I need to size pipe & wire for some post lights. There are distances ,enough that V-drop is a concern.

The post lights, however, will incorporate the usual edison screw base, with the retrofit fluoresants of a whopping 17W. Or around 1.4 A @ 120V.

As V-drop calc's vary greatly due to the amount of "umph" introduced into the calc, this would allow ( per calc only) somewhat of a reduced conductor.

I am crusing 220 to apply a demand figure to this, would 220-13 require i start this calc @ 180W per???

Steve,

Send me some numbers and I'll do a Volt-Loss calc. for you.

Need one way length[s], total load current [or Volt-Amps] per circuit, system voltage [nominal rating], voltage at the subpanel feeding these lighting circuits [under a high load would be best], type of conduit [magnetic or non-magnetic], power factor [list lamp wattage, then it's noted RLA and I'll figure PF].

If you want, I'll do one for the connected load, and one for max. circuit load @ 0.8 for LCL.

The 17 watt CFL [compact Fluorescent] must have had a typo' for the RLA. 1.4 Amps would put the line Volt-Amps at 168 VA, resulting in a PF of less than 10% [anything less than 50% is going to get the utility people raging mad!!].

Take an ampere reading yourself to get an idea of RLA.

Scott SET.

Just to put my 2 cents in here:

Shouldn't you figure the Voltage drop at some higher current rate? How can you be assured that this 17w lamp will always be there?
I would think the 180va (as originally stated) per fixture should be used to be sure.

That's probably .14 Amp

Bill

[This message has been edited by Bill Addiss (edited 06-02-2001).]

Thanks Guys;
there is much distance, and also a company main. man involved.
he is trying to squeeze a nickel for his company, which i can understand, that's everyday for me.
and your right, the fluor.elements may not always be in vouge, the posts may change to whatever...
all my bad math aside, i just need a code to stand on, and i'll figure it from there...
( i have a program, i cheat!)

There is no code to stand on when it comes to voltage drop, except by some really convoluted reasoning which probably wouldn't apply.

A real conservative voltage drop formula is 2KIL/circular mils. K is a constant & 12 would be nice & safe, I is amps & L is one way distance to the load. the answer is in volts, you figure the percentages.

You can also try the online calculator at http://www.electrician.com/indexold.html

Tom

Tom,
that is a good link, thanks.

i would rather explore convoluted vs. running 14-2 UF all over creation,,,

did you have something in mind???

I think you still need to give us some numbers.

Are you talking about 100 lamps about 1000' away? Or is this 10 lamps with one every 25'?

You might consider using 14-3 and 240 V then alternate the hot wire at each lamp.

You didn't say who will be inspecting the installation.

If no one, I am comfortable that if you put 20 lamps on a 14-2 or 40 lamps on a 14-3, it won't burn down anyone's house.

Someday might someone replace those 17 W bulbs with 75 W bulbs? It could happen. They will have a voltage drop.
But it still won't burn anything and even if someone sticks it in a 20 A breaker, the wire won't be melting.

I would suggest, rather, that you follow Bill's advice, using the 180va. figure. Whether the job will be inspected or not should NOT dictate the quality of work you do. Even if it calcs out that you should use #6 on the run, by all means do the job correctly. Just because it won't melt the wire or burn down the house is not a criteria for doing a half a** job.
(Yes, I stop at stop signs even if I don't see a cop)

electure;
I agree, it's not so much the calc i'm worried about, it's what i should be using as a load figure.
I will be pulling a permit for this, as it meets the criterior here.
The figures will be submitted at that time.
I WILL NOT be doing the work without this.

mama did'nt raise no fool!

Sparky,

Here's convoluted.

Voltage drop is not normally enforceable because it is a fine print note.

However, NEC's stated purpose is "the practical safeguarding of persons and property..." 90-1(a).

If excessive voltage drop would cause operating problems in any equipment that is required for safety, then a case could be made for installing larger conductors.

Tom

[This message has been edited by Tom (edited 06-03-2001).]

