I have a question concerning a tanning salon I'm quoting. The tanning equipment is coming in 230 three phase. The equipment manufacturer suggests a min voltage of 230 and a max of 235. The power company offers a 120/208 and a 120/240 high leg, and the bed manufacturer's rep states that the 240 would be acceptable on the high end of the spectrum. The GC is choosing to use the 240 high leg to eliminate the expense of buck and boost transformers for the equipment. The power company states they can adjust the service transformer to the needed voltage ranges. However the equipment has rather large HVAC requirements, and to save money the GC wishes to use 230v single phase units. For the sake of proper balance of the service and protection of the units I am looking for some codes that may convince the GC to install three phase HVAC units. I've tried common sense but to no avail. I know there will only be max line voltage between the phases in the units, but I'm wondering if the units need to be of a special internal configuration to accept the high leg of power. Most of the service providers here supply 120/208, and I haven't worked with a high leg service in some years now. My biggest concern at this point is could there be some damage caused to the HVAC units, now or in the future, if for some reason the high leg become grounded. Any thoughts on this? thanks
120/240 high leg service
- Thread starter Tarzan
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
You'll need to analyze how larger you 120 volts load are. If the percentage is small, then the 3 phase, 120/240, 4 wire Delta service might be a better choice. For cost effectiveness therefore the large equipment should be 3 phase 240 volts. The high leg should not be an issue.
beanland
Senior Member
- Location
- Vancouver, WA
Unbalance
Unbalance
I see your message as focusing on the possible unbalance caused by the single-phase 230V HVAC units. How much unbalance can the 230V 3-phase tanning beds accept? If the utility transformer is large and close, and if the service lateral/drop is short, you can have a lot of unbalance in the current and have little voltage unbalance. Motor-starting inrush might be a problem though.
Unbalance
I see your message as focusing on the possible unbalance caused by the single-phase 230V HVAC units. How much unbalance can the 230V 3-phase tanning beds accept? If the utility transformer is large and close, and if the service lateral/drop is short, you can have a lot of unbalance in the current and have little voltage unbalance. Motor-starting inrush might be a problem though.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
If I read this question properly, the answer is no, the unit's won't care that one leg is of a higher voltage-to-ground than the other; it's the line-to-line voltage that matters.Tarzan said:
Don't forget that the high-leg line still needs to be colored orange everywhere it's accessible.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
Tarzan said:
You mean 208Y/120V (3 ph, 4W) or 240/120V (high leg delta). A 120/208Y is how you denote a single phase, 3 wire, open wye system, and a 120/240V system is also a single phase, 3 wire system.
Please refer to NEC 100-I, FPN under "Voltage, Nominal" for a more thorough explanation of voltages and proper designations.
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