Electric water heater indicator light wiring?

[MushCreek]

I have a 30 gallon electric water heater in my shop. I don't use it all the time, so I shut it off at the breaker. The problem is when I forget to shut it off at the end of the day, and it's wasting electricity. I figured I'd add an indicator light right by the door to remind me. Light on= breaker on. Fine. BUT- the wiring (240 VAC) has two hots and a ground. That's it; no neutral. The question is- if I wire up a small 120 VAC light to the water heater, can I wire it to one hot leg and the ground. I know it will work, the question is whether it is legal/code/safe? Or should I find a 240 VAC light, or pull a neutral from a nearby 120 V box? or? Rewiring it is out of the question; the walls are all closed up. Thoughts?

 

[rlitman]

You could always put two indicator lights in series.

 

[sparky 1971]

While connecting a 120 volt bulb to one hot and the ground will make it light up, don't do that, it's not code/legal/safe. Just get an LED light bulb that will run on any voltage even though it's not code to have 240 volt lighting in a residential setting, I'd do it anyway.. It will probably be tough to find a single lamp, you may end up getting a four pack.

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[rlitman]

...Just get an LED light bulb that will run on any voltage even though it's not code to have 240 volt lighting in a residential setting, I'd do it anyway...

I don't think I'd be happy with a 240V wired Edison (E26) socket that someone can plug a 120V bulb into (even if it's probably safer than plugging a non-dimmable LED bulb into a 120V Edison socket wired with a dimmer; something that is totally allowed by code). I would be happy with something hard wired, like an LED puck light. Or how about a non-normal sized bulb socket, like an E14?

 

[sparky 1971]

I don't think I'd be happy with a 240V wired Edison (E26) socket that someone can plug a 120V bulb into (even if it's probably safer than plugging a non-dimmable LED bulb into a 120V Edison socket wired with a dimmer; something that is totally allowed by code). I would be happy with something hard wired, like an LED puck light. Or how about a non-normal sized bulb socket, like an E14?

I'm just trying to throw a simple option out. I suppose a keyless lampholder could be used and 240 only written on it with a Sharpie. I think if it were mine I'd be leaving the water heater on all the time or if I were really concerned, throw a relay and/or timer on it.

Now that I'm really thinking, why not use a 120 volt light above the panel? Tie it into one leg of the 240 off the breaker and use a neutral.

 

[mm08822]

Just buy a 240vac sealed indicator light and there is no future screw-up potential.

 

[iron block]

Most switching power supplies will accept 240VAC input. So how about figuring out something around an old laptop supply hooked to the mains, with a low-voltage indicator on its output?

 

[micromind]

Industrial pilot lights are available in 240 volts. 22MM or 30.5MM

 

[Shiftless]

It seems to me that most of the energy saved by having the water heater off for a day or a week would be negated by all the electricity it would take to reheat 30 gallons of water for a one time use. If this is just to wash your hands, it seems to me that you’d be better off leaving it on all the time unless you are gone for like a month. How much money do you save by doing all the on-off switching anyway? A dollar a week or ??

 

[MushCreek]

The problem is that the water heater often sits for fairly long periods. It only takes about an hour to get a tank of hot water, and then I can 'coast' for a couple days before it gets too cold. In the summer, I don't use it at all. I thought about a demand WH, but there is a shower, which guests use from time to time, and I couldn't get enough power to run a shower-size tankless WH. We put a timer on our house WH because they have a three hour 'expensive period', and it made a decent difference by shutting it off during peak hours.

I was thinking in terms of a light like micromind described. Something mounted in a box. I don't need or want a very bright light. I could rig one up on the panel, but that is out of sight, out of mind. I want it near the door, which is about 20' from the panel.

 

[sparky 1971]

The problem is that the water heater often sits for fairly long periods. It only takes about an hour to get a tank of hot water, and then I can 'coast' for a couple days before it gets too cold. In the summer, I don't use it at all. I thought about a demand WH, but there is a shower, which guests use from time to time, and I couldn't get enough power to run a shower-size tankless WH. We put a timer on our house WH because they have a three hour 'expensive period', and it made a decent difference by shutting it off during peak hours.

I was thinking in terms of a light like micromind described. Something mounted in a box. I don't need or want a very bright light. I could rig one up on the panel, but that is out of sight, out of mind. I want it near the door, which is about 20' from the panel.

If you only need to power it for an hour at a time, how about a relay and spring wound countdown timer? Get a two pole 30 or 40 amp relay with a 240 volt coil and run one leg through the timer and keep everything at the water heater. It would be a lot less screwing around and could be done fairly inexpensive. It would involve having to walk to the water heater to turn it on, but there wouldn't be a light to not notice is on at the end of the day.

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[MushCreek]

Now that's a good idea!

 

[The Cobbler]

throw a relay and/or timer on it.

this
or a mechanical timer with off only tabs on it. switch it on manually and have off tabs every 4 hrs or so

 

[pima67]

How about the KISS principle? Beautiful sign at the door. Not elegant but a lot cheaper.

