ptonsparky
Tom
- Occupation
- EC - retired
Single phase 240v
VD L-EG 6.3v
1500 watt resistant heater only
Three wire Direct bury cable, with 10' GRC on each end.
2 #4 al with #6 al EG
POCO transformer of 10 KVA, 1.2% impedance, unlimited on primary.
Voltage drop calculation (finding distance of existing circuit)
- Thread starter Dsg319
- Start date
- Status
VD L-EG 6.3v
1500 watt resistant heater only
Three wire Direct bury cable, with 10' GRC on each end.
2 #4 al with #6 al EG
POCO transformer of 10 KVA, 1.2% impedance, unlimited on primary.
ptonsparky
Tom
- Occupation
- EC - retired
FWIW, I have absolutely no idea what the answers could be. This is way over my pay scale.
xptpcrewx
Power System Engineer
- Location
- Las Vegas, Nevada, USA
- Occupation
- Licensed Electrical Engineer, Licensed Electrical Contractor, Certified Master Electrician
I already started working up a #2 AWG example, but I’ll also do yours. Give me the ambient temperature as well as raceway material if any.
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oldsparky52
Senior Member
- Location
- Wilmington, NC USA
I don't have any specifically.
I used to use VD=IR for sizing cabling at marinas (shore power for boats). I was just curious how close the real world would be to those calcs. It doesn't really matter for me now, but I'd like to know.
ptonsparky
Tom
- Occupation
- EC - retired
Ambient would be 50 F. Directly buried except 10' of rigid metallic at both ends.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
210313-1400 EST
Note: the original post was with a hair dryer, basically a resistance for the most part. Dsg319's results were generally correct, and more accurate instruments would likely have produced somewhat better results. Note: that he used a resistive load so that reactive loads are not of concern.
So I setup some crude experiments. The wire is Romex #14 copper of a nominal 50 foot roll. The room temperature loop resistance should be about 0.253 ohms from published wire tables.
With my General Radio LRC bridge I measured 0.242 ohms at DC, and 0.275 ohms at 1000 Hz. On the same bridge on low Q inductance I read 13.5 microhenrys at a low Q of 0.31 . This inductance at 60 Hz has an inductive reactance of about 0.005 ohms. Small compared to either AC or DC resistance measurements.
With a load current of 11.7 A thru the cable the voltage at the load end was 109.0 V and at the input end was 112.4 V, or a change of 3.4 V for the loop. Thus, the cable loop resistance calculates to 3.4/11.7 = 0.29 ohms. This is reasonably close to the 20 deg C table value of 2.53 ohms per 1000 ft. And because of the way the test was run there was some cable heating.
.
Note: the original post was with a hair dryer, basically a resistance for the most part. Dsg319's results were generally correct, and more accurate instruments would likely have produced somewhat better results. Note: that he used a resistive load so that reactive loads are not of concern.
So I setup some crude experiments. The wire is Romex #14 copper of a nominal 50 foot roll. The room temperature loop resistance should be about 0.253 ohms from published wire tables.
With my General Radio LRC bridge I measured 0.242 ohms at DC, and 0.275 ohms at 1000 Hz. On the same bridge on low Q inductance I read 13.5 microhenrys at a low Q of 0.31 . This inductance at 60 Hz has an inductive reactance of about 0.005 ohms. Small compared to either AC or DC resistance measurements.
With a load current of 11.7 A thru the cable the voltage at the load end was 109.0 V and at the input end was 112.4 V, or a change of 3.4 V for the loop. Thus, the cable loop resistance calculates to 3.4/11.7 = 0.29 ohms. This is reasonably close to the 20 deg C table value of 2.53 ohms per 1000 ft. And because of the way the test was run there was some cable heating.
.
xptpcrewx
Power System Engineer
- Location
- Las Vegas, Nevada, USA
- Occupation
- Licensed Electrical Engineer, Licensed Electrical Contractor, Certified Master Electrician
See attached.
Dsg319
Senior Member
- Location
- West Virginia
- Occupation
- Wv Master “lectrician”
Some day I hope to do basically same test except with a known footage just for giggles to see how close it could be. And also could include wire resistance as well as the load.
(Although I have recently learned it will not nearly be accurate with all the considerations to take into effect, raceway, temp, and I’m sure many others ). I would just like to see if it’s even within the ball park.
Shop I work at actually has a greenlee tool that can measure conductor lengths. Can’t think of what it’s called right now.
(Although I have recently learned it will not nearly be accurate with all the considerations to take into effect, raceway, temp, and I’m sure many others ). I would just like to see if it’s even within the ball park.
Shop I work at actually has a greenlee tool that can measure conductor lengths. Can’t think of what it’s called right now.
Dsg319
Senior Member
- Location
- West Virginia
- Occupation
- Wv Master “lectrician”
Wish I would have been this interested into electricity when I was wasting mine and the teachers time at school! Only to know a few years down the road I would fall in love with it, BUT thank God I take time to learn now, no time to learn like the present!
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