single phase 480

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benmin

benmin

Senior Member
Location
Maine
Occupation
Master Electrician
Installing a 480 single phase service for roadway lighting. Not familiar with 480 single phase. any pointers?
 
You need to determijne if is is a grounded or ungrounded system.
You might want to note 250.21(B) and 250.97
 
Most likely grounded system. Hot (480) neutral and ground. Took me a while to get my head wrapped around it. Light fixture ballasts don't care about one wire or two wire. #6 is usually the minimum wire size. 20 amp circuits. 20' ground rods at every pole. 40' at every service. 2" min conduit size.
 
weressl said:
That would be two phases of a 3 phase system. Otherwise it is not an ANSI recognized system voltage. As such, it is supplied by a two pole breaker(preferred) or two fuses, controlled by two pole contactor.
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Wrong 'ol wise one. As I said it took a while for me to get into it. It is one leg 480 volt to ground. 1 single pole breaker. Disconnects are usually standard 3 phase contactors feeding single pole breakers. The System is used throughout Florida and Michigan. I have no experiance with other states but I must assume they are the same. There are indeed also 480 volt 2 pole systems. 480 volt one pole systems are most common in Florida.
 
Cavie said:
It is one leg 480 volt to ground. 1 single pole breaker.
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We use this all the time for our lighting. You can really stretch those distances a LONG way without worrying about voltage drop at this voltage. It allows us to have delivery points about a mile apart. We use a fuse at the pot for our protection.
 
weressl said:
That would be two phases of a 3 phase system. Otherwise it is not an ANSI recognized system voltage. As such, it is supplied by a two pole breaker(preferred) or two fuses, controlled by two pole contactor.
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While not the majority of 480V systems, it is not so unusual to find single phase, 480V derived from a non three phase system at some of the farms our shop does work for.

The POCO does not mind using a different transformer and the farmer likes not having to pay for the expense of bringing three-phase all the way out to his hay field.
 
I have never seen a 1 phase 480v Hot & Neutral in use.My involvement has always been 3 phase distribution and lights connected phase to phase with fuses oft times in pole base handhole as LW says.

dick
 
ActionDave said:
While not the majority of 480V systems, it is not so unusual to find single phase, 480V derived from a non three phase system at some of the farms our shop does work for.

The POCO does not mind using a different transformer and the farmer likes not having to pay for the expense of bringing three-phase all the way out to his hay field.
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dicklaxt said:
I have never seen a 1 phase 480v Hot & Neutral in use.My involvement has always been 3 phase distribution and lights connected phase to phase with fuses oft times in pole base handhole as LW says.

dick
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When they supply 480 volts from a single phase source it is usually a transformer with 480 volt line to line and center tap is grounded so the voltage to ground is 240.

It is no different than a 120/240 single phase source except voltages are doubled. A 240 volt load will operate from line to neutral just like a 120 volt load does on a 120/240 system.
 
dicklaxt said:
I have never seen a 1 phase 480v Hot & Neutral in use.My involvement has always been 3 phase distribution and lights connected phase to phase with fuses oft times in pole base handhole as LW says.

dick
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Only place you will see this is in Highway lighting systems. Traffic signals will be 220
 
ActionDave said:
While not the majority of 480V systems, it is not so unusual to find single phase, 480V derived from a non three phase system at some of the farms our shop does work for.

The POCO does not mind using a different transformer and the farmer likes not having to pay for the expense of bringing three-phase all the way out to his hay field.
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My point was that it is NOT an ANSI recognnized voltage. The OP did NOT say anything about this being a Utility Service, in which case all bets are off as far as ANSI concerned, with certain exceptions where all MAJOR Utilities DO follow the ANSI Standard and the few, who still does not, does so for legacy reasons, mainly, and they are stuck with it.
 
Cavie said:
Only place you will see this is in Highway lighting systems. Traffic signals will be 220
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weressl said:
My point was that it is NOT an ANSI recognnized voltage. The OP did NOT say anything about this being a Utility Service, in which case all bets are off as far as ANSI concerned, with certain exceptions where all MAJOR Utilities DO follow the ANSI Standard and the few, who still does not, does so for legacy reasons, mainly, and they are stuck with it.
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If you come to where I live, I can take you for a little drive and show you many 240/480 single phase services in remote areas supplied by single phase primary lines from POCO. Majority of them supply irrigation equipment, and they use rotary phase converters to derive three phase. These systems only require 10 KVA max and a phase converter is the less costly way to go vs. having POCO supply a full three phase bank or even an open delta bank, plus additional primary conductors for what would be pretty long runs.
 
kwired said:
If you come to where I live, I can take you for a little drive and show you many 240/480 single phase services in remote areas supplied by single phase primary lines from POCO. Majority of them supply irrigation equipment, and they use rotary phase converters to derive three phase. These systems only require 10 KVA max and a phase converter is the less costly way to go vs. having POCO supply a full three phase bank or even an open delta bank, plus additional primary conductors for what would be pretty long runs.
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No doubt. The question remains: if they are so prevelant why didn't ANSI lists it as a 'standard' voltage system?
 
kwired said:
If you come to where I live, I can take you for a little drive and show you many 240/480 single phase services in remote areas supplied by single phase primary lines from POCO. Majority of them supply irrigation equipment, and they use rotary phase converters to derive three phase. These systems only require 10 KVA max and a phase converter is the less costly way to go vs. having POCO supply a full three phase bank or even an open delta bank, plus additional primary conductors for what would be pretty long runs.
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I could easily be wrong, but the 240/480 center tap source you are describing does not match what the OP, hvlv, and Cavie are describing. You have 240V to ground. 480V across.

They seem to have 480V to ground.
 
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