 

[MushCreek]

That reminds me of an incident where I worked many years ago. A very hung over machinist had loaded a hundred or so steel blocks on a big Blanchard grinder, and forgot to turn the magnet on. The resulting chaos was really something. Surprisingly, no one was hurt as the steel blocks flew around the shop. After that, he put a sign on his machine that said, ' Is the magnet on? Well, is it?' I'm afraid that I would tend to not see the sign after long periods of not turning the WH on.

 

[Sumboodie]

I understand this isn't answering your question, but it made me wonder if turning it off even saves money.
Sometimes I end up too far into thinking about a project when that project doesn't even need to exist.

From what I'm finding, the average water heater needs around 2 kWhr a day to maintain the temperature.

So anywhere from around $0.20 to $0.50, depending on your power rates.

Now to take 30 gallons of 70* room temp water to 120*, that takes about 12.5 Kw hr, or about $1.25 to $3.00.

So if you ran it 5x a month, $6.25 to $15
Vs leaving it on $6 to $15.

So unless you need water less than 5x a month, it's cheaper to keep it on... if my math is correct.

 

[dscheidt]

It seems to me that most of the energy saved by having the water heater off for a day or a week would be negated by all the electricity it would take to reheat 30 gallons of water for a one time use.

No. That’s not how physics works. Heat loss is proportional to temperature difference. Higher differential, higher loss.

If the heater cools down to room temperature, it’s lost whatever energy was required to heat the water to storage temperature, and it can’t lose any more. If you leave it on, you have a higher loss, because it stays hot, and keeps the rate of loss higher.

 

[MushCreek]

Another problem is that if you leave a water heater on for long periods without using it, strange stuff grows in the warm water. I remember that we had a WH for the shop gym, and no one had used it for a while. The water that came out was black, and smelled awful. Not what you would want to take a shower in!

 

[wyliesdiesels]

The question is- if I wire up a small 120 VAC light to the water heater, can I wire it to one hot leg and the ground. I know it will work, the question is whether it is legal/code/safe?

No dont do that. Not safe. Never use a ground for neutral return current

 

[wyliesdiesels]

Most switching power supplies will accept 240VAC input. So how about figuring out something around an old laptop supply hooked to the mains, with a low-voltage indicator on its output?

How would you connect that to the 240v circuit?

 

[wyliesdiesels]

We put a timer on our house WH because they have a three hour 'expensive period', and it made a decent difference by shutting it off during peak hours.

So how about doing the same with this WH?

 

[wyliesdiesels]

How about the KISS principle? Beautiful sign at the door. Not elegant but a lot cheaper.

Or a lighted sign with a pull cord. When you walk into the shop pull the cord turn the WH breaker on, when you leave the sign is on to remind you to turn the breaker off.

 

[walta]

I doubt you are saving much if any energy with this game.

The fact that the tank takes 3 days to cool off indicates it is well insulated and has very small stand by losses.

Heating the tank up from cold requires a huge amount of energy. Turning it off would make sense for a month or more but overnight is silly.

I do like the 240 Volt industrial pilot lights I put them on my well pump and air compressor.

https://www.amazon.com/Baomain-AD16-22D-AC220V-Energy-Indicator/dp/B00G9JQ0UA/?tag=atomicindus08-20


Walta

 

[djbmw]

Another problem is that if you leave a water heater on for long periods without using it, strange stuff grows in the warm water. I remember that we had a WH for the shop gym, and no one had used it for a while. The water that came out was black, and smelled awful. Not what you would want to take a shower in!

You have this HALF correct. If the water is warm, and not HOT, then it starts to grow all kinds of nasty. However, if the water temp is kept at 120 degrees or above,... you're much safer. Water heaters are generally set to 130 or 140 so leaving it ON is safer than turning it off and letting the water cool and foster the ickies.

 

[micromind]

I doubt you are saving much if any energy with this game.

The fact that the tank takes 3 days to cool off indicates it is well insulated and has very small stand by losses.

Heating the tank up from cold requires a huge amount of energy. Turning it off would make sense for a month or more but overnight is silly.

I do like the 240 Volt industrial pilot lights I put them on my well pump and air compressor.

https://www.amazon.com/Baomain-AD16-22D-AC220V-Energy-Indicator/dp/B00G9JQ0UA/?tag=atomicindus08-20


Walta

Those will fit in a standard 1/2" knockout hole (7/8").

 

[75gmck25]

How about installing a water heater mechanical timer and having it set to run only a couple hours a day? You can always turn it off with the external switch on the timer, but if you forget, the timer will turn it off in a short time.

When I was stationed in Hawaii, electricity was quite expensive. We had a water heater time and turned it on about an hour in the morning before work (shower, shave, etc.) and another 2 hours in the evening at about 6:00 pm (cooking, wash clothes, etc.). That covered almost every need we had for hot water.

 

[fitter30]

30 amp contactor with 120 vac coil wired to the light switch.

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