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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Tim Hite on August 22, 2019, 02:21:19 am

Title: Strange power situation
Post by: Tim Hite on August 22, 2019, 02:21:19 am
Today I advanced a show at a hotel. They had outdoor power that was recently installed. I plugged my trusty CT70 into the bottom of a duplex receptacle and got a flashing H-N indicating swapped hot and neutral. Also, got a voltage reading of 176.x VAC. Strange. Had some voltage from H-G. When I switched to Vd test the 176.x voltage read 118VAC.

I then plugged into the top outlet on the receptacle and got the H-N swap but with voltage reading 122VAC. Stranger.

Went to another duplex that's supposedly on the same circuit and got 12oVAC with reversed H-N.

I reported it to the events person and was told they would notify engineering. Was informed that "several"people had used the outlets with no issue.

Any ideas for the spurious voltage reading on half of a duplex?

I have a show there at the end of the September.
Title: Re: Strange power situation
Post by: Tim McCulloch on August 22, 2019, 08:02:45 am
Today I advanced a show at a hotel. They had outdoor power that was recently installed. I plugged my trusty CT70 into the bottom of a duplex receptacle and got a flashing H-N indicating swapped hot and neutral. Also, got a voltage reading of 176.x VAC. Strange. Had some voltage from H-G. When I switched to Vd test the 176.x voltage read 118VAC.

I then plugged into the top outlet on the receptacle and got the H-N swap but with voltage reading 122VAC. Stranger.

Went to another duplex that's supposedly on the same circuit and got 12oVAC with reversed H-N.

I reported it to the events person and was told they would notify engineering. Was informed that "several"people had used the outlets with no issue.

Any ideas for the spurious voltage reading on half of a duplex?

I have a show there at the end of the September.

We've found enough of that stuff that we have the client order (and pay for) 200 amp 3 phase 120/208v service.  We bring our own distro and cable package.

I don't care what's wrong with the hotel stuff, I won't use it.

This after finding a 120v 20 amp outlet in a ball room that was wired for 240v for a floor polisher or food service equipment.
Title: Re: Strange power situation
Post by: Chris Hindle on August 22, 2019, 08:19:37 am
Today I advanced a show at a hotel. They had outdoor power that was recently installed. I plugged my trusty CT70 into the bottom of a duplex receptacle and got a flashing H-N indicating swapped hot and neutral. Also, got a voltage reading of 176.x VAC. Strange. Had some voltage from H-G. When I switched to Vd test the 176.x voltage read 118VAC.

I then plugged into the top outlet on the receptacle and got the H-N swap but with voltage reading 122VAC. Stranger.

Went to another duplex that's supposedly on the same circuit and got 12oVAC with reversed H-N.

I reported it to the events person and was told they would notify engineering. Was informed that "several"people had used the outlets with no issue.

Any ideas for the spurious voltage reading on half of a duplex?

I have a show there at the end of the September.

I found something like that with at a festival in a church parking lot.
"It was fine last week"..
I put in my feeder and distro "Why are you not using our plugs?"
Midway through the show, the Priest comes up to FOH and says how amazing it sounds. "Last week, a guitar broke, and some of the big speakers weren't working."
Riiight. But it "worked" last week.......
I contacted "last weeks" soundco, and they lost a Fender tweed, 2 crowns, and 1 PSU for their PM-3K.

I still don't understand why folks are not metering before plugging in.
I had one hotel "electrician" freak out when I whipped out my Fluke before connecting his tails to my distro.
Ever seen 110 on the Green? Ya. Me neither.
The price of a Rat Shack meter, and the skills to use it. What does that really cost? Is a board, power amp, vintage guitar amp, or an entire rig NOT worth that investment?
Chris.
Title: Re: Strange power situation
Post by: frank kayser on August 22, 2019, 09:22:12 am
We've found enough of that stuff that we have the client order (and pay for) 200 amp 3 phase 120/208v service.  We bring our own distro and cable package.

