Barn wiring ground questions

[Jameseric]

My barn is 150 feet from the house. It is feed by (2) 4 gauge cables carrying 30 amps each. It has a fused disconnect at the house a fuse box in the barn. I plan to replace the fuse box with a non-fused disconnect at the barn entrance. From the new disconnect I plan to run 4 gauge cables to a new breaker box.

However, the barn does not have a ground wire or bonding to the house therefore I need to ground it at the barn.

How many conductors do I need between the new disconnect and the breaker box? Should I have 2 hots, neutral and ground or just 2 hots and a ground?

I will place the ground at the disconnect so that I can protect myself as soon as the power enters the barn. Please make any suggestions you feel are best in my situation.

Thanks.

 

[pattenp]

I'm not going to ask why you have 4/0 and only 30A. I assume when you say two 4/0 conductors from the house, that is the total number of wires. Is there not a neutral? The feed to the barn should be at least 3 wires.

 

[Jameseric]

I was going from memory and you are correct. It has neutral plus the 2 hots. Also it is not 4/0 it is 4 gauge.

 

[pattenp]

Under old code if you are in the US the 3 wire is okay. From the new disconnect at the barn you will need to run 4 wires to the new breaker panel in the barn. The ground and neutral will be landed together in the disconnect box on the same ground/neutral bar and the neutral and ground will be landed on two separate bars in the breaker panel with the neutral being isolated from the ground. You will need to run a #6 bare copper electrode ground conductor from the bar in the disconnect box to two 8ft ground rods driven 6ft apart.

 

[Jameseric]

Thanks that is just what I wanted to know.

James

 

[wyliesdiesels]

Are u sure the breaker or fuses feeding the #4 wire is only 30a? #4 wire if Cu is rated for 85a and if AL 65a....

 

[2ManyProjects]

Are u sure the breaker or fuses feeding the #4 wire is only 30a? #4 wire if Cu is rated for 85a and if AL 65a....

This...

My barn is 150 feet from the house.

...could have something to do with it.

 

[pattenp]

Jameseric, is the #4 feed to your barn copper or aluminum?

 

[ishiboo]

This...



...could have something to do with it.

#4 aluminum will easily do 60A at that length, fully loaded, with only slightly more than 3% voltage drop. Fusing for 30A is a bit odd, and there's more capacity to be had. Perhaps it's a tiny barn though?

 

[wyliesdiesels]

This...



...could have something to do with it.

No!!!! U have no idea! And several others agree!

Code wise, U dont lower a breaker rating to compensate for voltage drop!

If the wire is CU, a 70a load would still be under 3% VD....

 

[2ManyProjects]

#4 aluminum will easily do 60A at that length, fully loaded, with only slightly more than 3% voltage drop.

You might want to check the batteries in your calculator.

CM = K x I x L / E

For AL, "K" is 21.2; and "L" is of course the ROUND TRIP distance. So...

CM = 21.2 x 60 x 300 / 7.2
CM = 381,600 / 7.2
CM = 53,000

AWG 4 is only 41,700 CM, or well less than 80% of what would be required to hold voltage drop to 3% with a 60A load.

If you have a masochist streak, you can nail it down more precisely by running the AC calcs as shown at http://www.dolphins-software.com/IEEE_ExactFormulae.htm. But there's really no need, given the large discrepancy shown above.

Fusing for 30A is a bit odd, and there's more capacity to be had.

I agree.

Even a 40A breaker would limit current sufficiently that V.D. would be well below 3%; 50A would be marginally over that, but probably still usable.

Perhaps it's a tiny barn though?

"Perhaps" all sorts of things which we can only guess at.

 

[2ManyProjects]

No!!!! U have no idea! And several others agree!

I thought you were swearing off my posts?

Code wise, U dont lower a breaker rating to compensate for voltage drop!

Really? Exactly where is that practice prohibited?

If the wire is CU, a 70a load would still be under 3% VD....

"IF" is the biggest two-letter word in the English language. Until and unless whomever originally wired that barn pipes up and explains their thinking, there is precious little point in arguing over imagined scenarios.

 

[Stuart in MN]

You didn't mention where you live, that information would help as codes may be different depending on what state (or country) you live in.

Also, are animals kept in this barn? If so there may be additional grounding requirements.

 

[Pathfinders]

If you have a grounding question search Mike Holt on the web. I have attended several of his code classes on grounding, he travels around the country discussing grounding.

 

[NUTTSGT]

For the OP, do you have all screw in fuses ? Are they all 30 amp fuses and do you have a 60 amp service ?

 

[Jameseric]

I know this is an old thread but my new problem may be related.
My flux core welder has a jerky wire feed problem but a friend with the same make and model does not have the same problem. Yesterday we tried his welder at my shop and it had the same problem. When he returned home his welder acted normal again. We think the problem is the electrical service in my barn. My barn is fed by 3 wire service. It has a disconnect where it enters the barn and a 100amp breaker panel in the shop area that services the outlets, lights, welder, and compressor. I do not perform electrical service but I need to identify the problem so that I can hire someone to fix it right.

