Voltage drop on 1500 feet

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KnobnTube

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I searched and found a lot on voltage drop, but none that helped.
Situation is this:
Installing heaters for water on large farm.
Panel is At the barn. First heater is 50 ft away--2nd is 288 ft away from that one. 3rd is 288 ft from 2nd, 4th is 288 ft away from 3rd, 5th is 72 ft away from 4th, 6th is 480 ft from the 5th.
Total load is 27 amps with all heaters running. (#6 is 1466 ft away from panel)
At #2,3,4 and 5 there will be a drop to 4 more heaters 50 ft from those points.
Each heater is 3 amps at 120 volts.
My calculations using 4 different calculators found, have the wire at 300 mcm (4.8% drop)

OMG.
Am I nuts?
These are 120 volt water heaters for horse farm

Calculator
 
I searched and found a lot on voltage drop, but none that helped.
Situation is this:
Installing heaters for water on large farm.
Panel is At the barn. First heater is 50 ft away--2nd is 288 ft away from that one. 3rd is 288 ft from 2nd, 4th is 288 ft away from 3rd, 5th is 72 ft away from 4th, 6th is 480 ft from the 5th.
Total load is 27 amps with all heaters running. (#6 is 1466 ft away from panel)
At #2,3,4 and 5 there will be a drop to 4 more heaters 50 ft from those points.
You're putting all 27 amps at the end of the run, not distributing the load along it.
First segment is 50' with 27 amps.
Second segment is 288' with 24 amps.
etc

You have to work it out that way. The first segment might only be 10g, but I wouldn't waste my voltage drop there. Can you split this onto two circuits? Is 208/240v available? Consider sending a208/ 240v line out 1000-1200' to a transformer; the cost of the transformer might be less than the cost of the copper.
 

dpeter

Member
I get 22 heaters at 3A each for total of 66 amps. Perhaps you could post a line drawing of the layout?
 

KnobnTube

Member
I get 22 heaters at 3A each for total of 66 amps. Perhaps you could post a line drawing of the layout?
No idea how you get 22?
Even without the typo it was 6 + 4

Typo, others are at #1,2, and 3 heaters
Total of 9 on the line.
No other options. 120 volt is only option on voltage and this is only half, since
the other half was already moved to another run that is shorter.

This is underground cable aluminum.

No way to add equipment out in the fields. This is open pasture area.
 
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bob

Senior Member
Location
Alabama
No idea how you get 22?
Even without the typo it was 6 + 4

Typo, others are at #1,2, and 3 heaters
Total of 9 on the line.
This must be much more difficult than it looks. In you post you only mention 6 heaters.
Panel A to 1, 1 -2, 2-3, 3-4, 4-5, 5-6. # amps = 18 amps.
Where are 6-7, 7-8 and 8-9 located?
PA ---50-------H1---288------H2--288--------H3---288-------H4------72--------H5-----480----------H6
 
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bob

Senior Member
Location
Alabama
Using 3 amps per heater 18 amps total load 240 volts balanced load on #4 Cu VD @ H6 =3.4%


PA ---50-------H1---288------H2--288--------H3---288-------H4------72--------H5-----480----------H6


 
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KnobnTube

Member
Using 3 amps per heater 18 amps total load 240 volts balanced load on #4 Cu VD @ H6 =3.4%


PA ---50-------H1---288------H2--288--------H3---288-------H4------72--------H5-----480----------H6


Thanks, now drop 1 more heater vertically down off points H1, H2 and H3 for 50 ft distance and you have the layout perfectly


I came up with 1/0 aluminum triplex---5% total drop, 120 v to 113 volts at the end
 
Last edited:

KnobnTube

Member
This must be much more difficult than it looks. In you post you only mention 6 heaters.
Panel A to 1, 1 -2, 2-3, 3-4, 4-5, 5-6. # amps = 18 amps.
Where are 6-7, 7-8 and 8-9 located?
PA ---50-------H1---288------H2--288--------H3---288-------H4------72--------H5-----480----------H6
Because it is heaters 1,2,3,4,5,6 and then 1 more 50 ft away from point 2, 3 and 4,
making it 9
 

bob

Senior Member
Location
Alabama
Thanks, now drop 1 more heater vertically down off points H1, H2 and H3 for 50 ft distance and you have the layout perfectly
Is this in your origional post? I must need new glasses.
 

bob

Senior Member
Location
Alabama
One thing you have going is we calculated assuming all the heaters are on at the same time. That probably will not be the case.
 

kwired

Electron manager
Location
NE Nebraska
One thing you have going is we calculated assuming all the heaters are on at the same time. That probably will not be the case.
Don't know OP's location, but if it gets to zero deg F or below they will likely all be on at same time.



Another idea to reduce voltage drop is to run more than one circuit. Half of them on two circuits will cut amps in half. 120/240 three wire as mentioned would be better yet.

Voltage drop on a resistive load will reduce wattage. I would not lose any sleep over having 5% or even up to 10% drop on this install, the watering unit may get some ice in it when really cold but will not freeze solid, I have worked on enough of these to know that is all that matters.
 

kingpb

Senior Member
Voltage drop on a resistive load will reduce wattage. I would not lose any sleep over having 5% or even up to 10% drop on this install, the watering unit may get some ice in it when really cold but will not freeze solid, I have worked on enough of these to know that is all that matters.
Was thinking that same thing. The 3% and 5% are only recommended. If it will work with a 10% (or higher) drop and save you tons on cable costs, sounds like a winner. You can also purchase 240V rated heaters with a higher wattage rating then needed, then operate at 120V with the calculated voltage drop to give you the wattage you want.
 
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