I don't care what's wrong with the hotel stuff, I won't use it.

This after finding a 120v 20 amp outlet in a ball room that was wired for 240v for a floor polisher or food service equipment.


Rhetorical question: How does that happen?
Title: Re: Strange power situation
Post by: Brian Adams on August 22, 2019, 09:46:43 am
I remember a small show last year in a hotel ballroom, and they supplied a 4-circuit distro. 2 of the duplex outlets were fine, but 2 had 208 across H-N. I don't know why someone would wire it that way (although I can think of how they'd do it), but I told them it could kill somebody. They brought me another, which was fine, and said they tagged the bad one for their electrician to look at. Who knows if they ever fixed it though.

Always check your power before you plug in!
Title: Re: Strange power situation
Post by: Tim McCulloch on August 22, 2019, 11:31:17 am

Rhetorical question: How does that happen?

Stupidity.
Title: Re: Strange power situation
Post by: John Roberts {JR} on August 22, 2019, 12:31:54 pm
Stupidity.
Rhetorical means you don't have to answer....  ;D

JR
Title: Re: Strange power situation
Post by: frank kayser on August 22, 2019, 01:02:07 pm
Stupidity.


As my friend was fond of saying, "Stupidity is its own reward".
Title: Re: Strange power situation
Post by: Tim McCulloch on August 22, 2019, 01:46:45 pm
Rhetorical means you don't have to answer....  ;D

JR

Yeah, but my Asperger's and OCD make me do it.
Title: Re: Strange power situation
Post by: Rob Spence on August 22, 2019, 05:06:34 pm
Today I advanced a show at a hotel. They had outdoor power that was recently installed. I plugged my trusty CT70 into the bottom of a duplex receptacle and got a flashing H-N indicating swapped hot and neutral. Also, got a voltage reading of 176.x VAC. Strange. Had some voltage from H-G. When I switched to Vd test the 176.x voltage read 118VAC.

I then plugged into the top outlet on the receptacle and got the H-N swap but with voltage reading 122VAC. Stranger.

Went to another duplex that's supposedly on the same circuit and got 12oVAC with reversed H-N.

I reported it to the events person and was told they would notify engineering. Was informed that "several"people had used the outlets with no issue.

Any ideas for the spurious voltage reading on half of a duplex?

I have a show there at the end of the September.

If recently installed, perhaps one half of the duplex was a switched or dimmable one? The duplexes on my driveway lights are split for utility power on the bottom and Christmas lights on the top half?
Title: Re: Strange power situation
Post by: Tim Hite on August 22, 2019, 06:28:42 pm
If recently installed, perhaps one half of the duplex was a switched or dimmable one? The duplexes on my driveway lights are split for utility power on the bottom and Christmas lights on the top half?

Don't understand how I would get 176 volt reading, though.
Title: Re: Strange power situation
Post by: Keith Broughton on August 23, 2019, 06:48:02 am

I reported it to the events person and was told they would notify engineering. Was informed that "several"people had used the outlets with no issue.


I get really tired of these kinds of defensive answers.
Seems to me that's what they said about the shuttle rockets O rings... :o
Title: Re: Strange power situation
Post by: Tim McCulloch on August 23, 2019, 11:28:07 am
I get really tired of these kinds of defensive answers.
Seems to me that's what they said about the shuttle rockets O rings... :o

Several Morton Thiokol engineers tried to stop the Challenger launch, to no avail as they were overruled by corporate suits who were afraid of loosing the NASA contract.  Roger Boisjoly was one of those Thiokol engineers and the Challenger explosion haunted him for the rest of his life.

