Most if not all Plasma TVs come with 3 wire cords and instuctions that require the unit be plugged into a grounded circuit. My question, is the grounding of these units required for user safety only, or will operating them on a two wire non grounding circuit have a detrimental effect on the unit?
Grounding of Plasma TVs and other expensive stuff
- Thread starter monkey
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stickboy1375
Senior Member
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- Litchfield, CT
Would you really use a cheater plug on a plasma? I would go by the manufactures instructions...
- Location
- Massachusetts
stickboy1375 said:
From a safety standpoint any item that comes with a grounding cord is required to be grounded.
Take a look at 250.114.
If we forget that point for a moment I don't believe the lack of ground will have any effect on the operation of the TV itself.
If the TV is connected to an dish or cable it will be grounded anyway.
stickboy1375 said:
No, I never said I would. I asked if the grounding requirement was for safety only, or had something to do with the electronics.
Most of us would provide grounding for our stuff, but it helps to have the knowledge to be able to explain why to a customer.
cadpoint
Senior Member
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- Durham, NC
[/QUOATE]
If the TV is connected to an dish or cable it will be grounded anyway.[/QUOTE]
Are you saying that the shielding, outer wire casing is the Ground of Catv cable, I never thought of it that way ...:roll:
If the TV is connected to an dish or cable it will be grounded anyway.[/QUOTE]
Are you saying that the shielding, outer wire casing is the Ground of Catv cable, I never thought of it that way ...:roll:
- Location
- Massachusetts
cadpoint said:
Yes, the NEC requires the shield on coax to be grounded. Even the outer connection of an 'RCA' plug is connected to ground if it is connected to a device that has a grounding connection.
I am not saying this grounding can provide a reliable or code compliant fault path for the supply conductors to the unit.
What I was saying is that this grounding is generally unavoidable.
stickboy1375
Senior Member
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- Litchfield, CT
This is exactly why 810.21 (J) exists....
QES
Senior Member
- Location
- California
are you talking about the ground plug or the bonding tap in the back if of the equipment?
jim k
Member
- Location
- Northwestern Oregon
You can tell the customer that it's a good idea to protect these things with a surge protector. Surge protectors won't provide any surge protection unless they're plugged into a grounded receptacle.monkey said:
Another thought: I'm not sure if plasma TVs produce static electricity, but if they do, the grounding receptacle will dissipate static electricity.
- Jim Katen, Oregon
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- Massachusetts
jim k said:
Jim that depends on the kind of surge.
If it is a line to line surge the ground will have nothing to do with it.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Yes and no. A TVSS does not require a ground to operate, but on the point of use TVSS the ground becomers more important, and actually it creates a "faux" single point ground between the connected devices "ground" to keep the potential the same on a surge.jim k said:
But most importantly, no ground is required for a TVSS at the service.
jim k
Member
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- Northwestern Oregon
iwire said:
Good point.
Though if a customer were to ask about detrimental effects on the unit, I'm not sure that I'd go into too much detail about the various kinds of surges. I'd just caution that, without a grounded receptacle, the surge supressor will be less effective and the TV will be at greater risk.
-Jim Katen
- Location
- Massachusetts
jim k said:
I agree.
jim k
Member
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- Northwestern Oregon
tom baker said:
Hmm. I'm having a hard time understanding what you mean here. I don't suppose you've got a schematic handy?
My impression was that these things use a MOV to "clamp" the voltage and shunt the excess to ground (well, to the transformer, not the earth).
- Jim Katen
ELA
Senior Member
- Occupation
- Electrical Test Engineer
The ground prong is critical both for safety and EMI (electrical noise) protections of equipment.
Devices often have capacitive filters to earth inside. If the ground is left floating this eliminates the filters ability to shunt noise currents to ground.
In addition if you then rely on the satellite or cable ground, without having a third prong ground, you are likely introduce a ground loop which can cause audio and video problems. (120Hz noise current traveling down the shield to fseek ground at the satellite bonding point).
Devices often have capacitive filters to earth inside. If the ground is left floating this eliminates the filters ability to shunt noise currents to ground.
In addition if you then rely on the satellite or cable ground, without having a third prong ground, you are likely introduce a ground loop which can cause audio and video problems. (120Hz noise current traveling down the shield to fseek ground at the satellite bonding point).
Well since I think I know where Tom came up with the term "FAUX SPG" I can answer.jim k said:
On a Point-Of-Use TVSS you have MOV's installed between N-G, and L-G. The important one is the one installed N-G, and it acts like the bonding jumper at the disconnect clamping the voltage to a tolerable level. The MOV's selected in good units are very low clamping voltage like 10-volt or less (5 volts is ideal). So in the event it operates the voltage between N-G remains very low like the solid bonding jumper at the service.
- Location
- Massachusetts
ELA said:
Actually without the third prong you can not have a ground loop.
Often you will find peoples low tech / unsafe solution to a 'ground loop' is to eliminate the ground with the power supply conductors.
- Location
- Massachusetts
pfalcon said:
I agree with you but in the real world few shields are isolated.
ELA
Senior Member
- Occupation
- Electrical Test Engineer
iwire said:
Sorry but you are incorrect there sir!
Current flows from the TV hot lead through an EMI filter capacitor out down to the internal chassis ground then out through the cable in shield, to the cable bonding point,then to the service bond, to the neutral then back to the TV set. A complete current path that allows 120Hz ripple to flow through the shield. This then corrupts the video signal.
Ground loops mean many things to many people. This is one instance of current flowing through a shield and commonly referred to as a ground loop.
Ask any custom A/V installer.
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