Technical Help Badly Needed! - AVS Forum
Forum Jump: 
 
Thread Tools
Old 04-22-2013, 03:47 PM - Thread Starter
Member
 
tylt's Avatar
 
Join Date: Jun 2007
Posts: 17
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hopefully this is the right forum to post in. At any rate, we are in the middle of a kitchen remodel. I came home Thursday after the electrician had been there all day to find:

1. My Kinivo HDMI switch no longer works.
2. All of the HDMI ports on my tv no longer work.
3. One of our bedrooms that has a remote for the ceiling fan and light, had the light and fan stuck "on". Even flipping the breaker and then turning it back on resulted in the light and fan coming right back on. They replaced the in wall receiver and it works again.

I know very little about electrical goings-on. My general contractor and electrician think the electricity company is to blame. I have never in my life had a damaging power surge. Is it just coincidence that the first one happened while the electrician was there? He said that just turning the power on and off as they were setting up the sockets and can lights wouldn't damage electronics.

Any insight would greatly be appreciated. Thanks!
tylt is offline  
Sponsored Links
Advertisement
 
Old 04-23-2013, 02:33 PM
AVS Special Member
 
Ethan Winer's Avatar
 
Join Date: Apr 2003
Location: New Milford, CT, USA
Posts: 5,748
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 134
No idea, but maybe the contractor cut some wires in the walls? Of course they'll blame that on the power company! biggrin.gif

--Ethan

RealTraps - The acoustic treatment experts
Ethan's Audio Expert book

Ethan Winer is offline  
Old 04-23-2013, 03:02 PM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
He ran out of spots in the neutral/ground buss in the load panel, loosened some to double up the #14's.

Neutral currents had no place to go other than through the low level inputs.

You shoulda used a multiport outlet surge protector.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-24-2013, 11:49 AM
FOH
AVS Special Member
 
FOH's Avatar
 
Join Date: Apr 2010
Location: Midwest
Posts: 4,749
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Liked: 213
jneutron touched upon it being neutral related,

This is fascinating, and often mis-understood effect.
I would essentially guarantee .... that a neutral was opened up under load, thus excessive voltage greater than 120v was placed across some items for a period of time. It wouldn't necessarily have occurred at the panel, it could easily (and most likely) have occurred at a junction box, or a receptacle or switch box whereby joints were being made. It doesn't matter where it happened, they did it.

Surge from the power company .... yeap, right ... rolleyes.gif

The contractor is liable, it would only take a brief moment for this to occur, and often occurs when an electrician is making up a neutral joint (adding another wire, etc.), and the return path to the panel is opened up, thereby the low impedance path is gone, yet another route is availed to the via the other phase.

Now, for a brief period, there's series connected loads instead of the typical parallel connection. The least robust device gets cooked, the reason being the entire 240v is now dropped between the two loads. The smaller the load, the larger the voltage dropped across it. The larger the load, the smaller the voltage dropped across it. Hence, the damage occurs to the small, modest devices.

Then, the neutral joint is made up the manner the electrician intended, and the circuit is back to normal, however the damage is already done.


I'd be glad to detail this further if need be.


I hope this helps.

------------------------------------
Flat, Deep, Clean, Linear, and Loud
------------------------------------
Active 16.8kw, 7.3 system
(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
(2)Seaton SubM-HP, (4)18" IB
FOH is offline  
Old 04-24-2013, 02:03 PM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by FOH View Post

I'd be glad to detail this further if need be.
Cool..I've always wanted to know what that white wire was there for..rolleyes.gif and that black one, why is it called hot when it's cool to the touch??eek.gif

I wasn't thinking entire house float, just a few breakers worth.

I figured that maybe the OP had both legs of his panel powering his equipment, and if the electrician opened neutrals to the romex feeding the system, that the Y line filters would show the imbalance to the HDMI's. That's why I recommended a multiport device, it would bond all the equipment input grounds as common to the equipment third pin.

Had a kitchen reno about 7 years ago, the electricians did run out of buss positions for neutrals and grounds, so had to double up some. So it was my best guess.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 07:02 AM
AVS Special Member
 
commsysman's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,310
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 149 Post(s)
Liked: 259
The white wire is the return current wire, or "NEUTRAL" wire, which is connected to the ground bus in the electrical panel.

