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How do I heat an open tank of water with a colsed loop system?

Is one of the highest forms of flattery! Or was that a wee bit of sarcasm?


  • Eric_8
    Eric_8 Member Posts: 66

    The owner built a 40 x 80 shop. He is finishing a 20 x 40 part to live in for a couple of years until he gets his house built. I put PEX in the slab of the finished out part.

    Immediately after he builds the house he is going to build a small out building between the shop and the house to house an ASME rated, closed loop, pressurized wood boiler which will then heat the house, the shop, and provide domestic hot water (with a couple of indirects) in the shop and the house.

    In the mean time I have installed the indirect in the shop and am going to use a Noritz water heater to heat the shop and the indirect. Neither of us saw the value in going with a mod con boiler for 2 heating seasons. Also, to save room I am hanging the Noritz on the outside of his building. It will leave a couple holes to patch but he is OK with that.

    OK, so I am going to build my panel as if it was being "powered" off a primary loop coming in from the wood fired boiler, then just connect the Noritz in place of that loop. When we go live with the wood fired boiler it will be a simple matter to cut the line and connect it to the new loop. I will change the pump location and a couple of controls and I should be good to go.

    Of course, nothing can be that simple so here's the part that has me scratching my head.

    The owner has a large (42" x 42" x 42") stainless steel tank he is going to hang on one of the side walls. It is open to the atmosphere and will be filled with water. The level will be controlled by a float.

    I need to heat this water to 160 to 180 degrees. It will be emptied once per day so I have roughly 24 hours to get the job done. He will then empty it into a tank on his truck through a 1 1/2" rubber hose connected to the bottom.

    Oh, the tank has a tapping on the bottom I can connect to for water circulation. If needed I can have him get an additional tapping added but we really don't want to do that unless we have to.

    At the moment I am thinking a simple heat exchanger with an aquastat and a float of some type to shut off the circ whenever the tank is emptied.

    I thought about just putting the tank loop circ on a switch but that will just mean something to forget.

    We could go with some massive storage in the form of a bank of indirects but that would be cost prohibitive.

    Any ideas?
  • Richard

    from 160°-180°, open tank and empty every day? A steam boiler will do that. Is this even legal? What would require anything like this?

  • Eric_8
    Eric_8 Member Posts: 66

    He is a stone mason and claims if you use hot water to mix your mud in the wintertime it keeps your mud from freezing up as quick. I think the whole idea is nuts but hey...

    Owner moved here to the North Caroline Piedmont from central PA. He simply doesn't understand it doesn't get "that" cold down here.

    He very recently left a very strict branch of the Amish so he definitely has that "hey, just hook it up and it should work" mentality. Now don't jump my case for dissing the Amish. I got Amish blood running pretty doggone thick through my veins and I know 'em well. -grin
  • Eric_8
    Eric_8 Member Posts: 66

    Oh, and he has a tank on the back of his truck that he fills with this hot water then pressurizes with a gas air compressor. He used to tote the thing around on his wagon up in PA.
  • Richard

    don`t get me wrong , Amish people may be different from myself , but I respect they`re reasoning & beliefs.
    But heating a tank of that size to be drained daily, I think, will be a prob with HW.

  • phil the limey
    phil the limey Member Posts: 31

    i have some pretty cool evac solar panels that would make quick work of that. i imported 10 panels, used 2 and have been selling off the rest to pay for mine. i get 180 degree water even in winter
  • Eric_8
    Eric_8 Member Posts: 66

    Sorry man, I didn't mean to sound confrontational. I am just used to, if I say anything less than 100% positive about the Amish, getting my butt jumped by people who don't know more than what they saw on TV.

    OK, are you saying I am going to hae trouble getting it heated up to that temperature?
  • Richard

    I didn`t think you were confrontational at all, it`s just just heating-up an open tank to that temp with a HW boiler will be a TALL order.

  • Eric_8
    Eric_8 Member Posts: 66

    It will be insulated on all 4 sides, the bottom, and the top has a lid that sets on top of it and will be sealed.

    I don't want to do it but he is convinced he needs it.
  • RM,

    Didn`t want to do-it?, Why?. Whatever you could do to help keep the heat into this water will most certainly help, but again, reaching 180° "I think" will be impossible daily. Even solar requires daylight.

