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Home > Home Wiring USA Archive: NEC 1999 > Main Dwelling Design and Options > Overhead Temporary Service Pole (NEC 1999)

Suggested Wiring Procedures for an Overhead Temporary Service Pole (NEC 1999)

By Warren Goodrich
Suggested Wiring Procedures for an Overhead Temporary Service Pole (NEC 1999)

1 - RECEPTACLE STYLE AND TYPE

All receptacles on a temporary must be GFCI protected. ARTICLE 305/6/A and B If all receptacles on the temporary are on the same circuit, the GFCI mounted as the first receptacle on that circuit will protect all other receptacles on that circuit. The lead receptacle on each circuit must be a GFI receptacle.

You may use a GFI breaker on each circuit instead of the GFCI receptacle. Any direct connect circuit {connectors & wire nut style connection} is allowed not to be GFCI protected, until a receptacle appears on that circuit, then the GFI protection must appear when that receptacle appears Article 305-6-B. If the direct connect circuit is direct connected, at the end of line, without any receptacle on that circuit, then no GFCI is required. ARTICLE 305/6/A Code mute

2 - RECEPTACLE BOX / STYLE AND TYPE

All boxes on a temporary, except special applications, will be considered exposed to wet location. Therefore all boxes, fittings, and covers must be approved as weatherproof. ARTICLE 373/2 The receptacles on the temporary must have a weathershield mounted over the box. ARTICLE 410/57/B This will look like a plastic cover you would find over a thermostat in a motel hallway, except the weathershield must be approved as weatherproof and approved for the purpose. This weathershield might be clear or opaque. If the box is metal, you must bond the metal box to the grounding conductor. ARTICLE 250/146 The bonding method may be accomplished by installing a green ground screw secured to a threaded hole in the back of the box. The bonding method may, also, be accomplished by installing a self grounding receptacle approved for the purpose.

You can identify a self-grounding receptacle by the spring clip mounted at the yoke, to insure an adequate contact to the box. ARTICLE 250-146 This type of self-grounding receptacle is commonly used on conduit style commercial project where no grounding conductor is ran, but using the conduit as the grounding path. ARTICLE 250-146-B The boxes must be securely mounted to the structure of the temporary. ARTICLE 300/11

3 - POLE DIMENSIONS / STYLE / TYPE / DEPTH REQUIREMENTS

The following requirements will not be found in the NEC, but these requirements will most likely be required by either the Utility Company rules, or the Authority Having Jurisdiction. The Authority Having Jurisdiction will use the NEC articles referring to the requirement that any permanent wiring style must be substantially mounted to a permanently installed structure. You will find in the Chapter for temporary wiring that any service is not considered as temporary but must be referred to Article 230 for permanent service installations. ARTICLE 305/4

The pole on an overhead temporary should be a minimum of 5" thick.

The total length requirement, generally is, approximately 16’ long.

Special Note; If you opt for the 5’ deep pole set without braces, then add 2’ to the pole as described making the total pole length for the 5’ deep pole set option of approximately 18’.

"EXPLANATION" If you put 3' of post in the earth, [ braces are normally necessary on an overhead temporary if the pole is set to the 3’ depth for the pole service ]. Mount your receptacle box [or boxes] on the bottom of the assembly starting approximately 2’ 6” above finished grade - the receptacle assembly whether 1 receptacle or two receptacles should be taking up approximately 12" or space, then mount your disconnect or panel above the receptacle(s) - taking up approximately 1' 6", then mount your meterbase at 5’ 6” above finish grade to center of meter, then run your rise up the post to 12’ above finished grade level leaving the point of attachment at least 12’ above finished grade. Then secure the riser to the pole by using a strap near the bottom {just above the meterbase} and then a strap at the top of the riser {just below the weatherhead}. You must supply a set of feeders approved for a wet location, and sized by the maximum amp rating of the main disconnect(s) used on the pole and able to reach at least 3’ past the weatherhead into free air for the Utility Company’s connection., then you have used up approximately 16’ for the pole length with a foot of pole to spare.

4 - NIPPLE STYLE AND TYPE [BETWEEN DISCONNECT AND RECEPTACLES]

When you come out of the bottom of the disconnect or panel, you will find your bossed receptacle box conduit hole, offset, from the hole at the bottom of your disconnect or panel box. You can usually resolve this situation, by using an offset nipple. The minimum size nipple, for a total number of conductors of three to nine 14 Ga. / or three to nine 12 Ga. THWN conductors, which should be an adequate number for most applications from panel to receptacle paths, is 1/2". Chapter 9 Table 1 Note 4 You could use a 1/2" offset nipple, this offset nipple, will usually make your "existing offset condition" work out, by twisting the offset 1/4 turn, to lessen the depth of offset adjustment needed, in order to meet your receptacle box bossed hub / from your panel box knock out. The minimum size wire to your receptacles, through your offset nipple, from your over-current device [breaker or fuse], is 14 Ga. using a 15 amp maximum size overcurrent device. The minimum size wire to your receptacles, through your offset nipple, from your overcurrent device [breaker or fuse], is 12 Ga. using a 20 amp maximum size overcurrent device. The maximum wire size to a duplex receptacle is 12 Ga. on a 15 or 20 amp receptacle device. A 15 amp receptacle is allowed to serve a 14ga.-15 amp circuit and / or a 12ga.-20 amp branch circuit. Any form of receptacle must be and weather proof and GFCI protected. ARTICLE 305/6/A and B

These conductors must be protected by the proper minimum nipple size required by the size of the conductor being protected and the type of nipple being used.