The black wire is the ungrounded side of the circuit, which means its voltage can kill if you touch it while some part of your body is somehow contacting something grounded at the same time you touch it; this is why it is called "HOT".

The third wire, which can be bare or green also is connected to the same ground bus in the panel, but it carries no current unless there is a short-circuit in the device being powered by the circuit.

A "GROUND-FAULT INTERRUPTER" socket is now required by most electrical codes in bathrooms, kitchens, and other areas where the body is more likely to be inadvertently grounded and coming in contact with some "HOT' part of the device might be possible. Plumbing and running water are usually grounded, as is most concrete, so touching them and somehow contacting a hot circuit can be deadly.

The GFI can detect a very small current in the third wire, which could be through your body, and shut off the circuit in milliseconds, before you are dead. Also, if some inappropriate current leakage in some powered device takes place between the hot wire and 3rd wire, the GFI will shut off the circuit and its visible button will pop out to show that the fault has occurred. The GFI can also detect a small difference between the currents in the black and white wires, which will always be equal unless there is a circuit fault.

In a normal 110 volt circuit, the current to the device being powered goes through the black and white wires equally to pass through the device. That is a normal circuit. The third wire never has any current unless there is a fault in the device or a person's body inadvertently gets across the circuit.

In the US, a 220 volt circuit has two 'HOT" wires and a 3rd wire. Both "HOT" wires carry the current, and each one of them is 110 volts with respect to ground, but because their AC voltages are 180 degrees out of phase with each other the voltage from one "HOT" wire to the other is 220 volts RMS. There is no "neutral" wire in a 220V circuit, just 2 hot wires and a ground wire.

Installing a GFI at the point where your audio equipment plugs in can protect you against internal shorts in the gear that could cause metal parts of the equipment to become "hot" and be hazardous. A GFI is a good idea. It will kick off if a piece of equipment has an internal short or current leakage (which is usually not obvious).

Circuit breakers offer no protection against electrocution. They only prevent wiring from overheating and causing fires. They shut off the circuit only when the current flow in the wires exceeds a safe limit
commsysman is offline  
Old 04-25-2013, 09:33 AM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Hey there commsysman. Long time no talk. How you been? Hope all is well.

While I like you info and certainly agree, I was um, joking about that white and black wire thingy.. Hope you didn't post because of my joke, I did put some emoticons there. Course, it is always worth repeating every so often for those who don't work with electricity.

Ah, I'm not sure it all applies for those outside the US however..I only know this side of the pond.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 10:23 AM
 
SAM64's Avatar
 
Join Date: Apr 2011
Posts: 1,592
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 74
Quote:
The GFI can detect a very small current in the third wire,

No it can't. Your understanding of GFCI is flawed....and you spent two paragraphs on it wink.gif

A GFCI monitors the current flowing through hot an neutral, if there is an imbalance the assumption that a ground fault has occurred trips the circuit open.
Quote:
While I like you info and certainly agree,

...not as smart as you'd like us to believe...
SAM64 is offline  
Old 04-25-2013, 10:57 AM
FOH
AVS Special Member
 
FOH's Avatar
 
Join Date: Apr 2010
Location: Midwest
Posts: 4,749
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Liked: 213
^ ^ ^
Correct



Visualize ... a circuit with a hot going out, and the neutral coming back.


Stripped to it's essence, ...if anything goes out, and doesn't come back, the circuit opens up. That's GFI protection.


Back OT

The OP's scenario is fascinating. Many electricians acknowledge open neutral issues, but often fail to understand how the damage occurs. Just takes a brief moment, then they come down off the ladder to measure the receptacle(s), everything appears fine ... the damage already occurred to the connected items.

------------------------------------
Flat, Deep, Clean, Linear, and Loud
------------------------------------
Active 16.8kw, 7.3 system
(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
(2)Seaton SubM-HP, (4)18" IB
FOH is offline  
Old 04-25-2013, 11:26 AM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by SAM64 View Post

No it can't. Your understanding of GFCI is flawed....and you spent two paragraphs on it wink.gif

A GFCI monitors the current flowing through hot an neutral, if there is an imbalance the assumption that a ground fault has occurred trips the circuit open.
...not as smart as you'd like us to believe...

