Underground service cable, conduit or not?

[misterfixit]

Starting on the new shop, have an electrical question. First let me say that I'm out in the country and there are no inspections, which really only means there are no inspectors to ask how they want it. I am the only one who has to be satisfied with how it is done. I only say that not because I intend to cut corners, but because I am the final authority on this by default.

I have 325 amp transformer from utility company. Service goes underground to my meter base which has dual lugs. One set of lugs feeds the breaker panel for my house. The second set of lugs now goes to a 200 amp disconnect about 2 feet from the meter. From that disconnect I will take 4/0, 4/0, 2/0 URD to my new building breaker panel. I know that it needs to be 18" underground minimum, and that from 18" up has to be in conduit. I also know that URD is made to be direct burial.

My question is this: what are the pros and cons of placing the entire run in conduit? about 130 feet will be in the ground.

 

[wyliesdiesels]

You cannot use a 3-wire feeder off of a disconnect. It needs to be 4-wire- 2 hots neutral and ground

Also, URD is not permitted inside structure regardless of conduit.

I would do conduit the whole way. Cheap insurance against rocks damaging the insulation.

 

[misterfixit]

You cannot use a 3-wire feeder off of a disconnect. It needs to be 4-wire- 2 hots neutral and ground

Also, URD is not permitted inside structure regardless of conduit.

I would do conduit the whole way. Cheap insurance against rocks damaging the insulation.

3 wire URD is what the utility told me to use when we installed the disconnect

 

[Copymutt]

No inspection? You may pay dearly when you try to sell.
Jim

 

[misterfixit]

No inspection? You may pay dearly when you try to sell.
Jim

Not sure why. There is no one to inspect it.

 

[misterfixit]

You cannot use a 3-wire feeder off of a disconnect. It needs to be 4-wire- 2 hots neutral and ground

Also, URD is not permitted inside structure regardless of conduit.

I would do conduit the whole way. Cheap insurance against rocks damaging the insulation.

Maybe I used the wrong term? What I call the disconnect is a 200 amp single breaker in an enclosure. Is that the same thing?

 

[Kevin Essiambre]

Maybe I used the wrong term? What I call the disconnect is a 200 amp single breaker in an enclosure. Is that the same thing?

A couple of photos would help them figure it out.

 

[wyliesdiesels]

3 wire URD is what the utility told me to use when we installed the disconnect

The utility is wrong.

Never get electrical advice for NEC based wiring from a PoCo that does not have to wire things to the same code.

Maybe I used the wrong term? What I call the disconnect is a 200 amp single breaker in an enclosure. Is that the same thing?

yes that is the same thing. It is a disconnect. Doesnt matter what term or name is used, it does not change the requirement for a 4-wire feeder.

3-wire feeders have not been allowed since 2008.

You most definitely do not want a 3-wire feeder which would mean a bonded neutral. this creates the potential for a shock hazard.

you will need to make sure the neutral is isolate in the subpanel, which means purchasing a separate ground bar kit. you will also need 2 grounding electrodes.

You can review the diagrams on this thread, post #3:

https://www.garagejournal.com/forum/showthread.php?t=356460

 

[misterfixit]

The utility is wrong.

Never get electrical advice for NEC based wiring from a PoCo that does not have to wire things to the same code.



yes that is the same thing. It is a disconnect. Doesnt matter what term or name is used, it does not change the requirement for a 4-wire feeder.

3-wire feeders have not been allowed since 2008.

You most definitely do not want a 3-wire feeder which would mean a bonded neutral. this creates the potential for a shock hazard.

you will need to make sure the neutral is isolate in the subpanel, which means purchasing a separate ground bar kit. you will also need 2 grounding electrodes.

You can review the diagrams on this thread, post #3:

https://www.garagejournal.com/forum/showthread.php?t=356460

OK, just to make sure we both understand each other, this is not a sub panel to my understanding in that it is not fed from another panel, it is fed from the meter. Unless you are considering the disconnect the main panel? Utility company required a disconnect within 15' of the meter, it could either be on the main panel (if it was close enough) or seperate which it is in this case.

