[Top] [All Lists]

Re: [TowerTalk] whole house surge protectors

To: WA3GIN <>
Subject: Re: [TowerTalk] whole house surge protectors
From: Jim Lux <>
Date: Tue, 15 Apr 2008 20:43:49 -0700
List-post: <">>
WA3GIN wrote:
> Whole house protects the big gear like AC compressors, HVAC blowers, for 
> sensitive electronic gear like your HDTV, Ham Radio, PC you are required 
> to installed end-point surge protectors.

Not really.. A entrance panel transient suppressor doesn't know what 
kind of load there is. And most things like consumer PC power supplies 
can actually take a pretty good sized transient because they are 
basically a CLC filter feeding a doubler or bridge rectifier into a 
capacitor input filter to make a 300-400V DC bus, which then feeds the 
PWM circuit for the power supply.  Likewise your HDTV which almost 
certainly has a wide input switcher.  Your ham gear, on the other hand, 
could be rock solid or hideously sensitive, depending on when it was 
built and what the designer intended.

There's a fair amount of research out there that shows that most 
consumer gear can take 1000V transients without much trouble, as long as 
the energy is limited.  Obviously, there are exceptions. (and ham gear, 
in general, might be in that exception category.. price sensitive 
buyers, small production runs of stuff that's a clever idea by a ham 
works pretty well, but probably hasn't gone through anywhere near the 
sort of design and testing process that a piece of consumer gear that's 
looking for a UL sticker has done, and probably doesn't get hipot 
tested, etc.)

> I put all the expensive stuff on UPS which provided further protection, 
> i.e. low and high voltage protection as well as spike and surge...

Most inexpensive UPSes (i.e. non static-inverter type) don't do a very 
job on this.  They essentially have a solid state (or mechanical) relay 
that transfers from line to inverter output in less than 8 milliseconds 
(1/2 cycle), which most equipment that's connected to a UPS can handle. 
  The over/undervoltage trip is deliberately set fairly slow 
(millisecond sort of timescale), so that momentary transients don't 
cause nuisance transfers back and forth.

While you're on the straight through path with a UPS, you're just 
relying on whatever protection the UPS manufacturer put in, which in a 
cost sensitive market (e.g. the $50 UPS on sale at Best Buy) is going to 
be not much.. perhaps a couple MOVs.  Certainly not anything like a L or 
Pi network or a gas tube clamp.

Now, with a static inverter type UPS, where the path is always through 
the rectifier to the DC bus and then back to AC, yes, you get good 
transient suppression. But most folks don't use them because they are 
noisy and less efficient.  Likewise motor-generator sets.

I burned out plenty of stuff on movie and TV location sets where you are 
running off a generator with lots of ugly loads to make noise before I 
wised up on the transient suppression ability (or lack thereof) of 
UPSes. & I also learned that you cannot reliably extend the run time of 
a cheap UPS by just adding more batteries.  They carefully design the 
thermal properties so that the inverter transistor temperature is 
limited by running out of battery power before they cook.  Saves money 
on fans and heatsinks and bigger transistors.  There's a reason why the 
static inverter UPSes are (a lot) more expensive.

> Plenty of good gear available commercially.

Yes, catering to commercial & industrial markets,  but not a heck of a 
lot is available in "consumer" grade.


TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>