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Radiant with W/H

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  • #31
    Re: Radiant with W/H

    I'm going to do some checking but someone had me "help" put in his radiant lines for his small garage apartment. He was the designer-so to speak. He was NOT a licensed tradesmen.

    I think he used a somewhat standard water heater that had a side inlet/outlets. I'm going to check but I'm pretty sure that it does not have your coil inside for heat exchange. So basically you are using your potable hot water to heat with also.

    Makes me wonder if this is a good setup? You have a 50 gallon reserve (basically a 50 gallon or whatever size you use coil with x btu burner) for circulation and not the heat exchange into the coil. The temp would be your normal water heater temp coming out of the top and tempered to the desired range coming out of the top side outlet for heat.

    I estimate about 900 sq.ft. and he ran 3/4" throughout his slab.

    This is what I understand to be open loop. I azz-u-me you would use bronze pumps and least corrosive connections throughout.

    Thanks.

    J.C.
    Last edited by BobsPlumbing; 12-05-2008, 05:39 PM.

    Comment


    • #32
      Re: Radiant with W/H

      If he is using Potable water then what is what I would probably describe as open loop.

      Keep something in mind - if he IS using potable water to heat his floors, then you have a situation where bacteria can accumulate/form in his potable water in the floor. When he stops using his heating system in the Summer, all that stagnant potable water is going to be sitting in the water pipes in the floor. Then when the heating system starts going in the Fall for the first time, you'll be injecting all this nasty water into your hot water tank - potentially harbouring disease/bacteria, etc. This is why even with Polaris Boilers, which are a glorified high output hot water tank with a Hot, Boiler Supply, Boiler Return, and Cold outlet (all with potable water coming out of them or going to them), that you should still circulate the water through a a heat exchanger to heat your floors.

      The only time I would ever use Bronze Pumps and making sure that I have all non-ferrous components and/or corrossion resistant or proof components in my heating system is when you have radiant pipe without an O2 barrier. Hell even O2 barrier pipe still lets some Oxygen through.

      Comment


      • #33
        Re: Radiant with W/H

        Thanks Scott K. I have a schematic somewhere that shows piping the potable incoming into the return line. It can decrease efficiency some but keep water moving to battle bacteria as you describe. Good tips I'll pass on.

        Could an open loop system such as this work better (efficient & water heater last longer) than a closed loop water heater system with a coil heat exchanger?

        Or is it just different and not better at all?

        J.C.

        Comment


        • #34
          Re: Radiant with W/H

          Originally posted by JCsPlumbing View Post
          Thanks Scott K. I have a schematic somewhere that shows piping the potable incoming into the return line. It can decrease efficiency some but keep water moving to battle bacteria as you describe. Good tips I'll pass on.
          A combi hot water tank isn't built like a condensing boiler, low return temps can shock the boiler, and cause condensation in the flue gas.

          Originally posted by JCsPlumbing View Post
          Could an open loop system such as this work better (efficient & water heater last longer) than a closed loop water heater system with a coil heat exchanger?

          Or is it just different and not better at all?

          J.C.
          In my opinion, The open system is more efficient, and better for this application. Keep in mind every time you use a heat exchanger, you have a Delta T. That is, the temperature drop across the exchanger. Usually this is between 10-20 degrees you are losing in order to isolate the secondary loop from the possibly contaminated water.

          In a normal boiler install, I prefer the closed system with a plate heat exchanger. You are keeping the majority of the system away from potentially very dirty water, full of sediment. Also, in a system where glycol is needed, you can save putting glycol through the whole system, if you isolate the at-risk loop with a heat exchanger.


          Scott, in AB, our hydronic code stipulates if you have [in-slab] radiant loops tied to domestic water in a house, you must have a timed circulator re-introduced the heating water into the domestic system at 24 hr intervals
          West Trail Mechanical Ltd
          Service. Commitment. Expertise.

          www.westtrailmechanical.ca

          Comment


          • #35
            Re: Radiant with W/H

            Originally posted by bigPipe09 View Post
            A combi hot water tank isn't built like a condensing boiler, low return temps can shock the boiler, and cause condensation in the flue gas.





            In my opinion, The open system is more efficient, and better for this application. Keep in mind every time you use a heat exchanger, you have a Delta T. That is, the temperature drop across the exchanger. Usually this is between 10-20 degrees you are losing in order to isolate the secondary loop from the possibly contaminated water.

            In a normal boiler install, I prefer the closed system with a plate heat exchanger. You are keeping the majority of the system away from potentially very dirty water, full of sediment. Also, in a system where glycol is needed, you can save putting glycol through the whole system, if you isolate the at-risk loop with a heat exchanger.


            Scott, in AB, our hydronic code stipulates if you have [in-slab] radiant loops tied to domestic water in a house, you must have a timed circulator re-introduced the heating water into the domestic system at 24 hr intervals
            BigP - that is interesting and good to know about the 24 hour intervals - perhaps it's in my heating code but I just have overlooked it or not read it yet (too busy focusing on other things -is your heating code also found in the Teca manual?)

            Low return temps CAN shock a boiler, but you WANT condensation in the flue gas of a condensing boiler, or did I mis-read you?

