Voltage drop

[Joethemechanic]

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

10 AWG copper 1.02 ohms per 1,000

8 AWG Aluminum 1.03 ohms per 1,000

Me and topgone kinda came up with the same answer, just a different choice in materials.

How is one of us right, and the other wrong?


Are you sure you are a German?

 

[iwire]

10 AWG copper 1.02 ohms per 1,000

8 AWG Aluminum 1.03 ohms per 1,000

Me and topgone kinda came up with the same answer, just a different choice in materials.

How is one of us right, and the other wrong?

You seemed to be guessing, and I did not notice you recommend a wire size at the time of my post while Topgone took the time to show how he came up with his answer.

As far as any of us being 'right' that is imposable to say. Only the customer will know how much VD they are willing to deal with.

 

[iwire]

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?

Not a professional way to handle it, that is DIY stuff. I might do that on my own property but I would never recommend it on this forum.

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.

The OP asked how to figure the voltage drop, how about we stay on that for now?

 

[Joethemechanic]

Not a professional way to handle it, that is DIY stuff. I might do that on my own property but I would never recommend it on this forum.

If it was mine, I'd install one of these just to have something cool to talk about

 

[topgone]

I think that would operate the equipment fine.

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

Good point there.

Since the OP did not provide more details:

With a motor current of 8 amps, this could be a 1 1/2 hp motor.
The starting amps can be a s high as 40 amps. (See here) Say 42 amps to include lighting loads.
This translates into a 42 X 120/480 = 10.5 amps on the 480V side at pump starting.

And with the suggested #8 Al wire, the VD at the 2000-foot line end will be around 53.9 volts (11.2 %).

Like what you said, it all depends on how much voltage drop the owner can allow (as with pump start). If the owner wants no greater than 5% VD during pump start, then he can use #6 Cu, VD = 20 volts or 4.2%.

 

[Joethemechanic]

I'll bet his pump is something more like this. And they start easy.

Little Giant 9S-CIM Sewage Ejector Pump


The solids up to 2 inches in diameter. The 9S-CIM has a pump housing that is made from a strong cast iron material and is coated with a string epoxy coating that will help ward off any rust or corrosion that may form. The Little Giant 9S-CIM is a manual pump and the 9S-CIA is an automatic pump. The Little Giant Pump Series 9S has components such as the Pump Cover and the Housing that are also made from the Cast Iron and epoxy coated as well. This will help lengthen the life of the pump. The pumps’ impeller is made from a strong nylon and vortex material. The pump’s specifications are the 9S-CIM is a 4/10 horsepower pump that runs with an electrical supply of 115 or 230volts. All models come with a 15-foot cord but 20 foot cords are also available.The best part of the Little Giant 9S-CIM Sewage Ejector Pump is that it is 100% safe and factory tested. These pumps are more energy efficient than they used to be years ago. When you choose the 9S-CIM Little Giant Pump you will get a high performance pump with a great warranty. The 9S-CIM Little Giant Submersible Pumps cost range from $260.00 to $298.00 depending on where you shop.

On second thought even this pump is a little big for his 8 amp total load number, but ejectors do tend to start pretty easy, the impellers are small and they have low rotating mass.

 

[kwired]

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





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

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




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

You have a good copper price but your aluminum price stinks.

From one of my suppliers websites (I usually get slightly better price than what the website gives me, but is good reference for quick estimates):

6000 feet of 4 AWG copper THHN/THWN = $5356

6000 feet of 2 AWG aluminum XHHW = $1628

6000 feet of 3/0 AWG copper THHN/THWN = $21,110


Not knowing more about just what the OP has, before running any of these - especially 3/0 I would find out what it will take to get POCO to run service there - once there is power there the owner will find more loads they wish to run, but your supply will be designed for somewhat limited load.

 

[iwire]

You have a good copper price but your aluminum price stinks.

All of it was just from our pricing service, none where actually quotes but I noticed the AL price seemed off the map. Not sure why.

 

[iwire]

I'll bet his pump is something more like this. And they start easy.




On second thought even this pump is a little big for his 8 amp total load number, but ejectors do tend to start pretty easy, the impellers are small and they have low rotating mass.

I think we are all aware that typical centrifugal pumps are easy starting.

It will still hit locked rotor current for enough cycles to mess with the lights, now if that matters or not is up to the customer not us.

