Here is a link to the official explanation. It's a PDF, you need a reader to view.
http://www.ul.com/regulators/ReceptacleGrades_Kurten_JF2005.pdf
http://www.ul.com/regulators/ReceptacleGrades_Kurten_JF2005.pdf
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Thank you Albert for the detailed info. Reading it I notice that "Hospital Grade" means it has certain characteristics, like tolerance of "Abrupt removal" (yank the wire) which are probably important in the Hospital environment, but which IMHO are not relevant to the outlets we use for audio systems. They would be a good idea for some other plugs in my house (the ones that the vacuum cleaner gets plugged into). |
It's nice for those of us that have heavy weight power cables, because they're held more securely. Hospital grade sockets perform this function well because they're designed for health care environment where uninterrupted power is important. There are also several commercial grade sockets that have excellent grip. Almost any brand "premium socket" is superior to the .49 cent ones used in construction of new homes and apartments. Dozens of companies provide premium aftermarket outlets, and like power cables, some audiophiles use them and some do not. |
Albertporter...Of course a tight grip would be important for a heavy PC, but the "Hospital Grade" designation does not seem to offer this feature any better than commercial grade (as you note). When I was involved with heavy (64-pin) connectors and cables we usually provided for strain relief support of the cables, even though the connectors were a locking type. It seems to me that, for some of the audio equipment power cables I have seen, reliance on the simple 3-pin outlet would be unacceptable no matter how tight the grip. There are readily-available 3-pin plugs (and sockets) that twist to lock. These are, I think, used for higher amperage 220 volt applications, and I often wonder why audiophiles have not discovered them. |
">>Reading it I notice that "Hospital Grade" means it has certain characteristics, like tolerance of "Abrupt removal" (yank the wire) which are probably important in the Hospital environment, but which IMHO are not relevant to the outlets we use for audio systems."<< [Eldartford] =========== Probably true. Different Hospitals may have differering standards for what they require for the contact pressure of a hospital grade receptacle. One hospital that I know of in particular in my city, their Bio-Med department, requires a minimum of 4 ounces of resistance when removing a plug from an electrical outlet. By the way the only two manufactures of hospital grade outlets the hospital specs in any new installations or replacements is Hubbell and Leviton. Key word resistance, contact pressure. ============== On another forum, Audio Asylum, a non hospital grade receptacle that is spoken of very highly is the Hubbell 5362 (5-20R) receptacle. A non plated brass contacts with a brass non plated receptacle supporting yoke, strap. Another recommended Hubbell receptacle is the HBL8300H (5-20R) receptacle. Again non plated brass contacts and a brass non plated supporting yoke. Buy the way this is the receptacle that Albert Porter uses in his Cryoed "Porter Ports". I presently am using the Leviton 20 amp hosp grade outlets which I think sound very good. The Leviton outlet uses non plated brass contacts, but unlike the Hubbell outlets I have described where the Hubbell uses a brass supporting yoke, the Leviton uses a steel supporting yoke. Magnetic material.... I have read many negative comments in regards to a steel supporting yoke, strap. So now I will buy the HBL8300H and the 5362 Hubbell recepts and find out for myself. What is the rave out there now, the best outlet? Many talk of the Oyaide SWO-XXX http://www.audioexcellenceaz.com/oyaideoutlets.htm |
There are readily-available 3-pin plugs (and sockets) that twist to lock.I use exactly that for my 240 volt connections and have for several years. However, some aftermarket power cords void warranty if modifications are made, and if wired improperly could cause damage to your equipment or your home. The 120 Volt Hospital grade sockets I provided a link to as well as other aftermarket high quality outlets conform to roughly the same size specifications (fit in existing box) and wire identically to common household outlets. In other words, a heavier, higher grade product in the wall that requires no modifications to existing male plugs. |
>>"Jea48, please find the technical data to back up your statement. Dont just disagree , prove your statement"<< [Mapleleafs3] >>>>>>>>>> This may be on a grand scale but you will get the idea... http://205.243.100.155/frames/longarc.htm ======== |
One of the tests is the drop test. It goes something like this. The outlet is mounted 50 inches from the floor. A 3 foot cord with a hospital grade male cord cap and a 8 pound weight at the end of the cord is plugged into the hospital grade outlet. The weight is dropped straight down at the outlet height. The cord must stay plugged in and no damage done to the outlet to pass the test for hospital grade. |
Mapleleafs3 and Jea48 It should be noted that a loose electrical contact can and will heat up. This is where the fire hazard exists. The extra resistance will create hotter temperatures. They will also spark. So, no loose contacts so that sensitive equipment does not loose power (so many busy feet in a hospital) but also to avoid hotter than normal temperatures at the plug and in the receptacle. |
