I have installed two baseboard electric baseboard heaters in my
basement. One is 1000W and the other is a 500 W unit. They're both on
the same circuit breaker and joined at a junction box near the circuit
I'd like to add an indicator light (preferably on the first level) to
let me know if they are on. I think I need some kind of light to detect
I'm looking for a cost effective way to let me know if either (or both)
heaters are drawing current.
If you want to know if they are drawing current, you need something more
complicated than a pilot light, but if you want to know if current is being
supplied to the element, a 240 volt pilot light in parallel with the element
will do the job
Couple of ways to skin that one.
One I've used is a toroid coil.
Get a wound toroid inductor which has a big enough
center opening left to pass your Line conductor thru.
The inductor winding then acts as the secondary of a current
transformer. Connect the secondary to an LED indicator.
(Put a diode in series.)
Takes some experimenting. You only have about 2 Amps
to work with on the Line side.
(If you're conerned about an open-ckt secondary producing
high voltage, wire a 100 ohm resistor across the winding.)
You could also rewind a small AC relay with heavy wire
and put the relay coil in series with the heater ckt.
Much more work and experimenting.
Inductor might look like:
I googled current sensing relay. Here is one example you could use. You
could use a door bell or furnace low voltage transformer to power the light.
Wire a 120V lamp from one hot to neutral. (assuming you have one) You
could go to ground, but I don't think that is a really good idea.
Wire a diode in series, that will give you 110 (likely 120) .
It's not a good idea. You NEVER deliberately shove current down the
ground wire. Trips GFCIs (if involved), and continuous leakage current
can corrode ground connections. If the ground ever disconnects, everything
grounded downstream of the break goes live. Depending on the bulb,
it may be a lethal hazard.
No. It'll give you 240V halfwave. Not the same thing. This is likely
to be quite rough on incandescant bulbs, and I wouldn't expect it to
survive for more than a few moments.
[Obviously a typo, "across hot and hot".]
Ideal solution: Most neon bulb "assemblies" will work equally well
at both 120V and 240V.
These are most often seen as "neon AC testers" - plastic case enclosing
a neon bulb, a resistor, and two test leads. By running the test leads
across, say, a hot and ground, you can tell whether the circuit is live.
These devices usually work with anywhere from 90V to 600V. You may already
have one in your tool box.
A neon bulb itself is a glass object several times larger than a grain of rice.
1/2" long or less.
You can buy small "panel neons" at Radio Shack and other suppliers. Essentially
a neon bulb in a round (or square) package that directly insert into a hole
drilled in an enclosure of some sort. You may be able to find one that fits
in a cable outlet cover to make things neat. If you want to do that, take
an outlet cover with you when you buy the neon.
This is not to be confused with "panel LEDs" (which are much trickier to
drive off line voltage) or "panel incandescent bulbs" (which are very
voltage specific, and 240V panel bulbs are rather hard to find).
Neons are cheap (a suitable panel neon should cost considerably less than
$10. Often < $4) and draw very little power, and are usually what's used in
WARNING! Neon bulbs are "breakover" devices. Once the voltage across their
leads exceed 90V or so, they "breakover" and light up. This means that
they need to be current-limited or they fry. Neon AC testers have a
limiting resistor built in. Many panel neons do too. Make _sure_ that the one
you buy already has such a resistor in it, or you'll need to supply
your own (I seem to recall a suitable value is around 100K ohms, but
don't quote me). If the package gives a voltage rating, and says it
doesn't need/already has a resistor, you won't have to add one. It's
better to not have to add one - I don't like the idea of haywired
resistors on 240V.
One other caveat: Most panel neons have quite small (usually solder)
terminals or very thin wire leads. They're designed for 20ga wire or some
such. Connecting 14 or 12ga wire to that would usually require soldering
(which is difficult to do with such a gross size mismatch), and connecting
to such stiff conductors may break the terminals or subject to fracturing
the tiny solder joint. Certainly it'll be fragile.
I recommend using short (say 4") pigtails of stranded appliance (_not_
zipcord) single conductor wire (say 16-18ga) soldered to the neon, bare
wire/terminal connection covered in heat shrink tubing, and the other
ends of the pigtail wirenutted to the house wire.
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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