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Jimbo13
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# Posted: 24 Sep 2011 10:47pm
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I was looking at 120v instant demand water heaters as a option like the one below.
Will this provide enough hot water for a basic 10 minute shower assuming a low flo shower head and no competition?
I was also considering the beefier models.
http://www.plumbersurplus.com/Prod/Chronomite-SR-30L-120v-Instant-Flow-SR-Tankless-Wa ter-Heater/39346/Cat/474?utm_medium=referral&utm_source=googlebase&cvsfa=63&cvsfe=2&c vsfhu=3339333436
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MtnDon
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# Posted: 24 Sep 2011 11:14pm - Edited by: MtnDon
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Depends in part on how warm you like your shower. The first thing I look for is the temperature rise for a given flow rate. This one states Temp Rise at 0.5 GPM 49°F rise.
That means that at a flow rate of 1/2 gallon per minute if the water going in is 50 degrees F the water going out should be 109 degrees F. However if you draw more than that rate the water gets cooler. Also if the inlet water is only 40 degrees the max the output would be 99 F. At those temps you wouldn't even be using any cold water to mix in the hot.
My low flow shower head draws 1.3 GPM IIRC so that heater wouldn't work for me at all. Most low flow shower heads are in the 1.5 to 1.7 GPM range.
The powerdraw is very high at 3600 watts. At 120 VAC that is 30 amps = 10 gauge wire needed.
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Jimbo13
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# Posted: 25 Sep 2011 12:00am
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If I went withe a larger Water heater that needs a 240v30amp can I put a pig tail on it and use my dryer socket that is also 240v30amp and just use one at a time?
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MtnDon
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# Posted: 25 Sep 2011 12:10am
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If this is for a full time residence or even a cabin where there will be an electrical inspection, No.
You can look at what's out there. The only electric on demand heaters I know of use 50 to 75 amps at 240 VAC.
You might be better served with a small tank type heater. Turn it on ahead of time and then shower. Or propane.
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Jimbo13
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# Posted: 25 Sep 2011 12:15am
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Is the potential of electrical inspection the only concern?
This is a mobile tinyhouse and it probably doesn't meet any codes anyways.
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Jimbo13
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# Posted: 25 Sep 2011 12:16am
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Where i'm moving to I'm going to have a steady free electricity supply and it is going to be quite a travel to get any propane if I went that route.
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Montanan
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# Posted: 25 Sep 2011 11:22am
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If you have steady free electricity, I agree with MtnDon about a small tank style. Since we'll be on the grid, we opted for a standard tank style and with 5 of us using it, we went with a 40 gallon tank. We looked into the smaller point of use ones and they have the benefit of being compact enough to fit almost anywhere. That might be your best option.
For what it's worth, we did look into a tankless on-demand system but were advised that they don't work well if you don't have a lot of water pressure. I don't know if that's true or not, but since we were aiming for a gravity system for water, we went with the tank. (Of course, we ended up having to install a pump and pressure meter for the water...but oh well.)
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