Detached Garage Voltage Has Dropped to 103v

[WhoDat]

New guy here. Really interesting posts by everyone. Learning quite a bit. Hoping to get some ideas from you.

I have a detached garage that's about 30 feet from my house. It's feed by a 20-amp breaker from my main panel. There's an underground conduit that runs from my house to the garage.

I believe my load is low. At its peak power usage, I have two outside lights on during the night, occasionally cycle the garage door, run 3-4 trickle chargers for various 12 batteries, and turn on two internal 60-watt light bulbs as needed. For years everything has been working fine.

About a month ago I noticed that when I would attempt to open the garage door, the garage opener's lights would flash & the door would jitter as it tried to open (or close). Often just stopping. When I pressed the open/close button once or twice, the door would open (or close). Everything else continued to work.

I went camping last weekend & when I returned home, I couldn't get the garage door to open & all the lights were off. The garage presented as if it had no power.

Years ago, & inside the garage, an electrician installed a "master" switch which was really only a light switch. Back then I trusted that he knew what he was doing. Now I know better. Regardless, I cycled it, but couldn't detect any power. So, next I reset the breaker in the house panel, but that didn't appear to fix the problem either. It's an old breaker so I replaced it with a new one. Again, no apparent change.


I decided to insert a receptacle tester to an outlet next to the so-called master switch & to my surprise it showed that the receptacle was fine, displaying two ambers. No faults. I tested the actual voltage and it was showing 103v. (at other times when I tested it would be as low as 80-90v). I went back to the house panel & tested the voltage coming off the 20-amp breaker. It was between 119 & 121v. I've also removed the master switch & directly connected the wires using a 10-amp Wago connector. No change.

Needless to say, this amateur was totally stumped. A friend advised that I turn the breaker off until I got this figured out, which I did.

The next day I talked to a Coast Guard electrician (I'm the IT guy for the unit) who immediately suspected a problem with the neutral. After work I actually found a very loose neutral wire at the panel & it literally came out of the neutral bar when I touched the white wire. I corrected that & ran out to the garage expecting (hoping) to see everything was working again, but it wasn't. The voltage was still either very low at around 80-90v or 103v.

Each day after work I would test various things. A pattern emerged. If the Romex from the breaker was connected to the wiring in the garage, the voltage was at the low mark. If, however, I disconnected the garage wiring & tested just the voltage coming from the panel, the voltage was 103v.

I've been searching Google for insights as to what may be going on. I've found a couple of posts about the impact of extremely dry soil which would accurately describe my situation. But this is nothing new for my yard. Last year when it hit 115 degrees & after weeks with no rain, my power to the garage was fine.

To wrap up this incredibly long first post, I've disconnected the garage from the house panel so it's totally isolated. I have a 30amp RV box on the house where I've temporarily run a 25-foot, 10-gauge outdoor extension across the yard to an outdoor box that feeds off the garage. When I turn on the 30-amp breaker, the garage comes to life. Everything works. Zero flickering or jittering. I think this is important because to me it suggests there's probably nothing wrong with the wiring inside the garage (well other than the so-called master switch which I will replace with a proper sub-panel).

I'm starting to think I may need to attempt to pull new Romex, guessing that somehow, someway, my existing run has been compromised or damaged.

If anyone has read this far, 1) thanks, 2) apologies, 3) thoughts/suggestions?

 

[sparky 1971]

My guess is the underground wire is going bad, unless you have a bad connection between the house panel and the garage. If it really is run in conduit the entire length from the house to the garage, you should be able to pull new wire fairly easily.

The master switch is serving as a disconnect for the garage. It is a code compliant solution to the requirement for the disconnect. There is no need at all for a subpanel when you only have a 20 amp 120 volt circuit.

 

[WhoDat]

My guess is the underground wire is going bad, unless you have a bad connection between the house panel and the garage. If it really is run in conduit the entire length from the house to the garage, you should be able to pull new wire fairly easily.

The master switch is serving as a disconnect for the garage. It is a code compliant solution to the requirement for the disconnect. There is no need at all for a subpanel when you only have a 20 amp 120 volt circuit.

Happy to hear the master switch is still code compliant for my current usage. Thanks for replying.

 

[bryanrj]

There is a specially rated type of cable for underground. I ran about 75 feet out to a shed at my home over 20 years ago, with no problems so far. I have a small sub panel in the shed from where my lights and wall outlets are run. I am not an electrician, but my first thought when I began reading was your underground wire.