You got me. Egg on my face big time.

sigh, I scanned through it too fast...redface.gif

I'll remember you...newmann!!! wink.gif

(good catch)

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 11:37 AM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by jneutron View Post

Quote:
Originally Posted by SAM64 View Post

No it can't. Your understanding of GFCI is flawed....and you spent two paragraphs on it wink.gif

A GFCI monitors the current flowing through hot an neutral, if there is an imbalance the assumption that a ground fault has occurred trips the circuit open.
...not as smart as you'd like us to believe...

You got me. Egg on my face big time.

sigh, I scanned through it too fast...redface.gif

I'll remember you...newmann!!! wink.gif

(good catch)

Some day JN you may learn to not try to school well-educated, well-experienced people who work with a given technology hands on, day after day...
arnyk is offline  
Old 04-25-2013, 11:48 AM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by FOH View Post


The OP's scenario is fascinating. Many electricians acknowledge open neutral issues, but often fail to understand how the damage occurs. Just takes a brief moment, then they come down off the ladder to measure the receptacle(s), everything appears fine ... the damage already occurred to the connected items.

In some over simplified theory of equipment operation there is an infinite impedance between the power line connections and any of the active or passive circuits in the AV equipment. When you disconnect neutral, but retain the connection to hot, current stops flowing through the primary side of the power supply, the equipment stops working and that is that. You reconnect neutral, current resumes flowing and the equipment powers up without damage. That is life in the ideal world. Let me know when you find that ideal world!

In the real world there are leakage impedances between the power line connections and every circuit in all of the AV equipment. What the leakage impedances actually are varies all over the map. On a bad day disconnecting neutral allows the reference for some active circuits to float as high as the hot power line voltage - about 120 volts AC plus any spikes, etc. If the signal connections to those circuits are connected to safety ground or neutral or something like them, and they do not have adequate over voltage/over current protection, then some component parts may be permanently damaged.
arnyk is offline  
Old 04-25-2013, 11:51 AM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by arnyk View Post

Some day JN you may learn to not try to school well-educated, well-experienced people who work with a given technology hands on, day after day...

You very much need to listen to your own words there arny..

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 11:52 AM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by commsysman View Post


In the US, a 220 volt circuit has two 'HOT" wires and a 3rd wire. Both "HOT" wires carry the current, and each one of them is 110 volts with respect to ground, but because their AC voltages are 180 degrees out of phase with each other the voltage from one "HOT" wire to the other is 220 volts RMS. There is no "neutral" wire in a 220V circuit, just 2 hot wires and a ground wire.

In the US we also have 240 volt circuits with two hot wires, a neutral wire, and a safety ground wire.

http://www.nojolt.com/Understanding_240_volt_circuits.shtml

...
"I previously mentioned "straight" 240 volt appliances, but there is another class of 240 volt equipment; some appliances (such as clothes dryers and ranges) use 240 volt current to power their main function (drying clothes or cooking food) but use 120 volt current to power accessories such as the clock on your stove or the light inside the oven, or the digital readout on your dryer controls. That is why some 240 volt circuits have four wires:

1) A black wire which is often known as the "hot" wire, which carries the current in to the fixture.
2) Another "hot" wire which is red, which also carries current in to the fixture.
3) A white wire called the neutral which completes the electrical circuit for the 120 volt accessories only.
4) A bare copper wire called the ground, the sole function of which is to enhance user safety.

At one time, the code allowed for one insulated wire to function as both ground and neutral in 120 / 240 volt combo circuits, but now all such circuits must use the 4 wire scheme. This is why your new dryer (or electric range) might have 4 prongs on its plug and your old dryer receptacle only has 3 holes. In which case article 250.140 of the 2005 N.E.C. (National Electric Code) allows for the "pigtail" (the cord and plug assembly) to be changed to match the old 3 wire receptacle as long as certain conditions are met. The National Electric Code allows that, but your local code might not, so check first, or even better yet make a deal with the appliance dealer
"
arnyk is offline  
Old 04-25-2013, 11:55 AM
FOH
AVS Special Member
 
FOH's Avatar
 
Join Date: Apr 2010
Location: Midwest
Posts: 4,749
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Liked: 213
Regarding post #12

Arny, up there in post #4 is what occurred, I'm unsure what you intended. Is the above post of yours separate from the scenario discussed?

