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    HVAC Booster Fan

    I have a room that the wife is using as an office. It's the longest run of the ductwork, and it faces west with two large windows, and it gets warm and stuffy in the afternoons. It's a Lennox system, and doesn't have any zone capabilities, and I also can't use any Zwave thermostats due to the proprietary digital communications between the thermostat and the units. I had a HVAC guy who poo-pood on putting a booster fan on this run. Of course his suggestion was to install inline dampers on the 10 runs and do a flow survey with an airflow meter and 'balance' the system. That sounds like a few thousand dollars.
    I like my idea of installing an inline Fan and controlling it with Homeseer to be on when the room is occupied, and operating independent of the HVAC, and scavenging air from the other cooler rooms when the HVAC is off. His main complaint was that the fans are noisy. Well, maybe it shouldn't be running full tilt. So has anybody on here installed an inline Fan? What would be needed to install a variable speed Fan that could be controlled by Homeseer?

    #2
    I have a room like that and have installed two booster fans. (There are two runs to the room.) I'd listen to your HVAC guy.

    The booster fan will not be very effective if the duct that it's in does not receive enough input air to allow the fan to increase air flow. Instead, the fan will just get very noisy from the turbulence it creates, and airflow could end up being unchanged or even impeded.

    I had to go to some length to assure that my fans run only when there is sufficient air coming from the air handler. I have a two-zone system, and HS needs to know when only the one zone is calling, and then it has to wait for a couple of minutes for the main fan to get to full speed to be sure there is sufficient air supply to accommodate the extra capacity demands of the booster fans. If the second zone calls for AC while the fans are on, HS has to shut them off or they get very noisy. It was not a simple task.

    Does the room have its own air return duct? If not, part of the problem could be getting air back to the air handler.
    Mike____________________________________________________________ __________________
    HS3 Pro Edition 3.0.0.548, NUC i3

    HW: Stargate | NX8e | CAV6.6 | Squeezebox | PCS | WGL 800RF | RFXCOM | Vantage Pro | Green-Eye | Edgeport/8 | Way2Call | Ecobee3 | EtherRain | Ubiquiti

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      #3
      I also have a room like that and had installed one of those booster fans in the duct leading to it. It doesn't run all the time, just when it's cold mostly. I can manually turn it on when it's hot too, to help with cooling - but generally not because I do find it somewhat noisy. For winter use, I have it turn on a couple of minutes after the furnace calls for heat, then turn off when the furnace ends it's cycle. I have it tied to an event for my s-z-wave stat.

      Robert
      HS3PRO 3.0.0.500 as a Fire Daemon service, Windows 2016 Server Std Intel Core i5 PC HTPC Slim SFF 4GB, 120GB SSD drive, WLG800, RFXCom, TI103,NetCam, UltraNetcam3, BLBackup, CurrentCost 3P Rain8Net, MCsSprinker, HSTouch, Ademco Security plugin/AD2USB, JowiHue, various Oregon Scientific temp/humidity sensors, Z-Net, Zsmoke, Aeron Labs micro switches, Amazon Echo Dots, WS+, WD+ ... on and on.

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        #4
        I would recommend having the HVAC tech balance the system. You can have a giant fan in a system but if you don't have appropriate returns, or exhaust ms you won't get to the appropriate air-flow or static pressure level. Leave this too long and you kill your furnace/AC system.


        Sent from my iPhone using Tapatalk

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          #5
          I had to go to some length to assure that my fans run only when there is sufficient air coming from the air handler.
          It sounds like you had issues because you had two ducts feeding the room, and the two fans kinda fought each other. But, you would think the fans wouldn't have to be running full tilt to make good airflow, and I'd want a variable speed unit. Why does the main unit have to be running at all? Wouldn't the fans just suck air from the other rooms? I wouldn't think the main unit would have dampers that close when the fan isn't running, but even if it did the booster would just scavenge air from the adjacent room that Y's off from the main duct which this room stays cool because it isn't west facing. I just can't believe they have to be spun up to high db levels to get decent airflow.

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            #6
            Robert,
            How noisy is the booster? What size is the unit? What happens when the booster is on but the main unit is off? Can you feel a breeze coming out of the vent? For the record it's hard to feel a breeze coming out of the vent in this room.

            Kerat,
            I can understand running into issues if i shut off all the vents except this one room which would cause over-pressurization and stuff which would definitely cause issues. I don't see a booster fan sucking air into this room as problematic. The returns are huge, so I don't think the returns (Plural) is the issue. I think most of the problem is the thermostat is located where 75% of the air vents are located which is at the opposite side of the house from this room. And frankly, the duct work and insulation is immaculate in that attic, I'm not sure I want a bunch of yahoos installing 10 dampeners everywhere up there when if this fan could possible alleviate the problem.

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              #7
              I haven't measured the noise level, but when it's on you can hear it especially when the furnace is running low speed. It does provide a good push to the air out though. I forgot to mention that I have it controlled by a z-wave appliance module. Also didn't mention that the room it services is the only room in the house which doesn't have a cold air return. I'm thinking on sacrificing part of a linen closet and running a return to the adjacent room.

