Voltage drop over long wire runs?

[Mark42]

One outdoor lighting circuit runs about 250ft from the circuit panel to the last light fixture. It is 14 gauge and has multiple fixtures totalling 80 watts of CFL lighting. Today I added an additional 100 feet of 14 gauge at the end of the circuit to a pole light with a 26watt CFL totalling 106 watts and 350ft of wire on the circuit. So far, everything looks normal, the lights are bright and come on to full brightness in about 10 seconds or so, which is their normal performance.

How long a run of 14gauge can I run before I get voltage drop that will start to affect these CFL lights? I meant to put my volt tester on the wire before attaching the fixture but forgot. Now I cant reach inside to make contact in the bulb base to test voltage.

Any input about voltage drop and any impact to the CFL lights is greatly appreciated!

Thanks,

Mark.

 

[wajajaja02]

Re: Voltage drop over long wire runs?

google search "voltage drop calculator" and have fun,must be 5 pages on it

 

[Mark42]

Re: Voltage drop over long wire runs?

Duh.... Why didn't I think of that??? I found one and it calculates that the circuit is only losing 1-2 volts. Nothing to worry about.

I took out my voltmeter and tested the volts at a few different outlets in the house. To my surprise it reads 153 volts! Wow! 33 volts more than it should be. I remember a year or two ago testing the house volts and it was 119. I guess things vary a bit? Wonder if this is shortening the life of my TV, and other electronic equipment.

Maybe I should call the power company.

 

[rwise]

Re: Voltage drop over long wire runs?

If the outlets are really 153 volts you have a problem! That much over voltage will damage the things plugged in, 117.5 is optimal, here its 125. As for the 14 awg run no prob,,, just don't try to run an air compressor on it

 

[mthieme]

Re: Voltage drop over long wire runs?

Mark,
any chance you could post a pic or two?
I've been wanting to redo my outside lights and need some inspiration.
I was going to take barrel faced landscaping ties, cut them in two, sink them in the ground and run rope lighting through them. But, I've found out first hand, rope lighting doesn't last the 18 years claimed by the mfg.

 

[DrCox]

Re: Voltage drop over long wire runs?

If I am not mistaken when you purchase your wire does it not have an Ohms/(x)Ft. rating? its been a while since I have run residential but I seem to remember being able to do the calculations based on that.

Are you wiring them in Series, series parallel, parallel? The way you do it will also effect your overall voltage drop as well.

I too would like to see some pics, or a scat.

-DrCox

 

[Barnacle_Bill]

Re: Voltage drop over long wire runs?

Duh.... Why didn't I think of that??? I found one and it calculates that the circuit is only losing 1-2 volts. Nothing to worry about.

I took out my voltmeter and tested the volts at a few different outlets in the house. To my surprise it reads 153 volts! Wow! 33 volts more than it should be. I remember a year or two ago testing the house volts and it was 119. I guess things vary a bit? Wonder if this is shortening the life of my TV, and other electronic equipment.

Maybe I should call the power company.

You need to verify that with another meter and if it is that high, call the power co.

 

[waterinthefuel]

Re: Voltage drop over long wire runs?

We're in basic electricity in my aviation maintenance class right now, and rest assured, some meters can be way off. You need to not check the voltage with the same meter in different areas, you need to check the same area with different meters. Ask a neighbor to borrow his, go out and get one thats at least 20 bucks.

If your meter is a needle meter then forgetaboutit. It's not accurate at all. Even some cheap digitals aren't accurate.

 

[Bigprairie1]

Re: Voltage drop over long wire runs?

Mark
I agree with Bhile, that voltage needs to be tested with another meter. That is definitely too high.
As well, 350' linear feet with 14ga. sounds like it might be pushing it. I have tried to find some info that has some excellent rules of thumb for running wire over distance..but I'm still looking for it. I think for that distance of run you would normally be into 12 ga. with the assumption that someone at some point is going to want to plug something into that line other than a low watt bulb.
The saving grace thus far sounds like you aren't maxing out the current with that kind of wattage or load.
I too would like to see some pics if possible.
Are you joining it through a correct junction box? What are you doing for burial depth and conduit?
BP

 

[SS MAYFLOAT]

Re: Voltage drop over long wire runs?

157 volts is not good and can be damaging to electronics. Coffee pots should brew pretty quick . Sounds I would double check with another meter. I had a CFESA tech call me to one our stores pronto. Got there and his meter was registering 367 volts (208 is our supply). I then asked him then why is everything thing else working? I pulled mine out and it showed 208. He was using a Fluke, which I thought was a good meter. I use Fieldpiece.

As for the wiring, I would at least put an amploc on the line to see what the load is at the breaker. Voltage drops increase resistance which causes higher amp draw. Personally, I would have used 12 awg, but that is the Tim Taylor in me

 

[j_martin]

Re: Voltage drop over long wire runs?

