Voltage drop & conductor size

[OK Sparky 93]

I’m stretching here.

When it comes to Vd and wire size and distance, I want to play out a scenario. I don’t know actual distance, only guesstimating.

5HP motor 1 phase
21.9 nameplate amps
30.8 per table amps
Approximately 200ft
208 volt

Based on info #10 would only be good for about 115 feet.

There entire length would need #6. Another entity told customer they needed #8.

It currently has #10

The way I see it is at the least #6 would or could be installed to the point that the #10 could handle.
Does anyone see it differently? Would you see anyway #8 could be ran, unless the total distance is less than what I am estimating?

I don’t see the real need at this point to need to run #6 the entire distance. Just an intercept.

 

[LarryFine]

Guessing without any more info:

I would run something like #2 al from the source to the local panel or disconnect.

I prefer to land wires on terminals and avoid unnecessary splicing.

 

[augie47]

It would probably take one of the engineering type here to provide a reliable answer as we are dealing with motor loads.
Based on the 22 amps running load your #10 would be sufficient (5% drop) but the #10 is likely not sufficient taking inrush current into account.

Looking at charts from some of the pump manufactures it appears the #10 max distance is 150 to 180 ft.
Based on that I would think a #8.

 

[Knightryder12]

From my calcs with the info provided #8 would give you a 3.9% VD and #6 would give you 2.4% VD. So if you are not worried about meeting the energy code #8 should be good.

 

[wwhitney]

Based on the 22 amps running load your #10 would be sufficient (5% drop) but the #10 is likely not sufficient taking inrush current into account.

Is there an accepted engineering standard for doing a motor inrush voltage drop check? I.e. what current to use (some multiple of the nameplate FLC?) and what voltage drop is allowable at that current?

Cheers, Wayne