No subject

[Esterquest David F NPRI]

Brian--

I think you need to ask the question of just what hazards you wish to forestall.

If what you are trying to protect will not be harmed by a mere power interruption, then I don't perceive the need for uninterruptable power.

An isolation transformer is generally used for providing a DC block.  A classic case is a tech working on a "transformerless" piece of gearwith only two prongs on the supply plug, with the chassis exposed, and applying test instruments in which the chassis is truely grounded with a three-prong plug.  In this instance, the chassis of the gear being repaired could have a voltage on it (which would not matter in normal use because of non-conductive cabinet) which would be shorted by the ground of the o-scope.

There were once TV sets, (Muntz comes to mind as an example), which put 110 volts onto the anntenna depending which way the plug was inserted.  The protection offered by a isolation transformer on the power input was problematical because of capacitive coupling would still allow for a shock hazard to humans.  The correct repair was an air-core RF transformer at the   signal input to the TV.

I don't see that this is a consideration in your case beacause Heath, so far as I know, was diligent in providing a transformer to the power supply of its gear.

You need to ask yourself if your equipment would be damaged by low voltage.  If so, then you need power conditioning that will interrupt power in case of low voltage.  If you have some knowledge, you could rig up a relay with a control on the coil that would cause it to drop out when the voltage dropped to a pre-conceived level.  Electric utilities generally do not the the voltage drop below 102 volts in summer brown-outs unless they cut off power entirely.  The liability of burnt motors in refrigerators, freezers, and A/Cs is potentially large.

The only hazard I can indentify in your case is voltage spikes.  There are a number of remedies here.  First, you might consider putting an MOV protector on your entrance panel----use a UL-approved device available at your electric contractor jobber.  You might consider a self-regulating transformer--perhaps a Sola which uses a saturable core.  Get the kind that gives a quasi-sine wave as some gear will not tolerate the square-wave that the lesser Solas provide.  Your other choice is a Wanlass which is a parametric transformer.  This is expensive but it outputs a good waveform and gives good spike protection.

I don't know how this would go down with the V.P. in charge of interior decor in your house, but the ultimate isolation would be a industrial switch---the electrical box with a handle on the side that goes "clunk"-- right at your entertainment center.  If your gear is separated entirely from the power grid when it is not being used---or at least when you leave town---or when lightening flashes in the horizon---it will be better off than most anything else you could do.

In the instance of a direct lightning strike, there is essentially nothing that will be absolute safe.  Once lightning came in on the phone line and then into a table lamp-----after blowing its way through dry-wall---yeah, my wife and i sat straight up in bed on that one!  Live with the fact that you can do no more than improve your odds.

As far as wiring goes, you might consider using heavier gauge wire to supply your entertainment center.  You might consider supplying two or even three circuits dedicated to your center.  You might consider using industrial-grade devices (wall sockets) which have less resistance.  (I think of a buddy whose stereo modulated the light bulbs in the room.)

Oh, one final thing:  Don't neglect your antenna or cable service when you consider lightning.

Hope this helps,

David


-----Original Message-----
From: Brian Conrad [mailto:beijconrad at GDINET.COM]
Sent: Wednesday, May 23, 2001 7:48 PM
To: HEATH at LISTSERV.TEMPE.GOV
Subject:


I was wondering if we could start a discussion on a NEW subject.
    I'm in the process of designing a new house - and I want to Protect/Condition the Power feeding My Heath
Audio - and Home Theater equipment. I want to start with a sub-Panel just feeding that equipment - But should I feed the power into a UPS - and then through an isolation transformer. or???
    Any Ideas/Recommendations on how You Protect and feed Your Equipment??
                                        Thanks  -  Brian  [Heath Audio]

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