Overheard Today
- Thread starterEboy87
- Start date
First off I am NOT recommending that people remove the electrical ground connection, BUT this is not a totally black and white situation.
For instance in many high end audio recording studios, all the electrical grounds are removed from devices in the Racks, and what is implimented is a STAR ground configurion, where a ground connection is made to the chassis and the rack from all the devices and THEN that ground is connected to the electrical ground. So the devices do not really have the ground removed, BUT they are not using the grounding connectiion in all the individual electrical wiring for a ground connection. I have seen this also used in some location audio setups, where an independant ground system is used, and that this is then connected to the electrical ground.
Problem is there are a lot more problems than simply someone removing the third pin on electrical cords. I have found many many times where the actual outllet was wired incorrectly with the Hot and neutral connection reversed, where the ground is NOT connected, or where the ground is connected to the outlet case, and conduit, only to have the conduit connections coroded or broken along the way. I have found ground and neutral connections reversed. There is an issue that a lot of consumer equip does not have a ground connection instead relying on the double insulated rating of the device. I have found that it is these types of devices that many times are the sources of the ground noise. Pc's with switching power supplies tend to return quite a bit of noise on the neutral, and in a poorly constructed ground system this can cause problems. I have also found panel boxes that have a neutral bar and a ground bar, and have a place to use a bolt to connect the neutral to the case that this has been incorrectly used when there should only be the one connection of Neutral to Ground at the Service entrance.
I agree extension cords that have the ground pin removed should not be used, but for instance it could be argued if the device connected to them is a two pin connection then it IN this specific use is not a safety issue.
A oot of the problem goes back to how things were wired up in the past, the unwillingness of code regulations to impliment something that MUST be changed. There are may old buildings that do NOT have ground connections on outlets, but to make it look like they do have three pin recepticals that are only partially or not connected to electrical ground. Even in areas outside of the US there are still are devices that do not use three wire setup, as mentioned aloo at all the wall warts, notebooks, electrical lights, and many consumer devices even TV's.
There are a lot of oddities in code implimentations that cause potential problems. I can give you some examples:
In the US on 20 amp wall sockets, there is no requirement to have one breaker for one outlet, so in theory you can have many many wall sockets on a 20 amp connection over 12 awg wire, with additional outlets added over time. Will an over current situation pop the breaker, probably but there is STILL the possibility of overheating. Many homes have burned ot the ground based on two many heaters put on the same series of outlets.
In marine setups, many of the marina;s use a three phase setup for connection to the dock and then break out 120 and 208 connections, Problem is the power cords do not have double rated neutrals, and if you ask boaters who use shore power alot, you will get endless tales of burned connectors based on over load on the neutral and the damp environment.
Back to theatrical and event production, it is because of all the unknowns iin the facility wiring that so many companies now bring their own distro and cableing, and get it wired in to a company switch or back to the main breaker panel.
Again extension cords with ground pin removed are bad and dangerous, but at least YOU CAN SEE THE PROBLEM. The conditions that can really get you hurt are the ones hidden in the walls and connections.
Sharyn
For instance in many high end audio recording studios, all the electrical grounds are removed from devices in the Racks, and what is implimented is a STAR ground configurion, where a ground connection is made to the chassis and the rack from all the devices and THEN that ground is connected to the electrical ground. So the devices do not really have the ground removed, BUT they are not using the grounding connectiion in all the individual electrical wiring for a ground connection. I have seen this also used in some location audio setups, where an independant ground system is used, and that this is then connected to the electrical ground.
Problem is there are a lot more problems than simply someone removing the third pin on electrical cords. I have found many many times where the actual outllet was wired incorrectly with the Hot and neutral connection reversed, where the ground is NOT connected, or where the ground is connected to the outlet case, and conduit, only to have the conduit connections coroded or broken along the way. I have found ground and neutral connections reversed. There is an issue that a lot of consumer equip does not have a ground connection instead relying on the double insulated rating of the device. I have found that it is these types of devices that many times are the sources of the ground noise. Pc's with switching power supplies tend to return quite a bit of noise on the neutral, and in a poorly constructed ground system this can cause problems. I have also found panel boxes that have a neutral bar and a ground bar, and have a place to use a bolt to connect the neutral to the case that this has been incorrectly used when there should only be the one connection of Neutral to Ground at the Service entrance.
