Voltage drop

[Gaffen99]

Just want to pick the brains of the forum. If you had to run a circuit for 10 13 watt cfl lights and an ejector pump (say, 8 amps) 2000', what do you think would be the best way to do it? Obviously, the voltage drop is a factor.

 

[iwire]

8 amps at what voltage?

 

[Joethemechanic]

Just want to pick the brains of the forum. If you had to run a circuit for 10 13 watt cfl lights and an ejector pump (say, 8 amps) 2000', what do you think would be the best way to do it? Obviously, the voltage drop is a factor.

Lot of factors, aerial? length of spans?

underground?

no one size fits all solution

We don't even know where in the world this job is located, so we have no idea what if any electrical code if any applies.

 

[Dennis Alwon]

I assume 120V all the way. Well at 10 amps you would need a 3/0 copper for 2000'. Here is an online calculator.

 

[Joethemechanic]

I assume 120V all the way. Well at 10 amps you would need a 3/0 copper for 2000'. Here is an online calculator.

I was going to tell him to run it at 240 or if possible 480 and use a small step down trans in the 2 KW range.

But the trans is about 400 bucks I'll bet

 

[Joethemechanic]

I can see it done with 10/2 UF if you can make the run at 480 volts, but count on at least 400 bucks for each transformer you need and you will need at least one.

 

[templdl]

I agree with Joethemechanic and go with a 240-480 step up and then 480-120 step down assuming that you need 120v at the end.

Just think that you would be reducing the current by 25%. The cost of the transformer would be a good investment to assure a minimum voltage drop.

 

[Joethemechanic]

I agree with Joethemechanic and go with a 240-480 step up and then 480-120 step down assuming that you need 120v at the end.

Just think that you would be reducing the current by 25%. The cost of the transformer would be a good investment to assure a minimum voltage drop.

I think you could get away with 3.75 amps on 10 AWG and install one 15 amp 120V circuit in this outbuilding or whatever it is.


We have to remember the losses drop by the square of the current.

If we base our loss figures on 120V, and consider that our 1/1 (100%) figure

240 volts will 1/4 the loss in watts

480 will be 1/16 the loss in watts

 

[kwired]

I was going to tell him to run it at 240 or if possible 480 and use a small step down trans in the 2 KW range.

But the trans is about 400 bucks I'll bet

You don't suppose that cost less than 2000 (x3) feet of 3/0 copper as Dennis suggested?

@ 480 volts I still come up with wanting to use at least 6 AWG or even 4 AWG copper for voltage drop purposes.

To save $$$ I would run at least 2 AWG aluminum @ 480 volts.

 

[Joethemechanic]

What's a mile plus of 3 AWG Copper worth? Any kinda steep discount for buying a mile or more?

If it was mine, I think depending on the usage, I'd think about solar. My friend is a forklift salvage guy. Every couple of years he will get someone from down in the islands, South America or Central America, and they will be buying like a 20 foot container load of used electric forklift batteries from him. First time I saw it I'm like what's up with this guy and all these batteries. He tells me they use them for solar storage.

Well anyway, that's just me, I'd explore options before I ran all that wire. For all we know, the lights might only get used 4 hours a week for a men's prayer meeting in a cabin down by the lake and the pump is just for washing out coolers and fishing gear

 

[iwire]

What's a mile plus of 3 AWG Copper worth? Any kinda steep discount for buying a mile or more?

No real discounts on copper.

If it was mine, I think depending on the usage, I'd think about solar.

Go price it out and get back to us. Real equipment, not Harbor Freight junk.

My friend is a forklift salvage guy. Every couple of years he will get someone from down in the islands, South America or Central America, and they will be buying like a 20 foot container load of used electric forklift batteries from him. First time I saw it I'm like what's up with this guy and all these batteries. He tells me they use them for solar storage.

Oh, so you are suggesting a Sanford and Son job.:lol:

Well anyway, that's just me, I'd explore options before I ran all that wire. For all we know, the lights might only get used 4 hours a week for a men's prayer meeting in a cabin down by the lake and the pump is just for washing out coolers and fishing gear

If that is the case I would go with a small portable generator.

