SW6DE Hot Water Heater Operation

[TM Pilot]

Originally Posted by Bill

Instead, I think you want the light connected from the cold side of the switch (right side in the diagram) to neutral.
Bill

Bill,

1. The red indicator light has two 22 gauge wires. Are you saying to connect one wire to the black wire between the switch and hi-limit/T'Stat and the second wire to the white neutral wire between the electric element and electrical panel (see red line in picture#1)? Just don't want to get into a situation where the hi-limit/T'Stat is bypassed and the electric element is continuously energized (back fed) or I cause a short. Should I install a diode between the electric element and the indicator light?

2. Here are the specs for the Radio Shack red neon lamp catalog #: 2720712

Neon Lamp Assembly Including Bulb
(272-0712) Specifications Faxback Doc. # 38094

Voltage: .................................................. 120 VAC, 60 Hz
Typical Current: ........................................... 1.5 milli amp
Maximum Current: ............................................. 2 milli amp

NOTE: Not recommended to apply 2 milli amp or the life of the neon is
shortened by 1/3.

Maximum Current Tolerance: ................................. 0.5 milli amp
Life Expectancy: ..................................... Approx. 20,000 Hrs.
Color: .................................................. ............. Red
Mounting Hole Size: ............................................ 9/32 Inch
Leads............................................. ..................... 4.92", 22 ga.
Brightness (MSCP)............................................ ... 150 LUX

Specifications are typical; individual units might vary. Specifications are
subject to change and improvement without notice.
------------------------------------------------------------------

The wire between the switch and the hi-limit thermostat is 14 gauge. The two wires for the red indicator light are 22 gauge. When the 1440 watt electric element is on that's 12 amps in the circuit. Can a 22 gauge wire handle 12 amps? If the indicator light has a 2 milli amp limit wouldn't it fail if directly connected to a 12 amp circuit? Do I need a resistor or is one built into the neon light (I would assume it's built in - seems that way when I zoom into picture #2)? In your mod you linked to earlier, you had a green indicator light wired in. I didn't see how that light was wired in your schematic. How did you do it?

Am I overthinking this (diodes; resistors) or is hooking up an indicator light really this complicated/problematic? Knowing if the resistor was built in to the neon light would answer a lot of questions.

Bruce

[Bill]

Originally Posted by TM Pilot

Bill,

1. The red indicator light has two 22 gauge wires. Are you saying to connect one wire to the black wire between the switch and hi-limit/T'Stat and the second wire to the white neutral wire between the electric element and electrical panel (see red line in picture#1)?

Yes, that is exactly right.

2. Here are the specs for the Radio Shack red neon lamp catalog #: 2720712

Radio Shack specs have always been close to meaningless, but they have really raised the meaningless bar here. I'm not sure where you are seeing these words - they are not in the description or specs listed for the lamp.

The wire between the switch and the hi-limit thermostat is 14 gauge. The two wires for the red indicator light are 22 gauge. When the 1440 watt electric element is on that's 12 amps in the circuit. Can a 22 gauge wire handle 12 amps?

The 12-amp current flows through the heavy (#14) wire. The only current through the lightweight (#22) wire is the current that operates the lamp - about 1 mA.

Do I need a resistor or is one built into the neon light?

The resistor is built into the assembly. That is what makes it a 120-volt light, as opposed to 240-volt, for instance, which would have a different value resistor.

In your mod you linked to earlier, you had a green indicator light wired in. I didn't see how that light was wired in your schematic. How did you do it?

I think you are referring to the diagram for the Improved Water Heater Switch. In that diagram, the current to light the lamp flows from the Hot (black) wire, down through the left set of relay contacts, then down through the "Push to Turn Off Switch", and through the light to the neutral (white) wire.

Am I overthinking this?

Yes - it is much easier than you are thinking.

Bill

[Bill]

TM Pilot -

Feel free to skip this explanation. Sometimes I get carried away, but you seem interested, so I will plow ahead.

Electricity seems a lot more complicated than it really is, but that's mostly because of the strange words. Electricians make sure to use the strange words, and that's why they can charge big bucks. (OK, now who have I offended?)

It is sometimes helpful to note that the flow of electricity in wires is very similar to the flow of water in pipes. In each case, we are dealing with a FLOW. In plumbing, flow is measured in gallons per minute. In electricity, flow is measured in amps (or milliamps). Same thing.

In the case of your water heater diagram, TM Pilot, let's think of it this way.

At the top left of the diagram, there is a water supply. The supply pipe is labelled Black (Hot), and it is a BIG pipe - size #14. The amount of water available from this pipe is large, but you can take a lot of water or a little water or however much you want. The amount of water you take is determined by whatever you hook up downstream. We'll get there in a minute.