Thanks,

James

 

[CNGsaves]

^ ^ ^ Too little information. Country ?? Wire size ?? Distance ?? Pictures ??

 

[Kellyblues]

^ ^ ^ Too little information. Country ?? Wire size ?? Distance ?? Pictures ??

CNGsaves is right.

The more you share with us the better we can help. Pictures of termination locations ( breaker boxes, outlets etc) . Wire size AND type. Is it copper or aluminum? Big or small? Nedd lots more information.

From the hip I'm gonna say its a problem with a neutral wire. Most commonly less understood component of low voltage wiring. I know low voltage is technically 50 volts or lower. I wire 480 three phase hot sometime for a living. 99% of home wiring issues I help with are the result of someone not understanding the neutral, its not a ground.

 

[RickP]

Have you checked the voltage on each of the hots in the feed to the barn? Also, did you add the disconnect and subpanel to the barn that you were originally planning? Does the barn have its own ground?

 

[Jameseric]

Thanks for the fast replies.

Here is the additional information with pictures. In live in Maryland southeast on Washington, DC in Prince Georges County. The 4 gauge cable to the barn came with the house. I had the new boxes and the ground at the barn installed.

This is the panel that feeds the barn. The cables are 4 gauge copper with a bare wire which is being fed from the house main breaker panel.


This is the disconnect in the barn. It is tied to 2 ground rods that are spaced 8 feet apart and attached to the disconnect with 6 gauge copper cable.


And finally, this is the breaker panel inside the barn that feeds all of the barn services.


I hope these pictures and details help to explain the cause of the problem.

Thanks,

James

 

[Jameseric]

Have you checked the voltage on each of the hots in the feed to the barn? Also, did you add the disconnect and subpanel to the barn that you were originally planning? Does the barn have its own ground?

Rick, I did not check the voltage on each of the hots because all of my outlets and lights are functional normally. However, I will put a meter on it when I get out to barn again and report back.

 

[wyliesdiesels]

At quick glance i dont see anything done wrong.

What is the distance between the buildings?

Looks like u have a 3-wire feed.

Voltage readings while the welder is off and while welding would be helpful!

Odd that the feeding breaker is only 40a....couldve been larger...

 

[Jameseric]

At quick glance i dont see anything done wrong.

What is the distance between the buildings?

Looks like u have a 3-wire feed.

Voltage readings while the welder is off and while welding would be helpful!

Odd that the feeding breaker is only 40a....couldve been larger...

The distance 160 feet. I did some testing and found that the voltage drops from 121 down to 108-112 when I start my 240V compressor. I am assume the welder will have about the same draw but steady.
The 4 gauge cable was installed over 30 years ago before I purchased the house and land. It always had 30 amp service for a trailer that was parked in the middle of the field.
My feed to the barn is 2 hots and a ground that is bonded at the house main panel.

 

[wyliesdiesels]

If it were mine I would replace the whole run from house to barn with a 4-wire feed.

Bare grounds are not a good idea underground.

 

[Jameseric]

it is shielded underground

 

[wyliesdiesels]

What size compressor?

And voltage drop is normal when a motor starts but what i was wondering is whats the voltage while the compressor is running?

 

[RickP]

Rick, I did not check the voltage on each of the hots because all of my outlets and lights are functional normally. However, I will put a meter on it when I get out to barn again and report back.

James,

We're practically neighbors - I live near Route 214 in Anne Arundel County.

Your voltage readings don't look too bad, but maybe you have a problem with an intermittent ground, as Wylies suggested. You might try feeding the welder with another cable from the house temporarily, just to see if the problem is in the underground cable. All of your other wiring looks great, so I'd really have to suspect the 30 year old underground cable.

Good luck troubleshooting it...

 

[Jameseric]

The voltage is 119-120 while the compressor is running. I put a meter on the line and it is not showing any resistance. My buddy is coming back over tomorrow with his test gear and we are going to check it from the meter to the barn. We will also take readings while welding which should show us if it is the welder or the power source.

 

[wyliesdiesels]

Your voltage is normal.

Doubt the welder pulls more than the compressor.

What model is it?

What is the HP rating of the compressor?

 

[Jameseric]

Your voltage is normal.

Doubt the welder pulls more than the compressor.

What model is it?

What is the HP rating of the compressor?

Thanks for the input. We are going to test the equipment and the wiring today. The compressor is portable 29 gallon 5hp Craftsman 240V.

James

 

[Jameseric]

I checked and tightened all of the 240v connections. Now I am getting 237v-238v steady with the welder running. I think it is okay now. Thanks for all of the help.

 

[wyliesdiesels]

Let me guess- under tightened AL conductors...?