Tankless in Alaska


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Old 04-08-15, 10:11 AM
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Tankless in Alaska

Hello all. I have built a cabin in the interior of Alaska that has some pretty extreme winters. I may have backed myself in a corner plumbing in a Tankless water heater without really diving into the temp of the water(36 degrees in winter), BTU's needed Etc. I only need it to heat 1 thing at a time, 2.5 gal shower head max. Every business I talk to try selling me a $1200.00 tankless saying that I need the the btu's to heat the water. These are 8 GPM, 2-3 bathroom tankless heaters for family size homes! Are these people just trying to dip into my wallet or can I get away with a smaller tankless? Any information anyone can provide would be MUCH appreciated! I trust this place a lot more than a salesperson.
 
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Old 04-08-15, 10:25 AM
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You have to read the specifications for the tankless heater you are thinking about using, specifically the temperature rise vs. the flow in gallons per minute. If the incoming water is at 36 degrees and the temperature rise at 2-1/2 gpm is 70 or above you will probably be okay as 70 (rise) plus 36 is 106 degrees which is a warm, but not hot, shower. Anything lower, like maybe a 50 degree rise at 2 gpm will simply not cut it, giving you a reduced shower of only 86 degrees (or less) and THAT is cold as far as I am concerned.
 
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Old 04-08-15, 10:26 AM
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Hello. all tankless heaters are not created equal.. Tankless GPM are based on temp rise. Most advertised GPM for tankless units are based on 70f incoming water.

Additionally you need to increase the gas line to the unit as most cannot support the higher BTU rating. Most are in the 200K btu range vs a water heater that may have previously been there are in the 40k btu range.

Plus electric needs to be run also.

Tankless are more trouble then good IMO, but if you insist that its what you want we can guide you further..

Why not install a regular 40 gal water heater?

If you do go the tankless route with 36F incoming water I would suggest a buffer tank with recirc .. This will be pricey but its the only way to do tankless properly...
 
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Old 04-08-15, 10:31 AM
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I would think with most tankless water heaters the heat rise and flow rate are tied together. Up there I'd go for one rated for 4 or 5 gpm since that's usually based 45f temperature rise for the water. At the full 4 or 5 gpm and feeding it 40f water you'd get 85f water out. Backing the flow rate down to 2.5 should provide margin for a nice hot shower.

I assume this will be propane powered. Another thing to consider is the propane volume and it's ability to supply enough btu's worth of gas. I remember years ago calling my brother in law for the holiday. They were heating frozen pizza in the microwave. It was so cold the propane barely turned to vapor so they could only get a tiny, weak flame on the stove and oven wouldn't even light. But... not only do you need to worry about having fuel you also need to have enough liquid propane to produce enough vapor to supply the heater.

This chart will give you an idea of how many btu's vapor you can expect to get from various sized tanks at different temperatures. It's a big deal since even a smallish on demand water heater may produce 100'000 btu or some other big number.

 
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Old 04-08-15, 10:35 AM
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The noritz for example here is a 199k btu unit. 80f temp rise gets you 4.6 gpm. 80 + 36 = 116f shower @ 2.5 gpm shower head..

I would install nothing less then 199k btu unit... These heaters are 1200-1500 without installation.

Remember proper install if NG is increased piping. LP is different..

To me they are a waste of money.. I can install 4 tank heaters for what these cost. Thats a minimum 40 years worth of units...

http://support.noritz.com/download.p...ield=SpecSheet
 
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Old 04-08-15, 10:47 AM
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Thank you for the quick replies....

I have been trying to figure out if there is a way to squeeze in a regular water heater but the way I built the cabin I do not know if I will have the space. I will be taking a few measurements this weekend to see if that is possible and looking into how difficult running more wire will be. Do you think I could get away with a 30 gal for one bathroom? also, Because I'm a weekend warrior Is there any downside to shutting water heaters off (except in winter of course) when no one is around? would even save energy that way?
 
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Old 04-08-15, 12:15 PM
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First off you have NG or LP? You m,ay have stated that below im not sure..

Do you think I could get away with a 30 gal for one bathroom?
Yes and probably a 20 gallon maybe. Is there a bathtub??

If its a cabin for weekends I may even do an electric water heater. Takes gas and flue pipe out of the equation..

Often in small homes I install the table top 27 gallon units in the kitchen. Good use of counter space..

ProMax® Specialty Table Top 27-Gallon Electric Water Heater | A. O. Smith Water Heaters
 
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Old 04-08-15, 12:36 PM
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I had a customer that was happy with a 20gal 120v unit for taking a bath and doing dishes. It was only about three feet high ans didn't take up much room. It actually set on a shelf in the garage.
 
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Old 04-08-15, 01:43 PM
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I have LP and Pilot Dane has made an excellent point about propane and how much the outside temperature can determine the conversion into gas or vapor.

Reading more on this subject today, small electric water heater might be the best bet if I can fit it somewhere. I'm assuming they do not have many that run off 120? I had installed a regular run of 12/2 on its own 20 amp breaker for the tankless.... but I'm assuming that will not be enough. Ideas from here? Thanks!
 
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Old 04-08-15, 03:01 PM
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I had installed a regular run of 12/2 on its own 20 amp breaker for the tankless.... but I'm assuming that will not be enough.
The one I wrote about was actually on a shared circuit though it shouldn't have been. Here is a 1500 watt one that will run on your existing tankless circuit and is 18"dm x 25" high. Point of Use Electric Water Heater | 20 Gallon Tank | Whirlpool E1F20US015V 120V It would fit in a kitchen cabinet with shelf removed. Me, I'd put it next to the sink cabinet. Out of the way and plumbing would be easy using existing sink lines.
 
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Old 04-08-15, 04:30 PM
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I had installed a regular run of 12/2 on its own 20 amp breaker for the tankless.... but I'm assuming that will not be enough. Ideas from here? Thanks!
Maybe ray can help but isnt that wire ok for 240? I believe there is no neutral for the line to electric 240v water heater. Just two hots and a ground..

You will just need to change the breaker in the panel..

Wait for an electrician to verify...
 
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Old 04-08-15, 04:37 PM
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FYI AO smith makes 30 and 40 gallon models with dual 3000 watt elements for 120 v operation...

http://www.hotwater.com/Resources/Li...-(AOSRE50450)/
 
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Old 04-08-15, 04:42 PM
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Yes it will work for 240 but the circuit is too small for standard wattage 240v water heaters. For those you need #10 on a 30 amp breaker but if you look around you may find a water heater, especially mobile home intended, that will work on a 20 amp circuit. Look for 3800 watts or less.
 
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Old 04-08-15, 05:06 PM
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You've said "your cabin". Is it just you with the occasional guest or will there be others in the cabin on a regular basis? Your obviously conscious of the situation so I'm sure you would do just fine with a 30 gallon heater. The killer would be doing multiple things at the same time or close after each other. There are many who do laundry, run the dishwasher and take showers without consideration of what makes the water hot. Just a little planning can make your water heating capacity go a long way and not really affect your quality of life.

As for whether or not it's worth turning off a electric water heater while you're gone during the week I'd vote for leaving it on if it's within the insulated envelope of your cabin. Any heat that escapes from it will go into your cabin so it won't be wasted. That and you never know when you'll get to the cabin after a bad day and want a shower without waiting for the hot water.
 
 

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