Zatarra64
All around wannabe knowitall
- Location
- Phoenix, Az
- Occupation
- Electrical QA/QC
I have a question that I'm having a hard time finding a good answer to.
I'm not sure if this is the correct place to ask this.. I am not concerned with the ground to earth, just my connection from an equipment rack to the TGB.
Under ANSI/TIA-607B I see that all equipment racks are to have their own ground bar. All equipment items in the rack are to be connected to the ground bar. The ground bar is to be connected to the TGB. Testing from the ground bar to the TGB should be 00.1 ohm or less.
My question:
What is the proper way to physically measure this?
Please correct me if I'm wrong, but this is how I tested it.
Fluke VOM set to ohms. Measured across a spare piece of 6awg cable, got 00.1-00.2 ohms. Ran that cable from TGB to equipment rack. Measured ohms through the cable, across the TGB, back to the end of the new 6awg ground cable I'm about to install. I measure 00.4 ohm. Subtract 00.2 from the test cable for an estimated 00.2 ohm connection for the new cable. I then connect the new cable to the ground bar in my rack and measure again. My expectation is to measure 00.2 ohm from a bare metal point on my rack to the TGB, however I see 1.8ohm.
I measured each piece of equipment in the rack to the ground bar and I get 00.1 or less.
This rack was installed long ago, and the power strip in it only has black and white connected to facility power. The green is connected to the equipment rack at multiple points, as well as all the power grounds in the power strip. The metal conduit the power wires are routed through is bonded to the facility ground, and to my rack. Without my new ground cable connected to the ground bar, I measure 15.7 ohms from my rack to the TGB. Which I assume is through the metal conduit.
Did I measure those correctly?
How should that power strip be connected in a telecommunications rack?
Reading in 607b, it says NOT to have power ground connected to rack grounds. .. or am I miss interpreting it?
It is my understanding that having two separate ground points on one rack is a source of ground loops and can cause an audio signal to become distorted. Am I correct in assuming that the power ground and the ground bar are causing a ground loop?
Any guidance will be greatly appreciated.
Thank you.
Rob
I'm not sure if this is the correct place to ask this.. I am not concerned with the ground to earth, just my connection from an equipment rack to the TGB.
Under ANSI/TIA-607B I see that all equipment racks are to have their own ground bar. All equipment items in the rack are to be connected to the ground bar. The ground bar is to be connected to the TGB. Testing from the ground bar to the TGB should be 00.1 ohm or less.
My question:
What is the proper way to physically measure this?
Please correct me if I'm wrong, but this is how I tested it.
Fluke VOM set to ohms. Measured across a spare piece of 6awg cable, got 00.1-00.2 ohms. Ran that cable from TGB to equipment rack. Measured ohms through the cable, across the TGB, back to the end of the new 6awg ground cable I'm about to install. I measure 00.4 ohm. Subtract 00.2 from the test cable for an estimated 00.2 ohm connection for the new cable. I then connect the new cable to the ground bar in my rack and measure again. My expectation is to measure 00.2 ohm from a bare metal point on my rack to the TGB, however I see 1.8ohm.
I measured each piece of equipment in the rack to the ground bar and I get 00.1 or less.
This rack was installed long ago, and the power strip in it only has black and white connected to facility power. The green is connected to the equipment rack at multiple points, as well as all the power grounds in the power strip. The metal conduit the power wires are routed through is bonded to the facility ground, and to my rack. Without my new ground cable connected to the ground bar, I measure 15.7 ohms from my rack to the TGB. Which I assume is through the metal conduit.
Did I measure those correctly?
How should that power strip be connected in a telecommunications rack?
Reading in 607b, it says NOT to have power ground connected to rack grounds. .. or am I miss interpreting it?
It is my understanding that having two separate ground points on one rack is a source of ground loops and can cause an audio signal to become distorted. Am I correct in assuming that the power ground and the ground bar are causing a ground loop?
Any guidance will be greatly appreciated.
Thank you.
Rob