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Power Vent Hot Water Heater Question

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  • Power Vent Hot Water Heater Question

    I purchased a natural gas power vent hot water heater (getting rid of the power hungry 23 year old electric unit.) (My new unit reflects Kenmore - but was made by AO Smith.) Like all power vents, this unit uses air to mix with the fumes/gases to safely expel the very hot gases via PVC / CPVC to the outside. In my case, the water heater uses air from the room to mix with the outgoing gases, at the power vent. My question is, some manufacturers like AO Smith now have a fresh air intake adapter that attaches to the power vent and mixes outside air with the outgoing water heater gases. This reduces the negative pressure presented when 200 cfms are being extracted from the house. This saves money and keeps the home less drafty.

    Does any one see a problem with increasing the size of the PVC vent to 3" and adding an intake PVC vent directly to the power vent where the room air is introduced? I called AO Smith and spoke with someone in their Power Vent section. I didn't get a good feeling... I was far more knowledgebale than the rep. Long story short, the rep explained that it can be done, as there is no difference between power vent hot water heaters that use outside air or inside air. One unit simply provides a rubber union to connect a PVC pipe for the introduction of outside air.

    Thank you, Doug

  • #2
    Re: Power Vent Hot Water Heater Question

    Rinnia runs there fresh air supply inside of their IAPMO tested and approved exhaust vent pipe.This is a tankles heater

    What I don't understand about your question is you say you want to increase to 3".The smallest I have ever seen has been 3"

    What model number are you talking about.

    Comment


    • #3
      Re: Power Vent Hot Water Heater Question

      I might suggest having a professional look at it.
      Your terminology & interpretations might be confused here, not to mention that co poisoning is dangerous.

      Comment


      • #4
        Re: Power Vent Hot Water Heater Question

        http://download.sears.com/own/04233205e.pdf

        just looked at the manual.

        the vent you're referring to is for the air intake of the blower exhaust assy.

        the larger commercial heaters that i've seen have all had intake and exhaust vents. these were high efficiency heaters.

        so to answer your question. if you have adequate make up air as required, you shouldn't need a dedicated inlet vent.

        where is the heater installed that creates a draft?

        increasing the vent size in this case is fine for the air supply pipe. according to the manual the total developed vent length is 40' for 2'', taking into account the 90's and 45's.

        i would thing the inlet, make up air would have to be larger than the exhaust to keep from starving the blower.

        rick.
        phoebe it is

        Comment


        • #5
          Re: Power Vent Hot Water Heater Question

          My Kenmore water heater, reflected at the "DD" schematic from the diagram, has the ability to attach a make-up air vent tube. The directions don't support this but the product does. See diagram.

          http://download.sears.com/own/04233205e.pdf

          I would like to run a make-up air vent tube, as seen on the 50 gallon AO Smith home model water heater. See the below link. I would upsize to 3", from 2", PVC to avoid ANY starve for air to the power vent.

          http://www.hotwater.com/lit/im/media...184707-001.pdf

          My efforts are to reduce the infiltration of make-up air into my home (winter unheated dry air or summer hot and humid air). Many plumbers do not consider the fact that water heater power vents displace a lot of air from the home. When considered, a power vent without a positive make-up air connection is quite inefficient. The make-up air, without a positive make-up air connection, is often filled with dust that infiltrates the home via walls, cracks, attics, chimneys, wood stoves, etc... This aggrevates allergy and asthma issues.

          The reasons for the modification are comfort, energy savings and quality of inside air. Yes, we crack a window when we run our gas dryer. The air entering the window, when the dryer is running, is the same volume of air being displaced.

          When will a sealed combustion chamber dryer be introduced?

          Thank you,

          Doug

          Comment


          • #6
            Re: Power Vent Hot Water Heater Question

            If you have to crack a window open to run your 30 something thousand btu gas dryer, your house is way too tight. 'Controlled air infiltration' is alot better than trying to eliminate it all together. Your HVAC system might benefit from an HRV.

            Originally posted by Doc Doug View Post
            Many plumbers do not consider the fact that water heater power vents displace a lot of air from the home.
            I doubt anyone here will take that as a slap in the face, so lets move on. Natural draft water heaters do too. What percentage of the exhaust on your PV heater is dilution, and what percentage is actual combustion products? 2 piping this heater is only going to correct for dilution, and not combustion air.

            Comment


            • #7
              Re: Power Vent Hot Water Heater Question

              AO Smith now makes a hot water heater that I was describing three years ago.

              Using conditioned air to waste for combustion air makes no sense.

              Comment


              • #8
                Re: Power Vent Hot Water Heater Question

                3 years to make your point but you are right. I believe furnaces draw outside air in to cool the exhaust gas I don't know P.V. w.h. haven't done this sooner. It is a waste of conditioned air.



                What ever happened to duckbutter? I wonder if he ever started using a toilet seat bidet.

                Comment


                • #9
                  Re: Power Vent Hot Water Heater Question

                  The water heater you are talking about is called a power direct vent heater which has been around for many years. Direct vent heaters are required in homes that are air tight or if the heater is in a closet type space.

                  I clicked on your link and I get a file not found error.

                  Here is a Bradford white model http://www.bradfordwhite.com/images/...eets/116-B.pdf

                  Scroll to the second page you will see the intake air does not just hook up to the blower it also ties in at the base for the combustion air.

                  What you are talking about is just putting a vent pipe on the intake port of the blower. The heaters combustion air will still be drawn from the room.

                  My suggestion is if this is truly a concern by the right model that has been designed.
                  Ron Hasil Lic #058-160417
                  A-Archer Sewer & Plumbing specializing in:
                  Tankless Water Heaters | Drain and Sewer Cleaning
                  Sump and Ejector Pumps | Backflow RPZ Testing

                  Comment


                  • #10
                    Re: Power Vent Hot Water Heater Question

                    I wonder if the AO Smith sealed unit uses the same pipe to tie to the base for make-up air? (See link.)

                    Having the room's conditioned air for combustion and the outside make-up air for cooling the hot fumes to run through the plastic pipe is better than nothing. This would cut at least 80-90 percent of the conditioned air loss.

                    http://www.hotwater.com/lit/spec/res_gas/AOSRG45900.pdf

                    Comment


                    • #11
                      Re: Power Vent Hot Water Heater Question

                      Originally posted by Doc Doug View Post
                      I wonder if the AO Smith sealed unit uses the same pipe to tie to the base for make-up air? (See link.)

                      Having the room's conditioned air for combustion and the outside make-up air for cooling the hot fumes to run through the plastic pipe is better than nothing. This would cut at least 80-90 percent of the conditioned air loss.

                      http://www.hotwater.com/lit/spec/res_gas/AOSRG45900.pdf
                      The AO Smith unit does direct the make up air into the burn chamber. The pipe is under the the blower assambly.
                      Ron Hasil Lic #058-160417
                      A-Archer Sewer & Plumbing specializing in:
                      Tankless Water Heaters | Drain and Sewer Cleaning
                      Sump and Ejector Pumps | Backflow RPZ Testing

                      Comment

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