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Re: [TCML] NTC Thermistor surge suppression

Hi Dave,

Well, truth be told, I think if, God forbid, you, me, or any die hard coiler suffers a fire loss of electrical origin, there are probably numerous things that most of us do or have done to accommodate our insatiable desire for high voltage that probably aren't actually "up to code". A prime example is operation of an OIL-FILLED transformer inside of a permanent dwelling, since the gallons of dielectric oil could certainly pose a significant fuel load to complicate an active and uncontrolled fire situation, not to mention the obvious electrocution hazard. That's why electrically live oil-filled transformers are not allowed to be permanently installed inside of a permanent dwelling structure - they must be the dry type. 

Although we must each take responsibility for and accept the consequences our own actions, I think it's pretty safe to assume that the average subscriber to this forum is at least somewhat more electrically literate than the average person and many of us can use our discretion to "bend the rules" within reason, while maintaining relative safety. Like I said, I took precaution to insure that there was adequate clearance around the thermistor away from other wires and their insulation. I don't think 5 to 10 watts, at the most, of intermittent heat dissipation is going to significantly heat up the surrounding air space inside the breaker box to the point of having to consider the possibility of ignition of combustibles, with no direct surface to surface contact and a minimum of ~2" clearance around the thermistor body that should never exceed 220C. Bottom line is if I did have a fire of "electrical origin", I'm thinking that with one glance of the inside of
 my shop "man cave" work/play area from the adjuster, that thermistor in the service breaker panel would probably be the least of my worries! ;^o 

Keep it safe,
David Rieben

On Sunday, January 11, 2015 3:12 PM, Dave Halliday <dh@xxxxxxxxxxxxxx> wrote:

Is this to code?

If there is an electrical fire, will your insurance company honor your claim
if they find any non-code items in your breaker panel.

I would do an extension cord with a box with the thermistor wired into it.


> -----Original Message-----
> From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of 
> David Rieben
> Sent: Sunday, January 11, 2015 11:44
> To: Tesla Coil Mailing List; Gary Lau
> Subject: [TCML] NTC Thermistor surge suppression
> Hi Gary,
> Just wanted to thank you for providing me the eBay link to 
> those 1 ohm, 30 amp surge suppression thermistors. I actually 
> opened my breaker box and installed one in series with the 20 
> amp breaker that feeds my outlet that I run my variacs off 
> of, making sure to provided clearance of the thermistor body 
> from any wiring in the breaker box to allow for the surface 
> heating of the thermistor to ~200 - 220C. Virtually 
> eliminates breaker tripping with variac power ups.
> Thanks again,
> David
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