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Old 10-02-2015, 01:04 AM   #16
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Originally Posted by Habeed View Post
All the ones I can find with quick searches want 30 amps at 110 volts. So the only way is a small tanked heater like this one.

Edit : Ok, here's one. 0.5 gpm is what the manufacturer thinks it can handle.

You would need a 20 amp 3 way switch like this one I think.
Thanks for those suggestions, Habeed. That tankless unit is similar to the Chronomite model I have at work. It's good for delivering warmish water to a bathroom sink, but it restricts the flow so much that it might take ten minutes to fill a lobster pot at the kitchen sink. You'll notice the reviews of it are less than stellar.

I did look at that Ecosmart 2.5-gallon tank initially, and if that 3-way switch does the trick, I might have to reconsider it. Maybe the one-gallon version will work if the 2.5 won't fit under my sink.

Now I just need to convince myself that the cost of heating a small tank is negligible compared to the benefit of instant hot water, and that I won't torch the place trying to hook it up.
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Old 10-05-2015, 01:01 AM   #17
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I didn't delve too deep into mini tanks because of the amperage issue on the existing disposal circuit. I also didn't want the potential of a tank leaking in a cabinet, and I didn't like the idea of going back to heating a water tank after going tankless. It was easier for me just to put this whole project on the back burner, pardon the pun, because the problem wasn't serious enough to warrant a lot of trouble or expense.

Your lack of hot water, on the other hand, is a big freakin' deal, and I bet there's a few smart folks here who could offer better suggestions than my wild guesses about what is going on. Have you tried adjusting the temperature setting? If it's too low, the water may cool down too much before getting to your shower. If it's too high, causing you to turn the valve toward cold, the hot side flow rate may not be enough to keep the heater heating. If it's not something that simple, maybe you should get somebody to look at your installation because what you're describing sounds really fishy. Or perhaps a recirculator is the way to go for you.

And what's with the half-gallon-a-minute shower anyway? Maybe you just need to open that showerhead full-throttle and take a real shower because it sounds like you deserve it, man.

The suggestion of a three-way switch by bcgfdc3 to accommodate a point-of-use heater has me intrigued. Would that satisfy the requirement of a dedicated circuit? A small tankless unit that can plug into a 120v, 20A line and be appropriate for a 1.5gpm faucet would be the ideal. Does such a product exist?
Yes the response from @bcgfdc3 was interesting, and I think I could utilize a 3-way switch as he suggests in my kitchen, if I installed such a unit.

As for my shower habits, I think I was permanently imprinted to limit my hot water flow as a kid growing up with an undersized water heater. Regardless I found that 0.5 gal/minute hot water works well enough, with 0.6-0.7 being closer to my ideal flow. A secondary problem that I need to fix is getting the proper shower faucet washers. I replaced them years ago, but now find that the water flow begins to slow down after a few minutes, as if the rubber is expanding a little in the hot water flow and constricting it, suddenly causing the water to go from hot to cold. It is not like the water has slowed to the point that causes any showering problem, but enough to shut off the tankless heater when flowing at slower speed. I changed the temperature from 120F to 110F to help increase the flow rate, but still find it oversized when used for a single application.
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Old 10-05-2015, 01:17 AM   #18
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Not to change the subject, but isn't tankless point-of-use more popular in Europe? Meaning do they not have some proven designs and products?

I sort of like what @Habeed posted, the undersink instant-flow low-flow unit. Even though many reviewers were negative because of only getting tepid flow, that should be fine for washing hands. It might be a worthwhile compromise as compared to constantly heating a small tank of water.
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Old 05-03-2018, 11:57 PM   #19
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Re: Secondary tankless water heater under sink


Hey let's pretend that this thread isn't almost three years old. I started reading it last week when I realized that I started it myself, and by golly all of the advice is excellent, even though I didn't follow any of it.

Long story short, just last week I installed a 2.5-gallon electric tank under the kitchen sink, plugged it into the same circuit as the garbage disposal, and used an air switch to alternate power between the two. Works great.

Short story long, I decided that heating a couple of gallons of water was so much more practical than trying to run a 240-volt line to power an adequate point-of-use tankless unit.

Because the disposal and water heater together exceed the amp capacity of the circuit, a dual air switch conveniently keeps them from operating simultaneously. There's no interruption of hot water because there's plenty in the tank. To avoid drilling a hole through a quartz countertop, I mounted the switch behind the flip-out drawer in front of the sink with a 98-cent bracket. The disposal switch on the backsplash stays in the on position.

The tank was plumbed in-line with the hot water inlet, so as hot water is depleted from the tank, hot water from the tankless has reached it, thus eliminating the "cold water sandwich."

I had been reluctant to start heating a water tank again after going tankless a few years ago, but I think that keeping 2.5 gallons at 130 degrees could be a few cents cheaper than having the tankless fired up while I'm waiting for cold water to be flushed out of the line. As it is now, scalding hot water reaches the faucet within two seconds. I've decided to stop worrying about leaks because that's just the way it has to be now.

I'm pretty happy with this setup. It required no electrical upgrades or rewiring, and all-in it cost less than $200, free labor of course.
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Old 05-04-2018, 07:48 AM   #20
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Re: Secondary tankless water heater under sink


The link is for a water circulation system that uses the cold water to your kitchen sink as a return. It;s not an instant hot. https://www.homedepot.com/p/Undersin...T-E1/100037011

So how this works is when the temperature to the sink hot drops to 104 or lower it fires up and feeds the cooling hot back down the cold. Thus it acts as a circulation loop keeping the hot water available at the sink.
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