Tying Grounds Together?

[NC4AB]

Hopefully some one has run into this before and can provide some guidance:

Long story short, new shop is completed, the electrician upgraded the meter base to 320 amp with dual lugs, one set of lugs feeds the existing house panel, second set feeds the new shop which is ~ 100 feet from the meter base. As such each panel has its own ground rod(s) and the neutrals are bonded to the grounds in each panel per code. Inspections have all been completed and passed.

My question is when I run the TV cable from the house to shop am I not effectively tying the grounds between the structures together through the shield of the coax? Just curious if the ground rods should all be tied together with a copper wire for lightning protection.

TIA

Andy

 

[theoldwizard1]

... second set feeds the new shop which is ~ 100 feet from the meter base.

No disconnect at the meter ?? That does not sound right, but IANALE.

My question is when I run the TV cable from the house to shop am I not effectively tying the grounds between the structures together through the shield of the coax?

Yes, you are. Does it matter ????

 

[Stuff]

The shop and house ground rods are bonded together through the neutral connections to the meter base.

Yes, you are creating a parallel ground path but there is not much you can do about it.

 

[Fixin'Stuff]

To help protect the equipment in the shop, run the cable through one of these: https://www.amazon.com/dp/B00UZFLHNE/?tag=atomicindus08-20 on the outside of the building. Run a ground wire from it to the ground rod at the electrical service entrance. There should already be one of these at the end where the cable enters your house.

 

[larry_g]

Something in the foggy old memories of co-ax cable tells me that you only ground one end of the shield. If this true then you do not create a ground path from one building to the other.

Searched this out; http://www.belden.com/blog/broadcastav/Ground-Loops.cfm There are others but nothing definite if one or both ends should be terminated.

lg
no neat sig line

 

[wyliesdiesels]

OP should use a surge arrestor on the shop end of the coax...

 

[ishiboo]

OP should use a surge arrestor on the shop end of the coax...

I use surge arrestors on both sides of my cables... why protect just the shop?

Between the house and the barn there are 2 Cat6 cables (in 2" conduit) and then there's 2 more plus a 14-2 UF between the house and my Internet antenna pole. I don't have the 14-2 UF hooked up as I have nothing to protect it with.

 

[DC73]

Just curious if the ground rods should all be tied together with a copper wire for lightning protection.

Andy

If lightning strikes nearby, there could be a potential difference between the two ground rods. That means current would flow on the common connector which in your case would be the shield of the coax.

I did some power quality analysis in a previous life many years ago. This situation came up a few times, primarily with dual tenant situations. In each case, there was 2 separate electrical systems supplying the two tenants (mostly commercial buildings but one residence). Again in each case, one common tenant rented both spaces and proceeded to run ethernet and coaxial cables between the two spaces. When lightning would strike nearby, they were constantly losing computers and other sensitive electrical equipment to the surge. Surge protectors helped but often needed replacement after a storm. The definitive answer in each case was to bond the two ground rods together. After that, no more failures.

Your situation is a bit different in that both of your electrical systems go back to a reasonably close common point (the 320 A meter base). That helps but if you could easily tie the two ground rods together, I would do it.

My situation is very similar to yours and I will bond the two ground rods together if I ever run any type of communications cable between the two structures.

Good luck.

DC

 

[theoldwizard1]

Searched this out; http://www.belden.com/blog/broadcastav/Ground-Loops.cfm There are others but nothing definite if one or both ends should be terminated.

I know in automotive application, where the are using shielded twisted pair wire for very low voltages (variable reluctance speed sensors), only ONE END should be grounded.

 

[sberry]

Where is the ground wire in this scheme? These should be 4 wire feeds with unbonded neutrals, this is what the intention was for, to eliminate pathways from being used as current carrying conductors for neutrals.
I can see we are already fixed on lightening but that is only one concern and maybe even more minor in nature that the rest. So,,, yes, the rods are sposed to be tied together thru the 4th wire.

 

[theoldwizard1]

Long story short, new shop is completed, the electrician upgraded the meter base to 320 amp with dual lugs, one set of lugs feeds the existing house panel, second set feeds the new shop which is ~ 100 feet from the meter base.

Where is the ground wire in this scheme? These should be 4 wire feeds with unbonded neutrals, ...

He is coming right off the meter base.

I have never heard of a POCO allowing a 100' "entrance cable" with no disconnect !!??

 

[sberry]

He is coming right off the meter base.

I have never heard of a POCO allowing a 100' "entrance cable" with no disconnect !!??

Ok,,, I miss that but entrance goes 100;s of ft with only a ******/ pole disconnect. Its coming to the meter this way.

 

[sberry]

Ground the end at the service, leave the other float. With bonded neutrals at both panels we do not want anything metallic between buildings, operating currents would flow on it.

 

[NC4AB]

Thanks for the responses, I was out of town when the meter base and the underground wiring was installed, the wiring to the shop are a 2 hots and a neutral (3 wire service,) it is apparently allowed in the NEC code to supply a residence and (1) detached structure from the meter base with out a disconnects.

I should have read the contract closer and specified a meter / main combo then everything would have shared a common ground and the feeder to the shop would have been a 4 wire. The existing house panel is completely full and I was initially going to add another meter but the local Co-op technician talked me out of that (due to the ~$30.00 /month minimum meter fee).

Andy

 

[rlitman]

Something in the foggy old memories of co-ax cable tells me that you only ground one end of the shield. If this true ...

It is not. The shield is bonded to the chassis of the equipment, which connects to electrical ground at each end. This is in addition to the grounding block mentioned.

 

[DC73]

He is coming right off the meter base.

I have never heard of a POCO allowing a 100' "entrance cable" with no disconnect !!??

It's done all the time around here. Meter bases are typically in the alleys. Disconnects are on the outside the structures. I have about 100' to each of my disconnects from the same metering arrangement the OP has. Not sure about the electrical code but local fire codes require the disconnects on the structure so firemen can remove power in a fire.

DC