As you follow the water flow through the big pipe, you first come to a Switch. This is a shutoff valve that you operate by hand. You can completely stop the flow of water here. If the switch is set to let the water to pass (in other words, ON), then the next thing you encounter is a High Limit Switch. This is another shutoff valve, just like the first one, except that it operates automatically under emergency conditions. Then you get to a Thermostat Switch. Again, this is a shutoff valve that operates automatically, turning on and off based on some condition downstream.

So now you get to the Heating Element. Think of this as a cap on the pipe, with a hole drilled in the cap. When all of the switches are ON, then water flows out of the hole, and the amount that flows depends on how big the hole is. In the case of this appliance, the hole is big and a lot of water can flow through it. Where does the water go? Down the drain. The drain is labelled Neutral (white).

OK, so at the left side of the diagram we have a big pipe (size #14) that can supply a LOT of water. The pipe comes from the left side of the diagram, goes through the Switches (valves) to the Heating Element, where a LOT of water spurts out. In other words, a lot of current flows through the Heating Element.

Now let's go back to the beginning of that big pipe, and attach a second, much smaller pipe. And let's attach it just beyond the Switch, but before the High Limit Switch and the Thermostat Switch. This smaller pipe is size #22. At the end of this small pipe is the Light, which is represented by a cap with a hole drilled in it. The hole is very small, so even when lots of water is available, only a trickle of water actually comes through. Where does this water go? Again, down the drain, which is still labelled Neutral.

Conclusion 1. Whenever the Switch is ON, water will come out of the hole at the end of tiny pipe - in other words, the light is ON. It doesn't matter whether the High Limit Switch and Thermostat Switch are ON or OFF.

Conclusion 2. When we are looking at the amount of water that flows through the small #22 pipe, do we have to be concerned with the amount of water that is flowing through the big #14 pipe? No. They are independent.

---------------------------

Let me apologize in advance to anyone who feels that this little lecture is way off course. I agree. Perhaps it shouldn't be here, and I won't take issue with anyone who feels that. And I will be glad to take it down if requested.

Bill

[TM Pilot]

Thanks for both posts, Bill. Very helpful. I've only installed 12vdc indicator lights in vehicles - never 120vac indicator lights using neon gas. Just trying to anticipate and avoid any problems. Sound like this should be as simple as plug & play.

As far as the specs on the Radio Shack red neon lamp catalog #: 2720712, I got them from a picture of the back of the packaging and this link: http://support.radioshack.com/suppor...oc38/38094.htm

Indicator light should arrive Monday. With the holiday next weekend, will problem install in a couple of weeks. Will update with pictures then.

Thanks again.

Bruce

[TM Pilot]

Project complete! Water Heater electric element's new red indicator light works great!

Thanks, Bill.

[Bill]

Nice work, Bruce. I bet you get a lot of "how do I ...?" queries.

Bill

[ThePair]

I know this is an old thread, but I wanted to post something I found.

I, too, have succumbed to the error of accidentally plugging in the TM with the electric on, with no water (i.e. drained when leaving site, forgot to turn off heater, plugged in to recharge when got home, etc.) I saw the excellent thread to build a relay-based switch inside, which will automatically drop the 120V when the TM is unplugged, and will not reconnect the heater 120V until a button is pressed on the panel (http://www.trailmanorowners.com/foru...php?albumid=74)

I was researching the current parts to do this procedure, and came across this:

https://www.amazon.com/Shop-Fox-D453...dp/B00TGVLTZE/

I looked into this part, and it seems to be exactly what the mod does: it's a magnetic safety switch, and the 'ON' button will only stay on when there's 120V AC present on the line. If the 120V drops, the switch opens, and does not close again until 120V is restored AND the 'ON' button is pressed again. It's designed for power tools, so if there's a power outage, the tool doesn't start up again when the power returns. But, this seems like it should work just fine for this application. Plus, it's an easy install: one cut out on the panel, connect to hot and neutral, call it a day.

I've placed one on order, but I likely won't have a chance to install it until the spring (I'm likely going to store my TM for the winter tonight). I just thought I'd pass it along to anyone else who might be interested.

[tentcamper]

I made a simple indicator flag to remember to turn off the element. My thought came from when I use to work on the flight line and all those little flags to remind the flight crew to remove things before pre-flight.

I used a modified hospital red arm band.

[Bill]

Originally Posted by ThePair

I know this is an old thread, but I wanted to post something I found. I was researching the current parts to do this procedure, and came across this:

https://www.amazon.com/Shop-Fox-D453...dp/B00TGVLTZE/

This looks like great find. Wish I had known about it when I built the original. Because of the exposed terminals on the back of the unit, you will want to enclose it in an outlet box, but that is easy.

Good work!

Bill

[ThePair]

Originally Posted by tentcamper

I made a simple indicator flag to remember to turn off the element. My thought came from when I use to work on the flight line and all those little flags to remind the flight crew to remove things before pre-flight.

I used a modified hospital red arm band.

I used something less obvious, same concept. Overlooked it at last close-down, hence my interest in something that more fool-proof than I am foolish.