 

[iwire]

I assume 120V all the way. Well at 10 amps you would need a 3/0 copper for 2000'. Here is an online calculator.

Figure 3 x 2000' for 6000' of 3/0. I would expect to pay about $15K and the column 3 price is $42K.

@ 480 volts I still come up with wanting to use at least 6 AWG or even 4 AWG copper for voltage drop purposes.

6000' 4 AWG CU cost $3,900, Col. 3 $10,000

6000' 6 AWG CU cost $2,550, Col. 3 $6,600

To save $$$ I would run at least 2 AWG aluminum @ 480 volts.

6000' 2 AWG AL cost $6,300, Col. 3 $9,000.

 

[Joethemechanic]

Oh, so you are suggesting a Sanford and Son job.:lol:

He makes some serious money on used forklifts and parts. The profit margin is higher than on new machines. A couple of the big dealers went under around here. Guess who had the money to buy them out,,,,,,,,,

Not to mention, I have never heard a customer say anything bad about the guy

The used machinery business is no joke, and you should see the fortunes I have seen made on scrap metals


I guess this will be "off topic" but you get the idea

 

[Joethemechanic]

Why does everybody want to run such big wire? At 480 it's probably like 4 or 5 amps max. Even the motor starts on a ejector type pump aren't all that bad. It's a centrifical design. probably has a plastic impeller. Low rotating mass. And the load really doesn't have much effect until it gets up close to speed.

And if it was really all that bad, boost buck transformers that small are cheap

 

[iwire]

Why does everybody want to run such big wire? At 480 it's probably like 4 or 5 amps max. Even the motor starts on a ejector type pump aren't all that bad. It's a centrifical design. probably has a plastic impeller. Low rotating mass. And the load really doesn't have much effect until it gets up close to speed.

Because that is what it would take to keep voltage drop within reason at that voltage, current and distance.

And if it was really all that bad, boost buck transformers that small are cheap

Come on Joe, you know you can't use buck boosts to overcome voltage drop on changing loads.

 

[iwire]

He makes some serious money on used forklifts and parts. The profit margin is higher than on new machines. A couple of the big dealers went under around here. Guess who had the money to buy them out,,,,,,,,,

Not to mention, I have never heard a customer say anything bad about the guy

The used machinery business is no joke, and you should see the fortunes I have seen made on scrap metals


I guess this will be "off topic" but you get the idea

It has nothing to do with a professional electrical installation does it?

 

[topgone]

Sorry guys. I got confused. Lemme try:

10 x 13 watt CFL = 130 watts, assume PF = 0.65; VA = 130/.65= 200VA
8 amps @ 120volts= 960 VA
Total load = 1160 VA

As suggested, I believe it's better to run a 480 volts line and use a 480/120V transformer at the line's end.
Using 480 Volts, line amps = 1160/480 = 2.417 amps.
I would use #8AWG, Al

That would be an actual voltage drop (at 2.5 load amps) of 12.8 volts (2.7% voltage drop) or about 467 volts at the end of the 2000-foot line. That would be a fine install, IMO.

 

[Joethemechanic]

Come on Joe, you know you can't use buck boosts to overcome voltage drop on changing loads.

I's put the boost buck on the pump, and leave the lights alone, If they dim a bit when the pump starts, well so what? It doesn't sound like the place is an operating room. I've been known to dim the lights a bit when something starts.

Not even sure you would need it. with 10 AWG copper we are only talking like 4 ohms circuit resistance. I think I could live with that in a 4 amp circuit to save about 10,000 in wire.

My next question would be what's the soil like, If it's in NJ where he is, it could be nice sandy stuff. the ditch-witch might make light work of that.

 

[Dennis Alwon]

I thought the OP was looking to calculate the VD. I would never run 3/0 copper for this. 4/0 alum would be at least 1/3 the price but the transformer deal may be the best route. Bump it up and drop it down-- seems a little messy but I am sure it is done all the time.

 

[iwire]

That would be an actual voltage drop (at 2.5 load amps) of 12.8 volts (2.7% voltage drop) or about 467 volts at the end of the 2000-foot line. That would be a fine install, IMO.

I think that would operate the equipment fine.

The only question is how much the customer will tolerate dimming lights during pump start up.