Hotels are on my hit list of clueless goatfuckers who take liberties with public safety but are almost impossible to get inspected by the AHJ unless there is a death.
Title: Re: Strange power situation
Post by: John Roberts {JR} on August 23, 2019, 11:53:55 am
Several Morton Thiokol engineers tried to stop the Challenger launch, to no avail as they were overruled by corporate suits who were afraid of loosing the NASA contract.  Roger Boisjoly was one of those Thiokol engineers and the Challenger explosion haunted him for the rest of his life.
While history proved him (them) correct in their concerns it was not obvious at the time, or else the launch would have been scuttled. As I recall the O-ring failure was pinned on multiple subtle issues combined, including weather (low temperatures), while LOX is pretty damn cold all by itself.
Quote
Hotels are on my hit list of clueless goatfuckers who take liberties with public safety but are almost impossible to get inspected by the AHJ unless there is a death.
That list is very long...

JR
Title: Re: Strange power situation
Post by: Tim McCulloch on August 23, 2019, 12:14:56 pm
While history proved him (them) correct in their concerns it was not obvious at the time, or else the launch would have been scuttled. As I recall the O-ring failure was pinned on multiple subtle issues combined, including weather (low temperatures), while LOX is pretty damn cold all by itself. That list is very long...

JR

Roger and the others had the numbers to support their claims and to them it was a very binary choice - launch and die, or scrub the launch, live, and have corporate deal with the NASA fall out.

As for the long list, you've seen mine?  It's long for a reason.  I'm sure you've accumulated one after nearly 50 years in the industry...
Title: Re: Strange power situation
Post by: John Roberts {JR} on August 23, 2019, 01:20:37 pm
Roger and the others had the numbers to support their claims and to them it was a very binary choice - launch and die, or scrub the launch, live, and have corporate deal with the NASA fall out.
They can be very confident in hind sight.

If they could prove that tragic outcome on paper they apparently were unable to communicate that to their bosses. Even the worst scumbag boss would not intentionally send a shuttle up to explode.

More likely there was a "chance" of O-ring failure (there is always a chance of O-ring failure) and their bosses made a bad judgement call.   

This was a tragedy, and obviously wrong decisions were made in hindsight, but I am inclined to dismiss the typical hyperbolic extrapolations. They had a request for more funding to study the o-ring issue, denied.

It is no coincidence the President Regan was scheduled to deliver his state of the union address that night, so waiting for warmer weather was not embraced. Sadly in any large enough organization there will be high level decision makers who do not understand the technology they preside over.

I have refused to do something a VP once told me to do because it wasn't right (in my judgement). If it was so certain to happen perhaps they should have done more than write a memo.   
Quote
As for the long list, you've seen mine?  It's long for a reason.  I'm sure you've accumulated one after nearly 50 years in the industry...

Actually I sleep pretty good at night and have released many personal peeves.

JR
Title: Re: Strange power situation
Post by: Brian Jojade on September 17, 2019, 03:18:21 pm
Don't understand how I would get 176 volt reading, though.

Typically, when you see a high voltage reading, you've got a problem with a neutral connection.  If there are exactly equal loads on both branches of the circuit, the neutral connection doesn't have to be tied at the box. However, if the load gets mismatched, voltage will sag on one side and rise on the other.  That's how stuff burns up!
Title: Re: Strange power situation
Post by: Scott Helmke on September 18, 2019, 09:33:40 am
Maybe it's time to build a test plug that explodes dramatically when connected to miswired outlets.  Bonus points for having it spray soot all around the bad outlet as a warning to others.
Title: Re: Strange power situation
Post by: John Roberts {JR} on September 18, 2019, 10:02:00 am
Maybe it's time to build a test plug that explodes dramatically when connected to miswired outlets.  Bonus points for having it spray soot all around the bad outlet as a warning to others.
I invested some time into a smart power strip for backline muso's that would just not connect power if outlet was mis-wired (dangerously). It would even disconnect if it sensed current leakage from say a hot mic.   