            Concerning you wanting to isolate a boiler from "dirty water," and save on glycol; I realize glycol costs money but it's chump change to the price of adding a plate heat exchanger, a second pump for the glycol loop, a second back flow preventer and Watts 1156, parts, fittings, etc. Also - how dirty are we talking about? ARe you putting dirt in your piping system? Plus, how much could glycol possibly cost you to just put 50/50 in some boiler piping and other loops?

            One of the things I think is being overlooked is the importance of temperature control and controls in general. Heating water up to 120 - 130 - 140 degrees (typical hot water tank) costs more money than heating to 80-90-100 degrees - which are typical required radiant temps in a lot of applications (usually tile floors, hardwood, and low R-value floors - even in very cold ennviroments, and this is absolute coldest days of the year design temperature in floors). This is one application where a heat exchanger would be beneficial if you HAD to use a hot water tank, to lower those temps. No plate exchanger is 100% efficient. If you're sending 120 degrees through an exchanger, you're probably getting temps on the other side of the exchanger that are more realistic radiant water temps (90-100 maybe-ish). Controls though in order to use a HWT for double duty would have to be pretty sophisicated so as to not let the radiant floor water drop down too far and not impact the water temp in the tank too much to the point where the occupants notice it.

            I went to a tekmar little control "thingee," a while ago, and the guy said that their tests show that controls alone can save you anywhere from 5 to 30% on your heating bill. I'm no controls expert nor do I even do them for my job (we have a seperate control crew at my company) If you've ever taken the time to read an "essay" by tekmar to see some of the features of their controls and how they save you money you will sh*t yourself. Features they offer to not only reduce the heating bill but also enhance comfort.

            Comment


            • #36
              Re: Radiant with W/H

              Originally posted by Scott K View Post
              BigP - that is interesting and good to know about the 24 hour intervals - perhaps it's in my heating code but I just have overlooked it or not read it yet (too busy focusing on other things -is your heating code also found in the Teca manual?)

              Low return temps CAN shock a boiler, but you WANT condensation in the flue gas of a condensing boiler, or did I mis-read you?

              Concerning you wanting to isolate a boiler from "dirty water," and save on glycol; I realize glycol costs money but it's chump change to the price of adding a plate heat exchanger, a second pump for the glycol loop, a second back flow preventer and Watts 1156, parts, fittings, etc. Also - how dirty are we talking about? ARe you putting dirt in your piping system? Plus, how much could glycol possibly cost you to just put 50/50 in some boiler piping and other loops?

              One of the things I think is being overlooked is the importance of temperature control and controls in general. Heating water up to 120 - 130 - 140 degrees (typical hot water tank) costs more money than heating to 80-90-100 degrees - which are typical required radiant temps in a lot of applications (usually tile floors, hardwood, and low R-value floors - even in very cold ennviroments, and this is absolute coldest days of the year design temperature in floors). This is one application where a heat exchanger would be beneficial if you HAD to use a hot water tank, to lower those temps. No plate exchanger is 100% efficient. If you're sending 120 degrees through an exchanger, you're probably getting temps on the other side of the exchanger that are more realistic radiant water temps (90-100 maybe-ish). Controls though in order to use a HWT for double duty would have to be pretty sophisicated so as to not let the radiant floor water drop down too far and not impact the water temp in the tank too much to the point where the occupants notice it.

              I went to a tekmar little control "thingee," a while ago, and the guy said that their tests show that controls alone can save you anywhere from 5 to 30% on your heating bill. I'm no controls expert nor do I even do them for my job (we have a seperate control crew at my company) If you've ever taken the time to read an "essay" by tekmar to see some of the features of their controls and how they save you money you will sh*t yourself. Features they offer to not only reduce the heating bill but also enhance comfort.
              Ab has an actual code book, B214-01 Installation code for hydronic heating systems, endorsed by CSA and local and provincial jurisdictions.

              Yes you do want your flue gasses to condense on a condensing boiler, but like I said a HWT is not by any stretch a condensing boiler. I have seen them replaced within 5 yrs of installation due to fast wear.

              Back to the H/E issue, I was making reference to systems that actually are run with boilers, and when i said dirty water, i'm talking about rusty water from ferrous parts on your primary loop.

              That was only assuming you do it with ferrous pumps & trim. In a perfect system, with no ferrous pumps or trim, oxygen proof pipe(pex/al/pex), and no loops at risk of freezing, there really is no need for a heat exchanger. But when you run into one of these situations, there are some advantages to it. Like you mentioned even o2 barrier pipe isn't 02-proof. When you keep that loop closed, you are obviously also protecting your pumps and trim. Another reason why i have used H/E's, is when doing a reno job where we weren't replacing old copper piping, and didn't want to add glycol to that part of the system. As I'm sure you're aware, glycol will find leaks in old piping that water won't.

              Regarding the "chump change" price of glycol, let's talk about how much glycol goes into a header feeding a 250 car parking garage snow melt system (snow melt mix isn't a measly 20% glycol 80% water) with a 4 inch header.

              I'm trying to learn the ways of the Tekmar as well. I will say that i find it very user friendly, even though it is very sophisticated. I have an info CD about the TN-4 that I have been making my way through it when i've had the chance and wow is that thing well engineered. think I undertstand about 20% of what it can do right now.
              West Trail Mechanical Ltd
              Service. Commitment. Expertise.

              www.westtrailmechanical.ca

              Comment


              • #37
                Re: Radiant with W/H

                Thanks for all responses to this thread. I've learned alot. Now I might know about 2% of what radiant installers do.

                J.C.

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