General Electrical Safety in the Context of DIY audio

[Frank Breech]

Hi, All, I'm new to the DIY audio world and want to live to be able to listen to my recently-asssembled-but-yet-to-be-smoke-tested FPIII.  I've been poking around the forum for a general electrical safety thread but couldn't find a bunch of info aggregated together - just bits and pieces here and there.  I got some advice from my man, Grainger, as a tangent in a different thread, (here, if you're interested): http://www.bottlehead.com/smf/index.php/topic,351.0.html
but wanted to move out of there under a more appropriate heading and also take some of the pressure off of G-man and hopefully get some others to chime in as well.

So, I've read the entire FPIII manual and there's no need to repeat any of that safety info. I guess I'll just start with some general questions and some questions slightly more specifc to my situation -- Thanks, in advance for any guidance and advice.  I was telling Grainger that I've been using electricity for as long as I can remember but without any idea of what it is or how it works (I don't even know how to tell if my shoes have actual rubber soles!)... so go easy on me, please.

Vacuum Tubes:
This may be silly but is it ok to touch them (when they're off and not hot, I mean)?  I don't have any experience handling them -- the closest thing I can think of is old (and many new) projector lamps where you should not handle directly because the oils on your sking can damage them.  Are tubes the same/similar?

Electrical Grounding and Related Safety:
I live in an old apartment building.  I'm not sure if the handful of 3 prong outlets are actually grounded.  I'm going to buy one of these testers where you plug it in and the lights tell you what is right/wrong.  My question is: Is it possible for one of these testers to be wrong? 

I've read conflicting information on if the ground and the neutral conductors actually meet each other at some point at the entrace to the building.  If they do meet each other at some point, I don't understand how the ground could provide safety.  Can anyone explain?

Let's say I use my outlet tester and it shows no ground connected at my apartment.  What options do I have to ensure a safe experience?  Is a Ground Fault Interupter a good option in this scenario?  From what I've read about them, it sounds like it might be a good option even if I DO have a properly grounded outlet.  Any advice on a model that is a good performer and a good value?

I'd like to use a Surge Protector as well.  I've done some reading about them and many models use the ground as the means to shunt off the surge in power.  I guess this wouldnt' work if I'm dealing with an outlet with an unterminated ground pin.  There is another type that doesn't use the ground path but clamps down, stores the surge and slowly releases it over time - or something like that - a parallel circuit design vs a series circuit design.  Would a series style surge protector work in a building with no ground termination?

Assuming a series surge protector is good to use and a GFI is also a good idea, in what order would I hook them up?  I would think: stereo components plug into Surge Protector device; Surge protector plugs into GFI; GFI plugs into wall outlet. 

In the FPIII Instructions it is noted: "Make sure you stay away from mains wiring! ... if [a piece of gear] must be plugged in [while testing] consider use of an isolation transformer...which will create a current limit on what the AV mains can supply"   OK, so I've done a little iso transformer research and I don't exactly understand how it can "create a current limit."  Can anyone elaborate on this topic, offer an example and/or recommend an iso transformer model?

How can I be sure my MM is rated to test with the FPIII power supply?  The model I have is a Triplett 1101-A.  Also, I lost the alligator clips so I went to Radio Shack to get some more.  There is a pair rated for 5amps.  What kind of rating should I be looking for on the alligator clips?  Does the rating apply to the metal? the insulation? Both? 

I think that's it for now.  If all or any of this is covered somewhere else in the Bottlehead forum please feel free to save us all time and redirect me.  All knowledge and experience is welcome. 

Thanks again ...

Mike

[Laudanum]

Not specific info and not an answer to all your questions (some of which I dont have) but some general insight for what it's worth.

The a-clips for your meter ... if they fit your meter lead probes, they are fine.

Walk before you run.  If the outlets are 3 prong, they are probably fine.  But one of the testers you plan on buying will tell you.  Good thing to have.  Dont fret right now whether the outlets are ok or not, test and see.  If the tester says ok, it's ok.

The warning about line voltages is standard ... keep your free hand away when testing voltages with the FPIII plugged in.  Use the a-clip on the meters neg. lead attached to chassis ground point as suggested in manual and use the red lead to carefully probe the terminals listed in the manual.  The biggest "danger" here is shorting two terminals together with the probe as long as you keep your free hand away from the internals.  Just take some care and concentrate.