  • Rich Kontny_5
    Rich Kontny_5 Member Posts: 116


    What a great your first name :),If I am following you correctly you are using the Noritz as a temporary heat source pending a properly sized wood boiler to be put on line in the near future.

    I think you are going about this in a very cost effective way yet you are putting the cart before the horse so to speak in terms of the Noritz installed before the wood boiler.

    First you need to do a complete heat loss taking in to consideration the walls, windows, insulation,design temps(house and shop),location, overhead doors etc. Then you have to decide on the distribution system. (sounds like you already have {in-floor})

    After you have these variables established you can design a proper system. Just throwing pex in the slab does not mean you are going to heat this building properly. Spacing of tubing, length of tubing and piping arrangements all need to be factored in.

    There is no need and I would think no code compliant way that you can use an open tank for domestic hot water.The Noritz can be arranged with the indirect and a third piece of equipment known as "The Heating Box" to accomplish what you are trying to do.

    Presently I believe there is only one boxed unit that will properly separate the domestic from the hydronic system, that is "The Heating Box" made by NavienAmerica.
    Since you already have an indirect you may be able to use the open system model of "The Heating Box" and use the on demand for domestic use while using the indirect as a buffer tank for the hydronic side. This would take some dsign work but I believe is very workable if the space heating load is within the capabilities of the btu out put of the "Heating Box"

    The domestic needs including the periodic 165' dump you need could easily be met by a properly sized Noritz with the normal 125' water for house use met by stepping down the water temp with a properly sized tempering valve.

    When you put the wood boiler on line you would want to use a primary secondary type piping arrangement which would make the wood boiler as primary heat source while using the Noritz as secondary heat source.

    This may sound complicated but if I or someone like Hot Rod put pencil to paper I am sure you could accomplish what you want. The Amish are very frugal and probaly have very conservative household hot water needs.(this would help make this more economical to operate. I assume the Noritz would be LP gas?

    The key to this system and any system is proper design taking into account all the variables PRIOR TO INSTALLATION!

    Richard (Rich) Kontny

    Make Peace your Passion!
  • Eric_8
    Eric_8 Member Posts: 66

    1. I did do the heat loss, etc. I need just over 45K btu for the heating load. No way would I just throw tubing in. Of course you don't know me so you had no way of knowing that.

    2. Here is part of the problem. Heating the water as I need it is pretty slow. 180 gallon tank on his truck means 20 to 30 minutes to fill at normal flow rates (like through the Noritz).

    3. They ain't Amish no more! -grin They are enjoying their hot showers in the travel trailer they are living in until the shop is finished.

    4. I am already using P/S piping for the Noritz just so I won't have to change anything once the wood boiler comes online. When the wood boiler comes on line I will just disconnect the Noritz from the primary loop, tie in the boiler loop, and go for it.

    5. If we use the Noritz for backup it will be out on the boiler room. I have done wood boilers with gas backup before. I just make a primary loop header and drop my boiler supplies and returns into it, then take my secondary loops out of it like normal. Works like a charm.

    6. Yes, it is LP.

    7. Thanks so much for your input.
  • Eric_8
    Eric_8 Member Posts: 66

    Why don't I want to do it?

    Because he doesn't need it. He thinks he does, but he is basing it on the PA winters, not on NC winters. I really, really think if we do go ahead with it that he will regret investing the money, time, and hassle into it. He truly does not comprehend winters like we have here. Imagine if you spent the first 40 years of your life never going more than 45 miles from where you were born. That's this guy.

    I am about to tell him to try to make it this winter without and then if he needs it I will hook it up.

    BTW, he is fast becoming one of my best friends and depends on me a lot to steer him right in this crazy new world he is living in. He feels very intimidated by all the new stuff he has to deal with. If I told him NOT to do it he would listen. But I don't operate that way. He needs a coach, not someone to tell him what to do. I am very humbled by his friendship and trust and do not want to blow it. (We were friends before I started his job.)

    It is AMAZING to see a new world unfold before his eyes. He always says stuff like "Richard! I have running water! And the preachers aren't even going to come talk to me about it."

    Hard to explain if you haven't been there.

    On the other hand, when I was needing some firewood he was right there with his chainsaw to help me. The Amish have a LOT to teach us about helping each other if we would just stop and learn.

    I hope my friend does not lose the good things from his former culture as he immerses into the modern (and crazy) world.
  • There you go,

    I don`t think even Brad White himself could have explained-it any better than that, somehow I knew the "infallible HR had to enter the equation somewhere", anyway,, Good Luck with your project Richard!