Sorry, at a loss.

------------------------------------
Flat, Deep, Clean, Linear, and Loud
------------------------------------
Active 16.8kw, 7.3 system
(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
(2)Seaton SubM-HP, (4)18" IB
FOH is offline  
Old 04-25-2013, 11:56 AM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by arnyk View Post

In some over simplified theory of equipment operation there is an infinite impedance between the power line connections and any of the active or passive circuits in the AV equipment. When you disconnect neutral, but retain the connection to hot, current stops flowing through the primary side of the power supply, the equipment stops working and that is that. You reconnect neutral, current resumes flowing and the equipment powers up without damage. That is life in the ideal world. Let me know when you find that ideal world!
Here we go again arny. Please refer to qualified professionals, you are going to get somebody hurt with bad advice.

Lost neutrals are extremely dangerous. When one is lost, the potentials at the branches will indeed depend on the load split between phases.

The condition can also occur if the user has used both legs to power a interconnected system and neutral/ground are disconnected at the panel.

Seriously, your statement is dangerous. Please refer to a qualified electrician.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 12:30 PM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by jneutron View Post

Quote:
Originally Posted by arnyk View Post

In some over simplified theory of equipment operation there is an infinite impedance between the power line connections and any of the active or passive circuits in the AV equipment. When you disconnect neutral, but retain the connection to hot, current stops flowing through the primary side of the power supply, the equipment stops working and that is that. You reconnect neutral, current resumes flowing and the equipment powers up without damage. That is life in the ideal world. Let me know when you find that ideal world!
Quote:
Originally Posted by arny - same post 


In the real world there are leakage impedances between the power line connections and every circuit in all of the AV equipment. What the leakage impedances actually are varies all over the map. On a bad day disconnecting neutral allows the reference for some active circuits to float as high as the hot power line voltage - about 120 volts AC plus any spikes, etc. If the signal connections to those circuits are connected to safety ground or neutral or something like them, and they do not have adequate over voltage/over current protection, then some component parts may be permanently damaged

Just for future reference JN what you did is called out of context quoting and is considered to be intellectually dishonest in most of the western world. Perhaps you were raised in a community where the young people were not warned about such things in high school or middle school?
arnyk is offline  
Old 04-25-2013, 12:38 PM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by arnyk View Post


Silly goose. You'll pull any stunt in an attempt to save face...

What I copied was the dangerous concept you tossed out. Your second paragraph did nothing to correct that concept. Go back and read it again...he lost a fan switch as well. And quite honestly, If the overhead is powered via the same branch as some of the wall outlet equipment, that's another problem. A blown breaker for an outlet load shouldn't can the lights.

Lost neutrals are dangerous. When a system is powered by both phases, and the neutral is lost to that system, the resultant voltage on the lowest load will go up, sometimes to maximum of 220. I believe that is what fried the OP's HDMI's, as the chassis filters pulled the equipment ground of one too high for the HDMI's.

You always try some shtick or another to walk around your glaring errors...

jn.

ps. your odd "rebuttal/attack" post was weird, you messed up the quotes..

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 01:06 PM
 
SAM64's Avatar
 
Join Date: Apr 2011
Posts: 1,592
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 74
Quote:
Some discuss because they can. Others attack because they cannot.

poignant
SAM64 is offline  
Old 04-25-2013, 01:11 PM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by SAM64 View Post

Quote:
Some discuss because they can. Others attack because they cannot.

poignant

Indeed, one starts a paragraph out saying: "In some over simplified theory of equipment operation there is an infinite impedance between the power line connections and any of the active or passive circuits in the AV equipment." and this is criticized as if it is a guide for system design and practical operation.

What's unclear about "over-simplified"? Apparently for some, quite a bit!
arnyk is offline  
Old 04-25-2013, 01:42 PM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by arnyk View Post

Indeed, one starts a paragraph out saying: "In some over simplified theory of equipment operation there is an infinite impedance between the power line connections and any of the active or passive circuits in the AV equipment." and this is criticized as if it is a guide for system design and practical operation.

What's unclear about "over-simplified"? Apparently for some, quite a bit!
Diversion, diversion, diversion..

We can all read arny...

