Voltage Drop

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cowboyjwc

cowboyjwc

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This is simply for irrigation controls for a city parkway.

120v will be fed from a 20A breaker and will run 2800'

One calculation tells me 4/0 and one tells me 500 kcmil.

If 500 kcmil I'm thinking that it would just be cheaper to set another meter ped.
 
Definitely depends on your connected load. I calculated at 80% of your breaker (16A) and came up with 500 kcmil as well.
 
#12 stranded Aluminum fed from 277, with voltage drop gets you to 130 volts based on 16A!


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Keri_WW said:
Definitely depends on your connected load. I calculated at 80% of your breaker (16A) and came up with 500 kcmil as well.
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Yeah that's what I was coming up with too at, I think it was, 113v. Again simply a time clock for sprinklers.

Guess they could install a buck and boost down the line.
 
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cowboyjwc said:
Could be. That's why I was thinking buck/boost.
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You don't want to use a BB for a voltage drop with a varying load, as the load goes down the voltage goes up. step up and step down is the only way yo go when you have voltage drop and a varying load. if you only have one load then you could get away with BB, but remember electronics don't like to be over voltages, so if a load click off and the electronics are still on, the over voltage will damage the electronic controls,

I would use a very small 250va transformer to step up to 480, and another to step back down to 120.

I did a potable water control feed (22 conductors with spares) for the National Lake Shore campground here, that was about 2300', from the pump station to the reservoir, we changed many of the relays to electronic versions, to allow #12 for the run, saved the park a lot of money over running larger conductors.
 
I would say that anything that you do is going to have to be slightly ridiculous.

Unfortunately setting a new meter is going to cause the Owner to pay a bill every month for just the service and virtually no usage. However, I'm sure he/she can pay that bill for a long long time with the capital it would take to put in conduit and wire over 1/2 mile.

I'm sure the time clock uses a step down (wall wart) transformer. Have you considered proposing to install a solar powered setup in lieu of the feed? You might not even need the transformer.

Jason
 
hurk27 said:
You don't want to use a BB for a voltage drop with a varying load, as the load goes down the voltage goes up. step up and step down is the only way yo go when you have voltage drop and a varying load.
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Really? How does the buck/boost transformer work that it will vary voltage w/ load compared to a step up/down?

Also, why not go up to 600V (instead of 480)? Same wire...less current.
 
lakee911 said:
Really? How does the buck/boost transformer work that it will vary voltage w/ load compared to a step up/down?

Also, why not go up to 600V (instead of 480)? Same wire...less current.
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If you have a 30 volt voltage drop at 120v with lets say 10 amps of load, lets say a 3 watt timer, and a 1250 watt motor, so your voltage has dropped to 90 volts, now you use a BB to do a 32 volt boost, so you now have 122 volts with both loads running, let the motor turn off, and your timer will see 152 volts. Not good.

The BB will boost what ever voltage that is fed into it, by the adder voltage, so if you are trying to over come a voltage drop, the input voltage to the BB will rise as the load gets less.
 
let's see if I can simplify this a little more. This is city owned so paying the bill is not an issue as we have these meters all over town. We don't have 600v or 480v or 3 phase availible, this is for a green belt on the very edge of town. We need the voltage up because they also want some lights to light up the "Welcome to...." sign.

Step up / step down may be the way to go.
 
hurk27 said:
I would use a very small 250va transformer to step up to 480, and another to step back down to 120.
Click to expand...


Sounds like the easiest and least expensive solution to me. Running 480 volt single phase is just half the total distance of 120 single phase.Those transformer shouldn't be very expensive and the sign lights could be 480.

Calculate the light wattage at 480 instead of 120 should drop the load a considerable amount.
 
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