equipment power

[j92green]

I have a 208Y/120 panel with a 15A circuit supplying power to a chiller. The L1,L2,L3 voltage readings at the chiller are 243,242,245V. I'm a little rusty on my electrical... 1.How am I getting 240V on a 208Y/120 feed?
2.The chiller nameplate says 220V. I should be OK with the above measured voltages, right?

 

[rbulsara]

What are the voltage readings at 208/120V panelboard?

The nameplate means little.

 

[buzzp]

If the same voltages are at the panel board (I suspect they are) then their is a transformer tap somewhere that is set kind of high. It is common to see varying voltages in some regions based on the season, ie, phoenix will use more power in the summer so the system is loaded a bit more, pulling the voltage down a bit more, so the taps need to be a little higher.
Your chiller motor can handle running at these higher voltages (+-10%). However, you may be losing a small amount of efficiency by way of increased current draw since you are operating at a higher than nameplate volts. Assuming the load is constant.
Does this panel feed other equipment that may be located a ways away (high tap setting so downstream devices don't see to low a voltage)?

 

[jraef]

Along the lines of buzzp's thinking, was the chiller running when you measured the voltage? If not, the transformer may have been tapped a little high for THAT CHILLER! If the wire run from the panel to the chiller is long, it alone may be the "problem load" on the system that must be compensated for. If the voltage shows lower while the chiller is running, that is the case because the voltage drop would not show until the chiller was drawing full current.

"Venditori de oleum-vipera non vigere excordis populi"

 

[peebee]

For what it's worth -- I just found out our local utility's standard procedure is to set 480v (nominal) services up around 505v. In my opinion, that's crazy high. But I guess it works for them.

At least the above example is only a 5% overvoltage. Yours is a much higher 17%.

I too would be curious to see what happened to voltage both at the panel and at the chiller when the chiller is run loaded.

Also, my understanding is that motors generally prefer overvoltage to undervoltage (lamps, by contrast, prefer undervoltage). Any comments on that?

 

[buzzp]

Peebee, Your last comment about under/over voltage could be true in most cases just because of starting/running torque. However, at higher voltages the PF suffers (although the current actually goes up after about a 5% increase in nameplate voltage, also goes up as you reduce the voltage but at a faster rate).

Since his motor is 220V then is motor is seeing under a 10% voltage increase(110% of 220 is 242V). Although if other equipment is connected on the same feed then this high voltage could be causing problems with this other equipment.

 

[busbar]

 
Off topic a little, but 242V ø-ø corresponds to almost 140V ø-n(!)

 

[buzzp]

Good point busbar. Does the poster have 120v loads on this service as well? Other equipment on 208?

Have you confirmed the transformer is wired for 208/120? Maybe some retrofit happened and things were rewired at some point in time.

 

[peebee]

Update on the 505v service entrance I mentioned above -- after some screaming by the VFD vendors, the utility is out there dropping the voltage. I still have not heard what the new voltage actually is.