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  1. #1
    MurrayMinchin's Avatar
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    Tankless water heater / small water tank combo?

    Hi there,

    I'm building a darkroom and want it to have a hot water source independent from the rest of the house.

    I use a 16x20 Summitek Cascade print washer that sips 700 ml's a minute, but will need to change the print water-stop tray on a regular basis, do the same with the print holding tray, and will be occasionally washing masks at the same time.

    The cold water coming into the darkroom during winter months can be just a couple degrees above freezing this far north, and I used to drain the household water tank to everybody's chagrin.

    I was thinking of putting a low flow electric tankless water heater (starts working at .5 gallon a minute) on the cold water line right before a 10 gallon electric water tank. This way, if I'm using just a little hot water the tank should be able to do the job, but if demand increases the tankless heater will be pre-heating the cold water entering the water tank.

    Crazy? Brilliant? Certifiable?

    I don't care if it's going to cost a couple hundred bucks more if 1) I will not have to heat another huge water tank 2) the hot water doesn't go cold while my wife's in the shower, and 3) I will never, ever run out of hot water while in the darkroom again.

    Murray
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    Note to self: Turn your negatives into positives.

  2. #2
    M.A.Longmore's Avatar
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    You Ain't Crazy !

    Ron
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  3. #3

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    I did something similar in my DR, for about the same reasons.
    We have a tankless heater for the house, but for washing and such in the DR, the demand is smaller than the tankless's minimum flow, so it doesn't come on at all.
    I've installed a 2.5 gallon point of use heater under the DR sink which is fed by the hot water line. When my flow is high enough, it gets pre-heated water from the tankless. Otherwise it takes care of the low flow situations.
    It's nice to turn on the hot tap and have heated water within a second or so.

    A 10 G heater would probably work well. I do run out occasionally if I'm using a lot of straight hot water like for rinsing big trays. The 2.5 gallons doesn't last long and the tankless gives a slug of cold water every time you turn the water off and on again.
    Last edited by bdial; 05-17-2011 at 05:04 PM. Click to view previous post history.

  4. #4

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    I did something a little weird for water temp in the winter for my 11x14 print washer. I added 50' of tubing to the print washer feed line. I feed that extra line through two jerry cans and filled with water, which stays at room temperature. I get 70 degree wash water all the time for about $8.00 in materials, as I already had a couple old jerry cans. Yeah OK......I'm cheap.

  5. #5
    nsurit's Avatar
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    My house runs on tankless hot water heaters. You will never regret the decision unless maybe your water is very hard and that gums up the works of the water heater. Mine is rainwater, so hard water is not a problem. Endless hot water makes everyone happy. Bill Barber

  6. #6

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    Well, it looks like the tankless heater will not kick on. 700ml/min is less, by far, than the 0.5 gal/min needed to kick on the tankless (1/2 Gal = 1.89 L). Still, this is a credible idea and represents creative thinking on your part. Find some way to get the volume up, maybe?
    Geo.

  7. #7
    MurrayMinchin's Avatar
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    Well, I didn't get laughed out of the room so it mustn't be too much of a whack-job idea. I'll check into the spec sheets of different models and get back later.

    Thanks.

    Murray
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    Note to self: Turn your negatives into positives.

  8. #8
    MurrayMinchin's Avatar
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    I found a 'water mixing calculator' online, and it appears if I set my tank at 100 degrees fahrenheit and my winter cold water is at 37 degrees, the amount needed of each to reach 68 degrees is pretty much 50/50.

    So, if the washer sips water at a rate of 700ml a minute for an hour, it'll use 21 litres of hot water, or 5.5 gallons. If the tank is set even higher the hot water volume would be even less, so a 10 gallon tank would be plenty big enough. If I noticed the temperature dropping as the tank was getting drained of hot water, I could run another hot water faucet to 'kick start' the tankless heater to re-fill the tank with hot water again.

    Interesting stuff

    Murray
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    Note to self: Turn your negatives into positives.

  9. #9
    David Brown's Avatar
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    Quote Originally Posted by Dave_ON View Post
    I did something a little weird for water temp in the winter for my 11x14 print washer. I added 50' of tubing to the print washer feed line. I feed that extra line through two jerry cans and filled with water, which stays at room temperature. I get 70 degree wash water all the time for about $8.00 in materials, as I already had a couple old jerry cans. Yeah OK......I'm cheap.
    This is inspired! It's the same "mechanism" that refrigerators use to supply cold water out of the door.

    What is the lowest temp of your water coming in?

    And, I would expect that the same set-up would cool down the 85 degree water I get in the Summer.
    David
    Taking pictures is easy. Making photographs is hard.

    http://www.behance.net/silverdarkroom
    http://silverdarkroom.wordpress.com



 

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