Grounding question

[Tic]

Scenario:

A router, modem and NVR are plugged into a UPS that is plugged into an outlet.

A PC, monitor and printer are plugged into a UPS that is plugged into another outlet (in same room) about 15 ft. away from router/modem/NVR. The monitor has two inputs (VGA & DVI) and latter is connected to PC.

Question 1: If I run a VGA extension cable from NVR to monitor, will there be a ground loop or grounding problem considering both devices are on separate outlets (separate ground source)?

Question 2: Can both video outputs (VGA & HDMI) on the back of the NVR be used at the same time? [The VGA to PC monitor and HDMI to big screen TV in the family room.]

Thanks.

 

[nayr]

1. they are not separate grounds, they share the same grounding point in your panel.. infact they are likely even the same circuit given the distance, so they will be directly connected to eachother even before your panel.
2. Depends on the NVR, some do as long as both displays support the same resolution; mine will and in the spec it says it: >HDMI/VGA simultaneous video output

 

[Tic]

they are not separate grounds, they share the same grounding point in your panel.. infact they are likely even the same circuit given the distance, so they will be directly connected to eachother even before your panel.

Ok...same room, same circuit in the panel -- that makes sense. But if the other end of the extension cable is connected to a monitor/big screen TV in another room (different circuit), this will cause a ground loop problem, right? Two ends of the cable on different circuits or ground potential??? What measures would you take to remedy this? I'm pretty sure I'm not the only one who have thought about doing this.

Depends on the NVR, some do as long as both displays support the same resolution; mine will and in the spec it says it: >HDMI/VGA simultaneous video output

Thanks for reminding me to read the specs again.

UPDATE: Turns out both video outputs support simultaneous video.

 

[nayr]

no, not unless you ran an extension cord to a neighbors house with its own service.. every outlet in your house is the same ground potential even if its on another phase.. dunno where you got this idea from but you should just forget you think you know anything about it... its nothing you should be concerned about until you start bridging electrical circuits between physically separated buildings with individual main grounding points.

 

[Fastb]

Tic,

I assume newer construction, with 3 prong outlets.

The Protective Ground is common throughout the house. All grounds share a common connection in your breaker panel.
Neutral (white wire) is the larger of the two rectangular openings in your 3 prong outlet. All neutrals are electrically tied together back at the panel.
Hot (120AC) (black wire) (smaller rectangular opening) runs back to the breaker controlling that circuit (ie: all outlets on that breaker)
You have two phases of Hot. The voltage from one phase to the other is 240V. 240V circuits have a double breaker, typically for power hungry devices like dryers, water heaters, and electric stoves.

Safety-wise, you don't have a problem.

Let's take the complicated scenario where the two UPS units and devices are plugged into outlets that are on separate circuits, each with their own breaker. Yes, you could technically have a "loop", if Neutral or Protective Ground from the two circuits are tied together. Safety-wise, not a problem. The "loop" might be a concern to an RF engineer, because you created a "loop antenna". We're now off into the esoteric weeds. WRT your system description, I don't see a problem. Your equipment isn't hyper sensitive to Radio Frequency energy on the conductors, assuming the loop even picked up RF energy. Also, you're not running highly sensitive equipment, with high gain, low noise RF receivers or amplifiers. Such equipment often calls for a dedicated ground stake to get a super-clean earth ground. But again, this isn't your situation.

Sorry about the complicated answer. My intent was to put your mind at ease.

Fastb