Outdoor power-on light..(not power available indicator)?

Old 02-03-14, 06:44 AM
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Outdoor power-on light..(not power available indicator)?

I need to be to tell if an outdoor animal water tank deicer is actually drawing power. I have outdoor extension cords with 'power-on' indicator lights which
indicate that power is available.
But I need to know if the appliance itself is drawing power. Are there 'add-on' lighted plugs that glow to indicate that power is actually flowing through them?
Old 02-03-14, 07:33 AM
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Just feel it, is it getting warm?
Old 02-03-14, 09:39 AM
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I don't know of any device like you mention. Something like a Kill-A-Wall meter is the only thing commonly available to telly you that current is actually flowing to a device.
Old 02-03-14, 10:19 AM
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Are you trying to determine if the unit is working? Or do you want to know when it's working? A VOM meter can tell if it's working if you can get to the contacts with the probes.
Old 02-03-14, 10:40 AM
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A CT, current sensing switch might work for you. They are typically used to turn on a vacuum dust collector system when a power saw is used or a humidifier on a furnace. You could just connect it to a light.

You could probably also use a millivolt meter and a few turns insulated wire around one of the insulated conductors in the receptacle box.
Old 02-03-14, 04:56 PM
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Why a power-on light...

I have horses and their water tank is outdoors. To keep the water liquid, I use an immersion tank water heater. When it is -20F outside, it is convenient to look out at the corral at night and see the power cord light on...knowing there is power
going to the heater. Recently, however the heater coil died...but the cord lite remained lit, so I assumed that the tank had been heated, but it had frozen up nearly completely. I have used my Kill-O-Watt meter to check on whether or not the heater thermostat was working.
But again, it is not too nice to have to be out in -40F wind chill to double check power consumption.
I was hoping that someone made an add-on 'power-on' lite that glowed only when an attached appliance was actually working.
Old 02-11-14, 05:27 AM
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My Kill-O-Watt meter will tell me if the water tank heater is actually working. However, when it is -20F outside with a -55F wind chill it is not very convenient to be outside trying to check on the heater. Most appliances have an 'on' lite which glows when the appliance is actually on (for example, the lites on your stove). I have been trying to find an extension cord that actually has an 'on' lite that indicates that an attached electric device is actually drawing power, not that there is current available in the cord.
Old 02-11-14, 10:21 AM
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Current Monitor

As mentioned by Ray, a CT system may work for you depending where you install the current coil and relay. Time Mark, makes current monitoring relays and CT's. One issue would be temperature at the relay, as you can see -20 deg is the minimum. The CT detects the current flow and the relay closes your circuit for a small indication light. Here is a link: Time Mark Corporation

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Old 02-11-14, 12:38 PM
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Was about to mention a CT relay, but it has already been covered.

An old trick taught by my old man and grandfather was to pull out the Edison fuse in the fuse box feeding a Ritchie water and replace it with a light bulb when setting the thermostat. Nice visual indication that the heater was on or off.
Old 02-11-14, 04:29 PM
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Expanding on the idea of the previous post, you could construct a junction box with a test switch (regular light switch) and a test light. Put this indoors, for example next to the breaker panel and in the branch circuit going out to the heater. The light wires or leads are connected "across the switch" that is, one to each switch terminal.

Flip the switch to the "test" (the off) position and the light comes on if the heating element is in operation. This cools the heater for the moment since the light is limiting the current while using the continuity of the heating element to light up with. Flip the switch back to the "normal" (the on) position after doing the test.

The light could be anything from an incandescent (specifically not neon or LED) 120 volt pilot light sold at Radio Shack to a porcelain light fixture on a second junction box next to the switch box.

If the light does not come on then you know there is a problem with the heater outside.

Requires that the heater be the only load on the circuit downstream of the test box.

A "lighted switch" with no separate light would do the same thing but could give a false on reading due to phantom voltage since the switch handle light draws such a small amount of current.
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Old 02-11-14, 06:18 PM
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You want a current-operated switch. Some models are just for a DC load and others are for an AC load. I would use LED indicators for longest life and lowest power consumption. Here are a few current-operated switches.



current operated switch | eBay

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