Max pole spacing (neutral messenger)

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xguard

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Baton Rouge, LA
Can someone point me to the allowed maximum spacing between supports a triplex with neutral messenger? I'm assuming there is a limitation to how far apart the poles can be that support it. This is a feeder running between two buildings, there's a pole at each building about 160 feet apart. Thanks.
 
Unanswerable with the information given. You should be able to get the maximum allowed tension of the messenger. The actual tension will depend on the sag, and the maximum sag will depend on how high the attachment points are on the poles. Then you need to consider the moment imparted on the poles and their mounting structure.
 
I can't really offer much for the OP's question as this is not really an NEC thing. I would think the NESC would have some info. on this.
But I have to ask about the application. You indicate that is a feeder so Art. 225 would apply. In that case the messenger will need to be the EQC and will need to identify an insulated conductor as the neutral. If this is 120/240 single phase, then this can be done if you use quadplex. If 3 phase, then that presents other problems as there is no such thing as quintplex.
 
xguard said:
Can someone point me to the allowed maximum spacing between supports a triplex with neutral messenger? I'm assuming there is a limitation to how far apart the poles can be that support it. This is a feeder running between two buildings, there's a pole at each building about 160 feet apart. Thanks.
Click to expand...
I can help, just designed a 4/0-4/0-2/0 triplex run between a pole and two buildings, approx 150' each span. First, as retirede said, there is not enough information. You need to know the allowable sag, allowable tension, and the wire size.

You will need to do a little design. IT is not that hard, I have all the information you will need in the following links. Just go through it, it will will probably take an hour or two to design.

Triplex is available with 3 types of messenger: AAC, ACSR, and 6201. Also note that you can have full neutral or reduced neutral (messenger).


Here is a list of the different types, the breaking strength of the messengers, and the weight per foot:

This document has the formulas for allowable tension, sag, span, and ice loading on pages 29-31:
https://www.anixter.com/content/dam...erature/envirotectPowerCableInstallManual.pdf pages 29-31

Get to work, I want this designed and wire spec'd and ordered by tomorrow afternoon!
 
texie said:
If 3 phase, then that presents other problems as there is no such thing as quintplex.
Click to expand...
Maybe. I found some 5-conductor overhead cable from China.

It doesn't have a messenger, and all five conductors are XPLE.

Should be able to span distances with a support messenger.

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retirede said:
Unanswerable with the information given. You should be able to get the maximum allowed tension of the messenger. The actual tension will depend on the sag, and the maximum sag will depend on how high the attachment points are on the poles. Then you need to consider the moment imparted on the poles and their mounting structure.
Click to expand...
Seems like you answered it fine. thanks.
 
electrofelon said:
I can help, just designed a 4/0-4/0-2/0 triplex run between a pole and two buildings, approx 150' each span. First, as retirede said, there is not enough information. You need to know the allowable sag, allowable tension, and the wire size.

You will need to do a little design. IT is not that hard, I have all the information you will need in the following links. Just go through it, it will will probably take an hour or two to design.

Triplex is available with 3 types of messenger: AAC, ACSR, and 6201. Also note that you can have full neutral or reduced neutral (messenger).


Here is a list of the different types, the breaking strength of the messengers, and the weight per foot:

This document has the formulas for allowable tension, sag, span, and ice loading on pages 29-31:
https://www.anixter.com/content/dam...erature/envirotectPowerCableInstallManual.pdf pages 29-31

Get to work, I want this designed and wire spec'd and ordered by tomorrow afternoon!
Click to expand...
Thanks! I'll get right on it ;-)
 
texie said:
I can't really offer much for the OP's question as this is not really an NEC thing. I would think the NESC would have some info. on this.
But I have to ask about the application. You indicate that is a feeder so Art. 225 would apply. In that case the messenger will need to be the EQC and will need to identify an insulated conductor as the neutral. If this is 120/240 single phase, then this can be done if you use quadplex. If 3 phase, then that presents other problems as there is no such thing as quintplex.
Click to expand...
This is 120/240 single phase. It looks like two insulated conductors and one uninsulated. I'm assuming the bare wire is being used for both the neutral and ground. This is an existing installation but it's only about 15 years old. I'm not sure what the code required at that time. We are installing new service equipment and a panel that will be feeding this aerial feed. I'd prefer it was code compliant since we are tying into it.
 
retirede said:
Unanswerable with the information given. You should be able to get the maximum allowed tension of the messenger. The actual tension will depend on the sag, and the maximum sag will depend on how high the attachment points are on the poles. Then you need to consider the moment imparted on the poles and their mounting structure.
Click to expand...
Potential wind loading or ice loading come into play as well.
 
Just one more thing:. The only thing missing from those docs is temperature correction. I couldn't really find a simple chart or document on change in sag/tension die to temperature differences. I just ended up calculating the change in length manually based on the coefficient of thermal expansion which is about 6 millionths /degree F/ inch for steel and 12 for AL
 
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