Television circuits

[ATI]

Thanks all for reading this post, I have been reading for years. This is the first real issue I've had that I didn't know or could google the answer.

Scenario: Remodel of an existing restaurant/ installation of new LCD televisions

The issue is I just got reemed by the AV installer screaming that I ruined his newly installed televisions. I found the finish carpenters moved two of my piped metal boxes down to make there install fit better, they unscrewed the set screws and pulled boxes down with wires already installed. Problem is I lost the ground to my last 3 television receptacles, and he is saying I fried the insides of his residential TV's, they ran fine just had the tv lines from the grounding issue. Is this a likely scenario, wouldn't me pulling the ground and properly grounding the boxes remedy the line issue.

Second issue - He gave me more s*** about having 6 of his TV's on with a small merchandise room. Had to because he gave me the wrong specs on the TV's. I had never been asked to supply dedicated TV circuits but I did anyway. My question is why would there be an issue with installing a TV or TV's on the same circuit with some other lighting, or is he going way overboard.

There have been no lightning strikes or power outages or surges that I am aware of. Everything in the building is working and properly.

Thanks for any responses

 

[augie47]

My first inclination would be to call foul on both issues.
There might be some scenario where the loss of a ground would
have a negative effect on the tv's (wonder if the even have a grounding plug) as they might seek a ground thru the cabling.
I fail to see where sharing a circuit would cause a failure.
Someone with more AV experience may show where I am mistaken.

(It does add credibility to the "always pull a EGC" folks)

 

[sameguy]

Any blue print for this job?
Augie sounds right.
Tell the guy to take a flying leap, he should be talking to the GC or Carps. after getting the info. from you about the Carps. undoing your work.
You should tell the Carps. to keep out of your s''' ; by the way here is a back charge! If they get too pushy.

 

[sandking]

Another fine example why you should always pull a ground with the circuit. Not sure if this is the culprit or not in this situation, but it sure is cheap insurance.

 

[charlie b]

I am inclined to guess that when the carpenters moved the boxes, they caused a short circuit that fried the TVs. Were there any outlets in the boxes already? Were they energized when the carpenters moved them? Is there any sign of arcing in the boxes? In any event, you did not tell us anything about your install that could have led to the damage. Tell the AV person that you are not the cause of that problem, and that you will be glad to do any repairs to the wiring (i.e., to fix the carpenters' blunder) for an added charge.

As to the second question, I did not see any indication that there has been any damage to any of those TVs. Is that right? Is the AV person merely complaining about the way you wired the system? If so, and if your install was done in accordance with the specs given to you by the AV person, then tell that person you will be glad to revise the wiring, for an added charge.

 

[GUNNING]

Cheap Crappy TV's

Cheap Crappy TV's

If there was an electrical problem (overload) the circuit would have tripped. If there was a short and they are on a cable system it would have used the cable sheath as a ground and tripped the breaker blowing ALL the TV's. If there are only a couple of TV's, it is either a manufactured defect or perhaps operator error. Wrong connector in the back and or wrong screen. If the carpenters are altering the electrical its sabatage and there fault. If the guy doing the TV install jumped the gun and installed before final electrical check out, its his fault. Flat screen TV's are like computers they run on 12 volts and the ground is only involved when there is a dead short. Were the outlets wired backward maybe? If so then it might be the power supplies in the TV's and they can be fixed/replaced. Tell the AV install guy that supplied the crappy defective TV's to go fix the power supplies and or get the right screen displayed and quit crying. If there had been a problem with the electric it would have done them ALL in. I'm assuming some competency on your part here like checking the outlets with a plug tester or the job was inspected.

Our Utility has a saying "We supply the electric, we dont care how you use it.":lol:

 

[Speedskater]

My thoughts:

a] A short (H-N or H-G) at or before the outlets will trip the breaker, but it won't blow a TV.
b] If moving the boxes also resulted in wires getting reconnected to the wrong terminals we could have problems. with 120V on the N or G of some of the sets but not all the sets, when the signal cables interconnect the sets the chassis's may be at line level.
c] Was there any chance of a 240V hot to hot mis-wire?