 

[dogdog]

Not sure. I don't use romex wires for under ground runs... make sure you use the proper wires for under ground runs or over head runs... THWN / THHN if you are using stranded wires and conduits, make sure you use the electrical conduits grey pvc ones not white pvc ones that is for water., GRC/RMC if metal and not EMT, or wires that is marked direct burial if you are not using conduits...

as far a troubleshooting... I think only thing home owners can do is disconnect the electricity from the wire that run between the house and garage, and check the ohm on them. or find a electrician that have the megger meter that can test insulation on electrical runs.., 30' shouldn't be that hard to replace, just make sure you replace with proper wires and conduits.

 

[wyliesdiesels]

If the underground wire is really NM-b (Romex is a brand of NM-b) then it was not done correctly as NM-b is not permitted outside or underground regardless if its in conduit.

What color is the jacket of this wire? If its white yellow or orange then its the wrong wire.

If its gray, then it isnt NM-b, its UF-b which is permitted underground

If it is indeed NM-b underground, then it probably failed....

I wouldve metered the voltage on the breaker lugs before wasting money on a new breaker....

 

[WhoDat]

If the underground wire is really NM-b (Romex is a brand of NM-b) then it was not done correctly as NM-b is not permitted outside or underground regardless if its in conduit.

What color is the jacket of this wire? If its white yellow or orange then its the wrong wire.

If its gray, then it isnt NM-b, its UF-b which is permitted underground

If it is indeed NM-b underground, then it probably failed....

I wouldve metered the voltage on the breaker lugs before wasting money on a new breaker....

The jacket color appears to be gray. I have a a handful of new breakers, so really no $$ wasted, but I get your point.

 

[WhoDat]

Not sure. I don't use romex wires for under ground runs... make sure you use the proper wires for under ground runs or over head runs... THWN / THHN if you are using stranded wires and conduits, make sure you use the electrical conduits grey pvc ones not white pvc ones that is for water., GRC/RMC if metal and not EMT, or wires that is marked direct burial if you are not using conduits...

as far a troubleshooting... I think only thing home owners can do is disconnect the electricity from the wire that run between the house and garage, and check the ohm on them. or find a electrician that have the megger meter that can test insulation on electrical runs.., 30' shouldn't be that hard to replace, just make sure you replace with proper wires and conduits.

I've lived in the house since 1997, so whatever conduit was used was put there long before I moved in. I did have the garage rebuilt back in 2009, but I couldn't tell you if the contractor pulled new wire or not. Yeah I know, that's sad.

 

[WhoDat]

So, I have an idea that might help me confirm whether or not the run from the breaker to the detached garage is truly the issue.

If I run cable from the panel in my basement (using the 20-amp garage breaker) to my garage master switch, and then turn the breaker on, I should know very quickly if the garage returns to normal again. Basically doing something similar to the temporary extension cord I'm using, but hardwiring it between the panel & the garage, just temporarily outside the conduit.

I have a 4 inch opening where my dryer vents that's a only a couple of feet from the panel, so it would be fairly easy to run the wire out, across the backyard & temporaily connect to the garage for a test.

If test is successful & garage returns to normal, then I'll know I have to pull the wire in the underground conduit.

 

[mcbane]

I had similar symptoms at a well house. Was fed by UF cable in conduit but there was an electrical tape splice inside the conduit that had corroded badly.

If your conduit isn’t full of mud should be easy to pull new cable.

 

[ycgoat]

I would put my efforts into seeing if I can pull the old cable out. If you can get it to move, tie a mouse on the end of the cable and a string or the new cable. It could be the conduit is broken or came apart and caused your problem

 

[CJ7VFR]

What color is the jacket of this wire? If its white yellow or orange then its the wrong wire.

If its gray, then it isnt NM-b, its UF-b which is permitted underground

What year did the universal color for the jacket of UF-B become gray? In older direct bury installations prior to about 2001 or so, I have seen the jacket of some UF-B cables colored white. The feed to my father's garage, which was built and wired up in 1987, uses UF-B that has a white jacket with green labeling on it. You can see this where the cable comes into the house and the garage. Jim

 

[PCustoms]

What year did the universal color for the jacket of UF-B become gray? In older direct bury installations prior to about 2001 or so, I have seen the jacket of some UF-B cables colored white. The feed to my father's garage, which was built and wired up in 1987, uses UF-B that has a white jacket with green labeling on it. You can see this where the cable comes into the house and the garage. Jim

I ripped a lot out that was white with green lettering. House built in '85, not sure where wire came from.

