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#34226 - 02/05/04 09:45 PM Long wire runs
aldav53 Offline
Member

Registered: 08/22/01
Posts: 547
Loc: Chandler, AZ USA
I'm doing a job for a church and need to run a few 20a cicuits for lighting and cameras, probably 150 ft or more. Wondering if I should size up to # 10 wire?
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#34227 - 02/05/04 10:27 PM Re: Long wire runs
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
From http://www.dot.state.ak.us/anc/Engineeri...ireandCable.pdf
  • On 20A circuits, with one-way conductor lengths measured from panel to farthest receptacle, or center of lighting string (as applicable):
    1. #10 AWG for 120V circuits of 75 feet to 120 feet.
    2. #8 AWG for 120V circuits of 120 feet to 200 feet.
    3. #10 AWG for 277V circuits of 130 feet to 215 feet.
    4. #8 AWG for 277V circuits of 215 feet to 330 feet.





[This message has been edited by Bjarney (edited 02-06-2004).]

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#34228 - 02/06/04 07:17 AM Re: Long wire runs
seeks Offline
Member

Registered: 05/13/02
Posts: 24
Loc: bufalo, ny 14228
Voltage drop is dependant on the load. You should figure the voltage drop per the N.E.C., not some arbitrary standard. JUST BECAUSE IT IS PUBLISHED ON THE INTERNET, THAT DOESN'T MAKE IT RIGHT!
Certainly, if a client has a standard in place, you should comply with it. The document that is hyperlinked isn't even approved, it's a draft. I doubt your church conforms to a state D.O.T. DRAFT standard. This will assure a safe, proper installation.
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#34229 - 02/06/04 09:04 AM Re: Long wire runs
C-H Offline

Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
Seeks,

did you find anything technically wrong with the information Bjarney provided?

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#34230 - 02/06/04 10:10 AM Re: Long wire runs
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
seeks, you are welcome to propose something different. I don’t see where the posted material is a draft—apologies for my oversight. My purpose was to point out that one organization has significant experience in this area, and has found that their problems with voltage drop in receptacle circuits are reasonably minimized by using some basic considerations.

Obviously, cord-connected loads vary widely, and this may be one reasonable compromise. The material was not claimed to be a cure-all. Clearly the suggested is by no means mandatory anyplace else. But—a church could have their own ¾-horsepower floor waxer in a hallway or 1440-watt portable heater in a nursery, powered from a multi-outlet circuit. {Er, take your Ritalin, Garth.}

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#34231 - 02/06/04 10:11 AM Re: Long wire runs
Ryan_J Offline
Moderator

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
I'm with Seeks on this one. There is no blanket rule that can address voltage drop, as it is dependant upon the load served.
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#34232 - 02/06/04 12:40 PM Re: Long wire runs
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
What seeks says is correct, but IMO he was a little aggressive with his condemnation of Bjarney's info.

I agree with Bjarney's figures, for GP circuits I like to assume 80% loading of the branch circuit and staying around 3% drop.

Hey guess what, thats what those figures from Bjarney result in.

Most of the jobs I work have something in the spec. about moving up a size for every 75' to 100' of additional one way length.

Sure if you know all you are powering is a security camera transformer you could run 1000' with 12 AWG @ 120, but for general use in these branch circuit sizes, you will not break the budget figuring the load at 80% of the branch circuit size.

Start talking feeders and I would want to know the load not guess at it.




[This message has been edited by iwire (edited 02-06-2004).]
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#34233 - 02/06/04 01:08 PM Re: Long wire runs
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
aldav53

In case you are not familiar with voltage drop there are many variables.

I will give you some examples to show how much the load effects the length for a given amount of voltage drop.

Say we allow 3% voltage drop on a 120 volt circuit wired with 12 AWG.

A 1 amp load on this circuit and we could run 900 feet one way.

A 5 amp load on this circuit and we could run 180 feet one way.

10 amp load on this circuit and we could run 90 feet one way.

20 amp load on this circuit and we could run 45 feet one way.
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#34234 - 02/06/04 02:30 PM Re: Long wire runs
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Bjarney;

That'll teach you for trying to help!

Just joking!

What Bjarney has posted will be of assistance in figuring general consideration points for voltage drop issues.
It's not the "Be-All, End-All" 100% rule document, it's only a helpful approach item.

Would like to know how one would "Figure Voltage Drop Per The NEC". Isn't this only an FPN in the NEC (NFPA 70), or did I miss the Article(s) with the Mandatory Rules of Voltage Drop (Shall / Shall Not rules).

Keeping voltage drop low is a Design issue, and done in the best interest for the Client.

Use of the percentages shown in the NEC's suggested examples (FPNs in Articles 210-19(a) and 215-2 of 3% from "Sub Panel" to load, and 5% total from Service / Power source to load), are general use guidelines which work well for common installations.

For "aldav53"'s situation, the text presented by Bjarney can be used to design these branch circuits with compensation for voltage drop, without having to perform the actual Math of a volts lossed calculation.

The lighting loads will likely be the higher loads, and the most noticably effected from voltage drop.

Are the Cameras just CCTV types, or are they something which draws upwards of 50 Watts each?
The latter example type Cameras might have maximum voltage drop specifications per the Manufacturer (available Line voltage minimums / maximums specs).

Not trying to be an a$$, just get ticked off when members try to help out, then later get toasted.

With that being said, does my Dicketry here in this message, qualify as poor excuse / approach?

Oh no, a Logical Paradox!!!


This message has performed an illegal function, and shall be terminated. If this problem continues, contact the vendor.


Scott35
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Just Say NO To Green Eggs And Ham!

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#34235 - 02/06/04 05:43 PM Re: Long wire runs
scjohn Offline
Member

Registered: 07/04/02
Posts: 76
Loc: charleston, SC, USA
I would also consider the voltage coming in from the poco. Alot of the newer transformers supply you with a solid 125/245 system single and 125/215 3 phase, at least around here. Also we wire alot of boat lifts that are anywhere from 100 ft. to 1000 ft. or more from the main power. We generally go by the specs on the motor which includes a v/d allowance for 120/230. And everyone I have seen allow more than the 3-5%.

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