is loaded?

 

[kwired]

We installed a 75 k but phase a under load only puts out 198 volts not 208 . trace it out further the 277 primary from street only has 274 on phase a. is it worth up sizing this thing again at the expense of the H V A C guy. without a load we run only 201 one a 205 on b and c the primary run is less than 110 feet and the wire is over sized . Looking for help

What is voltage at service equipment? Is this oversized primary conductor just from a panelboard to your transformer or are you talking the length of service conductors also? Maybe POCO transformer is undersized, there is undersized or lengthy service conductors, or they have problem with a voltage regulator. Around here normal no load voltage on 208 systems will usually run near 215.

 

[ERIC LEDBETTER]

PRIMARY SIDE

PRIMARY SIDE

274 - A 277-B 277-C The local power company supply reads the same . I don't think it is withen the range for them to change . on that same note if you read the existing liebert units the same varies is observed however at 277/480 not an issue to warinty

 

[ERIC LEDBETTER]

POCO

POCO

I would like to prov that. The big part of this story is the building we are talking about will charge the ac co 12.5 million a day if power is lost . (Tela pacific ) need to exhaust all avenues before we go there. If we force a Change a stuff still don't work WOW .Thanks for helping I will keep checking back We are meeting there in 30 minutes

 

[don_resqcapt19]

274 - A 277-B 277-C The local power company supply reads the same ...

If this is the voltage at the primary of the transformer when it is under load, then you either have a poor connection somewhere, the transformer is undersized for the load or the transformer is defective, or you have the taps wrong.
Even if all 3 phases on the primary were at 274 volts, you should expect to see 205 volts on the secondary.

 

[ERIC LEDBETTER]

FIXED

FIXED

We ran a full load test this am and had 490 volts at primary and 214 secondary . The differences was the ambient temp at the out door transformer about 80 deg instead of 112 like yesterday would you agree this is a Nevada power issue? Or the building is undersized for what they need . Could this be an issue proving that the Nevada power transformer will fail if they do not act soon.
Thank you for the advice

 

[don_resqcapt19]

We ran a full load test this am and had 490 volts at primary and 214 secondary . The differences was the ambient temp at the out door transformer about 80 deg instead of 112 like yesterday would you agree this is a Nevada power issue? Or the building is undersized for what they need . Could this be an issue proving that the Nevada power transformer will fail if they do not act soon.
Thank you for the advice

I don't think there is an issue with the utility transformer. I expect that the grid voltage was low with the high air conditioning loads that would be required on a 112? day. I looks like you need to install some voltage recording equipment at the service and leave it in place for a month or two to see what the utility voltage is doing.
You could look at a constant voltage transformer, but they are very pricey. I think a 75kva one would be in the $40k range. The output voltage is held plus or minus 5% with an input range from minus 25% to plus 15%.

 

[ERIC LEDBETTER]

GOT IT

GOT IT

Thanks the info will be passed on to the building owners your help was much appreciated .

 

[ERIC LEDBETTER]

CONSTANT VOLTAGE TRANSFORMER

CONSTANT VOLTAGE TRANSFORMER

The constant voltage transformer should fix the issue with my equipment. Is there a legitimate concern every other piece of equipment is subject to the same harm from low and unbalanced loads this building is full of servers and Air conditioners. A spot check showed the same A phase under powered. This building (Tela Pacific) is quick to point out 12.5 million a day if power is lost

 

[tkb]

It sounds like THEY have a problem with the power company.
I would be reluctant to change the taps in the summer because of low voltage.

In the winter the demand on the POCO will be lower and the voltage may rise.

 

[__dan]

The constant voltage transformer should fix the issue with my equipment. Is there a legitimate concern every other piece of equipment is subject to the same harm from low and unbalanced loads this building is full of servers and Air conditioners. A spot check showed the same A phase under powered. This building (Tela Pacific) is quick to point out 12.5 million a day if power is lost

A line to line voltage imbalance exceeding 1% can cause motor losses, heating, to go up 25%. If the line to line voltages are exactly equal, motors can tolerate more +- % line voltage.

If the line to line voltage imbalance exceeds 1% regularly, you say the A phase has a lower voltage, file a voltage complaint with the utility. They may come out and put a data logger on it and are likely required by law to fix something out of spec.

The servers are usually multivoltage power supplies and tolerate a wide range. Voltage fluctuations and imbalances on the motors will throw the motor efficiency off by enough to cause some problem.

Should add a note about the transformer taps. Do not change only one tap to correct lower voltage on one line, each phase has to be tapped equally, the same. Line to line voltage imbalance at the utility is a utility problem.