 

[wyliesdiesels]

What year did the universal color for the jacket of UF-B become gray? In older direct bury installations prior to about 2001 or so, I have seen the jacket of some UF-B cables colored white. The feed to my father's garage, which was built and wired up in 1987, uses UF-B that has a white jacket with green labeling on it. You can see this where the cable comes into the house and the garage. Jim

not sure but ive seen gray UF-b from before 2001

you sure it says UF-b?

 

[The Cobbler]

not to sidetack the thread, but when I built my garage, I dug up & tied an existing 14/3 circuit for my shed into the garage sub panel removed from the house panel .when it came for final inspection of the panel, the inspector said I had the wrong wire for the shed, but I showed him the stamping on it, he said, oh, that's old wire, I thought it was a new install , and he was happy. it was white jacket from around 2000 or so . this was around 2016

 

[larry_g]

Have you disconnected the hot and neutral wires from the breaker and the garage end and checked the resistance between the wires and from the wires to earth ground? All should show an open. Anything not showing open will be a leakage path to somewhere.

lg
no neat sig line

 

[WhoDat]

Have you disconnected the hot and neutral wires from the breaker and the garage end and checked the resistance between the wires and from the wires to earth ground? All should show an open. Anything not showing open will be a leakage path to somewhere.

lg
no neat sig line

No, I haven't done that. I will add as "homework" for the weekend. Guessing I should follow something along the lines of this? https://electrouniversity.com/how-to-measure-ground-resistance-with-a-multimeter/

 

[CJ7VFR]

not sure but ive seen gray UF-b from before 2001

you sure it says UF-b?

Yes, it is UF-b. It is 12 gauge wire inside of a white jacket with green lettering. It looks and feels exactly like the gray jacketed cable except it is white. And it was just as hard to work with as the newer gray one! I thought I read somewhere that around 2001 or so is when the color coding for non metallic cable was universally put into place by the wiring manufacturers. IE white for 14 gauge, yellow for 12 gauge, orange for 10 gauge, gray for all sizes of UF-B ect. Jim

 

[Firebrick43]

Have you disconnected the hot and neutral wires from the breaker and the garage end and checked the resistance between the wires and from the wires to earth ground? All should show an open. Anything not showing open will be a leakage path to somewhere.

lg
no neat sig line

If its leakage, it will typically still show open with a multimeter, not enough voltage. You would need to use a megger to actually see the problem and that typically is not a DIY tool.

 

[larry_g]

If its leakage, it will typically still show open with a multimeter, not enough voltage. You would need to use a megger to actually see the problem and that typically is not a DIY tool.

I agree. However the OP has a multimeter and the test is easy to do. Small chance it will show a problem but it may. I always try the quick, cheap, and easy before jumping into the more difficult time consuming tests.

lg
no neat sig line

 

[wyliesdiesels]

If its leakage, it will typically still show open with a multimeter, not enough voltage. You would need to use a megger to actually see the problem and that typically is not a DIY tool.

Beat me to it

 

[Innovate1]

Maybe I missed it but I haven't seen anyone suggest to test the voltage directly at both ends of the run between buildings. This problem is more likely a bad connection than disintegration of the wire between buildings IMHO. (Unless someone put a splice in the run which shouldn't have been done). Test the voltage at both ends with some load on the garage end - just a light or anything since you always have low voltage it doesn't need to be a big load. Do that at the very first box in the garage - sounds like that would be the switch you mentioned. One the other end that's probably at the feeding breaker but might be a splice somewhere before it goes out of the building. No point in pulling the run between buildings if the issue is a bad joint in the buildings.

If the voltage at both ends is the same the problem is elsewhere. You could also disconnect both wires from the feed end and short them together and measure resistance between them on the other end. Don't have a resistance table handy but it should be under a few ohms.

 

[TractorJeff]

If he bypasses the underground wire like he wants to do. That would in effect prove out the bad wire underground. He mentioned his buddy is a Coast Guard Electrician. I know for a fact would have access to a Megger. All Ship wiring gets megger tested especially at overhaul.
I have seen UF wire from the 70's and 80's that was White Jacketed.

 

[lolaetype]

N


I decided to insert a receptacle tester to an outlet next to the so-called master switch & to my surprise it showed that the receptacle was fine, displaying two ambers. No faults. I tested the actual voltage and it was showing 103v. (at other times when I tested it would be as low as 80-90v). I went back to the house panel & tested the voltage coming off the 20-amp breaker. It was between 119 & 121v. I've also removed the master switch & directly connected the wires using a 10-amp Wago connector. No change.

I had a similar problem in our last house. The electrician traced the problem to a faulty breaker that wasn't seating fully in the panel.