Thank you all for the replies, especially Albertporter - that pdf seemed to be exactly what I was looking for. However, upon reading that pdf, it seems that the primary differences are "grounding reliability, assembly integrity, strength and durability." None of which seem to me to be capable of affecting the sound of our equipment... or am I missing something? And I don't think that requiring "X" amount of force to remove a plug from an outlet makes the outlet superior for our purposes although a snug fit is obviously necessary. Does the "grounding reliability, assembly integrity" somehow make the outlets less susceptible to rfi noise and the like? Or is the audiophile key here the fact that these recepticles come in a preferred choice of metal make-up, e.g. brass w/o a nickle finish? So to summarize, what is it about these hospital grade differences that make them sound better??? |
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Jea48, I have heard of that device but I have never used it. I remember hearing that the device is connected to the ground pin only. It has to stay connected to a hospital grade outlet with 4 oz of pressure for a certain amount of time. I concur with your statement about removing a plug under a load from an outlet will cause an arc, regardless of the type of outlet. |
All outlets get looser as stuff is plugged in and out many times. A "pull test" is a practical way for the maintenance staff to determine how far the degradation has gone, and when it is time to replace the outlet. Wearout should not be a concern for audio applications since it does not involve frequent plug/unplug cycles. |
Jea48, can you please explain the benefit of "Contact Pressure"? I mean I know what it means, but are you saying that the better contact pressure of hospital grade outlets is desireable because of an enhanced electrical flow, or as some others seem to be suggesting, that the benefits are in the power chord not being pulled out too easily/accidentally??? Thanks, Ray |
Hospital grade outlets cannot overcome the tenacity of human folly. In South Africa, a hospital noted that patients in a particular bed in the ICU unit were found dead on Saturday morning on a regular basis. Suspecting a serial killer, investigators set up a surveillance camera. What it caught was a cleaning person coming in on Friday night. That person would unplug the respirator for that killer bed, plug in the vacuum cleaner, clean the room, then plug the respirator back in when he/she was done. |
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>>"Jea48, can you please explain the benefit of "Contact Pressure"?'<< >>>>>>>>> Here is some reading material for you. I am not promoting their product. http://stereophile.com/artdudleylistening/1103listening/ ============== You will notice in one of my posts I mentioned the Hubbell 5362, 20 amp outlet. I stopped by an electrical supply house tonight and picked up a couple of them. I was given a couple of the HBL8300 (nickel plated) 20 amp hosp grade outlets a while back. Never hooked them up after reading the bad reviews about them. For what it is worth I grabbed an extra PC I had laying around. I plugged the PC into one of the new 5362 outles and pulled it out feeling the the pressure of the contacts. Pushing in, pulling out. LOL, LOL...Can't believe I just said that! Next I tried The HBL8300. Imho the plug pushed in harder and pulled out harder. Is it due stricly to the Hot and Neutral contacts or is it due to the hosp grade ground connector??? ============== 01-30-06: Nerspellsner >>"Jea48, I have heard of that device but I have never used it. I remember hearing that the device is connected to the ground pin only. It has to stay connected to a hospital grade outlet with 4 oz of pressure for a certain amount of time."<< >>>>>>>>> After reading your post now that I think about it your are right it tests the ground receptacle of the outlet. I still like your testing method though. Imo only the Hubbell would survive, that is the HBL8200 and the HBL8300 hosp grade. ==== Jim |
Follow Up ++++++ "Next I tried The HBL8300. Imho the plug pushed in harder and pulled out harder. Is it due strictly to the Hot and Neutral contacts or is it due to the hosp grade ground connector???" ============== I did not want to leave the impression that the difference in tightness was due to the ground prong, it was not. I did try the test with a two wire cord and plug also.... >>>>>>>>>>>> >>"It means that someone has been clever enough to charge audiopiles who don't know anything about electricity a ton of money for -- wire.'<< [Bojack] >>>>>>>>> Bojack did read page 2 of the link I provided. http://stereophile.com/artdudleylistening/1103listening/index1.html |
Nerspellsner, I found a few errors in the Stereophile article. Besides that one you mentioned, The Hubbell HBL8300I receptacle. The I does not stand for plated, it stands for ivory. The picture of the two outlets, the top outlet sure looks to me to be the non nickel plated Hubbell HBL8300H, not the plated HBL8300. On the whole they did a pretty good job with the article for being laymen when it comes to electrical. Jim |