If I still need 4 wire, ok fair enough. If using 4 wire, both the neutral and the ground connect to the same ground in the main panel? then to seperate grounding bars in the panel in the shop? And things like motor housing or equipment housings are connected to the 2nd ground, while the neutral wire is connected to the first? And never the twain shall meet?

 

[sparky 1971]

If you already have the URD, just throw a #4 USE in the trench with it. If you haven't bought it yet, get MHF. I wouldn't put it in conduit, it will be a ***** pulling that twisted stuff that far, just make sure there a no rocks in the backfill. I wouldn't worry about the URD not being allowed inside. I just got back from an underground install where I used URD. (The supply house didn't have a long enough piece of MHF and I didn't want to wait till next Tuesday). The state inspector and I had a good laugh about the awful things that could happen from that 18" of URD installed inside the shop.

If you want to use conduit all the way, get XHHW or THHN/THWN

It is a sub panel, the disconnect is considered the main panel.

 

[wyliesdiesels]

OK, just to make sure we both understand each other, this is not a sub panel to my understanding in that it is not fed from another panel, it is fed from the meter. Unless you are considering the disconnect the main panel? Utility company required a disconnect within 15' of the meter, it could either be on the main panel (if it was close enough) or seperate which it is in this case.

The definition of a subpanel is any panel past the first means of disconnect- this could be a main service panel, a safety switch disconnect, or a single breaker disconnect. Doesnt matter. Its all the same since they are all considered the first means of disconnect.

The single breaker you have is the first means of disconnect. The panel in the shop is most definitely a subpanel. you most definitely need a 4-wire feeder. This is a basic important concept and if done wrong (3-wire feeder) you create a potential for shock that could injure someone.

If I still need 4 wire, ok fair enough. If using 4 wire, both the neutral and the ground connect to the same ground in the main panel? then to separate grounding bars in the panel in the shop? And things like motor housing or equipment housings are connected to the 2nd ground, while the neutral wire is connected to the first? And never the twain shall meet?

yes the neutral and ground wires go to the same bar in the disconnect enclosure

But as to the subpanel, you are creating lots of confusion by calling the neutral bar a ground bar. Neutral and ground are NOT the same. Do not confuse the 2. Dont call the neutral bar a ground bar.

The neutral bar needs to be isolated from the enclosure. this means removing the bonding screw or not installing it, depending on panel manufacture. All neutral wires go to this bar.

then you install separate ground bars that are directly connected to the enclosure. All grounds go here.

Did you look at the diagrams on the thread i shared earlier? All of this is explained on there.

It may be a good idea to hire an electrician for this since basic concepts are in question here.

 

[misterfixit]

The definition of a subpanel is any panel past the first means of disconnect- this could be a main service panel, a safety switch disconnect, or a single breaker disconnect. Doesnt matter. Its all the same since they are all considered the first means of disconnect.

The single breaker you have is the first means of disconnect. The panel in the shop is most definitely a subpanel. you most definitely need a 4-wire feeder. This is a basic important concept and if done wrong (3-wire feeder) you create a potential for shock that could injure someone.



yes the neutral and ground wires go to the same bar in the disconnect enclosure

But as to the subpanel, you are creating lots of confusion by calling the neutral bar a ground bar. Neutral and ground are NOT the same. Do not confuse the 2. Dont call the neutral bar a ground bar.

The neutral bar needs to be isolated from the enclosure. this means removing the bonding screw or not installing it, depending on panel manufacture. All neutral wires go to this bar.

then you install separate ground bars that are directly connected to the enclosure. All grounds go here.

Did you look at the diagrams on the thread i shared earlier? All of this is explained on there.

It may be a good idea to hire an electrician for this since basic concepts are in question here.