157 V would be the peak voltage if it was 117V rms, which is the measurement we use.

Some meters can be switched from rms to Peak. A Mercury DVM is actually a peak reading voltmeter, and would read that voltage.

hope it helps
John

 

[Mark42]

Re: Voltage drop over long wire runs?

I brought my multi meter to the office today and it reads 156.6 volts on the 200v setting, so I guess the meter is broken.

The meter is a GreenLee DM-50 model Digital tester, does 300 v AC-DC, diode, resistance, mA and special 1.5 battery check. Your typical homeowner tester. A while back the internal fuse blew. I couldn't find a replacement, so I called Greenlee, and they send a new fuse free of charge. I was pleasantly surprised.

Today I called Greenlee and asked about the Lifetime warrantee on the meter. They said it is now out of production, being replaced by the DM-40 model, and they would send one out to me free of charge. Wow, can't ask for more than that on a 15 year old meter that got a lot of use.

The DM-40 spec:

The Greenlee DM-40 Digital Multimeter is a hand-held testing device
with a backlit display and the following measurement capabilities:
AC and DC voltage, DC current, temperature (K-type thermocouples
only), and resistance. It also checks diodes, verifies continuity, and
tests 1.5 V and 9 V batteries.

Now I know the DM-40 is available online on sale all over for about $33 or so plus $10 shipping. But for free, and having more features than my old DM-50, I am thrilled to get it replaced. Not even shipping charges. Nice company to stand by products they don't even make anymore.

Think I'll look for Greenlee when I need my next electronic measuring tool.

BTW, I am adding two or three more 3' post lights down the front walkway and back walkway. This should give some nice even lighting on all the walk ways, drive way and side yard where Daisy the dog does her business at night. When the lights are in I'll post some pictures.

 

[Mark42]

Re: Voltage drop over long wire runs?

A little update on the multi tester. It was delivered the other day. I opened it and was playing around with the settings and reading the owners manual when I read the part about it taking a 9V battery......

It takes a 9V battery? OMG, I forgot about that. So I open up the old tester and take out the 9v and test it with the new tester, its only got .5v left and drops to zero if left on the tester. So I put a fresh 9v in the old tester, and Bingo! It works as good as new! :redface:

Oh well.... Now I have two testers.:redface:

 

[SS MAYFLOAT]

Re: Voltage drop over long wire runs?

Oh well.... Now I have two testers.:redface:

I keep 3 on my truck, but I work on 3 phase equipment and use them for doing amp draw readings. Mine do have a low battery icon that lets me know when they are low. Yep, a low battery will cause some headaches for sure. Glad you got it figured out Mark

 

[NelsonQ]

Re: Voltage drop over long wire runs?

A little update on the multi tester. It was delivered the other day. I opened it and was playing around with the settings and reading the owners manual when I read the part about it taking a 9V battery......

It takes a 9V battery? OMG, I forgot about that. So I open up the old tester and take out the 9v and test it with the new tester, its only got .5v left and drops to zero if left on the tester. So I put a fresh 9v in the old tester, and Bingo! It works as good as new! :redface:

Oh well.... Now I have two testers.:redface:

Nothing wrong with that and great to see a company stand behind their products. I'm sure if you called them back they'd tell you to keep it anyway

 

[Arthur Laursenist]

Re: Voltage drop over long wire runs?

Keep in mind that you need a 20A breaker for number 12AWG and a 15A for 14AWG.You can use 12AWG on the 15A Bkr. but you can't use 14AWG on a 20A BKr.

 

[bluto3166]

Re: Voltage drop over long wire runs?

Here's the link to Mike Holt's electrical forum, more specifically the voltage drop calculator. You will need amperes ( watts/voltage ). This is for AC not DC. Have fun.

http://www.mikeholt.com/documents/freestuff/other/VoltageDropCalculator.xls

 

[j_martin]

Re: Voltage drop over long wire runs?

Here's the link to Mike Holt's electrical forum, more specifically the voltage drop calculator. You will need amperes ( watts/voltage ). This is for AC not DC. Have fun.

http://www.mikeholt.com/documents/freestuff/other/VoltageDropCalculator.xls

Voltage drop would be the same for AC ( at power frequencies) and DC.

hope it helps
John

 

[Mark42]

Re: Voltage drop over long wire runs?

Just came in to take a break from working on the lighting. Today three more pole lights are being added, one on each side of the driveway, and one half way down the walkway to the front door. These are smaller versions of the carriage lamp I put in a few weeks ago, and will only stand about 3-1/2 feet tall.

I read where voltage drop is greater when the wattage is higher. The total wattage on this circuit is less than 200 watts. And at then longest run is only a 26 watt lamp. All bulbs are CFL and work great. I'm using the coiled bulbs and they have been working good even in the sub zero temps, although they take a minute or two to reach full brightness in those temps. Generally they come on bright at the flick of the switch.

The lights used to be incandescent, totalling 360 watts, without the four new pole lamps. Now I save over 160 watts over the incandescent, and get more lights and more lumens for my money. All these lights cost less than 4 cents an hour to operate at $0.18/KWH.