 

[ATI]

The circuit was never touched other than losing the ground when set screws were released. It runs at 117V and has never been off since the circuit was energized. The only issue was the lines running up the TV when watching television. Interference with the signal due to the loss of a ground is what I figured. Issue is with no faults or miss-wires of the circuit could I have blown the interior of the TV just by losing the ground. My guess is he's taking his frustration out on the wrong guy because it took him 2 days to stick a plug checker in.

Secondly the circuit I had grouped with a few TV's and the merchandise was rewired. The TV's work perfectly, very nice picture. On the original walkthrough with him he wanted the TV's on dedicated circuits, which I told him I would accomodate ( I had never had such a request ). From the TV guy we could install 10 TV's per circuit ( no specs ), which ended up overloading a few circuits. I reworked the electric and grouped the final circuit with 6 TV's and the merch room wich was just 4 cans and 2 outlets. The circuit amped out fine and all was good.

He then found out the circuits were tied together and he blew a gasket. Probably due to problem 1. My question was as long as the circuit was not overloaded, could there be an issue with the TV being on a circuit together with other things that I'm not aware of.

 

[GUNNING]

Besides the contractual agreement....no.:happyno:

It will limit the size of the load he can put on that circuit. That is what dedicated means.
Might be a bit of OCD or he might of wanted to turn off only the TV's at a given time -like closing time. Get more information. You started with bad info, get a change order. Its amazing how money can change minds. Smooze and put the onus in his hands and give him a price. If he wants dedicated tell him he would need a new panel.

 

[kwired]

Don't most LCD televisions have a DC power supply usually within the supply cord and all that plugs into the television itself is the two DC supply conductors? If that is the case the presence or absence of the EGC will not matter one bit to the television.

 

[grich]

Most I've installed lately have a standard 3-conductor IEC power cord like you would have on a computer.

 

[hurk27]

Well first someone needs to edumacate this AV person, almost all consumer appliances are design to work on almost all electrical systems found here in the USA (Old and new) given the voltage and capacity of the circuit is not exceeded, even then many TVs like computers can range from 100 volts to 220 to allow for European usage and are even convertible from NTSC to the European PAL scan format, the ground in these cords (if it even has one) only references the chassis, it will not have any reference to the electronics in the set, the load is DC this means it is most likely a switch mode power supply that will isolate the internal DC circuits from the AC in from the wall, I don't know how many of these LCD TV's I have seen used in older houses with not one EGC through out the house, many of these TVs are on a circuit shared with half the house, I can not think of one theory that in these cases would cause a problem with one of these TV's.

I know allot of home owners who have been using these TV's like that for a few years and have never had a problem, my 60" Sony Bravia I have has been on my living room circuit that is shared with my office and dinning room since 2009, and its still works like brand new, and the wife also uses the vacuum on that circuit also when she vacuums the living room.

 

[renosteinke]

My home was built in 1957 .... meaning no ground. Two-prong receptacles. I wonder if the AV guy would still sell me one of those fancy sets?

Otherwise ... what's with his getting mad with you, if he already knows the carps took your stuff apart? Looks like it's their problem, not yours.

TV's ruined? Have him prove it. Then tell him to collect from the carps. Attitude? Tell him to pay your bill, then find someone else to fix it. You deserve respect.

Indirectly, this brings up the all-to-common problem of getting proper instructions. I've lost count of the times I've had the customer actually place a piece of tape where they want the receptacle to be .... only to later have them complain that it's on the wrong wall, etc. Somehow, to them, it's still my fault.

 

[GUNNING]

Yes sir, let me change that right away...

Yes sir, let me change that right away...

Customer is Always right. :thumbsup:


Until the check clears.:thumbsdown:

 

[yankj]

I would suspect that you have a multi-wire circuit and the carps lost the neutral at least momentarily (enough to fry TVs; they will go in a heartbeat when you lose neutral). A good reason to have surge suppressors on TVs, computers, etc.; believe me, I know.