I agree extension cords that have the ground pin removed should not be used, but for instance it could be argued if the device connected to them is a two pin connection then it IN this specific use is not a safety issue.
A oot of the problem goes back to how things were wired up in the past, the unwillingness of code regulations to impliment something that MUST be changed. There are may old buildings that do NOT have ground connections on outlets, but to make it look like they do have three pin recepticals that are only partially or not connected to electrical ground. Even in areas outside of the US there are still are devices that do not use three wire setup, as mentioned aloo at all the wall warts, notebooks, electrical lights, and many consumer devices even TV's.
There are a lot of oddities in code implimentations that cause potential problems. I can give you some examples:
In the US on 20 amp wall sockets, there is no requirement to have one breaker for one outlet, so in theory you can have many many wall sockets on a 20 amp connection over 12 awg wire, with additional outlets added over time. Will an over current situation pop the breaker, probably but there is STILL the possibility of overheating. Many homes have burned ot the ground based on two many heaters put on the same series of outlets.
In marine setups, many of the marina;s use a three phase setup for connection to the dock and then break out 120 and 208 connections, Problem is the power cords do not have double rated neutrals, and if you ask boaters who use shore power alot, you will get endless tales of burned connectors based on over load on the neutral and the damp environment.
Back to theatrical and event production, it is because of all the unknowns iin the facility wiring that so many companies now bring their own distro and cableing, and get it wired in to a company switch or back to the main breaker panel.
Again extension cords with ground pin removed are bad and dangerous, but at least YOU CAN SEE THE PROBLEM. The conditions that can really get you hurt are the ones hidden in the walls and connections.
Sharyn
Sorry, boy and kid, to be the one to tell you the sad truth: Ever looked closely at your MacBook(Pro)'s power supply? Notice there's NO electrical connection when using the power cord instead of the two prongs? The "AC Mains electrical earth equipment ground" has already been "lifted" for you.
I've run my MacBook power supply from two hots of a 208V, 3Ø supply: NO ground and NO neutral. Robert-Juliat Cyrano followspots have an IEC convenience outlet on them. With the proper adapter, viola!, power for my laptop at my followspot! The Apple power supply is auto-sensing/auto-ranging from 100-240VAC.
Now if you two want to do it for aesthetics reasons, or because you need the extra 6' of length, that's fine. But in this particular, specific instance, it is not a safety issue!
Nevermind. I was wrong. Mark (MIB, Gafftaper, etc.) this time and date. Yes, that "little silver circular thingy" IS in fact, an electrical as well as a mechanical, connection.
Still, see this thread.
You are actually both right.... the older style Mac power supplies do not have the ground connected (plastic post), the newer ones have the metal post that serves as a ground. The other annoying thing about Mac power supplies is that there are different supplies with different ratings that all look the same (except for small print). For my high school that used hundreds of Apple laptops of various models, this was very annoying as using the wrong supply with the wrong laptop causes the supply to overheat and eventually burn out.
Anyways, when worse comes to worse and it's 10 minutes until the concert starts, I generally grab a microphone and mic the amp if I cant get rid of the buzz. It's much safer than trying to mess with the wiring!
Anyways, when worse comes to worse and it's 10 minutes until the concert starts, I generally grab a microphone and mic the amp if I cant get rid of the buzz. It's much safer than trying to mess with the wiring!
Eboy87
Well-Known Member
Wow, good to hear from you again Peter. Been busy I take it? I agree on mic'ing, unless it's bass, I always mic the cab. Bass gets DI, either out of their amp or some point before it.
I do wish it was easier to differentiate between the different Apple power supplies. I haven't looked at the specs, but I know a friend of mine who got a MacBook Pro at the beginning of the year has a smaller power brick than us with older ones, about the size of the regular MacBook ones. I'd be willing to bet they all have different ratings.
I do wish it was easier to differentiate between the different Apple power supplies. I haven't looked at the specs, but I know a friend of mine who got a MacBook Pro at the beginning of the year has a smaller power brick than us with older ones, about the size of the regular MacBook ones. I'd be willing to bet they all have different ratings.
