critique requested

[petersonra]

I created some drawings to assist people in wiring up transformers, specifically sizing wiring, grounding, and OCPD. I realize it does not cover all possible conditions, just the ones we encounter most. Also, does not allow for some things the code does, but it seems simpler if there are fewer choices.

 

[Smart $]

Only thing I see that you may want to include is the SSBJ changing to EGC after the secondary OCPD.

The text in the second image is fairly small, distorted, and for the most part unreadable on my end...

 

[petersonra]

Only thing I see that you may want to include is the SSBJ changing to EGC after the secondary OCPD.

The text in the second image is fairly small, distorted, and for the most part unreadable on my end...

here is the text.

NOTES:
1. ABBREVIATIONS
EGC - EQUIPMENT GROUNDING CONDUCTOR
GEC - GROUNDING ELECTRODE CONDUCTOR
GES - GROUNDING ELECTRODE SYSTEM
OCPD - OVER CURRENT PROTECTION DEVICE (TIME DELAY FUSE OR INVERSE TIME CIRCUIT BREAKER)
SBJ - SYSTEM BONDING JUMPER
SDS - SEPARATELY DERIVED SYSTEM
SSBJ - SUPPLY SIDE BONDING JUMPER

2. PRIMARY CURRENT IS CALCULATED BY DIVIDING TRANSFORMER VA RATING BY NOMINAL PRIMARY VOLTAGE.

3. SECONDARY CURRENT IS CALCULATED BY DIVIDING TRANSFORMER VA RATING BY NOMINAL SECONDARY VOLTAGE.

4. NOMIINAL VOLTAGES ARE TYPICALLY 480, 240, AND 120.

5. STANDARD RATINGS IN AMPERES FOR OCPD ARE 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, AND 200.
ADDITIONAL STANDARD AMPERE RATINGS FOR FUSES SHALL BE 1, 3, 6, AND 10.
IF EITHER OCPD RATING EXCEEDS 200A, ENGINEERING REVIEW IS REQUIRED.

6. PRIMARY OCPD RATING NOT TO EXCEED 250% OF PRIMARY CURRENT.

7. PRIMARY CONDUCTORS? MINIMUM CONDUCTOR AMPACITY 125% OF PRIMARY CURRENT.?AMPACITY MUST ALSO EQUAL OR EXCEED?PRIMARY OCPD RATING.

8. EGC MUST ROUTE WITH PRIMARY CONDUCTORS INSIDE SAME CABLE, RACEWAY, OR ENCLOSURE. SIZE PER T250.122 USING RATING OF PRIMARY OCPD IF A WIRE. EGC CAN BE BARE OR GREEN INSULATED WIRE, A METALLIC RACEWAY LISTED FOR USE AS AN EGC, THE METALLIC ENCLOSURE (OR A PROPERLY BONDED PANEL IN THE ENCLOSURE) THE CIRCUIT CONDUCTORS ARE ENCLOSED WITHIN, OR SOME COMBINATION THEREOF.

9. SBJ SIZED PER T250.66. MUST BE AN UNSPLICED WIRE, BARE OR GREEN INSULATED.

10. GEC MOST BE AN UNSPLICED WIRE, BARE OR GREEN INSULATED, SIZED PER T250.66. CONNECTS TO GES, GEC TERMINAL OR GEC BUS BAR.

11. SSBJ MUST ROUTE WITH SECONDARY CONDUCTORS INSIDE SAME CABLE, RACEWAY, OR ENCLOSURE. SIZE PER T250.66 IF A WIRE. IT MAY BE A BARE OR GREEN UNSULATED WIRE OR A METALLIC RACEWAY LISTED FOR USE AS AN EGC.

12. SECONDARY CONDUCTORS ?MINIMUM AMPACITY 125% OF SECONDARY CURRENT?AMPACITY. MUST ALSO EQUAL OR EXCEED?SECONDARY OCPD RATING.