We all know that musicians would just plug in around the safety device denying them power. The show must go on... ::)

JR
Title: Re: Strange power situation
Post by: Jeff Bankston on September 18, 2019, 10:33:09 pm
I remember a small show last year in a hotel ballroom, and they supplied a 4-circuit distro. 2 of the duplex outlets were fine, but 2 had 208 across H-N. I don't know why someone would wire it that way (although I can think of how they'd do it), but I told them it could kill somebody. They brought me another, which was fine, and said they tagged the bad one for their electrician to look at. Who knows if they ever fixed it though.

Always check your power before you plug in!
A guy on a job wired up a new 75kva 120/208 3 phase transformer. A guy checking new outlets was getting 196 volts between hot and neutral. I pulled the transformer cover and neither the cold water ground or the ground rod was connected to the XO lug. I connected them and everything was alright alright. An electrician has got to connect with the XO. Has anyone seen the XO ?
Title: Re: Strange power situation
Post by: Rob Spence on September 20, 2019, 04:47:51 pm
The strangest power thing I ever encountered was all human caused.

Brand new engineering building for a computer company. My role was network manager and manager of the group of computer system managers.

Town power was 25kv. Power transformers were ordered. Pretty big power. Two substations I think. 4 labs with 10 each 100a 3 phase overhead bus bars. Oh, and the building and lights etc too.

Transformers arrived, they hooked them up and turned on the power. Blew up every connected device. I only cared about the freight elevators but...

The manufacturer assumed that the 25kv really meant 13.8kv which is a very common street voltage, so they built for that.

The manufacturer didnít check with the customer

The electricians had loads connected when they turned on the mains

The electricians didnít meter things before turning on the mains.

Me, we had to lay plywood across mud and use lift gate trucks to move in the first dozen mainframes instead of using the loading dock and elevators.

Two years later the adjoining building was built. 4 substations this time. I had one computer room that was 100í x 300í with a pair of 100a bus bars every 10í plus lots of cooling.

This time the switch gear had meters. Good thing. The 480v bus read 600v. They blew it a second time but fortunately did not connect the building. Whew. The PoCo dropped a big ass transformer outside and patched it in while we waited for replacement transformers.

Sigh...

Edit : fix the bus
Title: Re: Strange power situation
Post by: John Roberts {JR} on September 20, 2019, 06:55:06 pm
bus,,,,  buss sells fuses.

JR
Title: Re: Strange power situation
Post by: Rob Spence on September 20, 2019, 09:48:44 pm
bus,,,,  buss sells fuses.

JR

Oops, I need a drink 😁
Title: Re: Strange power situation
Post by: Jeff Bankston on September 21, 2019, 12:51:16 am
buss ? I rode a buss.

https://www.youtube.com/watch?v=tZkouut-9RQ
Title: Re: Strange power situation
Post by: John Roberts {JR} on September 21, 2019, 09:13:39 am
buss ? I rode a buss.

https://www.youtube.com/watch?v=tZkouut-9RQ
even wierd Al spelled it right...

you can buss your girlfriend...

JR

@Rob no worries , I spelled it wrong before the early/mid 80s....
Title: Re: Strange power situation
Post by: Jeff Bankston on September 22, 2019, 01:01:50 am
even wierd Al spelled it right...

you can buss your girlfriend...

JR

@Rob no worries , I spelled it wrong before the early/mid 80s....
lol ! I spelled it buss on purpose. I was wonderin if anyone would catch that. Excuse me while I catch the bus.

http://www.youtube.com/watch?v=h0PlwVPbM5k


Title: Re: Strange power situation
Post by: Kevin Graf on September 22, 2019, 08:54:03 am
A guy on a job wired up a new 75kva 120/208 3 phase transformer. A guy checking new outlets was getting 196 volts between hot and neutral. I pulled the transformer cover and neither the cold water ground or the ground rod was connected to the XO lug. I connected them and everything was alright alright. An electrician has got to connect with the XO. Has anyone seen the XO ?
Connecting to Planet Earth is not the correct solution for a voltage mis-wire problem.