Studioray, I installed the Hubbell 5362 outlets for my ARC VT50 power amp and my Sonic Frontiers Line One preamp. Plugged things back in and turned the system on. Right off I could hear a difference. As I have read from others the bass was deeper. I first started with a Female vocal and did notice siblence sounds, the dreaded sss sss. I was hoping that was due to the fact the outlets were new and needed some break-in time. For lack of anything else I could think of to plug into the two outlets and let them cook for about 24 hours, I used two table lamps with 3 way bulbs. I turned the switches on the lamps to the highest wattage. Tonight I unplugged the lamps and plugged back in the equipment. Turned things on, let the system warm up for about a half hour and sat down for a listen. Siblence were gone. The bass from my system is deeper. The sound is darker, sound stage more layered. The Hubbell 5362 beats the Leviton Hospital Grade outlets hands down. It has to be that steel supporting yoke,strap. Or maybe the Hubbell is more dampened. I still have to change the outlet for the CDP, one thing at a time. And then there is the outlet cover plates. I am presently using the Leviton magnetic Stainless steel plates with a nylon trim screw. I know Nerspellsner, I am guilty, busted! This weekend I will experiment with the nylon outlet cover plates. Also I am Still going to try the Hubbell 8300H Hosp Grade duplex outlets. I just need to make up my mind whether I am going to buy the Cyroed outlets. Studioray, You did not mention in your thread if you have dedicated audio branch circuits. |
Hi Jae48, yes I do have one dedicated line coming from the main circuit breaker box at present. Right now it only contains just a consumer grade receptacle - meaning one dual outlet. I have an Arrow Hart 8200 on the way to me, which I've read some good things about, and so that will replace the outlet that's there. Although I've been an Audiogon member for awhile, I've only recently stumbled upon the whole clean power/dedicated line thingy, and as of right now cannot even tell you which components are plugged into the dedicated line. I figure when the AH8200 comes, I'll either 1) Run only the amp and pre-amp from the dedicated line and run the PC (which is my CD player) and everything else from a common house line, or 2) Do the "split everything off of one outlet" approach and see how that sounds. In my case, "everything else" is a lot of audio recording gear as my main listening place is also my workplace, which is a recording studio. So I've often got at least a dozen things on at one time that never get shut off and remain on constantly: outboard effects processors, microphone preamps, mixing boards, power conditioners, etc.. I know that this is not the audiophile best case scenario, but I spend only enough time at home to sleep, and so my studio has become my listening room. Cheers, Ray |
Jea48, I find it interesting to know that the "pull pressure" of hospital grade recepticles is tested for the hospital environment. I didn't know that and I work in a hospital. However, I'm sure our maintenance personnel are aware of that. One thing to note, at least in our hospital, is that the red recepticles are the only recepticles that are used for normal power and power from the back-up generators. The red recepticles are used for computers, ventilators, etc. Also, it takes between 10 to 15 seconds for the generators to come on line, so there is a slight interruption in power, except for anything also plugged into a battery supply. Our ventilators have a builtin backup battery supply of about 30 minutes. Thanks for the education! |
Facts: Hospital grade plugs provide more robust grounding than a regular plug. They are built to a better quality. Grounding and isolation transformers are very important to medical equipment. The 15 and 20 amp (three prong plugs) are not suitable for use around flammable materials. There are explosion proof 15 and 20 amp hospital grade plugs that look totally different than a regular plug. You have to insert these turn them a quarter of a turn. These are usually found in older operating rooms. No one at a hospital checks the force required to remove a plug. (My boss is going to laugh when he hears that.) I am a biomed tech and I work on and test medical equipment. |
Switching to a duplex outlet without nickel plating on the internal brass components is not a bad thing. Using some contact cleaner with it is even better. My house, which is only a few years old has the newer, designer outlets and switches. These things are junk inside but cost more, go figure. I recommend the hospital grade outlet just for a tighter, more secure connection. |
Quote Chapter 4 of NFPA 99 (2005 edition) addresses the electrical systems in health care facilities. It requires the electrical installation to be in accordance with NFPA 70, National Electrical Code (4.3.2.1). Following are some of the commonly referenced requirements: Leviton Hospital grade plug and receptacle testing. Hubbell white paper for testing of hospital grade receptacles used in Canada. Cheap basic Receptacle tension tester. |
I just wanted to add, in addition to the robustness of the connection and overall build quality, hospital grade receptacles are built to be wired with a redundant ground conductor (required by NEC Article 517, Health Care Facilities). It will NOT do this on it's own however. You need to wire back to the panel with hospital grade AC (aka hospital grade BX) or hospital grade MC (not as common). With the AC/BX cable you have the metal armor w/ drain wire as your first ground path (which is how regular AC/BX works) and an additional insulated conductor for a second redundant ground (unique to hospital grade BX). With hospital grade MC (uncommon), you have two insulated grounding conductors (instead of one, which regular MC has). Note the metal armor on MC cable is not listed as a ground. |