              Robert
              HS3PRO 3.0.0.500 as a Fire Daemon service, Windows 2016 Server Std Intel Core i5 PC HTPC Slim SFF 4GB, 120GB SSD drive, WLG800, RFXCom, TI103,NetCam, UltraNetcam3, BLBackup, CurrentCost 3P Rain8Net, MCsSprinker, HSTouch, Ademco Security plugin/AD2USB, JowiHue, various Oregon Scientific temp/humidity sensors, Z-Net, Zsmoke, Aeron Labs micro switches, Amazon Echo Dots, WS+, WD+ ... on and on.

              Comment


                #8
                HVAC Booster Fan

                Listen to the advice here and your tech. Balance the system. Static pressure is a key thing on hvac systems, and if it's wrong, you aren't running efficiently and over time, decreasing the usable age of your equipment.

                I had a new system put in about 3 years ago and went with a variable speed blower because of static pressure issues. It was the cheap way of dealing with the problem VS adding in more returns. It's still not right and if I could ever convince the wife to rip up walls to add in more returns, I would do it.

                You either have a leaking duct, or not a big enough return. Air is like water, it will flow to the path of least resistance, if it doesn't have a path, you won't get flow and just a pretty spiny thing. Adding a blower will do very little if the air doesn't have a place to go. Think of it like an air traffic jam.

                Oh and balancing a system has nothing to do with adding dampers. It's making sure airflow is as perfect as it can be. Most spec houses are built wrong when it comes to hvac because it is the last thing to be installed and rarely considered. So what we thing of big returns, really aren't. I have 2 big returns on my house and it's not enough for the square footage.

                Comment


                  #9
                  Originally posted by tome10 View Post
                  It sounds like you had issues because you had two ducts feeding the room, and the two fans kinda fought each other. But, you would think the fans wouldn't have to be running full tilt to make good airflow, and I'd want a variable speed unit. Why does the main unit have to be running at all? Wouldn't the fans just suck air from the other rooms? I wouldn't think the main unit would have dampers that close when the fan isn't running, but even if it did the booster would just scavenge air from the adjacent room that Y's off from the main duct which this room stays cool because it isn't west facing. I just can't believe they have to be spun up to high db levels to get decent airflow.
                  Inline fans are axial fans. The main fan in the air handler is usually a squirrel cage fan. Squirrel cage fans are typically much quieter for a given air flow compared to axial. Also, residential HVAC units rarely have back flow prevention dampers that close when the air handler shuts down. That's a feature for commercial and industrial systems, especially with parallel air handlers.

                  Sent from my Pixel XL using Tapatalk

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                    #10
                    So say I wanted this Fan.
                    https://hydrobuilder.com/vortex-s-li...FQQpaQod26AFSA

                    Supposedly it comes with a standard plugin. What would you use to control the speed-on/off via Zwave?

                    Comment


                      #11
                      Originally posted by tome10 View Post
                      Why does the main unit have to be running at all? Wouldn't the fans just suck air from the other rooms? I wouldn't think the main unit would have dampers that close when the fan isn't running, but even if it did the booster would just scavenge air from the adjacent room that Y's off from the main duct which this room stays cool because it isn't west facing. I just can't believe they have to be spun up to high db levels to get decent airflow.
                      I think you are someone who needs to try things for himself. You may be right about what your system needs. But you are also taking a risk by not heeding the advice of a trained tech and people who have had personal experience. (As a mental exercise, imagine someone with no practical experience in your area of expertise, concluding that something you think is risky is the obvious best course of action.)
                      Will Rogers expressed it a bit more graphically.
                      Mike____________________________________________________________ __________________
                      HS3 Pro Edition 3.0.0.548, NUC i3

                      HW: Stargate | NX8e | CAV6.6 | Squeezebox | PCS | WGL 800RF | RFXCOM | Vantage Pro | Green-Eye | Edgeport/8 | Way2Call | Ecobee3 | EtherRain | Ubiquiti

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                        #12
                        Originally posted by Uncle Michael View Post


                        Omg I am saving that quote!!!


                        Sent from my iPhone using Tapatalk

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                          #13
                          Originally posted by Kerat View Post
                          Omg I am saving that quote!!!
                          He did have a way with words.
                          BTW, I did not intend that link as a put down. I am one of those who insists on trying things that others tell me is a bad idea or a waste of time. I'm usually wrong, but I often learn something important that way, and occasionally I turn out to be right.
                          Mike____________________________________________________________ __________________
                          HS3 Pro Edition 3.0.0.548, NUC i3

                          HW: Stargate | NX8e | CAV6.6 | Squeezebox | PCS | WGL 800RF | RFXCOM | Vantage Pro | Green-Eye | Edgeport/8 | Way2Call | Ecobee3 | EtherRain | Ubiquiti

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                            #14
                            Nothing wrong with the road less traveled. I can't find anything to control the speed with. There's 3 speed wall switches for ceiling fans which means I would have to have a larger switch box and wiring if I was to mount it in the wall. I guess i could just Ieave the switch in the attic. I don't think I would need full tilt, maybe low or medium.

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                              #15
                              I am not an HVAC guy but I have done a lot of remodeling of older houses which included room reconfigurations. It is not easy to change duct work. Most people opt not to spend money to change ducts. In my opinion, there are very few houses that have HVAC systems that are optimized for the house layout. And almost everybody closes vents in rooms that are not used. I think the risk of damage to your HVAC system from using a booster fan is extremely low.

                              However, the fan you are considering seems a bit extreme! Maybe something smaller to start with?

                              Steve Q


                              Sent from my iPad using Tapatalk
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