No offense, and none taken on my part, but the concepts are not in question. It is confusing though, since an experienced electrician I have known for several years told me to do it this way, and you (who I don't know but accept that you are also an electrician) are telling me its wrong. What I was trying to make sure of is that we are not speaking of different things, I know different locations and areas of the country often have different names for things. And yes it may be "by code" but I've done a bit of trade work in my time and everyone in this area calls them 'ground'.

All that aside, my original question still stands. what are the pros and cons of putting the cable in conduit or not?

 

[rburke65]

Regardless of what kind of wire/cable is decided upon, run the pvc conduit. Run a larger size than mandated. Run an extra one while your at it....heck, go crazy and run 2 extras.

 

[misterfixit]

Regardless of what kind of wire/cable is decided upon, run the pvc conduit. Run a larger size than mandated. Run an extra one while your at it....heck, go crazy and run 2 extras.

Sarcasm? or have I missed something?

 

[sparky 1971]

Conduit. Pros: less chance for damage to the wires due to rocks, tree roots, etc., and if a wire would somehow get damaged, new can be pulled. Cons: expense and it may be difficult to pull the wire.

Direct bury. Pros: expense, ease of installation. Cons: more likely to be damaged,if that would happen, you have to find the bad spot and repair it, or redo the whole thing.

I have always done the direct bury for my own projects. Paying jobs get whatever the customer wants.

 

[klassenl]

You most definitely do not want a 3-wire feeder which would mean a bonded neutral. this creates the potential for a shock hazard.

Can you elaborate further on this point. How can a bonded neutral at a sub panel be a shock hazard yet a bonded neutral at the main ne fine.

 

[spudley]

I'm going thru very sandy soil with next to no rocks and I'm using MHF in pvc conduit.

Many guys run an extra pvc conduit for possible future use while your trench is open.

In my location, (and it may be NEC required) it's 18" to the top of the pvc which means a 20" deep trench, direct bury is minimum 24" deep.

Also, two ground rods from your sub panel, minimum 6' apart.

If you want to do it right, you'd be wise to follow Wylie's advice.

 

[Kevin Essiambre]

If you're going to have a trench open, I'd run several conduits, even if you don't use conduit for the cable you're running.

The conduits could be used for phone or internet, a generator, or even a water line.

I wouldn't run less than 3 conduits. If you don't use them, they can be capped for future use.

 

[sberry]

I wouldn't run any extra.
Your local guy may know, maybe not. If there are no inspections I am always suspect. If you are clear about which panel is which its not Wylies opinion it's a fact. Ain't no how no way he is not telling you the correct way.

 

[Lennyzx11]

One thing could come up later.
People and lending institutions are using home inspectors to check out purchases before buying now. I did since I was out of state on my last one.

He caught a double tap and a bonded ground to neutral in the box to the garage.

I commended him on his attention to detail and he said that most of the home inspection training programs train them to look for specific items such as these.

So could be a point to consider if a resale may ever happen down the road.


Sent from my iPhone using Tapatalk

 

[sberry]

Not all inspectors are like,that. I should have took a pic of one I saw a while back. A 3rd grader knows better.

 

[03.]

Regardless of what kind of wire/cable is decided upon, run the pvc conduit. Run a larger size than mandated. Run an extra one while your at it....heck, go crazy and run 2 extras.

Sarcasm? or have I missed something?

Very common to run an extra or two while the trench is open, provided the cost is not prohibitive, later you may want a phone line or a cat5 or who knows what else, but instead of another dig you just pull it in. I normally install a draw wire as I go to npmake life easier in the future. Larger size is a good idea too.

 

[Bretny]

I have direct burial running right through my driveway with no conduit. Been fine for 7yrs. My father has conduit ran under just one parking spot. Conduit is cracked(I assume) and full of water. We had to replace the wire once. He also wanted to upsize the sub pannel but cant with the conduit that's there.

It's a **** shoot really but my vote is to save some money and just to DB wire. 30yrs from now when the new owner wants to change the wire size in the conduit you paid for it may also be cracked or full of water.