  • tim smith
    tim smith Member Posts: 2,752

    Richard, why don't you just put a 4 gpm tub fill on tank off Noritz, fill tank with 160 degree water then bring up the last 20 degrees with a heat exchanger for tank w/ recirculation pump. This could be piped off the Noritz also and with tees set up for future wood boiler. Just a thought. Tim
  • mark schofield
    mark schofield Member Posts: 153
    solar help ?

    Thats about 42 cu.ft of water. If you dump the hot water every morning and then refill and use the evac tube panels as Phil suggested with a heat exchanger to pre heat the water during the day, that might give you a big start on heating your load. You could even put another exchanger in the tank to preheat the DHW. I have two 30 year old Grumman solar systems on my and the daughter's house. I'll never not use solar. Even in this area- Madison CT. good luck.
  • bruce_21
    bruce_21 Member Posts: 241

    A mason friend of mine does it this way: He puts his 50 gal drum full of water in the middle of his sand pile at the site and plugs in an electric heater which drops into the water drum, covers the whole mess with an insultarp. He worked right thru last Jan and Feb here in NW Conn. A big advantage is the site owner pays to heat the water and sand and all he has to do is drive to the job in his car. This is probably one angle that the dear Amishman wouldn't be scouting for, but its cool because my friend writes it into his contracts.
  • hot_rod
    hot_rod Member Posts: 22,158
    A concrete wall I hope...

    if he plans on hanging about 180 gallons or 1500 pounds of water on a wall :)

    Sounds like an ideal arrangment for a drainback solar. That tank would be the drainback tank. 120 square foot of collector would do a nice job, three 4X10 panels. I happen to have some used ones.

    Do you really need 160- 180? That's way beyond what most of those plastic truck tanks will handle.

    in your climate solar should heat that load 70% of the year or more.

    A simple copper coil in the tank would be an excellent back up HX.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • bigwilly104
    bigwilly104 Member Posts: 50

    is the highest the noritz models will go. but its seams like reinventing the wheel with a heat ex. or inderect. if you find out how long it takes to fill the tank just set a timer to open a solinoid valve early enough and the float will do the rest. If the guy leaves for work at six make sure the tank is full by five and he still gets a shower. if the tank is insulated it wont loose to much temp in a hour or two.
  • Eric_8
    Eric_8 Member Posts: 66

    He has a galvanized tank for his truck.

    But hey... I like the copper loop idea. Let me roll it around in my head.

    Thinking about the solar too. Kinda reluctant to go with solar because we are doing the wood heat within 2 years. But hey... nothing is off the table.

    Oh, and the tank? I said hang off the wall but it will also have legs. We are talking a pole barn so he has some strong "legs" to work with. But I am not touching the tank hanging part. I won't go near that part! I will heat it but that is all. I don't need to spend the rest of my life wondering if it is going to fall down and kill someone.
  • Rich Kontny_5
    Rich Kontny_5 Member Posts: 116
    Use the...

    Noritz during a non priority period to fill the dump tank, use a piping arrangement so the inlet to the Noritz goes through a double wall heat exchanger (a pre-heated feed source in other words). Amtrol makes a dual HX storage tank that would do this.

    This would give you a reliable high temp water source with preheated inlet water for energy savings. Even though the wood system sounds economical it is not free in terms of time. If you only need this dump water several times a day it is foolish to overfire the wood system to obtain this. Also an open top cylinder is a very energy wasting storage device. Think of the steaming condensate lost to the atmosphere not to mention the humidity problems.

    I would make an arrangement where the wood is the primary heat source for normal needs while I would make the Noritz the primary heat source for the dump load.

    Srap the open tank concept other than to fill it with the 6-8 GPM Noritz and to dump it ASAP. Proper backflow protection is a must!

    Make Peace your Passion (Bless our troops)

    Rich Kontny
  • Richard Miller_3
    Richard Miller_3 Member Posts: 61

    Well, I got him talked out of it!

    But I am heating his temporary living quarters (a travel trailer) with a fan coil unit this winter.

    We are going to try to build one ourselves. A "friends" project, not as a business thing. He helped me split wood for a 9 hour day this summer plus many other things. So I am going to help him out with this part of it. Should be fun to play with it.

This discussion has been closed.