 

[Jmellc]

There should be 2 neutrals spliced in the switch box. Check them for good connection. Check for good connections on the switch terminals. Pull the receptacle and check for good connections on it. Of course, do this with power off. Also possible that neutral is damaged in between. If you get full voltage from line to ground but less from line to neutral, the neutral is your issue. Also, see if any of the garage receptacles are wired by "backstabbing" into rear slots. This is a shabby wiring method that is widely done for being fast and cheap. In fact, check switch for this too. Most 20 amp devices nowadays won't take backstabs but some did in the past and you never know what someone installed. Neutral is still likely main issue but things can pile on.

 

[WhoDat]

not sure but ive seen gray UF-b from before 2001

you sure it says UF-b?

Over the weekend I confirmed that the cable going into the garage is gray. I couldn't find any writing on the sheath at all. I just double-checked the panel in the basement. There doesn't appear to be any gray cables. I disconnected the black wire from the garage breaker & then pulled it all the way out so I could find the cable, among the many, going into the panel. There doesn't appear to be a gray cable, it appears white. The sheath has 12 - 2 With Ground written on it. I understand that all this may suggest that two different cables were used. I plan to run a continuity test (assuming at least one wire is still connected) to truly verify I've identified the cable going from the panel to the garage.

 

[dogdog]

you said you have a master switch right ? the portion of the inside wire between the breaker and the master switch if it is inside , it doesn't needed to be grey / UF-B... I would verify both portion of the cable... white sheath on 12 gauge wiring might be older wires... new one are always Yellow for 12Gauge, and white for 14guage. it's pretty simple to do... I think 6 test per portion of the wires. if you really want to chart it, and reduce redundant test maybe 4 tests...

intermanets.

The cable jacket is color-coded for quick size identification; White - 14 AWG, Yellow - 12 AWG, Orange - 10 AWG, and Black - 8 AWG and 6 AWG.

 

[wyliesdiesels]

you said you have a master switch right ? the portion of the inside wire between the breaker and the master switch if it is inside , it doesn't needed to be grey / UF-B... I would verify both portion of the cable... white sheath on 12 gauge wiring might be older wires... new one are always Yellow for 12Gauge, and white for 14guage. it's pretty simple to do... I think 6 test per portion of the wires. if you really want to chart it, and reduce redundant test maybe 4 tests...

intermanets.

the switch he referred to was in the garage. the white cable he pulled out was on the house side at the panel.

2 different ends of the run.

It is possible the white cable splices to the gray cable somewhere inside in a junction box but we dont know how far the OP pulled the cable out from. is there a conduit that the OP can see the cable coming from?

 

[sparky 1971]

Over the weekend I confirmed that the cable going into the garage is gray. I couldn't find any writing on the sheath at all. I just double-checked the panel in the basement. There doesn't appear to be any gray cables. I disconnected the black wire from the garage breaker & then pulled it all the way out so I could find the cable, among the many, going into the panel. There doesn't appear to be a gray cable, it appears white. The sheath has 12 - 2 With Ground written on it. I understand that all this may suggest that two different cables were used. I plan to run a continuity test (assuming at least one wire is still connected) to truly verify I've identified the cable going from the panel to the garage.

Over the weekend I confirmed that the cable going into the garage is gray. I couldn't find any writing on the sheath at all. I just double-checked the panel in the basement. There doesn't appear to be any gray cables. I disconnected the black wire from the garage breaker & then pulled it all the way out so I could find the cable, among the many, going into the panel. There doesn't appear to be a gray cable, it appears white. The sheath has 12 - 2 With Ground written on it. I understand that all this may suggest that two different cables were used. I plan to run a continuity test (assuming at least one wire is still connected) to truly verify I've identified the cable going from the panel to the garage.

It probably is two cables. A romex from the panel to a junction box where it transitions to UF going to the garage. Usually, it's a Bell box on the outside of the house with a PVC going down. On old houses I've seen where someone drilled a hole through the foundation into the basement and mounted the box inside, over the hole. Find that box and check the connections. Be prepared to have to destroy the box in order to get it apart. I've used a hammer on more than one rusted Bell box. When putting it back together drill a 1/8" hole in the bottom and use anti seize on the screws. You may still have bad underground wire, but eliminate all of the easy things first.

 

[Innovate1]

This ^. Quite likely the spice between the two different cables is the issue. Hopefully you can find the splice in a box and it isn't hidden somewhere.

 

[75gmck25]

I have some old 120 volt UF cable (I think) outside my house and its colored white. If you look at the wires on the end its very obvious that is not standard NM-type cable. Each wire inside is covered with insulation (as usual), and then the entire area inside the jacket is filled with some type of rubber material. Its very difficult to separate the three wires inside because the rubber filling material makes it all stick together. There are no markings on the cable.

