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  • #16
    Re: Tankless flush

    Originally posted by MPMGinAL View Post
    Here's my delima. We are on IPC. The IPC states that a thermal exspansion device must be installed if there is a potential for the pressure in lines to increase beyond the pressure setting of PRV. Couldn't that happen with a tankless since pressure and temp are directly related? At the moment that you turn hot water off at the fixture wouldn't pressure be higher than say the cold water line? And they must have a t&p. doesn't say tankless, or tank-style, or gas or electric. Just says water heater or hot water storage tank.

    I'm assuming by PRV you mean " pressure relief valve" and not " pressure reducing valve". If so, every manufacturer recommends a 150 psi relief valve (isolation kit PRV's are at that rating) and the pressure increasing above that is highly unlikely.

    Comment


    • #17
      Re: Tankless flush

      [quote=MPMGinAL;214023]Nice job rick.

      The water is not going to heat unless there is flow, so there is no need to install t&p. quote]


      I think the releif valves that come with the install kits are pressure releif only not temp.

      Comment


      • #18
        Re: Tankless flush

        Originally posted by Jay Mpls View Post
        Gas volume is ok with the little bit of 1/2" run there.It looks like a 3/4x1/2 90.

        actually it's a 1'' x 3/4'' 90 with a 3/4'' ball valve csa rated.


        I'm assuming 1/4 lb gas pressure? Gas-wise those are thirsty little units.
        Here in Mpls our water runs about 4 grains hardness and the mfg's recommendations on most are flush one a year.
        It's friday and now I want a chili burger. :-(
        Fish or none.
        mark, it's actually a big tommys burger. 405 @ pico

        rick.
        phoebe it is

        Comment


        • #19
          Re: Tankless flush

          [quote=plumbertim1975;214069]
          Originally posted by MPMGinAL View Post
          Nice job rick.

          The water is not going to heat unless there is flow, so there is no need to install t&p. quote]


          I think the releif valves that come with the install kits are pressure releif only not temp.
          The only time you install a T&P is when your code inspector won't pass it until it has one.

          The problem with T&P's on tankless are......when they fail...they fail in the open position and the heater doesn't know the difference between that and an open fixture. Not only will you have running water, it will be hot water to boot!

          All pressure only relief valves need to be sized for 150 psi and the max btu rating of the heater. If the btu rating is lower than the output of the heater your PRV will weep.

          Comment


          • #20
            Re: Tankless flush

            You gota love your tankless to go through all the maintance..
            The people buying dont want to think about what its going to take to keep it going
            They just want it, because there neighbor got one

            Comment


            • #21
              Re: Tankless flush

              Originally posted by DELCASE View Post
              You gota love your tankless to go through all the maintance..
              The people buying dont want to think about what its going to take to keep it going
              They just want it, because there neighbor got one
              Can't say I agree with that statement.

              Comment


              • #22
                Re: Tankless flush

                [quote=OnceandforAll;214142]
                Originally posted by plumbertim1975 View Post

                The only time you install a T&P is when your code inspector won't pass it until it has one.

                The problem with T&P's on tankless are......when they fail...they fail in the open position and the heater doesn't know the difference between that and an open fixture. Not only will you have running water, it will be hot water to boot!

                All pressure only relief valves need to be sized for 150 psi and the max btu rating of the heater. If the btu rating is lower than the output of the heater your PRV will weep.

                Ummm, actually you only install a t&p on a storage type water heater, not on a tankless. You never install a t&p on a tankless water heater, there is no storage

                Only a pressure relief is required.

                I had a watts 210 on a tankless once, idiots.
                sigpic

                Robert

                Comment


                • #23
                  Re: Tankless flush

                  [quote=westcoastplumber;214226]
                  Originally posted by OnceandforAll View Post


                  Ummm, actually you only install a t&p on a storage type water heater, not on a tankless. You never install a t&p on a tankless water heater, there is no storage

                  Only a pressure relief is required.

                  I had a watts 210 on a tankless once, idiots.

                  Gonnna disagree. Temperature and pressure go hand in hand. What difference does it make not having a storage vessel? The system is still a closed loop reguardless of storage capacity.

                  --The Temperature / Pressure needs to go somewhere

                  Okie

                  Comment


                  • #24
                    Re: Tankless flush

                    Wait! that wasn't Onceandforalls post?

                    Comment


                    • #25
                      Re: Tankless flush

                      I saw that too.

                      Comment


                      • #26
                        Re: Tankless flush

                        Originally posted by OkieBill View Post


                        Gonnna disagree. Temperature and pressure go hand in hand. What difference does it make not having a storage vessel? The system is still a closed loop reguardless of storage capacity.

                        --The Temperature / Pressure needs to go somewhere

                        Okie
                        If Temp/Pressure go hand and hand ...what does it matter if is a PRV and not a T&P?

                        When the unit is operating it is a OPEN LOOP system. True, that when the system is turned off it is theoretically a closed loop.....but when the unit shuts down it is not heating water, so there is no temperature rise....it can only cool down. Pressure will build, but not much.

                        Did you know in some jurisdictions by putting a drain in a heating loop....it's considered an open loop system? Even though it isn't really.

                        Comment


                        • #27
                          Re: Tankless flush

                          Originally posted by OnceandforAll View Post
                          If Temp/Pressure go hand and hand ...what does it matter if is a PRV and not a T&P?

                          When the unit is operating it is a OPEN LOOP system. True, that when the system is turned off it is theoretically a closed loop.....but when the unit shuts down it is not heating water, so there is no temperature rise....it can only cool down. Pressure will build, but not much.

                          Did you know in some jurisdictions by putting a drain in a heating loop....it's considered an open loop system? Even though it isn't really.
                          I'll tell you what the code interpretation officer for the whole state told me.

                          "It doesn't matter if you're right, do what your codebook says or you fail inspection."

                          So it doesn't matter who's correct. Some codes & areas have NOT put tankless sections in their books so EVERYTHING must be treated as a tank installation irregardless of the practical science or "common sense".

                          J.C.

                          Comment


                          • #28
                            Re: Tankless flush

                            Originally posted by JCsPlumbing View Post
                            Some codes & areas have NOT put tankless sections in their books so EVERYTHING must be treated as a tank installation irregardless of the practical science or "common sense".J.C.
                            Actually, in a case like that the manufacturer's installation instructions would probably take precedent. Especially where warranty and safety issues are concerned, requiring that things be done as they always have been could get the jurisdiction having authority into a legal pickle.

                            Comment


                            • #29
                              Re: Tankless flush

                              Originally posted by Plumbus View Post
                              Actually, in a case like that the manufacturer's installation instructions would probably take precedent. Especially where warranty and safety issues are concerned, requiring that things be done as they always have been could get the jurisdiction having authority into a legal pickle.
                              Whichever is determined to be more stringent by the code interpretation official.

                              So if the mfg. doesn't require a T&P and the current code writing does, then the more stringent application would apply. (Or the other way around) So a T&P would be required.

                              Once again, irregardless of science or common sense.

                              J.C.

                              Comment


                              • #30
                                Re: Tankless flush

                                Originally posted by JCsPlumbing View Post
                                I'll tell you what the code interpretation officer for the whole state told me.

                                "It doesn't matter if you're right, do what your codebook says or you fail inspection."

                                So it doesn't matter who's correct. Some codes & areas have NOT put tankless sections in their books so EVERYTHING must be treated as a tank installation irregardless of the practical science or "common sense".

                                J.C.

                                As I stated earlier in the thread:

                                The only time you install a T&P is when your code inspector won't pass it until it has one.

                                Comment

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