If I am hired as the electrician to design a job my goal will be to design it with minimal voltage fluctuations as those lead to complaints.

 

[kwired]

I think we are all aware that typical centrifugal pumps are easy starting.

It will still hit locked rotor current for enough cycles to mess with the lights, now if that matters or not is up to the customer not us.

If I am hired as the electrician to design a job my goal will be to design it with minimal voltage fluctuations as those lead to complaints.

Do soft starters work or is there soft starters for single phase induction motors? I have had applications occasionally where it was worth consideration yet never found anything that I absoulutely knew would work and have never tried to do this with single phase motors. They are great for three phase applications. I have seen power tools with soft start but they are usually universal motors and not induction motors.

I have seen controllers for single phase submersible pump motors but they more like a VFD drive and have leads for both main and aux winding and are not a general purpose in line soft starting device, and cost more than the motors they drive.

 

[iwire]

I wired up some combination single phase soft start / motor brakes on bench grinders, they worked well.

 

[Gaffen99]

Thanks for all the input, guys. The deal is i have a large facility, that have tunnels through out the property. They have asked me to install lighting and power for ejector pumps in all these tunnels and run them on emergency panel, which of course is located at the farthest place possible. I didn't think of raising the power up to 480 and then dropping it back down, that is a good idea. That is why I asked, thanks. I have thought about running a feeder out and tapping it to a small panel or disconnect at different locations, any thought on that.

 

[Gaffen99]

And sorry if I wasn't to clear on my original post, but it is always fun when you guys go off topic.

 

[kwired]

I have thought about running a feeder out and tapping it to a small panel or disconnect at different locations, any thought on that.

It complicates the voltage drop calculations a little but otherwise nothing wrong with it. You need to calculate drop on each segment of the run since the load will be different on each segment.

 

[Ragin Cajun]

Thanks for all the input, guys. The deal is i have a large facility, that have tunnels through out the property. They have asked me to install lighting and power for ejector pumps in all these tunnels and run them on emergency panel, which of course is located at the farthest place possible. I didn't think of raising the power up to 480 and then dropping it back down, that is a good idea. That is why I asked, thanks. I have thought about running a feeder out and tapping it to a small panel or disconnect at different locations, any thought on that.

If that's the case a single larger xfmr feeding the panel and the smaller xfmrs at the loads. I can't imagine there being a problem with light flicker on starting. How often is someone going to be there when the pump starts. Just be sure they understand that.

RC

 

[T.M.Haja Sahib]

Voltage regulator in place of transformers?

Voltage regulator in place of transformers?

Some advantages:

1)One voltage regulator for each tunnel instead of two transformers.

2)Incoming supply wires need not be sized for voltage drop; only sized for load current.

3)Optimum voltage for loads.

 

[kevin]

Stepping the voltage up to 600 instead of 480 most likely will result in a smaller conductor size and a lower overall cost.

 

[Leestarkweather]

Why is everyone talking 6000 Feet?

Why is everyone talking 6000 Feet?

The distance to the load is 2000 Ft. Whether it is 120V (1 Phase and 1 neutral wire) or bumped up to 480V 1-Phase (2 phase wires), the circuit only takes 2 wires plus a grounding conductor.

This really should be accurately discussed when comparing the installation costs. 4000 Ft. of wire, not 6000 Ft. of wire, plus the ground wire which is needed in any scenario.

 

[Joethemechanic]

2,000 feet times 3 is 6000 feet of conductor.

If you want to split hairs and call it 4,000 plus 2,000 of ground.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

 

[hurk27]

The distance to the load is 2000 Ft. Whether it is 120V (1 Phase and 1 neutral wire) or bumped up to 480V 1-Phase (2 phase wires), the circuit only takes 2 wires plus a grounding conductor.

This really should be accurately discussed when comparing the installation costs. 4000 Ft. of wire, not 6000 Ft. of wire, plus the ground wire which is needed in any scenario.

The problem your missing is 250.122(B) any time you increase the wire size for voltage drop you must also increase the EGC proportionately according to circular mil area of the ungrounded conductors, this in many cases results in the EGC being required to be the same size as the other conductors, so yes you must price out 6000' of wire, most cable above #10awg will have a reduced EGC and would not be allowed.