13. SECONDARY OCPD RATING NOT TO EXCEED 125% OF SECONDARY CURRENT. MAY ROUND UP TO NEXT STANDARD SIZE OCPD RATING.

14. IF THE SECONDARY OCPD IS A MAIN CB IN A LISTED LOADCENTER, THE SBJ CAN BE A GREEN SCREW SUPPLIED BY THE LOADCENTER MANUFACTIRER RUN THROUGH THE NEUTRAL BAR INTO THE CASE OF THE LOAD CENTER. THE SBJ IS ONLY ALLOWED IN ONE OF THESE LOCATIONS.

15. IF THE SECONDARY OCPD IS A MAIN CB IN A LISTED LOADCENTER, THE GEC CAN BE CONNECTED TO THE LOADCENTER NEUTRAL BAR.THE GEC CAN ONLY BE CONNECTED IN ONE OF THESE TWO PLACES.

16. OTHER CONFIGURATIONS ARE POSSIBLE BUT WILL REQUIRE ENGINEERING REVIEW.

17. SBJ, SSBJ, EGC, AND GEC MAY BE BLACK INSULATED MARKED WITH GREEN TAPE AT ALL TERMINATIONS FOR WIRES LARGER THAN #6.

18. GEC MUST BE PROTECTED FROM PHYSICAL DAMAGE BY BEING ENCLOSED WITHIN A LISTED RACEWAY OR ENCLOSURE FOR SIZES SMALLER THAN #4. IF ENCLOSED WITHIN A METALLIC RACEWAY, IT MIST BE BONDED TO THE RACEWAY AT THE POINT IT ENTERS THE RACEWAY AND AT THE POINT IT LEAVES THE RACEWAY.

 

[petersonra]

I realized I forgot that control xfmrs 1000VA and smaller do not require a GEC. I need to add that.

 

[augie47]

What is the basis of the 125% in (7) & (12) ?

 

[petersonra]

What is the basis of the 125% in (7) & (12) ?

I think I got carried away with 125%. I am going to remove that.

Good catch.

 

[cadpoint]

Just noting things I saw and thought about?

You list SDS - SEPARATELY DERIVED SYSTEM but never state or use this term in the
illustration.

Technical writing is tough, now you can have the reader follow your desired thought process, but you have to cover all the bases.
Or is this some type of descriptive writing and through the use of abbreviations and notes in a given order or is it just get all techncial and not worry about it. But alias your trying to tell a story, so you need a begining a middle and and end. If I had not read the OP, would everyone else know what their looking at; take for example the two inserts bracket inside #'s 1 & 2, and even a re-write of # 1. You can insert the main subject (transformer) easily through out various notes.

In the Drawing you showed the GEC, in dash below the SSBJ. First, the GEC should be closer to the secondary conductors and not dashed. All The SSBJ while less important should be dashed and usually plays a dashed roll in transformers.

I took the liberty of re-prositioning renumbering your work, I might have dropped(missed) one # resetting everything! The only thing I didn't do was try to put all the numbers in the order of sequence of the given abbreviations.

Isn't # 13 really part of note # 12, or is it; Other transformer arrangements are possible but will require
engineering review. I just don't understand why this statement stands alone, or should this be the last note all together.

IMO
On the drawing presentation of your work all capitols on that page is allowed.
As presented the abbreviations and notes, it's a tough to read all capitols unless you maintain the drawing aspect of things.




ABBREVIATIONS
EGC - EQUIPMENT GROUNDING CONDUCTOR
GEC - GROUNDING ELECTRODE CONDUCTOR
GES - GROUNDING ELECTRODE SYSTEM
OCPD - OVER CURRENT PROTECTION DEVICE (TIME DELAY FUSE OR INVERSE TIME CIRCUIT BREAKER)
SBJ - SYSTEM BONDING JUMPER
SDS - SEPARATELY DERIVED SYSTEM
SSBJ - SUPPLY SIDE BONDING JUMPER

NOTES:

1. NOMIINAL VOLTAGES( for transformers) ARE TYPICALLY 480, 240, AND 120.
or – Nominal Voltages for this presentation of transformers are typically 480, 240, AND 120.