Please keep in mind that any conductor # 4 or larger must be protected with plastic bushings. PVC is not exempt from the plastic bushing requirement. ARTICLE 300/4/F

5 - DISCONNECTS / SIZE / STYLES / TYPES / MINIMUM SIZES PER CIRCUITS

Your overcurrent device [breaker box or fuse box] can be of an array of sizes, each size creating new requirements. I will attempt to approach the majority of your choices.

If you use a type service panel limiting only one circuit in the box, you may use a minimum rating of 15 amps, weatherproof service rated panel. ARTICLE 230/79/A

If you use a type service panel with only two circuits in the box, you must use a minimum rating of 30 amps, weatherproof service rated panel. ARTICLE 230/79/B

If you use a type service panel with more than two [three or more] circuits in the box, you must use a minimum rating of 60 amps, weatherproof service rated panel. ARTICLE 230/79/D

You must use a service rated panel equal to or larger than the demand load calculated for your project as required by ARTICLE 220

It is allowed that if you have six or less [breakers or disconnects] {that are grouped}, a main disconnect, and / or, breaker is not required as long as they are permanently secured to the service panel, and considered as main breakers. ARTICLE 230/71

Please keep in mind, that if you use a single main overcurrent device smaller than the maximum rating of your service panel, you may reduce the feeder size to equal your main overcurrent device maximum rating, but you must provide the maximum demand load to the equipment to be used.

The main overcurrent device, must be locked in place in the panel, to be used as a main overcurrent device.

Please keep in mind, that although you are working with a "temporary", Article 230 must still apply as a permanent service, and be treated as such.

Please keep in mind that any equipment being utilized as a service panel must be service rated.

6 - NIPPLE / STYLE / TYPE [BETWEEN METER AND DISCONNECT]

Your nipple between the service panel, and the meterbase, must be sized by the feeder sizes which must be sized by the total of your service panel main over-current device/s maximum rating, or provide the maximum demand load of the equipment to be used on this service.

If your service panel main over-current device size is 30 amps [which must be locked in place if a breaker], you may use a feeder rated no less than a 30 amp rated conductor, from the transformer, through to the main lugs of the service panel, or the lug of your main over-current device.

If your service panel main over-current device size is 60 amps, [which must be locked in place if a breaker], you must use a feeder rated no less than a 60 amp rated conductor, from the transformer, through to the main lugs of the service panel, or the lug of your main over-current device.

If your service panel main over-current device size is 100 amps [which must be locked in place], you must use a feeder rated no less than a 100 amp rated conductor, from the transformer, through to the main lugs of the service panel, or the lug of your main over-current device.

If you use a "main lug only" panel, and you have only one circuit available in the service panel and the box is 15 amp rated you may use a feeder rated no less than a 15 amp rated conductor.

If you use a main lug only panel, and you have only two circuits available in the service panel and the box is 30 amp rated or less you must use a feeder rated no less than a 30 amp rated conductor.

If you use a main lug only panel, and/or you, have, three or more, circuits available in the service panel, and the box is 60 amp rated, or more, you must use a feeder rated no less than the maximum rating, of the service box over-current device, and / or, of the maximum rating of the service box itself, if the over-current device was not installed by the manufacturer, and / or, if the service box is a main lug only panel. This feeder may have to be rated, as much as, 200 amps, or more, depending on the maximum rating of the service panel over-current devices, and whether the main over-current device can be easily changed to a larger over-current device, or there is no over-current device in the service panel. NEC Table 310-16 and 230/42 and 240/6/D

You must use the 60 degree column found in table 310-16 to decide the ampacity of your conductors if that conductor is smaller than #1. You must use the 75 degree column found in table 310-16 to decide the ampacity of your conductors if that conductor is larger than #1. This is true regardless of the temperature rating of the insulation of that conductor. 110-14

7 - METERBASE / SUPPLIER / REQUIREMENTS

Some Utility companies will furnish that meter base for your temporary. Some Utility companies require you to furnish your meter base. You really should call your local Inspector and your local Utility company to confirm what rules apply in your area concerning that meter base. Also check with them concerning any special local rules applying to temporary services. Some Utility companies even will furnish the entire temporary and electricity for one set fee. This is where you really should make those two contacts both the AHJ and your serving Utility Company for specialized local rules.

8 - STRAPS / WHERE REQUIRED

You must support the pipe with straps. The NEC states that you must install a strap near each end of the conduit. Check the support requirements of the style and type of conduits you are using. Keep in mind that if the conduit is installed below the height of the meterbase chances are that conduit will be subject to physical damage. Please confirm that the conduits being installed below approximately 6’ are approved where subject to physical damage.