 

[hurk27]

I would suspect that you have a multi-wire circuit and the carps lost the neutral at least momentarily (enough to fry TVs; they will go in a heartbeat when you lose neutral). A good reason to have surge suppressors on TVs, computers, etc.; believe me, I know.

I don't think a surge suppressor will give you much protection from a lost neutral, maybe slightly if the circuit had some balance, but if the other leg was loaded heavily I think the surge suppressor would be toast along with the TV

 

[kwired]

I don't think a surge suppressor will give you much protection from a lost neutral, maybe slightly if the circuit had some balance, but if the other leg was loaded heavily I think the surge suppressor would be toast along with the TV

I have seen two times a surge supressor (plug in type) that was well cooked and the protected equipment worked just fine after problems were sorted out and repaired, both times involved lost neutral on service or feeder. I imagine the specifics of the surge supressor can make a difference. Neither one was cheapest nor most expensive one you can find.

 

[grich]

... many TVs like computers can range from 100 volts to 220 to allow for European usage and are even convertible from NTSC to the European PAL scan format, the ground in these cords (if it even has one) only references the chassis, it will not have any reference to the electronics in the set, the load is DC this means it is most likely a switch mode power supply that will isolate the internal DC circuits from the AC in from the wall...

So even a lost neutral wouldn't necessarily fry a TV with a universal switching supply...it would just throw off a little more heat and keep working.

 

[renosteinke]

Way back, when I first went out on my own, I had a very irate, nearly violant man appear at my door. Oddly enough, he was looking for another resident, a guy who this forum would describe as an unlicensed, partly trained, moonlighting trunk-slammer. That was my introduction to the 'trade.' Oh, the cause of all the anger? A loose neutral blew up the TV set.

I've never heard of a TV set 'getting fried,' burned up, or killed. It seems they always "blow up."

Now, let's fast-forward thirty years or so. I make a poor connection in an office ceiling, and that night the neutral is lost. I got to replace a couple ballasts, several surge-protective power strips, and the one power supply (to a stereo) that was not protected by a power strip. Oh, and a GFCI receptacle let the smoke out, too. It seems that nest of neutral wires tied into several circuits, far more than the usual two or three. Oops.

Bad juju happens. In my case, the stage was set by someone not following the rules, and combining neutrals .... forget the UL listing data, by the time you get 7 wires under that big wire nut, you're setting the stage for one to work loose, even with pre-twisting.

In the earlier case, the customers' outrage was fueled by his own attempt to cheat the system. You want a responsible contractor, HIRE ONE.

So, yes, an open (or high impedance) neutral can cause all manner of voltage swings, swings that WILL kill electronics. Consider power strips cheap insurance.

And, yes, the bad manners of the customer in this story suggests that the customer isn't completely innocent.

 

[hurk27]

I have seen two times a surge supressor (plug in type) that was well cooked and the protected equipment worked just fine after problems were sorted out and repaired, both times involved lost neutral on service or feeder. I imagine the specifics of the surge supressor can make a difference. Neither one was cheapest nor most expensive one you can find.

Not saying it is impossible as I too have witnessed a few cases when TV's and other electronics were protected by TVSS in cases they were not designed for, in one case I posted on hear many years ago it was a power surge from the POCO where a 69kv line landed on a 7.2kv local feed and sent a 950 volt surge that lasted about 15 seconds before their cut out cleared the fault, we had a few fires from that one and it was the TVSS that caught on fire, the dwellings that had more then a couple TVSS devices on each phase tripped the main and branch circuit breakers protecting the electronics, so we know that when an MOV is over voltage beyond their rating and will turn into a dead short or can blow open, this in itself can give some protection in a lost neutral event, but they are not designed for this and we shouldn't be promoting them as such without also giving the understanding that in most cases this is beyond their capability and design purpose.

This is why I don't try to promote this on here, I would not want to see some of the newer apprentice electricians thinking this can be depended upon for protection in a neutral loss event, we must remember we have people on this forum at all different levels of learning in our trade, and we should be promoting the true intent of what a device is intended for.