isolated phase arrangement

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Bill
Why don't you have the bottom of the cabinet removed? This way 300.20 is not an issue.

Also, if this is a service, the utility company will have plenty to say about this installation. I know in the area where we work, this is true. I have installed a few isolated phase installations in the past, but now the utility here does not like to see them anymore, unless there is an open bottom entrance to the enclosure.

How many raceways are you installing?
 
Pierre C Belarge said:
Bill
Why don't you have the bottom of the cabinet removed? This way 300.20 is not an issue.

Also, if this is a service, the utility company will have plenty to say about this installation. I know in the area where we work, this is true. I have installed a few isolated phase installations in the past, but now the utility here does not like to see them anymore, unless there is an open bottom entrance to the enclosure.

How many raceways are you installing?
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The main dist. panel is installed about eight inches above the floor. There are three 5" raceways. Here the utilities authority ends at the transformer vault. The state inspector might not go along with the way i'd like to do this installation. Also my project manager is very involved on this job, so he's going to be squeemish about cutting slots, much less replacing the whole bottom of the tub. One would think it would be an easy sell: ten times easier on the terminations, a very clean looking end result, etc., but i'm not sure they get it. They tend to think: "wrestle the conductors into place how ever you have to and put the cover on."
 
Who's going to be affected by the cost difference? That's who should decide (beyond code compliance, of course.)
 
LarryFine said:
Who's going to be affected by the cost difference? That's who should decide (beyond code compliance, of course.)
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Cost is an interesting concept. Is it more time/cost effective to wrestle those 600's back and forth across the bottom of the tub and criss-crossed around each other, compared to having them emerge pretty much right where they will lay into the lugs, having allowed a little time for cutting narrow slots in the tub between the raceways?
 
Bill,
There is also a long term cost. The impedance of the system is higher when an islolated phase installation is used. If the conductors are on the load side of meter the long term energy cost may exceed the cost savings on the installation.
Don
 
don_resqcapt19 said:
Bill,
There is also a long term cost. The impedance of the system is higher when an islolated phase installation is used. If the conductors are on the load side of meter the long term energy cost may exceed the cost savings on the installation.
Don
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How is Z affected when the conductors cannot be kept the same length because some will emerge directly beneath the lugs others will have to be routed to center of cabinet and then final phases to opposite side of a large cabinet? It seems the isolated arrangement will also compensate somewhat on this point, since the conductors would emerge almost directly beneath the lugs, they would be nearly exact in length.
 
Bill,
The seperation will be a bigger increase in the impedance than the small difference in length. Also if there is any length difference you have a code violation.
Don
 
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