Is soil under a building foundation assumed to be wet?

[Eligio Budde]

In an existing parking lot, I need to install a camera system. I need to ground the telecom cabinet but I want to know if I can just drive a 5/8'' by 10' copper rod and have good earthing impedance or if I have to add civil work and back fill compound. OR, if it's just OK to ground all the equipment to the grounding conductor of the mains line.

 

[wayne440]

Sorry, the crystal ball here is down for maintenance. Seriously, it is practically impossible to provide a useful answer to your question remotely with the information provided.

 

[davidbeach]

If the camera is line powered, the power supply includes a ground. If the camera is battery powered it doesn't need a ground.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[crshears]

If the camera is line powered, the power supply includes a ground.

Quite true; but the OP seems to want to know what to ground the power supply to . . .

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Eligio Budde]

To clarify a little:

The system to be implemented is a set of PoE cameras feeding video to an outdoor telecom cabinet which will have the PoE and data equipment necessary to power the cameras on and transmit video feed to a remote site.

As per TIA-607, I understand I should supply grounding for the telecom equipment separately from that of the mains line, however this isn't mandatory.

One of the options is to insert a ground rod to ground the cabinet and the chassis of the equipment to be installed, however, IEEE Std 142-2007 specifies 5 ohms ground impedance for sensitive equipment. Since I can't just drill the current foundation to just test the soil BEFORE placing a bid, I want to know if it's safe to assume the soil behind a foundation would be wet and with low impedance (the soil seems to be clay), or if the safest route is to assume I will need to make room to put grounding back fill.

The other option is to ground the cabinet and the chassis of the equipment using the grounding wire of the mains line. However, I don't know if there's any other restrictions (my knowledge of the IEEE recommended grounding practices is, to be honest, far from perfect).

 

[Palletjack]

5 ohms.. I’m betting it’s going to take way more than 1 8’ rod.
How close to the service ground rod will yours be? Don’t want to set yourself up for ground currents.

 

[wayne440]

If you are aiming for TIA-607b compliance, you will almost certainly need "way more than 1 8' rod" as mentioned previously.

Here is a brief excerpt from TIA-607b

"...The building/shelter and outdoor cabinet should be encircled by a ground ring consisting of a bare
solid tinned or un-tinned copper No. 2 AWG conductor or bare tinned or un-tinned copper conductor
not smaller than No. 1/0 AWG buried to a depth at least 0.76 m (2.5 ft) or 152 mm (6 in) below the
frost line, whichever is deeper. It should be installed at least 0.9 m (3 ft) away from the building.
Ground rods, 2.4 m (8 ft) minimum length and 16 mm (0.625 in) diameter should be driven to a depth
of not less than 3 m (10 ft) below the depth of the ground ring and attached using exothermic
connections. These ground rods should be made of copper, copper clad steel, stainless steel or
galvanized steel and be Listed for the purpose. There should be a minimum of four grounding rods
located at each corner of the building/shelter or outdoor cabinet. The building/shelter and outdoor
cabinet ground ring should be bonded to the tower ground ring in at least two points using the same
size conductor and buried to the same depth as the tower and equipment building/cabinet ground
ring. Also, the building’s foundation (concrete footings) should have the rebar electrically connected to
the building ground ring..."

 

[Eligio Budde]

Isn't that excerpt from the antenna tower annex? In any case, if those are the requirements seems like aiming TIA-607 compliance will be economically unviable.

How close to the service ground rod will yours be? Don’t want to set yourself up for ground currents.

The building grounding ring begins 150 meters from where the cabinet will be placed. That's my other concern, since IEEE Std 1100-2005 warns about separate grounding structures for the reason you mentioned.

 

[wayne440]

The quoted portion is from Annex B- but an outdoor cabinet is an outdoor cabinet whether or not a tower is present.
If you were installing an outdoor telecom cabinet for yours truly and quoted compliance to TIA-607, I would expect (rightfully or not)
the ground ring, rods etc. as that section reads.

Standards compliant (TIA-607, R56 etc.) grounding/bonding plans are almost always "economically unviable" when you are bidding against someone
else who may (or may not) just drive one 8 foot rod and call it done.

 

[jghrist]

I could see having the ground ring and rods where there is an antenna that could be struck by lightning. The ground is for surge protection, not electrical safety. The ground must be connected to the equipment ground wire to satisfy NEC and provide electrical safety. As Wayne says, if the contract specs call for compliance with TIA-607, then you probably have to provide more grounding, but make sure that if this is being bid, your competitors also quote the same thing.