Replacing a two prong cord with a GFI cord. (what about arc fault?) A rubegold.

[drgonzonm]

I am wondering how safe it is is to replace a two prong cord on an amp with a surplus GFI'ed cord. (say an old hand hair dryer cord). 
Then I am wonder about using arc fault breakers with two prong amps?  I know its a rubegoldburg approach.  Both of these safety devices work on a two wire system. 

A while back, there was a thread about Japanese power, and the difficulty of properly grounding an amp.

I know the NEC has changed since I last played with electricity in an industrial environment.   Back then the inspection authorities were insisting that all none double insulated appliances were grounded, many had to have GFI cords. 

I will take plus 1s from any one who posts saying a three prong plug and removing the death cap is a cheaper approach. (I will concede that relying on technology to protect is not smart, especially a physical solution is simpler and probably more reliable).    Just thinking outside the amp chassis (box)

[davidwpack]

Hmm. I've wondered about stuff like that too. I've got the 2011 NEC guidebook. Article 640 is about signal processing and amplification. I'll have to thumb through that later.

[dpm309]

To be on the safe side, I would replace the 2-prong cord with a 3-prong cord and remove the death cap. I have done this on several amps and is not very time consuming. Just my 2 cents.

[pompeiisneaks]

Besides GFCI seems wrong for this use.  The point of GFCI is to protect people from shock due to water immersion, thus why they're now mandated by code around bathrooms and hot tubs etc.  For amps, like stated, so long as you do a great job earthing the chassis, and don't have a death cap, it should never need a GFCI.

~Phil

[PRR]

I'm undecided about GFI on an amplifier. A proper 3rd-pin ground "would" be totally safe, except the other guy's gear is ungrounded and may have a cap wrong-way, or be on another building circuit, or stage box, or.....

I am totally in favor of GFI for general use in garage, cellar, and yard. I go with the in-fuse-box types for most "near dirt" circuits. I've reverted to in-outlet GFI for outdoor work-- easier to reset than going down cellar.

I have strong opinions against "arc fault". The idea is good. The implementation is flawed. The makers have pressured the AHJs to require arc-fault on many circuits. I am re-wiring a 1948 house and this means $500+ extra cost for a product I believe will false-trip often and fail to trip on many real faults.

IF your amp wire is reliable and robust, I can not see any reason to put arc-fault in the amplifier, or even in a stage-box. If your (or your bandmate's) amp cord is crap, the answer is to replace the crap, not add crap failure detection.

[PRR]

Oh, and aside from safety, high-gain audio amplifiers "usually" have less hum if common is tied to common of the building AC power. This may be similar to the "neutral" of a 2-pin outlet, but you can't know which is neutral. (60% swapped in my last house.) The U-pin is a much better bet for hum reduction, since it is somewhat less likely to be mis-wired.

[drgonzonm]

Besides GFCI seems wrong for this use.  The point of GFCI is to protect people from shock due to water immersion, thus why they're now mandated by code around bathrooms and hot tubs etc.  For amps, like stated, so long as you do a great job earthing the chassis, and don't have a death cap, it should never need a GFCI.

~Phil

17 years ago, in a safety meeting, some one purposely dropped a running drill in a five gallon bucket of water.  The gfi did not kick, we had to put about a cup of table salt into the water before the GFI kicked.  The water in central Vermont was naturally soft, not a lot of minerals, so the GFI not kicking was not surprising. 

Like PRR said, it is not cheap to upgrade an old electrical system. Last time I checked, the arc faults were $27 and that at a contractors discount.  I suspect that an arc fault would trip if the death cap failed.  not sure about a death cap failure on a GFI with the green wire not attached.  I guess I will pull the tubes and fuse on my M8e, and short across the death cap with a slow blow fuse.   

I have someone close who uses amps, and lives in a house with a two wire system, so sometimes, a three prong plug is not a realistic choice. 

[PRR]

> sometimes, a three prong plug is not a realistic choice.

I am rewiring a 1948 house, all 2-wire. Will cost about $1000.

A cremation here is about $1000. You want a party and a plot, much more.

> running drill in a five gallon bucket of water

Water is a side-issue.

When there was metal plumbing everywhere, you could easily touch ground.

But on 110V systems the real issue is that 110V through dry skin is less-fatal, 110V through soaked skin is more-fatal. That drill had no skin?

I have real doubt about arc-fault tripping on a failed chassis cap. It isn't clear WHAT the arc-faults detect. They derive from GFIs and the observation that one popular brand of outlet, when it gets hot, the insulating plastic goes leaky. If it is a 3-pin circuit, the leakage will trip a GFI slightly before the plastic starts to drip. However other brands don't heat-leak even as they disintegrate. The core idea, detecting actual arcing, would be easy except MANY common appliances arc normally. Vacuum cleaner and drill motors especially. OTOH the basic fire-problem the AF attempts to cure, hot contacts, may not arc at all, and may be nearly undetectable except by monitoring the voltage drop across the plug.

[drgonzonm]

On another forum, I reading complaints that a technician failed to correctly diagnose a bad PT, because he didn't test the amp on an arc-fault circuit. 

Regarding what arc faults do, I suspect different manufacturers react differently. Much like the AMD chip and the old 286, 386 cpus.  meet a set of conditions, certify and get it on the market. 

PRR, regarding your house built in 1948, and its electrical upgrades, Are you rewiring the majority of the house, that is new panels, new breakers and new wires?  If, so, code requirement?  Had a friend, who had a rental and had to replace one bedroom's wiring. because an adjoining wall, the the Authority having Jurisdiction, required a complete rewire of the 500 sqft apartment, and a new panel.  (Inspector felt, that more than 25% of the wiring was being replaced.) Since it was considered commercial property by city code, the work had to permitted and done by a licensed journeyman.  (It cost more to repair the damage to the walls and the roof, than it cost to rewire). 

In the 80's, one of my co-workers, had an near fatal accident, he slipped on some algae, growing on top of a transformer and fell into the secondaries (4160v).  He was using distilled water to wash dirt and grime off the insulators.  In the lab, we monitored RO water with an ohm meter (mega-ohms). 

If my memory serves me correctly, any water classified as hard water will conduct enough electricity at 110v to trip a GFIC.  some soft waters will do the same. 
Regarding, hot tubs and pools, their chemistry is one which provides enough electrolytes to trip a GFIC, again relying on memory, any 110v pool light needs to be gfi protected.  Thank you know who, for LED lights. 

PRR no disagreement with you regarding what I call a false sense of safety. 

[shooter]

In the lab, we monitored RO water with an ohm meter

I Picked up a can of wasp spray the other day so I could get to the mailbox, on the label It says;
"non conductive to 32,500v"  I started laughing, thinking of the poor lab human getting zapped as the chemists re-formulate till they get it to hi-tension specs

[PRR]

> code requirement?

Two permits. Service Entrance (I had this done by licensed company to ensure smooth cooperation with the power company), done; and essentially ALL inside wires (was insufficient outlets on #14 with no Ground and rotting cloth jacket), just starting.

It was a recycled 10-pole main breaker box (apparently replaced original 12-fuse fusebox); now 30 poles of a type to take AF/GFI breakers.