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HRV and Whole-House Fan

LodiDave69 | Posted in General Questions on

I live in Lodi CA and have a whole house fan which brings in a lot of dust. I want to install a Lennox HRV3-195 system in my single story slab foundation house of 1650 square feet,
Should I remove the whole house fan??

Thank you

DAvid Fudala

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  1. exeric | | #1

    This is an interesting question. I have a WHF and don't have that problem at all. Are you close to a construction site or agricultural acreage (lots of dirt plowing)? If that problem outweighs the normal advantages of a WHF for conditioning the air then I would say get rid of it.

    Whole house fans always seem to be advertised as fresh air generators by manufacturers. That's wrong. They do that but their main function is to condition the air in the house at times when the outside air temp is close to what is more comfortable to humans. For instance, in the shoulder season where I live in California right now it gets down to 48F at night and up to 80F in the day. The average temperature right now is around 65F. It's a little chilly in the house most times because it fluctuates a few degrees around that 65F average. So I open windows and turn the WHF on for around 5 hours midday to warm up the house to 70F. That's really what a WHF is meant for - to shift the outside temperature average to accentuate heat or cold in the house. It works really well for that in California in shoulder seasons and also in summer in locations that cool down to 65F at night. Some places don't. It's cheap and efficient air conditioning here.

    It would be sad If you don't, or can't use it for that because of the dust. If you don't then get rid of it and get an HRV/ERV if your house is tight enough to justify it.

  2. exeric | | #2

    I should add one more thing. Don't expect an HRV to fulfill the same function of conditioning the air temperature as a WHF will do. Just as WHFs are sometimes falsely advertised as fresh air generators some HRV/ERV manufacturers falsely advertise their products with a bypass function as being able to condition the air temperature. Neither product will fulfill those opposing functions well or efficiently due to the vast difference in air flow between HRV/ERVs and WHFs. It's simple physics.

  3. LodiDave69 | | #3

    I use the WHF in the late evenings, but I have noticed more dust accumulating on the inside of the house, living in Lodi we get a lot of dust off of the delta since we get a westerly breeze in the evenings. I am considering the HRV system for cleaner interior air. Also my house is so sealed that when I do run heating or air I have a negative air flow being sucked in from the outside if I open a window or door.

  4. erik_brewster | | #4

    Sounds like you should get rid of the WHF. I grew up with one. It's impossible to filter the intake air, so you are dealing with unfiltered air. Can't solve your dust issue that way. Also, with smoke from wild fires, you are going to have problems, too. When conditions are right, they are nice, though. I don't know how you would seal your house with a WHF. the one I grew up with had louvers and we would tape plastic sheet over in the winter.

    The HRV you listed seems reasonable. I would strongly suggest putting a MERV13+ filter box on the input. Probably need to have a pretty big (20x20 or bigger or multiple smaller ones) to keep your pressure drop down. I did that and haven't had problems with my HRV during the fires recently. I did individual runs to the bedrooms, but a common return in the kitchen. If I did it again, I would make individual returns. Closed bedroom doors really throws off the flow in that room. If you are going to make an improvement with your AQI by dumping the WHF and going HRV, might as do it well the first time.

  5. LodiDave69 | | #5

    I already have a whole house Electronic Air Cleaner,, but as I said I have a negative pressure in the house because it is so air tight. My entire system is in the garage, so they want to use the attached procedure

  6. exeric | | #6

    I've been looking at the schematic you posted that ties the HRV in with the furnace and air handler system. It's far from ideal. The problem is the air handler system has to be running to get air circulation through the vents. That means fresh air will normally only be coming in to the house when your thermostat detects that the home needs to be cooled or heated. The alternative is to run the air handler all the time. An air handler consumes a lot of energy. I'm not sure how important that is to you but I'd be concerned about that. A dedicated Panasonic ERV with it's own ducting consumes 30 watts. Yours will consume probably 10 times the energy mine does. That would occur even when there is no temperature change required in your house because you'll still have to turn on the air handler. As I said, not ideal.

    Another thing is that HRV/ERVs need to be located in conditioned space so a garage location won't work unless it's air conditioned. If it's not then the HRV won't work correctly.

  7. LodiDave69 | | #7

    There is another diagram. This Unit can be connected as HRV/ERV unit will ensure the
    air handler/furnace blower motor is operating whenever
    the HRV/ERV blower is ventilating so the system will run as programed and will also run when the main system is on. According to Lennox the main unit can be installed any place, it is the insulated ducting that brings in the air??

  8. LodiDave69 | | #8

    Please see the below attachment of this system HRV3-195

  9. exeric | | #9

    I understand. Your system will work. If one was designing and building your own home from the start one wouldn't do it this way. However, now that the house is built and is just being retrofitted it would be expensive in labor to install a dedicated HRV system with its own ducting. I was just saying that it won't be very efficient because you need to run the air handler fan, which uses a lot of power, to get fresh air to the room vents. A dedicated system which uses the HRV's own fans to move the air will use 30 to 50 watts for a home your size. The combined use of the HRV's own fans and the air handler fan will probably use 300 to 500 watts. But it is what it is. You'd also pay a lot more in labor to put in a dedicated duct system at this point.

  10. LodiDave69 | | #10

    Thank you for the feed back. What brand name of system would recommend

    1. exeric | | #12

      I'd love to recommend a drop in substitute HRV/ERV for existing ducting for a whole house HVAC system that is both efficient and works. But I don't know of one that fulfills both requirements. Perhaps an HVAC specialist on this forum who does that for a living knows of one that can do both. Maybe there are air handler fans that can be retrofitted alongside a new HRV that are ECM fans and don't burn so much power, as Jon suggested. Someone else here might know that. Other than that I can't think of a good solution without retrofitting a dedicated duct line for the HRV. That's what I did on my home, but it involved self teaching, a lot of work, and space for an HRV in conditioned space. I buried the new r-8 flexible 6" diameter ducts under cellulose in the attic. It doesn't sound like you're up for that.

  11. Jon_R | | #11

    Note that if you retrofit an ECM blower motor, power draw may drop to a much more reasonable ~80 watts.

    If you can't, a 2x over-sized HRV running at a 50% duty cycle will save a significant amount of furnace blower energy - while still providing good air quality.

  12. LodiDave69 | | #13

    What is your feed back on a UV system in the HVAC? Do you have any recommendations??

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