geothermal hvac with dsh

Paul_JohFebruary 6, 2012

I am about to install a Geo system with a desuperheater. I understand that I need to install a buffer tank and supply the regular hot water tank. Am I right in thinking that I Marathon with better insulation qualities is better, or should I save a lot of $$ and get a brand name whatever 85 gallon tank with a decent warranty? Also, if the tank is not powered, will the water still destroy the anode?

Not sure if this question is better handled here or in plumbing....


Paul Johnson

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A Buffer tank will provide more available hot water, and the desuper heater will be utilize more than connecting it directly to the water heater.

The amount of money you save heating water installing a Marathon I believe is not worth the expense. The cost to rise the temperature of 80 gallons of water 70 degrees is about 41 cents at 10 cents per kilowatt during the heating cycle. Compared to $1.31 using electric resistive heat. Heating water during the cooling cycle is free.

Last, Water quality 'I believe' effects the anode rod.


Here is a link that might be useful: Modern Geothermal

    Bookmark   February 6, 2012 at 10:43PM
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so, a marathon tank is a waste when I just need a storage tank? As long as the AC runs the DSH keeps the water up to temperature -- right? we will run the AC 10+ month a year (in Mississippi) We need the heat today, could have used the air conditioning last week...

    Bookmark   February 7, 2012 at 1:28AM
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The anode will dissolve whether the heater is powered or not. It may go slower if the water is cooler, but I can't tell you if the rate change is significant.

    Bookmark   February 7, 2012 at 2:54PM
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The marathon has a lifetime tank warranty... its plastic/poly... there is no anode and no need for one. So its not a decision of 'payback' time in this case is in many others. Its a case of do you want to lug it out and replace it in 10 or so years. My electric coop will sell me a 85 gallon for 875.00 or a 50 for 713.00. Home depot wants 1003.00 for the 85 marathon and doesn't list regular 80 but a 12 year warranty 50 gallon is 435.00.

Doing a cost evaluation.. if your doing geo you probably plan to stay in the house for more than 10years.

lets compare 50 gallon models

initial install GE 435.00

13 years not counting inflation 435.00 and my bad luck missing the warranty

thats 870.00 not counting labor inflation and possible mess clean up for 13 years.

My water heater is coming up on time to be replaced and I will replace it with a marathon... I don't care so much about the efficiency as I do the 15 steps up from the basement and breaking my back in a fourwheeler accident in 2000.

I will gladly pay the 713.00 bucks.

    Bookmark   February 7, 2012 at 9:46PM
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