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Joined: Jun 2006
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so would one be correct in stating that 180amp fuses be used on the high side followed by a 1/0 conductor to a kva 100 which is grounded to the structure followed by the low side 4/0 conductor which in turn terminates to a mlb200amp panelboard
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Joined: May 2003
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45x72x30 feet or inches?!
Feet way to go!
Inches, it may not fit, especially with 12" clear to combustable matierial, possibly entirely too small. You wouldnt have workspace in the room....
*And should be locked with panic hardware from inside.
[This message has been edited by e57 (edited 06-05-2006).]
Mark Heller
"Well - I oughta....." -Jackie Gleason
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450.5 (1) CONNECTIONS. the transformer shall be directly connected to the ungrounded phase conductors and shall not be switched or provided with over current protection that is independeant of the main switch and common-trip overcurrent protection for the 3-phase 4-wire system does this mean i use the same size fuses on the 3 phase 3 wire side as i do on the 3 phase 4 wire side.
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Joined: Jun 2006
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all of the measurements are in feet
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Joined: May 2003
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An Artical... Note I think one of the illistrations in this is off...
Mark Heller
"Well - I oughta....." -Jackie Gleason
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OK, just one more hint: Starting to think I have said too much? The ratings or settings of the overcurrent protective device obtained from Table 450.3(B) are based on the transformer-rated current and whether or not secondary protection is provided. According to Table 450.3(B), the maximum ratings or settings of overcurrent protective devices for transformers rated 600 volts and less are separated into two categories: primary only protection and primary and secondary protection.
According to Table 450.3(B), transformers with currents of 9 amperes or more must be protected by either of two methods. Method 1 requires primary protection only and is set at not more than 125 percent of the primary side rating. Method 1 does not require secondary side overcurrent protection. Method 2 requires secondary side overcurrent protection to be set at not more than 125 percent, provided the primary side overcurrent protection is set at not more than 250 percent of the primary side rating. Although not required, following either protection method will free the user from any further protection requirements of Table 450.3(B). According to this table, smaller transformers have protection requirements that are less restrictive. For overcurrent protection of motor control circuit transformers, see 430.72. 450.5 is for autotransformers... [This message has been edited by e57 (edited 06-05-2006).]
Mark Heller
"Well - I oughta....." -Jackie Gleason
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Joined: Jun 2006
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so i would pass by bonding the grounding condutor to the grounded conductor at the 200amp disconnect is that correct
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Joined: May 2003
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I have said too much?
You obviously have not done this before, and we here are always willing to help, but at this point you'll have to do some studying before we can go any further....
[This message has been edited by e57 (edited 06-05-2006).]
Mark Heller
"Well - I oughta....." -Jackie Gleason
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due to the fact that the secoundary side is operating mostly electronics it is a must that this side also be protected.also in a step down situation i am decreasing the voltage so why would my over current protection on the line side be 200%
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Joined: Jun 2006
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your right i have not had to ever before had to select the primary side of the transformers size conductors. they have always been in place prior to the install so pardon my ignorance to understanding how this conductors minumum size shall be. there is a formula so the question at hand is do i take 250amps multiply that by 125% which gives me around 314 and divide that number 0.0057 which are the windings listed amounts of seperation to derive the answer of 175 amps and if i were going to use a thhn conductor that a 1/0 would be of proper size. the temperature inside this room is around 100 degrees at its peak
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