9 - FEEDER / STYLE / TYPE / SIZE

If you are using this temporary on a residential application, you may size your feeders by 310/15/B/6 allowing a reduction in size from that required for commercial use. If you are using this temporary on a non-residential unit you must size your feeder by Table 310/16

Special Note: Keep in mind that the charts must be adapted to meet the requirements of Article 110-14 . If the conductor is smaller than a #1 AWG. then the temperature rating of the conductor as per the ampacity in Article 310/16 must be limited to 60 degree centigrade [such as the column for TW conductors] regardless if the conductor is rated 75 or 90 degree such as THHN Conductors. If the conductors are used as a feeder for a residential setting then you may disregard the temperature limitations and use the Table 310-15-B-6 exclusively. This use of Table 310-15-B-6 may be controversial when used on a residential setting yet on a temporary. Please contact you local AHJ to confirm that you are allowed to use this table in your local area.

In this application you must use a conductor approved for a wet location ,and approved as a service conductor [with a "W" in it's identification]. Please leave approximately 3’ sticking out beyond the weatherhead allowing enough conductor length that the Power Company may have enough to work with during their connection to your service entrance conductors. Please identify the neutral with either a white or gray identifying means.

The following feeders are accepted practice to use in this application to serve as a feeder to an overhead temporary, but this list does not name all conductors approved for this application.

COPPER FEEDERS

30 amp rated contained within a conduit = 10 Ga. THWN / OR / THW / OR / XHHW

60 amp rated contained within a conduit = 4ga. THWN / OR / THW / OR XHHW

100 amp rated contained within a conduit = 4 Ga. THWN / OR / THW / OR XHHW {residential}

200 amp rated contained within a conduit = 2/0 THWN / OR / THW / OR XHHW {residential}

ALUMINUM FEEDERS

30 amp rated contained within a conduit = 8 Ga. THWN / OR / THW / OR / XHHW

60 amp rated contained within a conduit = 3 Ga. THWN / OR / THW / OR XHHW

100 amp rated contained within a conduit = 2 Ga. THWN / OR / THW / OR XHHW

200 amp rated contained within a conduit = 4/0 THWN / OR / THW / OR XHHW

Special Note; If you are using aluminum wiring you must use anti-oxidation inhibitor [Nolox] at each connection of that aluminum conductor.

10 - RISER PIPE / TYPE / STYLE / MINIMUM SIZES

Accepted practice will lead you to Sch 40 PVC due to a cost factor.

You may use Sch 80 PVC, EMT, Rigid conduit or several other types of conduit in this occasion.

Special Note; If you are using the riser as support for the Lateral coming from the power pole then you must use a minimum size rigid conduit of 2”

11 – TRANSFORMER

Your Utility Company will flag the area where they plan to set your transformer, and your Utility Company will furnish your transformer for you.

12 - GROUNDING REQUIREMENTS

You must drive a 1/2" x 8' minimum size made grounding electrode [Ground rod] at your temporary.

You must then run the grounding service conductor up the pole to the service panel. Article 250/52/C/2

You must not use an aluminum grounding electrode in direct contact with the earth. Article 250/52

You must not use an aluminum conductors as a grounding service conductor in direct contact with the earth. Article 250/64/A

Absolute minimum grounding service conductor is a # 8 copper for 100 amp or less and # 6 copper for more than 100 amp. Article 250/66

Grounding service conductor sizes between a ground rod and a service panel are as follows;

30 amp feeder = # 8 copper grounding service conductor Article 250/66

60 amp feeder = # 8 copper grounding service conductor Article 250/66

100 amp feeder = # 8 copper grounding service conductor Article 250/66

200 amp feeder = # 6 copper grounding service conductor to a made

electrode. [ground rod] Article 250/66/A

13 - GENERAL INFO ON TEMPORARY

APPROVED LENGTH OF TIME TO BE USED

The maximum allowable time for any type of temporary wiring are as follows; 90 DAYS on non construction type projects. Article 305/3/B

LIFE OF CONSTRUCTION PROJECT where on a construction site as long as construction process is an active construction project. Article 305/3/A

Special Note; The temporary wiring style running from the temporary on the load side of the overcurrent device is rather forgiving on a temporary wiring condition. You must show that the temporary wiring is under a controlled supervision. [ NOT SERVICE EQUIPMENT ] Article 305

Special Note; Pole braces are required on an overhead temporary mounted 3/4 of the way to top of the pole and made in a “V” pattern toward the serving utility pole, unless pole is proven to be buried 5’ or more below undisturbed dirt surface by most AHJs.

This document is based on the 1999 national electrical code and is designed to give you an option, as a self-help, that should pass minimum code requirements. While extreme care has been implemented in the preparation of this self-help document, the author and/or providers of this document assumes no responsibility for errors or omissions, nor is any liability assumed from the use of the information, contained in this document, by the author and / or provider.

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