2. STANDARD RATINGS IN AMPERES FOR OCPD (used for transformers can be) 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, AND 200.
ADDITIONAL STANDARD AMPERE RATINGS FOR FUSES SHALL BE 1, 3, 6, AND 10.
IF EITHER OCPD RATING EXCEEDS 200A, ENGINEERING REVIEW IS REQUIRED.

3.PRIMARY CURRENT IS CALCULATED BY DIVIDING TRANSFORMER VA RATING BY NOMINAL PRIMARY VOLTAGE.*

4. PRIMARY OCPD RATING NOT TO EXCEED 250% OF PRIMARY CURRENT.

5. PRIMARY CONDUCTORS? MINIMUM CONDUCTOR AMPACITY 125% OF PRIMARY CURRENT.?AMPACITY MUST ALSO EQUAL OR EXCEED?PRIMARY OCPD RATING.

6. SECONDARY CURRENT IS CALCULATED BY DIVIDING TRANSFORMER VA RATING BY NOMINAL SECONDARY VOLTAGE.

7. SECONDARY OCPD RATING NOT TO EXCEED 125% OF SECONDARY CURRENT. MAY ROUND UP TO NEXT STANDARD SIZE OCPD RATING.

8. IF THE SECONDARY OCPD IS A MAIN CB IN A LISTED LOADCENTER, THE SBJ CAN BE A GREEN SCREW SUPPLIED BY THE LOADCENTER MANUFACTIRER RUN THROUGH THE NEUTRAL BAR INTO THE CASE OF THE LOAD CENTER. THE SBJ IS ONLY ALLOWED IN ONE OF THESE LOCATIONS.

9. IF THE SECONDARY OCPD IS A MAIN CB IN A LISTED LOADCENTER, THE GEC CAN BE CONNECTED TO THE LOADCENTER NEUTRAL BAR.THE GEC CAN ONLY BE CONNECTED IN ONE OF THESE TWO PLACES. ENCLOSURE (OR A PROPERLY BONDED PANEL IN THE ENCLOSURE) THE CIRCUIT CONDUCTORS ARE ENCLOSED WITHIN, OR SOME COMBINATION THEREOF.

10. EGC MUST ROUTE WITH PRIMARY CONDUCTORS INSIDE SAME CABLE, RACEWAY, OR ENCLOSURE. SIZE PER T250.122 USING RATING OF PRIMARY OCPD IF A WIRE. EGC CAN BE BARE OR GREEN INSULATED WIRE, A METALLIC RACEWAY LISTED FOR USE AS AN EGC, THE METALLIC12. SECONDARY CONDUCTORS ?MINIMUM AMPACITY 125% OF SECONDARY CURRENT?AMPACITY. MUST ALSO EQUAL OR EXCEED?SECONDARY OCPD RATING.

11. SBJ SIZED PER T250.66. MUST BE AN UNSPLICED WIRE, BARE OR GREEN INSULATED.

12. SSBJ MUST ROUTE WITH SECONDARY CONDUCTORS INSIDE SAME CABLE, RACEWAY, OR ENCLOSURE. SIZE PER T250.66 IF A WIRE. IT MAY BE A BARE OR GREEN UNSULATED WIRE OR A METALLIC RACEWAY LISTED FOR USE AS AN EGC.

13. OTHER CONFIGURATIONS ARE POSSIBLE BUT WILL REQUIRE ENGINEERING REVIEW.

14. SBJ, SSBJ, EGC, AND GEC MAY BE BLACK INSULATED MARKED WITH GREEN TAPE AT ALL TERMINATIONS FOR WIRES LARGER THAN #6.

15. GEC MOST BE AN UNSPLICED WIRE, BARE OR GREEN INSULATED, SIZED PER T250.66. CONNECTS TO GES, GEC TERMINAL OR GEC BUS BAR.

16. GEC MUST BE PROTECTED FROM PHYSICAL DAMAGE BY BEING ENCLOSED WITHIN A LISTED RACEWAY OR ENCLOSURE FOR SIZES SMALLER THAN #4. IF ENCLOSED WITHIN A METALLIC RACEWAY, IT MIST BE BONDED TO THE RACEWAY AT THE POINT IT ENTERS THE RACEWAY AND AT THE POINT IT LEAVES THE RACEWAY.

