Bulb Out Indicator circuit

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1) The type of wall switches with a neon lamp which glows when the switch is OFF (handy for finding the switch at night) can also be used to "test" to see if there is a load on the other end.
2) It is downright silly to use a delicate and limited life lamp for an HEATER. Do it right the first time and BUY and install "pump house heaters" which automatically come on when the temperature gets below 40F or so.
The best way of protecting pipes is with the special heat tape that turns itself off as it gets warm.
But LAMPS?
You have to be kidding!
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John Gilmer wrote:

Lamps have been used for decades to mark and heat insulated fire extinguisher cabinets mounted outdoors. The marker light is mounted in the bottom of the cabinet and is daylight and thermostatically controlled. I think it is a simple and elegant solution to the problem of keeping the extinguisher useable and marking it's location. If it works I see nothing wrong with it. -- Tom H
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Tom Horne wrote:

<snip>
I think I see John's point there, light bulbs *do* tend to burn out more frequently than low temperature heaters do, and *regular* bulbs don't stand up to vibration or frequent switching on too well either.
But it's the OP's nickel and problem, and if he's willing to monitor the indicators faithfully, so who are we to tell him what to use?
I do hope my seriesed 6 volt bulb idea proves workable though, it seems elegantly simple.
******************************************************************
Do you happen to know if those outdoor fire extinguisher cabinets use multiple bulbs for redundancy?
I bet the newer ones are going to use resistance heaters and LED lamps, following the way the traffic light industry has shifted.
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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Jeff Wisnia wrote: snip

The ones I serviced when I was doing fire equipment work had two bulbs and the tamper alarm in the top of the cabinet would emit short alarm bursts if the interior of the cabinet got too cold, i.e. <40 Fahrenheit. -- Tom H
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Tom Horne wrote:

I thought outdoor fire extinguishers were filled with calcium chloride solution instead of water in the winter. That stuff generally doesn't freeze.
Bob
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zxcvbob wrote:

Foam extinguishers of the now obsolete chemical variety had to be protected from freezing and they were the only appropriate protection then available for some hazards. I have not heard of an antifreeze solution that can be used with modern foam extinguishers either. In some environments it is necessary to keep the extinguisher shell warm enough to avoid super cooled metal contact injuries to users. An example of such an environment is a cold storage warehouse. -- Tom H
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Tom Horne wrote:
<snipped>
In

I guess, but it seems like it's wasting to have to dump heat into an environment like that. If it wuz my dollars, I'd try and find a material with low thermal conductivity that they could cover the shell with to avoid that problem.
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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Jeff Wisnia wrote:

Jeff You cannot apply any material directly to an extinguisher without voiding it's laboratory listing. Once it leaves the factory you cannot modify it in any way. That is why an insulated and heated cabinet makes sense in that application. There being no need for a marker light in a lighted warehouse environment you would probably use a different heating method for the cabinet than the one I was talking about earlier were the waste heat from the marker light is used to keep the extinguisher cabinet interior above freezing. -- Tom H
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Tom Horne wrote:

You learned me sumpin' there Tom!
So much for my parsimonious idea.
The Devil is always in the details, isn't he?
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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John Gilmer wrote:

Not if there's much cable conected between the switch and the lamp John.
The capacitance between the black wire and the neutral (and ground) wires will let enough current flow to light the neon lamp.
It's the same effect which causes neophytes using digital meters to report that there's voltage on wires which should be considered "dead". There *is* a voltage there, or the meter wouldn't read anything, but it's being fed through such a high impedance (capacitive reactance) that no useful load can be powered from it. (Except maybe that neon bulb we're talking about here.}
Try it yourself!
Jeff
<snipped>
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near the lamp you want to monitor; cap the other end of the fiber with a lens. When the light is on the lens will glow.
A Google search will point to lots of resources.
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Spammers are VERMIN. Please kill them all.
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