 

[mcspeed]

I put an addition on my house where the patio concrete would limit access to electric panel. Knowing I would need to run wire sometime in the future I buried 1 1/4” conduit. Glad I did as I have since pulled # 3/3/4 wire to power new building and another #12 wire for outdoor lighting.

This would have been waaaay more difficult and expensive had I not buried the conduit before the concrete pour. It’s a cheap insurance policy to plan ahead.


Sent from my iPhone using Tapatalk

 

[nadogail]

Is your service cable susceptible to physical damage? Conduit should provide adequate protection from physical damage.

 

[misterfixit]

Thanks to all for the help and suggestions. First let me say that I'm not questioning Wylie, just making sure we are using the same terms and speaking of the same things. A pretty good friend of mine has been an electrician for as long as I have known him. He doesn't run a full time business anymore, hey we all get old. He's the one who told me how to do it.

Second, I intend to do it right.

As far as inspections, I don't know what to tell you. There isn't one, I'm not skipping it, or not calling, there is no one to call. Who inspects your television installation?

As for the cable and whether to bury it or not.......it will be as deep as the trencher will put it which should be around 36" deep. I'm also burying a new water line at the same time (have to move my water meter, long story, so new 1500' water line to house. At that point I will also take water to the shop). The area is pretty much rock free, sandy loam.

 

[misterfixit]

Oh yeah, forgot about the extra conduits. I've thought for a long while about what to have in the shop. We don't even have a landline phone at home, we do all cell. Internet is satellite and it pretty much creates a vacuum if you know what I mean. We live in a metal building 'barndominium' and cell service inside is not great. One plan I had it is to install a cell signal booster in the new building, that would allow me to use the hot spot feature for internet over cell.

 

[wyliesdiesels]

No offense, and none taken on my part, but the concepts are not in question. It is confusing though, since an experienced electrician I have known for several years told me to do it this way, and you (who I don't know but accept that you are also an electrician) are telling me its wrong. What I was trying to make sure of is that we are not speaking of different things, I know different locations and areas of the country often have different names for things. And yes it may be "by code" but I've done a bit of trade work in my time and everyone in this area calls them 'ground'.

All that aside, my original question still stands. what are the pros and cons of putting the cable in conduit or not?

I thought it was a utility that told you to use 3-wire. Now its your buddy?

Regardless, 3-wire feeders to detached structures, have not been allowed since 2008 code cycle. You said your buddy has not been doing this for awhile and so he is behind on code and proper way to do things.

It doesnt matter what terms are used though. 3-wire feeders are no longer allowed PERIOD. This is for good reason.

this is all explained in the FAQ thread i linked to earlier.

In regards to calling neutrals, grounds, that is totally incorrect. There is a HUGE difference between grounded conductor (neutral) and grounding conductor aka equipment grounding conductor (or ground for short). Mixing those up could prove deadly if someone thinks theyre touching a ground wire and it turns out to be a neutral with current running through it.

As to the conduit questions, i think that was answered by others.

Can you elaborate further on this point. How can a bonded neutral at a subpanel be a shock hazard yet a bonded neutral at the main be fine.

Its because of parallel pathways. If the feeder neutral should develop a bad or high resistant connection (I've seen it happen before), the neutral current can flow on an alternate pathway (such as a person touching something that is grounded) due to the bonding screw being in place in the subpanel. The bonding screw puts everything metallic and connected to the panel enclosure at the same potential.

Alternate pathways include communication lines, metal conduit, metal plumbing, metal gas lines, etc etc. It can even go through someone standing barefoot on concrete. My wife got shocked one time touching a light switch that was not grounded (pre-grounded yoke switches) standing barefoot on tile floor. the switch was broken and the hot leg was connected to the metal chassis. The current went through her arm and down her leg. I pushed her away from it in case she got locked onto it.

I put an addition on my house where the patio concrete would limit access to electric panel. Knowing I would need to run wire sometime in the future I buried 1 1/4” conduit. Glad I did as I have since pulled # 3/3/4 wire to power new building and another #12 wire for outdoor lighting.