Read what I said dude.
Quote:
Your second paragraph did nothing to correct that concept. Go back and read it again

We are speaking about a lost neutral in a system that may have been powered by both phases of the load panel. Within that context (which you so rudely misunderstood) smile.gif, removal of the neutral will not just provide leakage currents, like the line input filter, but rather, the entire load of one phase in series with the entire load of the other phase. The larger load wins here of course, the smaller load receives 220. Not leakage current, but full voltage.

That is where your leakage thingy was in error.

It was not my intent to use out of context to make something up, sorry you read it that way.. You just forgot the actual context of my lost neutral/two phase scenario.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 02:12 PM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by jneutron View Post


We are speaking about a lost neutral in a system that may have been powered by both phases of the load panel. Within that context (which you so rudely misunderstood) smile.gif, removal of the neutral will not just provide leakage currents, like the line input filter, but rather, the entire load of one phase in series with the entire load of the other phase. The larger load wins here of course, the smaller load receives 220. Not leakage current, but full voltage.

Four situations:

Normal system. For simplicity each box is a load and all loads are the same. This system has 120 volts across every load. Both voltage sources are 120 volts but they are 180 degrees out of phase with each other, just like a normal US home.



System with broken neutral. For simplicity each box is a load and all loads are the same. This system still has 120 volts across every load. Both voltage sources are 120 volts but they are 180 degrees out of phase with each other, just like a normal US home.



System with broken neutral and unbalanced loads. For simplicity each box is a load and all loads are the same but some loads are disconnected. This system now has < 120 volts (actually about 34volts) across the loads on the right and > 120 volts (actually about 206 volts) across the load on the left. Both voltage sources are 120 volts but they are 180 degrees out of phase with each other, just like a normal US home.



Normal system. For simplicity each box is a load and all loads are the same. We disconnect some loads and unbalance the load on the system but the neutral line keeps the voltages balanced. This system has 120 volts across every load. Both voltage sources are 120 volts but they are 180 degrees out of phase with each other, just like a normal US home.

arnyk is offline  
Old 04-25-2013, 02:28 PM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by arnyk View Post




System with broken neutral and unbalanced loads. For simplicity each box is a load and all loads are the same but some loads are disconnected. This system now has < 120 volts across the loads on the right and > 120 volts across the loads on the left. Both voltage sources are 120 volts but they are 180 degrees out of phase with each other, just like a normal US home.

Exactly. Thanks for taking the time and effort to draw it, much appreciated.

Now, the one I kept...think of this entire picture as being the home av setup. Perhaps a sub on one line, all the rest on another. Once neutral is broken to the system, the 220 will not divide evenly. If neutral and ground are allowed to float, the chassis (or internal ground) will float towards opposite rails. That would toast an HDMI input.

edit: ah, the picture is still missing one ingredient. Most homes will not share a common neutral from the panel to the system, there will be independent romex's. So if an electrician disconnects both neutrals and grounds from the busswork as I initially stated, the chassis grounds will certainly head to the opposite rails, forcing the hdmi's to handle 220.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 02:54 PM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Here's what I was speaking about.

The way normal houses are fed power is via romex. Arny's pic assumes the hots are connected at the system, but typically that isn't the case in a house. It is at the main load panel though.

If a system is wired where some components are one hot leg (red), and others are the second hot leg(black), then if the neutral and grounds are removed at the same time, the imbalance will toast the HDMI line I put at the bottom.

It's not really difficult to do this, sometimes it only takes loosening one or two screws at the load panel. Since ground and neutral are by code on the same buss, if they double up or run out of locations for the conductors, somebody could do that.



jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 02:59 PM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by jneutron View Post


edit: ah, the picture is still missing one ingredient. Most homes will not share a common neutral from the panel to the system, there will be independent romex's. So if an electrician disconnects both neutrals and grounds from the busswork as I initially stated, the chassis grounds will certainly head to the opposite rails, forcing the hdmi's to handle 220.

More like this, eh?



In my example, the worst unbalanced loads were supplied with 206 volts instead of their accustomed 120. If they were light bulbs their life would be short, indeed. If they were electronic gear the results would range from no damage at all, to just popped line fuses in the equipment, to serious damage.
arnyk is offline  
Old 04-25-2013, 03:02 PM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by arnyk View Post

More like this, eh?



