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SwedishRider
Rider on the Storm
Premium
join:2006-01-11
not Sweden
kudos:1
reply to nunya

Re: Voltage Drop Tolerances

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said by nunya:

That only get's you VD to the panel. There's more VD in the circuits that are distributed from the panel.
What is the output voltage of your generator under load?

I don't know what it is under load. I have an inexpensive meter and it was saying the generator was pushing 125 volts with no load at the 120v outlets on the genny. I hooked it to my house and while it had a few items running, an outlet in the utility room was measuring 120ish volts. The run from the panel to that outlet was short... but pretty much all the critical stuff I'd need to run during an outage is in that room.

Ideally the maximum VD for feeder and branch should be less than 5%.
With the generator being that far from the house, and the VD of your branch circuits being an unknown and variable (each will be different), I would consider an upsize to 8 AWG. The price difference would be minimal. If you've already run #10, I wouldn't sweat it.

#10 has been hardwired from the panel to the inlet.. it's 45-50 feet. Then, I have a weatherproof #10 cable from that inlet to my generator, but it's a bit shorter that I need (I expanded my deck). So if I were to make up another weatherproof cable, would upping it to #8 for that 30ish foot run be worth the upgrade? I already have the 30A 4-prong male and female fittings for on the #10 wire... would they fit the #8?

EDIT: added wire pics.


nunya
LXI 483
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join:2000-12-23
O Fallon, MO
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What's the difference in price for 8/4 SO vs 10/4 SO? I'm showing 8/4 @ $2.60 / ft, and 10/4 @ $1.60 / ft. So it would be about an extra dollar per foot.

A Leviton 2711 L14-30P will accept #8.
--
If someone refers to herself / himself as a "guru", they probably aren't.


SwedishRider
Rider on the Storm
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join:2006-01-11
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said by nunya:

What's the difference in price for 8/4 SO vs 10/4 SO? I'm showing 8/4 @ $2.60 / ft, and 10/4 @ $1.60 / ft. So it would be about an extra dollar per foot.

A Leviton 2711 L14-30P will accept #8.

I'll have to check with the electrician that I do business with... I don't know local pricing.

At your pricing, is it worth the $30 extra bucks? Or is this chasing a problem that doesn't exist?


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
If you are going to make a new cord anyway, I would upsize it. It's $30 bucks.
--
If someone refers to herself / himself as a "guru", they probably aren't.


SwedishRider
Rider on the Storm
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join:2006-01-11
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said by nunya:

If you are going to make a new cord anyway, I would upsize it. It's $30 bucks.

Sounds like a plan.

Just out of curiosity, is there a practical way to measure the actual voltage drop of my system? I have a Greenlee AM-6 Multimeter.


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
said by SwedishRider:

Sounds like a plan.

Just out of curiosity, is there a practical way to measure the actual voltage drop of my system? I have a Greenlee AM-6 Multimeter.

Good luck.

You'd need to measure before its under load, then put it at max load (30A) to see the maximum drop.

As Nunya said, if it's too late, don't sweat it.

BTW Nunya, I see a lot of people talk about their 10/4 SO extension cord on 30A receptacles. Aren't 10/4 SO's rated for 25A? What's the dealio?


SwedishRider
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said by alkizmo:

Good luck.

You'd need to measure before its under load, then put it at max load (30A) to see the maximum drop.

As Nunya said, if it's too late, don't sweat it.

BTW Nunya, I see a lot of people talk about their 10/4 SO extension cord on 30A receptacles. Aren't 10/4 SO's rated for 25A? What's the dealio?

I'm more curious than anything else. I think the 10 gauge between the inlet and the panel is fine... and I'm not going through the hassle of ripping that out and going with bigger gauge. But as long as it's not a ridiculous amount, nunya is right, it makes sense to go with 8 gauge for the longer cord I need from generator to inlet. If I wasn't making up a new one, I wouldn't spend the money, but since I need a longer length anyway, why not..

Speedy Petey

join:2008-01-19
reply to alkizmo
said by alkizmo:

BTW Nunya, I see a lot of people talk about their 10/4 SO extension cord on 30A receptacles. Aren't 10/4 SO's rated for 25A? What's the dealio?

If I may.
10/4 cord (wh, bk, red, grn) is allowable to use Column B in T400.5(A)(1) if the white only carries the current imbalance, as in this situation.
Column B lists #10 @ 30A ampacity.


Coma
Thanks Steve
Premium
join:2001-12-30
NirvanaLand
reply to SwedishRider
said by SwedishRider:

it makes sense to go with 8 gauge for the longer cord I need from generator to inlet. If I wasn't making up a new one, I wouldn't spend the money, but since I need a longer length anyway, why not..


I have 80' 8ga run to my shop where I keep the generator but it only outputs 30A so a 10ga suicide cord is fine.

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November is National Epilepsy Month


PSWired

join:2006-03-26
Annapolis, MD
reply to SwedishRider
Pull the cable off the inlet breaker back at the panel and short the hot and neutral together. Plug in the cord and measure the resistance between hot and neutral with your meter back at the end if the cordset. Use ohm's law (V=IR) to calculate voltage drop with the resistance you measured (in ohms) and your worst case current (30 A).

Edit: 240v circuit, short the two hots, ignore the neutral.


leibold
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Sunnyvale, CA
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reply to alkizmo
said by alkizmo:

said by SwedishRider:

Just out of curiosity, is there a practical way to measure the actual voltage drop of my system?

You'd need to measure before its under load, then put it at max load (30A) to see the maximum drop.

Actually the idle voltage of the generator is not a useful number. To measure the voltage drop you need to measure the voltage while the generator is under load. The first measurement is done at the generator and the second measurement is done near the biggest load. The difference between the two measurements is the voltage drop.

The resistance measurement suggested by PSWired See Profile is technically correct but in real life faces the problem that most multimeters aren't very precise for low ohm readings and even a small difference in value has a large effect on the resulting calculation.
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SwedishRider
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1 edit
I was thinking more like running a high demand appliance, like an electric dryer, and maybe one more thing to get close to the 6000 running watts point, and then energizing one of the farthest outlets and see what kind of voltage it's getting.

If the voltage drop should be no more than 5%, then would it be correct to say that the voltage should be no less than 114v at that outlet (5% of 120v is 6v, so 120-6=114v)?


SwedishRider
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join:2006-01-11
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reply to nunya
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Here it is: 35' of #8 with an upgraded 30A 4-prong plug. I'll run some tests when I get some time to see what kind of voltage drop I'm getting. But at this point, I have 35' of #8 from generator to inlet, and 50' of #10 from inlet to panel.