 

[petersonra]

Thanks for the comments.

This is actually two separate sheets of a two drawing set. The illustration is sheet 1 and the notes sheet two.

To make it readable I had to take the notes, copy them from the drawing into notepad, and than copy and paste to the forum so all the formatting was lost. I don't know why but the copy and paste operation inserted some question marks and took out some spaces.

The reason that the SBJ and GEC are dashed in is because there are optional locations for these conductors. These can either be at the xfmr or at the panelboard. There is supposed to be a note about this, but it seems to be missing.

 

[electricalist]

Good job. There arent alot of electricians I know that see the benefit of thesr types of work.
My buddy was doing one on basic services but with his he found more people liked not really knowing what they were doing.

Sent from my SPH-D710BST using Tapatalk

 

[don_resqcapt19]

The only color requirement for GECs and SSBJs is that they not be white or gray. They are permitted to be green, but not required to be.

Note 12, if the metallic raceway is used as the SSBJ it must be a nonflexible raceway, not just a metallic raceway that is permitted to be used as an EGC.

The notes don't really separate out the conductor and transformer overcurrent protection. Those rules are independent, but often a single OCPD can serve both functions. For example if the transformer primary OCDP is rated at 125% or less of the primary current, the transformer secondary winding does not require overcurrent protection. The secondary conductors require overcurrent protection, but the transformer itself does not. The rules in Article 450 apply to the protection of the transformer itself, and the rules in Article 240 apply to the protection of the conductors that are connected to the transformer.

 

[petersonra]

The only color requirement for GECs and SSBJs is that they not be white or gray. They are permitted to be green, but not required to be.

Note 12, if the metallic raceway is used as the SSBJ it must be a nonflexible raceway, not just a metallic raceway that is permitted to be used as an EGC.

The notes don't really separate out the conductor and transformer overcurrent protection. Those rules are independent, but often a single OCPD can serve both functions. For example if the transformer primary OCDP is rated at 125% or less of the primary current, the transformer secondary winding does not require overcurrent protection. The secondary conductors require overcurrent protection, but the transformer itself does not. The rules in Article 450 apply to the protection of the transformer itself, and the rules in Article 240 apply to the protection of the conductors that are connected to the transformer.

I will adjust note 12.

This document is intended to simplify things, in part by limiting the number of choices shop people would have to make. As one of the notes mentioned, other configurations can be acceptable, but it has to pass through our engineering department first.

It also does not allow for larger transformers, as the largest OCPD mentioned are 200A. Again, just to make sure it passes through engineering first. I think I am going to change that to 150A. That way there is no reason to use parallel conductors that introduces another thing into the mix. It is not like we do many xfmrs with OCPD in excess of 150A anyway. If we did, i would want one of our engineers to bless what is being done.

 

[electricalist]

Will this document include a feeder schedule?

 

[petersonra]

Will this document include a feeder schedule?

In some format each project has it. This document is more generic.

I may create a generic 120/240 single phase load center diagram. Might as well have a template for it available.

 

[electricalist]

Thats what I thought as well.
With no parallel feeders a feeder to choose from schedule would be a nice addition.
I dont like to lower an electricians value but lowering some of the calculations will save time = money.

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[petersonra]

Thats what I thought as well.
With no parallel feeders a feeder to choose from schedule would be a nice addition.
I dont like to lower an electricians value but lowering some of the calculations will save time = money.

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we do not have any electricians. panel wirers don't spend 4 or 5 years as an apprentice learning the electrical code. the kinds of things we do tend to be pretty repetitive, so lends itself somewhat to rote learning of a few things without going into a lot of detail.

 

[electricalist]

Well either way I think its good to come up
with things like you are.

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[petersonra]

Well either way I think its good to come up
with things like you are.

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They are good panel wirers, and are quite adept at following drawings, but I don't think they even have a code book.

I hope it will help on the design side as well. The fewer choices, the less chance of a mistake there as well.

I wonder how much room I might have left for tables of values that could be used to further reduce the need to look things up.