Unlike projector lamps,  it's ok to touch the tubes.

I dont know all the surge protector types,  just the standard sacrificial MOV type units and the series type units (Like the Brick Wall).   I think they all require the modern, 3 prong grounded receptacle.  But again, fret that part only if your outlets dont check out.    Others will elaborate here, the specifics of how these all work is beyond me.   But as a side note, I just had my all in one unit (Surge, filtering, voltage reg and UPS) for my home theater system go out on me.  I was surprised to find that my TV picture quality has slightly suffered with it out of the system.   The point is that discussion of these units will probably expand beyond surge protection and into audio (or video) quality.   

My 2 cents.

 

[Grainger49]

Mike,

I will wade in too.

I'll jump to your meter.  I used a Triplett years ago.  Of course the 120V AC incoming is safe with it on the right scale.  If it has multiple scales any scale above 170V AC is good for the incoming AC and output of the high voltage on the transformer.  Any DC scale above 380V is good for the rest of the checks. 

Assuming you have different scales, for a given reading try the scale that maxes out above the expected voltage.  The safest way is to place your meter lead with the meter on the highest voltage scale and adjust down till you have the most accurate reading without going above the maximum of the scale.  This applies to digital or analog meter with adjustable scales.  For an autoranging meter just set on AC or DC as appropriate and read the voltage.

Once you buy the tester, and I have never seen one wrong, you need to verify that the three prong sockets are correct.  Since they are an obvious add on they could be ungrounded and have the hot and neutral swapped.  That is the worst case scenario.  I have watched too many Holmes on Homes.  If the hot and neutral are swapped you should contact your landlord to have that corrected.  If the ground is missing that is just how it is in older ungrounded circuits.

Current code requires a grounded service and grounded circuits to have the ground and neutral "bonded" in the panel.  That just means that there is a wire connecting the ground buss with the neutral buss in the service panel.  That makes the neutral a "grounded conductor."  If your service panel is ungrounded then this "bonding" will not be there.

The ground, and grounded neutral, gives the hot lead a low impedance path to ground.  It is trying to make the lowest resistance path to ground something other than you if you touch the hot lead.

Since it is an apartment you probably don't want to do anything if the three prong outlet is not grounded, it is too expensive.  For those who own their place you can drive a grounding rod into the earth and connect it to the ground wires.  That is a bad idea if you already have a ground, two ground paths are not better than one.

Ground Fault (Circuit) Interupters (also called GFCI and I'll use GFIs from here forward) need a grounded circuit to function properly.  They are required by most local codes in wet areas.  For instance in my garage, outside outlets, laundry, kitchen outlets near the sink and all bathrooms are protected by a GFI circuit.  They can be either a GFI circuit breaker or the first outlet on a string of outlets containing a GFI.  This doesn't work without a grounded circuit. 

And again they are intended for areas where you might be wet.  But it doesn't hurt as a safety device.  The problem is they are not very reliable.  Once tripped a few times they don't work as well, often becoming a nuisance.

Sure protectors stop the hot wire from going to too high a voltage.  200V MOVs are used for 120V circuits.  They go between the hot and neutral, no ground connection.  You can also put the same MOV from neutral to ground and hot to ground.  I have seen that.

Power strip surge protectors most often use MOVs.  Some are more sophisticated.  Few are that effective against a lightning strike.  That is the kind of surge that happens most often.

Isolation transformers sized just for the device being tested are limited to the few watts, 5 or 10, they can supply and then the fuse or circuit breaker goes out.  The FP III input plugged into the wall has 15 amps @~120V available, about 1800 watts.  You will be testing the FP III voltage only shortly.  If you are concerned find if there is a Bottlehead in your area who will look over your shoulder while you make your tests.

I hope this helps.

[Doc B.]

I'll just throw in that if you are going to do any changes to your wiring like ground rods, check the local code first. For example where we are the requirement is two ground rods, I think at least six feet apart. I think that is probably pretty common these days.

[Frank Breech]

Hey, Guys,
Thanks very much so far ....
Looking forward to getting back to you on some of these points within the next day or so.

Thanks again

Mike