This would have been waaaay more difficult and expensive had I not buried the conduit before the concrete pour. It’s a cheap insurance policy to plan ahead.


Sent from my iPhone using Tapatalk

3-wire feeders are not allowed anymore. you need 4-wire

 

[Dagny]

Pretty hard to go with wylie.

 

[wyliesdiesels]

Pretty hard to go with wylie.

huh?

 

[misterfixit]

I thought it was a utility that told you to use 3-wire. Now its your buddy?

I'm sorry I didn't completely explain everything to your satisfaction. Full disclosure:
1. Buddy told me what I needed
2. started making plans and list of what I need to buy, wish lists, dreams,
etc.
3. knew there was no city or county inspection, but we are on rural electric co-op, so I called them to see if they needed to inspect
4. spoke to who I think is an engineer, could be the guy who mops floors not sure, and got the 'official' no inspection needed/required/available
5. bought the disconnect and prepared to mount it, which requires co-op to come out and shut off power at the transformer (I'm on almost 27 acres, no neighbors within about a mile, I'm the only one on the transformer)
6. had the Co-op send a guy to shut off the power, I mounted the disconnect, guy came back to turn on power again. At that point I asked about the wire, mentioned I was told to use the URD 3 wire, and was told 2 things- a. that's what they use to the meter, and b. they don't care what I put behind the disconnect.

Hope that clears up any confusion or suspicion on your part, if not just ask me.

3-wire feeders are not allowed anymore. you need 4-wire

As I said early on in this thread, I was going to do it right, not sure why you are still beating this horse, I've not argued against 4 wire at all. I've only tried to cure my confusion and make sure terms are consistent and understandable by both of us.

 

[klassenl]

Its because of parallel pathways. If the feeder neutral should develop a bad or high resistant connection (I've seen it happen before), the neutral current can flow on an alternate pathway (such as a person touching something that is grounded) due to the bonding screw being in place in the subpanel. The bonding screw puts everything metallic and connected to the panel enclosure at the same potential.

Alternate pathways include communication lines, metal conduit, metal plumbing, metal gas lines, etc etc. It can even go through someone standing barefoot on concrete. My wife got shocked one time touching a light switch that was not grounded (pre-grounded yoke switches) standing barefoot on tile floor. the switch was broken and the hot leg was connected to the metal chassis. The current went through her arm and down her leg. I pushed her away from it in case she got locked onto it.

This indeed correct.

In the past 3 wire feeds have been acceptable but only if you install a new ground. Either rods or a plate. This eliminated that "parallel path" issue.

 

[wyliesdiesels]

This indeed correct.

In the past 3 wire feeds have been acceptable but only if you install a new ground. Either rods or a plate. This eliminated that "parallel path" issue.

no thats incorrect.

A rod or plate does not eliminate the parallel pathway issue. One could still be shocked if the bonded neutral develops a bad connection and they touch something metal or are standing on concrete. this is because electricity takes all pathways. this is why 3-wire feeds were eliminated. The bonded neutral is the issue.

And grounding electrodes were always required on detached structures.

 

[Kevin Essiambre]

no thats incorrect.



A rod or plate does not eliminate the parallel pathway issue. One could still be shocked if the bonded neutral develops a bad connection and they touch something metal or are standing on concrete. this is because electricity takes all pathways. this is why 3-wire feeds were eliminated. The bonded neutral is the issue.



And grounding electrodes were always required on detached structures.

The guy you quoted is from Canada, I can confirm that Canadian code used to let us run 3 wire, and bond the neutral to ground, and install a grounding electrode (plate, rod, etc) in a separate building.

Our Canadian code has changed, now we must run 3 wire plus ground(4 wire), and we can only bond neutral to ground at the service entrance gear.

Our Canadian code also doesn't require a grounding electrode at every separate building. I think barns are the one thing that still require them.

 

[nh_yota]

One thing could come up later.
People and lending institutions are using home inspectors to check out purchases before buying now. I did since I was out of state on my last one.