How about using the maximum allowable lamp wattage per the fixture labeling. Then use standard voltage drop calculations incorporating the maximum lamp currents possible and the actual distance.

I would not have concern if the lampholders were for a 17CFL lamp, but the med base lampholder invites trouble, lots of folks wouldn't know to change just the lamp in the retro, and:
. The building might change owners.
. Mr Cheap might realize how many 100 or 150 watt A lamps he can buy for the price of 1 CFL retro.
I've had a call to repair a C/B when the new tenant of a store moved in, only to find that he had crammed the light track full of heads with 150 watt PARs. He asked me to put in a bigger breaker, and probably had someone else do it after I told him what he didn't want to hear.

All good concerns here, you guys are a great sounding board

Tom,
would 110-4 be applicable?

Redsy,
that would be plain enough english for most people.....

electure,
i'm thinking of submitting my prints and figures under the guise of 215-5 ( even though these are branch circuits)

>However, NEC's stated purpose is "the practical safeguarding of persons and property..." 90-1(a).

If excessive voltage drop would cause operating problems in any equipment that is required for safety, then a case could be made for installing larger conductors.

If it were necessary for safety, then I would insist upon it.

But my point was that it is not necessary for safety (perhaps I should have said it that way directly). So the only problems I see is if the AHJ requires a different calculation (e.g., 180 W per fixture) or someone someday actually puts 150 W bulbs in many of the fixtures (a voltage drop will occur).

I was not suggesting ignoring the code or anything else dumb!

Just because it won't melt the wire or burn down the house is not a criterion ...

Where is the requirement that the outdoor wire be sized for 180 W fixtures at the actual distance?

Where is the requirement that the outdoor wire be sized for 180 W fixtures at the actual distance?

Dspark;
people call us because they figure we wire per code, which , in this case, is why i am utilizing the expertise of my fellow tradesmen on line

Sparky,

110-4 would not be of any help.

Actually, this issue has been beat to death many times, especially on the IAEI board. Voltage drop cannot be enforced under the NEC. I've heard of some jurisdictions adopting a voltage drop requirement. What a nightmare that would be. Can you just imagine the box fill problems you'd have running 10-2 romex in a house?

Tom

Tom;
thanks,
then i am simply adding to the confusion here. I think i will simplify things by using the 180W figure, passing the plans into the state, and asking for their approval / disapproval.

I know this sounds like a copout, but there is a level of 'protection' in my doing so.
besides, even the main. man knows better than to pull the lions tail...

I would not consider it a copout. If I were the plans reviewer, I would use 220-3 (b)(11) Other Outlets. "Other outlets not covered in (1) through (10) shall be computed based on 180 VA per outlet."
Another view is to use the VA rating of the equipment and lamps for which the fixture is rated and totally disregard the retrofit, which only serves to lower the voltage drop as well as lower power consumption.
As already stated, voltage drop is not enforcible, but is calculated to give a safe installation, which is in the interest of all of us here is this field.
Just another 2cents worth.

Thank you WARREN1 ,

that particular code ,may in fact be a solid enough statement to represent my figures.

I am grateful to have you all as a resource on this, i will attempt to reciprocate the favor if i can

Just a thought. If this exterior lighting is to be used as egress or security lighting, then it would be considered a safety issue. (We have some cities where you have to meet with the police & fire depts. @ night and walk them around commercial sites with a lightmeter, and it better coincide with the pointXpoint diagram you had to submit for plancheck, or you won't get a Cert of Occ.

[This message has been edited by electure (edited 06-05-2001).]

electure;
what a grand twist! there are actually a given amount of lumnems required to acuire the term 'security lighting'

this is interesting...

electure, bought up a point.

I remember a complex where the exterior landings on 3 story - 6 apartment he unit(s) had wall mounte Lighting fixture on each landing. Some "penny pincher?" decided to for-go the wall mounted landing fixtures and use the illumnation from the " not near-by " parking lot lighting standards.

At that time, and probably still does, the UBC 3313 reuired 1 footcandle at floor level for exit illumination.

The wall lights were "cut-in".

Glenn