[Speedskater]

Lots of people use Hospital Grade AC Receptacles in their audio and video systems,  but I see that some of the newest U.S. models include a Tamper Resistant (TR) feature to meet 2008 NEC Article 517-18(c).  Most TR receptacles have a spring loaded plastic flap in the slots to keep a kid from shoving a screwdriver or paper-clip into the receptacle.  But these Hospital Grade receptacles have internal switches that dis-connect the outlet.  This negates the advantage of using Hospital Grade receptacles in your system.

Some of the new units are HBL8200Sx & HBL8300Sx

[drab]

Why would it negate any advantages? Wouldn't a hospital grade receptacle
still grip tighter than normal receptacles? I thought that was the only advantage.

Mike

[Speedskater]

But, it adds two tiny little switches inside the receptacle and probably a higher price.

[Wayner]

First, hospital grade outlets have an isolated ground. The flange of the outlet, which is connected to the ground in normal outlets is isolated from the ground screw in hospital grade outlets. That is to keep the potential for spark down as most hospitals have oxygen tanks (good for helping fires along). The 2 switches inside the outlet must be depressed before the outlet will work. This is a new safety feature. Although I think that if your dumb enough to stick a butter knife in an outlet, the Buffalo theory should be exercised.

Wayner

[drab]

First, hospital grade outlets have an isolated ground. The flange of the outlet, which is connected to the ground in normal outlets is isolated from the ground screw in hospital grade outlets.

I've never heard that before, and I don't have one around to check, but i don't know what good that will do you if you
mount an ungrounded metal flange with a metal screw to a grounded metal box. Presto groundo.

Although I think that if your dumb enough to stick a butter knife in an outlet, the Buffalo theory should be exercised.

I'll go along with that! I guess if your really worried about a solid connection and safety you could just hard wire
your gear.

[Wayner]

Isolated outlets have a green triangle symbol on them. The reason for this is to isolate the outlet ground from the metal junction box and conduit, to keep noise down for sensitive hospital equipment.

Wayner

[drab]

Isolated outlets have a green triangle symbol on them.

Only if the receptacle is orange, otherwise it has an orange triangle.
Anyway, a hospital grade receptacle can be an isolated ground or not, just like any receptacle.

The reason for this is to isolate the outlet ground from the metal junction box and conduit, to keep noise down for sensitive hospital equipment

Yes, but they are both grounded, just separately. There is no fire prevention factor in an isolated ground.

Mike

[satfrat]

There is more to the actual sonics of an AC duplex other than whether it is hospital grade. Just because a hospital grade outlet will hold onto an aftermarket power cord more strongly doesn't necessarily mean that it will improve the sonics to your liking. You'll actually need to listen to them and compare to find this out for yourself. All hospital grade duplex's are not created equal and they do effect the audio sonics in my humble opinion.

Cheers,
Robin

[Speedskater]

The Tamper Resistant part is rather new!  It's required in the children's department.

Article 517-18(c)
(C) Pediatric Locations. Receptacles located within the
rooms, bathrooms, playrooms, activity rooms, and patient
care areas of pediatric wards shall be listed tamper resistant
or shall employ a listed tamper resistant cover.

So not all Hospital Grade AC Receptacles are "TR".  I would look for non "TR" receptacles,  but NEC 2008 requires "TR" receptacles in most home outlets, so you may be required to use a "TR" receptacle.

The HBL8200Sx & HBL8300Sx models donot have an isolated ground.

[ctviggen]

An outlet with an isolated ground would have two grounds, one from the outlet to the metal box (the isolated ground) and another from the outlet to the ground wire in a grounded system.  The two grounds are isolated from each other.  For this to work, there would have to be all metal conduit back to the electrical panel. 

See this, for instance:

http://www.proavmagazine.com/industry-news.asp?sectionID=1771&articleID=620099

[Speedskater]

I have heard of home owners (mistakenly) paying extra for isolated ground receptacles for their A/V rooms when the house was wired using NM (Romex) and plastic outlet boxes.

[drab]

For this to work, there would have to be all metal conduit back to the electrical panel. 

Or a separate ground wire. Generally you would use a solid green or bare wire for the mechanical ground
and a green/yellow insulated wire for the iso ground.

I have heard of home owners (mistakenly) paying extra for isolated ground receptacles for their A/V rooms when the house was wired using NM (Romex) and plastic outlet boxes.

Only a mistake if they are wired improperly. If the outlet is dedicated and runs directly to the panel, then it is unnecessary.(Assuming plastic boxes and NM)
If the ground wire is used to feed the ground terminal of any other outlets, then an iso ground makes sense. You just
have to have two ground wires in the circuit, one for grounding all other outlets and one for the iso ground. Use a romex
with an extra conductor and tape it green on both ends.

[Mike B.]

For some unknown reason many got the idea that a isolated ground outlet was what they wanted. The real important features to look for are no nickel plating on the hot and neutral parts. All brass or other non magnetic metal contacts. And, a grip that holds very well. There are other important characteristics but they are more subtle. As always, this is my humble opinion.