In my example, the worst unbalanced loads were supplied with 206 volts instead of their accustomed 120. If they were light bulbs their life would be short, indeed. If they were electronic gear the results would range from no damage at all, to just popped line fuses in the equipment, to serious damage.
No. Sorry we cross posted. look at my drawing. one post up, you 'll see what I mean.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-25-2013, 03:09 PM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,387
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked: 1178
Quote:
Originally Posted by jneutron View Post

Quote:
Originally Posted by arnyk View Post

More like this, eh?



In my example, the worst unbalanced loads were supplied with 206 volts instead of their accustomed 120. If they were light bulbs their life would be short, indeed. If they were electronic gear the results would range from no damage at all, to just popped line fuses in the equipment, to serious damage.
No. Sorry we cross posted. look at my drawing. one post up, you 'll see what I mean.

jn

Well if we want to go all the way, we post what a house's breaker box actually looks like:

(simplified)

or the real thing:

arnyk is offline  
Old 04-25-2013, 03:33 PM
FOH
AVS Special Member
 
FOH's Avatar
 
Join Date: Apr 2010
Location: Midwest
Posts: 4,749
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Liked: 213
I'm glad everyone understands it now, diagrams are better than my simple explanation up at post #4.

Although it could happen at the panel, it'd most likely occurs in a J-Box (or equivalent), w/the individual making up joints hot.

Kirchhoff was on to something, wasn't he? It's easiest understanding the potential for damage, when simply examining two series resistances dropping different amounts of voltage depending typically on how robust the device is.

In design and construction, spec'ing entirely dedicated circuits, w/dedicated neutrals would alleviate such issues. That said, that way, way overkill, and too costly for most. However, a competent electrician shouldn't be opening a neutral under load. Working circuits hot is commonplace, so care must be taken.

------------------------------------
Flat, Deep, Clean, Linear, and Loud
------------------------------------
Active 16.8kw, 7.3 system
(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
(2)Seaton SubM-HP, (4)18" IB
FOH is offline  
Old 04-26-2013, 08:53 AM
AVS Special Member
 
jneutron's Avatar
 
Join Date: Mar 2007
Posts: 1,879
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 17
Quote:
Originally Posted by FOH View Post

However, a competent electrician shouldn't be opening a neutral under load. Working circuits hot is commonplace, so care must be taken.

With the equipment turned off, maybe the assumption was that there was no load? Who knows..

We certainly do agree however, it wasn't a powerline transient...

Ya know, I was also thinking about a cable box. I have a box in the basement that splits telephone, tv, and internet off the cable input to the house, the coax goes up to the box next to the tv, and an hdmi cable goes to the tv from the box. The box feeding the tv is two prong, the tv 3.

If the coax carries ground up to the entertainment system, and somebody disconnects neutral/ground to my tv at the load panel, that may also pop the hdmi's in the cable box and tv.

Again, a multiport supressor contraption would stop that.

jn

Some discuss because they can. Others attack because they cannot. (unknown attribution)
A good man knows his own limitations...(Dirty Harry)
Lead, follow....or get out of the way..
jneutron is offline  
Old 04-26-2013, 10:07 AM
FOH
AVS Special Member
 
FOH's Avatar
 
Join Date: Apr 2010
Location: Midwest
Posts: 4,749
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Liked: 213
jn,
I understand your points, but for additional clarification, which I'm sure you can appreciate ...
Quote:
Originally Posted by jneutron View Post

With the equipment turned off, maybe the assumption was that there was no load? Who knows..

We certainly do agree however, it wasn't a powerline transient...

A couple items; the equipment on/off status wasn't stated, but in the scenario I layed out, it had to be on for the damage to occur.

Also, a competent individual would assume nothing. The work performed would be executed as if it's hot, and under load.

Quote:
Originally Posted by jneutron View Post

Again, a multiport supressor contraption would stop that.

You've used this term a handful of times, are you referring to the normal ... one of several types of protective devices primarily aimed at the line voltage market, but also possessing a section of I/O for "F", RJ11, RJ45, etc?

Like this below?





Thanks

------------------------------------
Flat, Deep, Clean, Linear, and Loud
------------------------------------
Active 16.8kw, 7.3 system
(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
(2)Seaton SubM-HP, (4)18" IB
FOH is offline  
 
Thread Tools


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off