Iso Ground

They do by being dedicated/isolated. They are critical in hospital and computer equipment. A dedicated ground insures that the internal DC inverter/transformer power supply has a reference point while operating. Regulated power supplies like this require a solid grounding reference. Sometimes you see power cords to laptops with no ground. The rely on the neutral and "float" a ground.
 
In a hospital it's all about redundancy, the wiring method has to be able to carry a ground fault as well as the wire EGC. Computer equipment has been better built for the last thirty years. I lived through the dedicated ground, K rated transformer, super neutral craze. Now that energy is better spent worrying about an asteroid collision with Earth than it is worrying about isolated ground purity. Ninety percent of them don't get run correctly and no one notices.
 
herding_cats said:
They do by being dedicated/isolated. They are critical in hospital and computer equipment. A dedicated ground insures that the internal DC inverter/transformer power supply has a reference point while operating. Regulated power supplies like this require a solid grounding reference. Sometimes you see power cords to laptops with no ground. The rely on the neutral and "float" a ground.
Click to expand...
They're pretty much obsolete. People wasted good money on IG systems that did nothing.
 
herding_cats said:
You would need two grounds. One isolated and one not. The 24x24 need the non IG, but the the load side need isolated or dedicated back to the panel. The idea of IG is that it is not reliant to case grounding on boxes, and other areas that might fail ground connections.
Click to expand...
What do ground rods have to do with isolated grounds?
 
herding_cats said:
New hospital builds use them today. Server data centers too.
Click to expand...
Not in patient care vicinities, in these areas they are purposely connected together for redundancy as Dave mentioned, see 517.13. In other areas they are under the requirements of 517.16

Data centers are stuck in the old days.
 
infinity said:
Okay you mentioned in post #20 that you need two ground rods one of them being an IG ground rod whatever that means.
Click to expand...
No not two ground rods. 2 paths of grounding. IG is dedicated ground that is isolated to insure a quality ground back to the main service where there is one ground rod. Though, double ground rods are common in areas with PEX plastic plumbing main.
 
herding_cats said:
No not two ground rods. 2 paths of grounding. IG is dedicated ground that is isolated to insure a quality ground back to the main service where there is one ground rod. Though, double ground rods are common in areas with PEX plastic plumbing main.
Click to expand...
Unless you can prove 25 ohms on one rod, two rods are required on all new services, has nothing to do with isolated grounds. The earth is not allowed for EGC purposes, see 250.4(A)(5)
 
ActionDave said:
I always thought isolated grounds were for getting rid of electrical "noise" that causes sensitive audio and payment systems or other electronics to go haywire. In the early days they solved some problems. They serve no purpose here in the 21st century.
Click to expand...
It was done in the early days of locknut worshipers, where a loose locknut or coupling would cause noise. Now a ground is pulled in almost every thing not relying on the integrity of the metal conduit system, so it is no longer needed.
 
roger said:
Unless you can prove 25 ohms on one rod, two rods are required on all new services, has nothing to do with isolated grounds. The earth is not allowed for EGC purposes, see 250.4(A)(5)
Click to expand...
Yes that's what I was getting at. I've heard guys say to use a separate rod for the sole connection of all the isolated grounds and not connected to the GES which is not code compliant.
 
tom baker said:
But an IG receptacle can have its IG bonded at the box where it’s installed
Click to expand...
Then it probably isnt isolated anymore, especially if metallic raceway wiring methods are used. Heck, residential wiring with NM cable and plastic boxes is essentially an IG circuit, especially if it is a dedicated circuit.
 
hillbilly1 said:
It was done in the early days of locknut worshipers, where a loose locknut or coupling would cause noise. Now a ground is pulled in almost every thing not relying on the integrity of the metal conduit system, so it is no longer needed.
Click to expand...
There's metal conduit strapped to metal joists with metal fasteners, all of it interconnected and a loose lock nut causes noise that brings the system down?
 
You must log in or register to reply here.
Top