 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
207.200.116.66
In Reply to: RE: no-ground outlet posted by remi on June 01, 2007 at 09:00:26
I'm no electrician. Advice I've read repeatedly here is NOT try to set up a separate grounding mechanism such as you propose - apparently quite dangerous.
Your box may be what they tell me is BX, meaning a metal box actually grounded already through a metal flexible conduit to the breaker box and house ground. If that sounds like what you see, then you have a ground. I'm not sure any house could have been built to code for much of the last century without at least that kind (or an alternate) grounding scheme.
Please check with our electrically gifted guys here before you try anything else.
ELECTRICITY CAN AND DOES KILL!!!! Know what you're doing first, please.
Follow Ups:
Many houses were bilt ungrounded during the mid 50's (where I live, at least).
Doesn't smell good at all.
Would it be REAL bad to use my CDP with such an electrical system? (After all, I had a computer, micro-wave oven, washing machine, espresso machine, coffe grinder, etc. running with a lack of ground for the last three years...)
Thanks for the safety warning ;-)
Again, you really should consult an electrician with your concerns. In fact, you could probably consult with your local government building authority to find out how the house is grounded, being that they would have had to conform to some kind of code in the 1950s and there would have been inspections.
Meantime, if your computer, washer, etc. are all working fine, I'm not aware of any reason your CDP shouldn't work equally well for now.
I still suspect you have the BX type grounding I described, which was very very common in the post WWII era.
When I installed my outlet, there were two wires.
I figure that, whatever the type of ground it may be, it should use a third wire, right?
Plus : the surge protection of my computer has a red LED for ground (would be green if grounded).
Last question : except for lack of shielding, what are the risks in using a device that should be grounded but is not (knowing that so many electric and electronic devices are built without a grond prung)?
There are two kinds of audio equipment in the USA. One kind uses three wires in the AC, where the third wire is commonly called 'ground.' This is a safety wire that is supposed to be connected to the neutral back at the power entry circuit breaker or fuse panel (where both are connected to earth). Its purpose is to carry fault current if the hot wire or something attached to it comes loose inside the equipment and touches the metal case. The fault current will cause the circuit breaker or fuse to open.
If the power circuit does not connect the third wire, as appears to be your case, then such a fault would make the metal case "hot" and anyone who touches it and a grounded object at the same time could be killed by electrical shock.
The other kind is called "double-insulated." It is designed so that the hot wire or anything connected to it cannot come into contact with any exposed metal. The AC safety-earth connection is not used as it is not needed. Some such equipment is provided with IEC connectors so that audiophiles can use their favorite fancy power cords, but either the third pin is not present, or is not connected to anything inside. Much of it uses captive two-wire power cords.
The safety wire, which I prefer to call the "AC safety-earth," is the cause of a lot of trouble and confusion in audio. Many audiophiles think it improves the sound by magically removing interference and noise, and some go so far as to install separate earth rods for their audio system circuits. This is dangerous and illegal, but may improve the sound.
The safety-earth wire goes everywhere in a house where the wiring is up to date. It is far too long to be an effective RF ground, and may pick up a lot of RF noise from non-audio appliances. A separate ground rod may improve the sound in such cases, but is dangerous because the fault current would have to pass through the earth to the AC system ground at the entrance panel, and the voltage drop may be too high to be safe during a fault condition. It is also highly dangerous in the event of a nearby lightning strike.
Your risk of injury is probably low, but is still real. If your landlord is not interested in bringing your wiring up to code, contact a local tenant advocate for advice about your rights. Perhaps a letter from a lawyer outlining the landlord's legal exposure would be sufficient motivation to get the problem fixed.
Good luck.
I can try to answer from my limited knowledge, but it's really limited!
BX has only 2 wires. Common in housing after WWII. But that does NOT mean it isn't grounded, it is! It's grounded by using a metal box in the wall that is connected by flexible metal conduit in the wall all the way to the grounding system in the main electrical box to your house. The backstrap of the outlet duplex is connected to that circuit by the metal screws that hold it to the wall box in your room, so the entire system IS grounded in that kind of configuration. That's what I have in my house. You don't see 3 wires for a reason, but it's still grounded.
Of course, I have no way of knowing if your house is wired that way, but I'm guessing it might be. You can verify that with your local building permit office, since they will know from the original permit in the 1950s. Or you can have an electrically sophisticated guy tell you more or actually look into your wall box and determine it. It's a good idea to do one or the other.
Meantime, I'm told (and here's where my electrical theory and knowledge falters) that 2 prong appliances are "internally grounded" in some way. I have no idea what that actually means or whether it's as safe as earth grounding that 3 prong stuff uses. Consult one of our experts here.
I have no idea what your LED is telling you and won't even hazard a guess. Do you see the emphasis on HAZARD?
(1) pull the receptacle wall cover plate.
(2) with a volt meter insert one test probe into the the 6/32 threaded hole in the center of the duplex receptacle, the one used to secure the wall cover plate.
Insert the other test probe into one of the two receptacle power outputs holes, slots. Does the meter read 120V nominal? If not, remove the test probe from that hole and insert in the other slot. If still no voltage reading, there is not an equipment ground present.If a nominal reading of 120V was present from one slot of the receptacle to the yoke, strap, of the receptacle that does not mean a good equipment ground is present. A multi-meter is a high resistance reading device. In other words very little power is needed for the meter to give a voltage reading of 120V nominal.
If a test voltage of 120V was present I would then use a test load to check for good continuity conductivity. This can be done with a pigtail lamp socket and a 100 watt 120V light bulb. Just insert the leads of the pigtail socket inplace of the test leads of the multi-meter.
Just a note on BX.
In the Northeast of the US BX was used in homes. As for the Midwest in single family houses a 2 wire NM cable (romex trade name) was used. The electrical rough-in wall box was metal. In multi story apartment buildings BX or rigid conduit was used.
Easy way to check, pull the receptacle from the box. Of course make sure the power is turned off first at the receptacle. Once the receptacle is removed look inside the box. If the wiring is 2 wire NM cable a clamp will be seen at the back of the box securing the sheath of the NM cable. With BX a 1/2" connector with a supporting lock nut will be seen with the 2 wires exiting the connector.
Thanks for providing some info to this guy. I really am out of my depth here, but was concerned about his radiator idea from what I'd already read from other more knowledgeable inmates.
I have an Arcam Alpha 9 CDP. Even though the power cord is a three wire with a 3 wire IEC female connector, the CDP male IEC connector does not have a blade for the equipment grounding conductor receptacle of the IEC connector of the pc. In other words the case of the CDP is not grounded.
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
