Bizarro AV circuit spec's

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e57

e57

Senior Member
Location
San Francisco, CA
I'm sure we all have come across the various other trades that we communicate with in order to provide their electrical needs. Many of which have the understanding of out lingo just enough to get themselves into trouble. Much like a skit I think I saw in some movie where a man was in Japan and practices his Japanese skills enough to mess it up real good i.e. 'this tastes good' at diner came out as "tastes like Godzilla's socks" I realize that much of our lingo is Greek to most - but it does warrent some due diligence on my part not to have the work priced and done for them...

So far on this one job I have gotten some real winners:
  • Irrigation contractor wants 100 AMP's for himself - turns out his controller is 100 watts...
  • Likewise the Plumber has 5 -100 HP pumps (WHAT?!?!?) :cool: turns out they are 100VA each.
Then the AV guy....
  • "Insulated ground conductors" on all wiring (NM job - this would mean a change to MC or conduit...)
  • "Dedicated circuits unless otherwise noted" - only a few were noted as "Dedicated" as a double positive made all 30 outlets for thier stuff "Dedicated"
And the winner - all circuits on one phase. When questioned on this - "don't you mean single phase?" No - all on the same phase! This one I have actually come across before - and am starting to think it is some sort of snake oil that the AV crowd is serving up - anyone else get this one yet???

Doing a little sneaking around to see what the other side is up to I find crap like this.
#1
#2 (bottom of page ten)
#3

Only things that come to mind are the words "Full Wave Rectified DC Current" and "Snake Oil"
 
Security101

Security101

Senior Member
Location
Northern Indiana
e57 said:
This one I have actually come across before - and am starting to think it is some sort of snake oil that the AV crowd is serving up - anyone else get this one yet???
Click to expand...

In their defence (AV Guys) as I have done a little bit of it myself and have had some issues - it can happen.

Some issues I have had:
X10 must be on a single phase or other equipment must be added to "jump the signal" to the other phase - if not it just wont work...

120vac FM intercom systems - same thing...

Some other AV-LV communications also wont crossover without issues.

It does seem like snake oil but when you add the coupler or bridge it seems to work up to 98% of the time (that's why I don't use it or spec it much as it's not 100% - power-line carrier devices that is)

So, who knows??:wink:

Jim
 
brantmacga

brantmacga

Señor Member
Location
Georgia
Occupation
Former Child
e57 said:
[/LIST]And the winner - all circuits on one phase. When questioned on this - "don't you mean single phase?" No - all on the same phase! This one I have actually come across before - and am starting to think it is some sort of snake oil that the AV crowd is serving up - anyone else get this one yet???
Click to expand...

that's not an uncommon request, and it can prevent noise problems. i have moved circuit positions to one line to alleviate noise problems myself.

as for the landscape contractors 100A service, that reminds me of a job with a fence installer. they told me the operator required "a 30 amp house plug". i asked for the nema # for that device, and their reply was, "you know, just a regular house plug, but put it on a 30A breaker". turns out they had a .30A trickle charger.
 
e57

e57

Senior Member
Location
San Francisco, CA
Security101 said:
In their defence (AV Guys) as I have done a little bit of it myself and have had some issues - it can happen.

Some issues I have had:
X10 must be on a single phase or other equipment must be added to "jump the signal" to the other phase - if not it just wont work...

120vac FM intercom systems - same thing...

Some other AV-LV communications also wont crossover without issues.

It does seem like snake oil but when you add the coupler or bridge it seems to work up to 98% of the time (that's why I don't use it or spec it much as it's not 100% - power-line carrier devices that is)

So, who knows??:wink:

Jim
Click to expand...
There are no PLC or other Line voltage modulated data things like X-10 or any other type data on the electrical system whatsoever. (That said I can tell you a funny X-10 story sometime in another topic)


brantmacga said:
that's not an uncommon request, and it can prevent noise problems. i have moved circuit positions to one line to alleviate noise problems myself.
Click to expand...
I have come across this spec once or twice - and normaly I just laugh and say sure. But now I need to know where this idea comes from. IMO there is relitively little chance of any difference electrically in what most consumer electronics are plugged into - since they are for the most part fed by rectified - regulated/filtered DC power supplies directly after the cord, quite often a two-prong cord at that... Any alieviated noise issue that could be corrected by swapping phases would be evidence of other problems of grounding - not phase relationship. They are not even asking for what would be best for most types of noise issues IMO - Central grounding buss for the chassis and rack equipment.

I really don't understand how two items that both take AC change it to DC on the otherside of a transformer isolating it from the AC, will act any different from one phase to the other. I'm seaching for a colorfull non-technical anaolgy - say you have a device that you pump ice cream into. In one side you put French vanilla and out comes regular vanilla. And likewise you pump in chocolate, out comes vanilla, put in some spumoni - same thing - plain vanilla.... rocky road = plain vanilla... Or am I missing something?
 
electricmanscott

electricmanscott

Senior Member
Location
Boston, MA
I look at it from a different perspective.

Whatever the av guys want they get, who cares. The fact is they think it is better, they convince the customer it is better and I make more money.

Ther are legit reasons for most of the requests. Sure some of them may be theoretical but they are reasons.
 
Z

zbang

Senior Member
Location
Roughly 5346 miles from Earls Court
e57 said:
I have come across this spec once or twice - and normaly I just laugh and say sure. But now I need to know where this idea comes from.
Click to expand...

I suspect that it stems from the usual misunderstanding of earthing/grounding. Somewhere along the line, somebody noticed that if they used outlets all on the same phase, the hum went away, and they've been doing it that way ever since. (I've had people insist on using only one phase of a 3-phase panel, where all the outlets they were using are 6" from the panel, and that was their only source. I've also seen people put sound reinforcement on A, the instrument amps on B, and lights on C. They theory there is that the noise from the dimmers won't affect the other phases. They don't think about how it'll affect the shared neutral...)

e57 said:
IMO there is relitively little chance of any difference electrically in what most consumer electronics are plugged into - since they are for the most part fed by rectified - regulated/filtered DC power supplies directly after the cord, quite often a two-prong cord at that... Any alieviated noise issue that could be corrected by swapping phases would be evidence of other problems of grounding - not phase relationship.
Click to expand...

This is part of my argument against all the line conditioners sold to audiophiles. If this device really needs a power conditioner to perform at it's peak, then IMHO it has a cheapa55 internal power supply. I'd love to see a double-blind study of audiophile power conditioners :D.
 
e57

e57

Senior Member
Location
San Francisco, CA
zbang said:
I suspect that it stems from the usual misunderstanding of earthing/grounding. Somewhere along the line, somebody noticed that if they used outlets all on the same phase, the hum went away, and they've been doing it that way ever since. (I've had people insist on using only one phase of a 3-phase panel, where all the outlets they were using are 6" from the panel, and that was their only source. I've also seen people put sound reinforcement on A, the instrument amps on B, and lights on C. They theory there is that the noise from the dimmers won't affect the other phases. They don't think about how it'll affect the shared neutral...)
Click to expand...

Much of this could be handled with a heavy ground buss - but rarely do I get asked for one of those. As for the 'other phases' this type of crap is really messing up my load calc's, and may drive the building into a new transformer because of it.

zbang said:
This is part of my argument against all the line conditioners sold to audiophiles. If this device really needs a power conditioner to perform at it's peak, then IMHO it has a cheapa55 internal power supply. I'd love to see a double-blind study of audiophile power conditioners :D.
Click to expand...
So would I....
 
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