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Smaller Munchkin & More Stored Water

Mijola
Mijola Member Posts: 124
I've been working with a contractor to get an indirect water heater and munchkin boiler installed. He initially quoted me a 140 with a 40 Gal indirect.

He did not do any heatloss calcs. My calcs using the slant fin software tell me my heat loss is around 57k btus on a design day.

I'm heating primarily with radiant floors and panel radiators.

When I questioned the selection of the 140M, he agreed that based on the size of my home, the 80M would work for the heat load, but I would not have enough hot water for the whirlpool tub, etc since the 80M would not be able to instantly heat the water.

He recommended another 40 Gal indirect water heater. Is there any benefit to having TWO 40's vs ONE 80 Gal?
I don't have any height problems so, an 80Gal would fit.

Any opinions would be appreciated.

Comments

  • jim sokolovic
    jim sokolovic Member Posts: 439
    First hour ratings comparison...

    I was looking at HTP's first hour ratings comparison for one 80 gallon vs. two 40 gallon indirects. The output for the two 40 gallons, at the same boiler BTUH output, is astonishingly higher. The surface area of the heat exchanger coil for the 80 is about the same as the two 40's added together. Curious to know the reason - can you tell us, Guy?
  • Earthfire
    Earthfire Member Posts: 543
    munchkin questions

    Check out http://www.htproducts.com/index.html# You'll be able to get the info you need straight from the horses mouth. Opinions are nice, everybody has one.
  • Mijola
    Mijola Member Posts: 124


    I'm not sure, but I don't think you can look at the the output and double it simply because the boiler water getting to the second indirect tank has been stripped of BTU's because it's already been used to heat the first tanks water.

    Is that correct?
  • I'd pipe the coils in parallel to prevent that.

    > I'm not sure, but I don't think you can look at

    > the the output and double it simply because the

    > boiler water getting to the second indirect tank

    > has been stripped of BTU's because it's already

    > been used to heat the first tanks water.

    >

    > Is

    > that correct?



  • I'd pipe the coils in parallel to prevent that.

    > I'm not sure, but I don't think you can look at

    > the the output and double it simply because the

    > boiler water getting to the second indirect tank

    > has been stripped of BTU's because it's already

    > been used to heat the first tanks water.

    >

    > Is

    > that correct?



  • I'd pipe the coils in parallel to prevent that.

    I also think that you are on to the reason the 80 puts out less than the two 40's piped this way.

    Noel
  • jim sokolovic
    jim sokolovic Member Posts: 439
    The charts that I have from HTP are old...

    but it still looks like the two 40 gallon indirects blow away the single 80, even if you consider 140,000 BTUH going to the 80, and 70,000 BTUH going to each 40!
  • Cliff Brady
    Cliff Brady Member Posts: 149
    Consider a thermostatic mixing valve

    to increase the 40 gallon indirect capacity by running it at 130 to 140 and using a mixing valve to supply reasonable temperature to you bathrooms and sinks while straight hot water is piped to your dishwasher and clothes washer for better cleaning.

    Not that it helps much for bath tubs, but a Gravity Film Heat exchanger can recover a lot of waste heat going down the drain stack to preheat your cold water feed to your water heater. Works especially well for showers. See gfxtechnology.com
    for more info.
  • Mijola
    Mijola Member Posts: 124


    Wow!
    Thanks for the tip on the GFX. I had never heard of it, but it sure makes a lot of sense.
    Won't help much for the big tub, but it will help with the showers.
  • Guy_5
    Guy_5 Member Posts: 159
    recovery

    I was going to respond with my take on this, but then I decided to get together with our engineering department and find out what they have to say. I will let you all know tomorrow.
    Guy
  • jackchips_2
    jackchips_2 Member Posts: 1,338
    One answer

    to your question of benefits is that you will still have hot water if one of the tanks go down. If you do go with two be sure they are piped with equal spacing or reverse return.
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    My ideal DHW package.

    Would consist of one of those humonguous copper coil in a can DHW heaters, like the Thermomax or it's sister. Use the tank as part of the main circulation system. It adds mass to the low mass high efficiency boiler. Makes for longer on times and longer off times. I've spoken to the folks at HTP about briningone out suited for use with the Munchies, but they said they could barely keep up with current demand. Maybe some day, but not now.

    If you go with the larger Ergo-Turbo max, make sure you use an approved temperature limiting valve on the outlet of the tank to avoid soft tissue scald suits. They don't fit ANYONE well...the suits that is.

    ME
  • jim sokolovic
    jim sokolovic Member Posts: 439
    Thanks, Guy...

    I won't be able to read this site til I come back to work on Monday, and I didn't want to miss anything - can you E-mail me the information, and any pertinent ratings charts if they have changed on the Superstor models?
  • tommyg
    tommyg Member Posts: 9


    Guy,

    So what do the engineers at HTP have to say?
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    An 80,000 btu water heater


    which is what you will have when the indirect is in priority.

    Correct me if I'm wrong but, do you relly think your whirlpool will require more than that?

    You need to look at the recovery of the indirect.

    I would keep the tank at 140 and knock it down with a thermostatic mixing device.

    I will bet you NEVER run it out of hot water.

    Mark H

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Never say never....

    'cause as soon as you do, they will impart loads beyond your wildest imagination, and run out of hot water...

    The correct statement is "You should virtually never run out of hot water!"

    Been there, said that, had to eat cold crow sandwiches for a week:-)

    ME
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    So how does crow taste?


    You are right ME.

    I stand corrected.

    Hope the arm is healing up fast!

    Mark H

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Crow tastes...

    kinda like Bald Eagle;-)

    The arm is doing well. I'm working it with 12 ounce curls of Michelob Ultra tonight.

    I intend to try and pick up a heavier one, maybe a Guiness or some such later in the week. Doc said to avoid stressing it the first week, hence Ultra.

    Thanks for asking!

    ME
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    Bald Eagle Recipe


    I asked the owner of a Maine Lodge about that once.

    Told her I had shot one and didn't want it to go to waste.

    (Now to all you anti-hunters, I have NEVER so much as aimed at an Eagle so lighten up!)

    She told me she didn't know of any recipes.

    Take care Mark!

    Mark H

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    The secret recipe is....

    the same as it is for Spotted Owls! And for those people that read this and think I've ever seen a bird of prey thru the sights of a killing machine, fughedabowdit... It's a joke, get it???:-)

    ME
This discussion has been closed.