South Dakota Auto vs. On vs. Recirc Fan Setting

Discussion in 'Maintenance and Troubleshooting' started by grizzwold, Dec 8, 2015.

  1. grizzwold

    grizzwold New Member

    Hi all -

    First, I want to say this is my first post but I have been a lurker for a couple years, and this is a great site. I have learned so much regarding buffer tanks, how to choose a geo installer, etc. But now I have a question.

    I have a 4 ton Hydron Module two stage forced air geo unit (HXT048). Two zone ranch home (one upstairs, one down), each zone has a vented gas fireplace in the main living area in proximity to the Honeywell thermostats. Two inches of spray foam on the attic deck before fiberglass for the remainder (R-50), including over covers for the cans, zip sheathing, bibs in the walls, rigid foam behind outlets and in window headers, spray foam on the rim joist, Anderson 400 series windows, etc. HRV for ventilation. I haven't had it blower door tested yet, but I'm confident it will come back pretty tight.

    What I'm running into is whenever I run a fireplace or there is cooking in the kitchen or the sun shines in the south facing windows, the place obviously keeps the heat, which is good. However, on AUTO setting, the fan only runs when the thermostat calls for heating, so that heat isn't being circulated but that particular area starts to get warm.

    Conversely, I've read that although it's an ECM motor and doesn't draw much current, there is no need to have it on all the time, and it could cause humidity to reenter the home during the cooling season.

    I spoke w/installer, who I think is great, and he says he recommends AUTO, his is in AUTO, but do what makes us feel comfortable. (He did explicitly say, though, that the humidity being introduced was overstated because the condensate goes straight to the drain.) Which brings me to the Recirc setting. I see it calls 35-37% of the time, which is probably enough to recirc all those kinds of heat I mentioned before.

    So to get to the meat of the question, what are your recommendations for a set it and forget it in terms of fan setting in my situation? Does Recirc make sense for me? AUTO? On?

    Thanks!
    G
     
  2. ChrisJ

    ChrisJ Active Member Forum Leader

    Is this the fan setting on the thermostats or HRV? How is the HRV set up? It's own ductwork or integrated into the heating and cooling ductwork?

    Chris
     
  3. grizzwold

    grizzwold New Member

    These are fan settings on the thermostats themselves. The HRV is plumbed into the HVAC.
     
  4. ChrisJ

    ChrisJ Active Member Forum Leader

    Is the recirc only option to run at the 35-37%? When the thermostat calls to recirc the HRV comes on with it correct.

    If you can switch to ON when running the gas fireplaces then you're only mixing the air when you need to, except for the times of solar gain.

    I would not use recirc in summer. Is there a way to limit the HRV in summer to not always run when the system runs to cool?

    Chris
     
  5. grizzwold

    grizzwold New Member

    From what I was able to understand, in addition to running when the system is running, the recirc will run an additional 35-37% of the time. A kind of middle point between AUTO and On.

    The HRV is a single point tied into the supply and return ducting. It is not tied to the geo's run as I understand it.

    I could use recirc in the non-cooling season (most of the year here) and go to AUTO during the cooling season, but I'm wondering if there are any strong reasons to not use the Recirc option and/or just leave it on.
     
  6. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Under no circumstances should fan be run in any mode other than auto during cooling season in any climate where excess humidity is a comfort concern.

    I beg to differ with the statement that "the condensate goes straight to the drain". The average high efficiency air handler coil contains approximately 100 square feet of fin and coil surface area per ton of capacity. In a humid climate every square inch of all that metal is wet and holds lots of water that will be quickly blown / re-evaporated into the ductwork during the compressor off cycle.

    If the house is tight and ductwork is in conditioned space I see no issue with fan set "on" during heating season for most even temperature distribution from point sources.
     
  7. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I agree with engineer. I would add dampered outdoor air to the fire places for combustion air.

    Mark
     
  8. mrrxtech

    mrrxtech Member

    I don't know what an HRV is, but I have experience with a gas fire place being in the same room as the thermostat for a geothermal heat pump, plus the sun shining into a 5 foot door and window.
    To move the air I have a ceiling fan since there's a Cathedral ceiling where the heat tends to collect if the ceiling fan is off. I use the fan to equalize the air temperature in the room.
    To keep the house warm I have to lower the gas fireplace bulb thermostat setting and raise the heat pump thermostat setting to allow the fireplace to cycle less and the heat pump to cycle more often. There is a balance in the house temperature and Great Room temperature that can be reached, but as the temperature changes I have to make thermostat adjustments.

    I would recommend ceiling fans for the rooms with fireplaces, and use an exhaust hood or under counter exhaust system for the cook top depending on whether it's on an exterior wall or on an island.

    For now I'm chasing room temperature comfort by making the two thermostat adjustments as necessary, but eventually I'll need to automate.
    I realize that most people don't want to make heating and cooling a daily science project, just set the thermostat and forget it. Somehow that gizmo in the basement keeps the house comfortable. Hey, where's the remote?
     
  9. Leon Korner

    Leon Korner New Member

    I recommend you to try automatic fireplace. My family is using it for a year and we are fully satisfied. It has a smart system so you won't have to worry about temperature changes! Besides, they have luxurious look and are eco-friendly! I've bought mine from Planika!
     

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