He caught a double tap and a bonded ground to neutral in the box to the garage.

I commended him on his attention to detail and he said that most of the home inspection training programs train them to look for specific items such as these.

So could be a point to consider if a resale may ever happen down the road.


Sent from my iPhone using Tapatalk

Double-tapped breakers are legal if the breaker is designed to allow it. Home inspectors assume all breakers are the same.

 

[wyliesdiesels]

The guy you quoted is from Canada, I can confirm that Canadian code used to let us run 3 wire, and bond the neutral to ground, and install a grounding electrode (plate, rod, etc) in a separate building.

Our Canadian code has changed, now we must run 3 wire plus ground(4 wire), and we can only bond neutral to ground at the service entrance gear.

Our Canadian code also doesn't require a grounding electrode at every separate building. I think barns are the one thing that still require them.

Aww ok makes sense. Seems CEC changed when the NEC changed. And for good reason

As to not requiring grounding electrodes, that doesnt make sense to me since grounding electrodes are for shunting lightning.

 

[NUTTSGT]

The guy you quoted is from Canada, I can confirm that Canadian code used to let us run 3 wire, and bond the neutral to ground, and install a grounding electrode (plate, rod, etc) in a separate building.

Our Canadian code has changed, now we must run 3 wire plus ground(4 wire), and we can only bond neutral to ground at the service entrance gear.

Our Canadian code also doesn't require a grounding electrode at every separate building. I think barns are the one thing that still require them.

This is why it can be very important to use a location in your profile. It doesn't need to be exact but can make a big difference on advice given or questions asked.

 

[mcspeed]

I thought it was a utility that told you to use 3-wire. Now its your buddy?

Regardless, 3-wire feeders to detached structures, have not been allowed since 2008 code cycle. You said your buddy has not been doing this for awhile and so he is behind on code and proper way to do things.

It doesnt matter what terms are used though. 3-wire feeders are no longer allowed PERIOD. This is for good reason.

this is all explained in the FAQ thread i linked to earlier.

In regards to calling neutrals, grounds, that is totally incorrect. There is a HUGE difference between grounded conductor (neutral) and grounding conductor aka equipment grounding conductor (or ground for short). Mixing those up could prove deadly if someone thinks theyre touching a ground wire and it turns out to be a neutral with current running through it.

As to the conduit questions, i think that was answered by others.



Its because of parallel pathways. If the feeder neutral should develop a bad or high resistant connection (I've seen it happen before), the neutral current can flow on an alternate pathway (such as a person touching something that is grounded) due to the bonding screw being in place in the subpanel. The bonding screw puts everything metallic and connected to the panel enclosure at the same potential.

Alternate pathways include communication lines, metal conduit, metal plumbing, metal gas lines, etc etc. It can even go through someone standing barefoot on concrete. My wife got shocked one time touching a light switch that was not grounded (pre-grounded yoke switches) standing barefoot on tile floor. the switch was broken and the hot leg was connected to the metal chassis. The current went through her arm and down her leg. I pushed her away from it in case she got locked onto it.



3-wire feeders are not allowed anymore. you need 4-wire

3-wire feeders are not allowed anymore. you need 4-wire

You had me worried for a minute. I stated incorrectly. 3/3/3/5 is the wire I used.


Sent from my iPhone using Tapatalk

 

[alfredeneuman]

I have direct burial running right through my driveway with no conduit. Been fine for 7yrs. My father has conduit ran under just one parking spot. Conduit is cracked(I assume) and full of water. We had to replace the wire once. He also wanted to upsize the sub pannel but cant with the conduit that's there.

It's a **** shoot really but my vote is to save some money and just to DB wire. 30yrs from now when the new owner wants to change the wire size in the conduit you paid for it may also be cracked or full of water.

Actually all underground conduits eventually fill with water.

 

[spudley]

Actually all underground conduits eventually fill with water.

Why is that? I mean that would require some kind of joint or glue failure. That isn't happening in houses with plastic plumbing glued under pressure joints so why in the ground?