 

[WhoDat]

I ran a small test this weekend. I tested the voltage inside the garage while being powered by my temporary solution where I'm providing power via an unused 30amp RV outlet and a 10 guage outdoor extension cord. As expected voltage was 119 at the master switch & at various outlets inside the garage. This was with the garage completely disconnected from the panel in the basement.

I turned off the 30 amp breaker, then I re-connected the garage to the cable bundle that runs to the panel, but is currently not connected to a breaker, neutral, or ground. So basically just capped wires floating in the air. Then I turned the 30 amp breaker back on.

Yesterday afternoon with the outside temp's around 82 degrees, the voltages was only around 95v when I tested it in the basement. This am however, it's 116v. It was about 65 degrees this morning when I tested.

I plan to test again this afternoon when it's 90. I have a hunch the voltage will drop back down.

I'm still working on trying to find the Bell or junction box where the white cable from the panel is probably connected to that gray cable going to the garage.

 

[PCustoms]

Delete

 

[WhoDat]

No, not sure why I would though. In my living room I have a high end line conditioner for my TV & other audio equipment. It's currently showing 119v.

 

[PCustoms]

No, not sure why I would though. In my living room I have a high end line conditioner for my TV & other audio equipment. It's currently showing 119v.

I misread something you wrote and was going down the wrong path.

Seems you isolated the issue to the underground feed. Time to trench in a new one

 

[dogdog]

Just identify the section that cause this issue or replace the whole thing front to back and call it a day. that would be much easier.

you are trouble shooting a section of wires embed some where inside home drywalls that most likely have a bad connection you don't know where it is.... it's going to be PITA to find... not sure if there are any reliable gadgets to trace it... I know the circuit tracers / tone generators ***** and more confusing to use than it is be useful. maybe an electrician can recommend a device that for you. unless you don't mind knocking down some walls to find out.

Drywall patching is easier than pulling your hairs out.

also note I think this is the reason why NEC doesn't allow junction box inaccessible...

 

[sparky 1971]

New guy here. Really interesting posts by everyone. Learning quite a bit. Hoping to get some ideas from you.

I have a detached garage that's about 30 feet from my house. It's feed by a 20-amp breaker from my main panel. There's an underground conduit that runs from my house to the garage.

I ran a small test this weekend. I tested the voltage inside the garage while being powered by my temporary solution where I'm providing power via an unused 30amp RV outlet and a 10 guage outdoor extension cord. As expected voltage was 119 at the master switch & at various outlets inside the garage. This was with the garage completely disconnected from the panel in the basement.

I turned off the 30 amp breaker, then I re-connected the garage to the cable bundle that runs to the panel, but is currently not connected to a breaker, neutral, or ground. So basically just capped wires floating in the air. Then I turned the 30 amp breaker back on.

Yesterday afternoon with the outside temp's around 82 degrees, the voltages was only around 95v when I tested it in the basement. This am however, it's 116v. It was about 65 degrees this morning when I tested.

I plan to test again this afternoon when it's 90. I have a hunch the voltage will drop back down.

I'm still working on trying to find the Bell or junction box where the white cable from the panel is probably connected to that gray cable going to the garage.

If you can't find the box, how do you know it's conduit from the house to the garage? The box should be at the other end of the conduit. I have a suspicion that you have a piece of conduit sleeving the UF above grade at the garage and you're gonna need a shovel to replace the wire.

 

[WhoDat]

It's all good & I really appreciate all the input & questions!

 

[WhoDat]

This is just an update to my original post. Two weeks ago I reconnected my garage to the panel in my basement. The lights, garage door opener, etc. all worked without issue. The PNW has been getting a LOT of rain. Yesterday I got around to checking the voltage in the garage. It was back up to 119v. This may shed some light on the whole dry vs wet earth theory.

And yes, I realize I still have to resolve this the correct way.

 

[Norcal]

you said you have a master switch right ? the portion of the inside wire between the breaker and the master switch if it is inside , it doesn't needed to be grey / UF-B... I would verify both portion of the cable... white sheath on 12 gauge wiring might be older wires... new one are always Yellow for 12Gauge, and white for 14guage. it's pretty simple to do... I think 6 test per portion of the wires. if you really want to chart it, and reduce redundant test maybe 4 tests...

intermanets.

Please note that that "color code" only started after 2002, so still relatively recent, NM-B, or UF-B, dates back to the mid 1980's, plain old NM, or UF, is older.