[cryoparts]

This discussion comes up every now and then.  IMO, it no longer matters if a receptacle is "hospital grade" any longer.  Sure, 5-6 years ago, this was an indicator of a receptacle being built to a high standard, but these days, we are fortunate to have many "audio grade" receptacles available.

There are many brands and models of 'audio grade' receptacles on the market now, some great, some good, many average.  As Robin said, you have to listen to different models, in YOUR system,  to determine what sounds best in YOUR system.

Peace,

Lee

[Speedskater]

For this to work, there would have to be all metal conduit back to the electrical panel. 

Or a separate ground wire. Generally you would use a solid green or bare wire for the mechanical ground
and a green/yellow insulated wire for the iso ground.

I have heard of home owners (mistakenly) paying extra for isolated ground receptacles for their A/V rooms when the house was wired using NM (Romex) and plastic outlet boxes.

Only a mistake if they are wired improperly. If the outlet is dedicated and runs directly to the panel, then it is unnecessary.(Assuming plastic boxes and NM)
If the ground wire is used to feed the ground terminal of any other outlets, then an iso ground makes sense. You just
have to have two ground wires in the circuit, one for grounding all other outlets and one for the iso ground. Use a romex
with an extra conductor and tape it green on both ends.

The problem comes up when the home owner doesn't understand this logic and just uses the words.  The electrician not knowing the goal just installs the parts and collects his money.

[PhilNYC]

This discussion comes up every now and then.  IMO, it no longer matters if a receptacle is "hospital grade" any longer.  Sure, 5-6 years ago, this was an indicator of a receptacle being built to a high standard, but these days, we are fortunate to have many "audio grade" receptacles available.

There are many brands and models of 'audio grade' receptacles on the market now, some great, some good, many average.  As Robin said, you have to listen to different models, in YOUR system,  to determine what sounds best in YOUR system.

Peace,

Lee

That said, most "audio-grade" receptacles are priced higher...

Many receptacle manufacturers make receptacles that are labelled "specification-grade", which refers to a higher standard of build quality and materials, while not necessarily adhering to the specifics that are required to be "hospital grade" (eg. tamper-proof, etc).

[ctviggen]

For this to work, there would have to be all metal conduit back to the electrical panel. 

Or a separate ground wire. Generally you would use a solid green or bare wire for the mechanical ground
and a green/yellow insulated wire for the iso ground.

No, that wouldn't work.  The main (possibly only) reason for an isolated ground is to limit the amount of noise from other components that would get radiated onto the power supply wires (hot, neutral, possibly ground).  For that to happen, there has to be a shield around the wires, which means all metal conduit and metal boxes all the way back to the power source, typically the main breaker box. You also have to use a metal plate to attach the outlet and ground the isolated terminal to the metal box (and the metal conduit to a ground, which should occur at the main breaker box). The grounded metal should act as a Faraday shield. 

A single wire running to the breaker box is absolutely useless as a Faraday shield, thus defeating the main purpose for an isolated outlet.  You've spent extra money for nothing.

[Glen B]

For this to work, there would have to be all metal conduit back to the electrical panel. 

Or a separate ground wire. Generally you would use a solid green or bare wire for the mechanical ground
and a green/yellow insulated wire for the iso ground.

No, that wouldn't work.  The main (possibly only) reason for an isolated ground is to limit the amount of noise from other components that would get radiated onto the power supply wires (hot, neutral, possibly ground).  For that to happen, there has to be a shield around the wires, which means all metal conduit and metal boxes all the way back to the power source, typically the main breaker box. You also have to use a metal plate to attach the outlet and ground the isolated terminal to the metal box (and the metal conduit to a ground, which should occur at the main breaker box). The grounded metal should act as a Faraday shield. 

A single wire running to the breaker box is absolutely useless as a Faraday shield, thus defeating the main purpose for an isolated outlet.  You've spent extra money for nothing.

Seconded. 

[cryoparts]

That said, most "audio-grade" receptacles are priced higher...

Yes, but there are some good options on the market for as low as $50 USD.  One can spend more (much more!), but doesn't have to, unless they are so inclined.

Many receptacle manufacturers make receptacles that are labelled "specification-grade", which refers to a higher standard of build quality and materials, while not necessarily adhering to the specifics that are required to be "hospital grade" (eg. tamper-proof, etc).

Yes, a good example is the Hubbell 5362.  Compare this model to the Hubbell 8300H and you will notice that the 5362 is much beefier.

I used to stock a wide variety of spec grade and hospital grade receptacles.  I now only stock "audio grade" as I decided that the minimal price difference was not worth sourcing the spec and hospital grade models any longer.

Peace,

Lee

[Mike19]

Hi everybody. Very interesting thread.

I am thinking of installing a dedicated circuit as a DIY project (I buy the hardware and a construction pro friend does the work for $20/hr.).

But, it seems like it will be too expensive. Parts Express has a Wattgate 381 "Audio Grade" receptacle for $148 and Belden "Audiopile Grade" 12g power cable for $8/ft. Will probably need 50' from fuse box to attic, down to wall. Hardware cost already $548 and that's w/o the grounding stuff posted above.

Anyone know where I can get cheaper wire and audiophile grade receptacle? Do Need 12g wire (seems to be for DIY power chords rather than dedicated circuit)?