The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
Earthquake in New Zeeland
by RODALCO
11/27/16 11:25 PM
Calling all Non-US members!! (Non-US only)
by Tjia1981
11/27/16 06:33 AM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 9
Texas_Ranger 8
Trumpy 8
sparkyinak 7
Who's Online
0 registered (), 99 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Page 1 of 2 1 2 >
Topic Options
Rate This Topic
#44740 - 11/10/04 01:39 PM 3 phase delta
Kelley Offline
Member

Registered: 07/18/04
Posts: 28
Loc: Masachusetts
I was at a site today (new sewer pump station) that will be supplied from a 3 phase delta. Upon checking the meter socket for power i read 240v to ground on a phase, 0 volts to ground on b phase and 240v to ground on c ph. i get 240 v phase to phase. i dont have much experience on this type of system but i thought b phase was the high leg? i'm a little confused does anyone have an answer as to what i should be reading?

thanks
Kelley

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#44741 - 11/10/04 01:57 PM Re: 3 phase delta
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
Your readings are fine.

You have a 3-phase, 3-wire corner grounded delta system, there is no high leg.

A high leg can be found with 3-phase, 4-wire delta systems.

[This message has been edited by iwire (edited 11-10-2004).]
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

Top
#44742 - 11/10/04 02:10 PM Re: 3 phase delta
Kelley Offline
Member

Registered: 07/18/04
Posts: 28
Loc: Masachusetts
so 240 to ground on a and c phase is ok. thank you iwire

Kelley

Top
#44743 - 11/10/04 04:48 PM Re: 3 phase delta
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
 
For 240V delta, regardless of system grounding method, be aware that it is a serious misapplication to use less than 250V fuses or other than 240V circuit breakers. 120- or 120/240V-rated circuit breakers are not intended to be used with 3-wire delta electric services. [See UL white book.]

Top
#44744 - 11/10/04 06:02 PM Re: 3 phase delta
John Steinke Offline
Member

Registered: 04/03/01
Posts: 509
Loc: Reno,Nv., USA
Congratulations! You have found the ONE TIME you fuse/switch the "neutral!"

Top
#44745 - 11/10/04 07:40 PM Re: 3 phase delta
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
John,
You can't use a fuse in this grounded conductor unless the fuse is used for motor overload protection. You treat this grounded conductor just like any other white wire.
Don
_________________________
Don(resqcapt19)

Top
#44746 - 11/12/04 03:39 PM Re: 3 phase delta
maintenanceguy Offline
Member

Registered: 12/02/01
Posts: 303
Loc: Southern NJ, USA
By Bjarney:
____
For 240V delta, regardless of system grounding method, be aware that it is a serious misapplication to use less than 250V fuses or other than 240V circuit breakers. 120- or 120/240V-rated circuit breakers are not intended to be used with 3-wire delta electric services. [See UL white book.]
______

Please explain more.

Top
#44747 - 11/12/04 05:58 PM Re: 3 phase delta
John Steinke Offline
Member

Registered: 04/03/01
Posts: 509
Loc: Reno,Nv., USA
resq- You're quite right- the only times I've encountered this type of power, it was used to power well pumps, and the control voltage came off a transformer.

The UL "White Book" says, under "Circuit breakers, moldes case..." that:
"breakers rated 125/250....are suitable for use....where the voltage to ground does not exceed 125v."
I believe that the "White Book" is available at UL's web site.

Top
#44748 - 11/12/04 09:39 PM Re: 3 phase delta
frenchelectrican Offline

Member

Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
also with delta breaker you can not use the slash on the label like 120/240 volts it must be straght 240 volt becaue of line to ground is pretty high btw it will stated in nec but i cant rember where it is excatally located

merci, marc
_________________________
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


Top
#44749 - 11/13/04 04:35 AM Re: 3 phase delta
CharlieE Offline
Member

Registered: 04/23/04
Posts: 204
Loc: Indianapolis
240.85 Applications. A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker’s voltage rating. A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1–3 to indicate such suitability.

A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker’s voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker’s voltage rating.

FPN: Proper application of molded case circuit breakers on 3-phase systems, other than solidly grounded wye, particularly on corner grounded delta systems, considers the circuit breakers’ individual pole-interrupting capability.
_________________________
Charlie Eldridge, Indianapolis Utility Power Guy

Top
Page 1 of 2 1 2 >



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals