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  1. #1
    Join Date
    Oct 2006
    Location
    Midwest
    Posts
    282
    I'll be replacing my gas furnace & air conditioner soon and I'd appreciate your help with some questions.

    I'm not clear on how the "humidity control" function works on these Infinity/Evolution t'stats. Do they require that the blower run constantly even when cooling or heating aren't called for? Or can the t'stat fan be set to "Auto" & still get the "humidity control" benefit?

    Do the additional capabilities of these controls require new wiring with more conductors or will existing 4 or 5 wire t'stat cable work?

    I understand the logic in having multiple speeds for heating & cooling depending on the outside temperature, but I'd be very interested in your opinions regarding the value of (or need for) additional humidity control. Is this a solution for a problem that is not that significant? My house was built in 1994 and is pretty tight & well insulated.

    Thanks for your help ....

  2. #2
    4 conductor furnace to T-stat. 2 or 4 conductor to AC unit depending on model. There is some wierdness with the number of conductors to the outside unit, but usually a maximum of 4. An outdoor air temperature sensor (2 conducter) may need to be added. There is also the ability to sense temperature in a different location than the control. Humidity is sensed at the control.

    The stat can be set for cool or heat or autochangeover meaning, it will pick the right mode.

    Humidity won't be dead on. Just close. Humidity generally helps pick the fan speed. There *MAY* be some variation intemperature too, but there is no need to be in constant fane mode. A test runs at 1 PM every day for about 5 minutes at high speed to test the filter.

    If your house is TIGHT, you may want to consider an HRV or heat recovery ventilator as part of the "Infinity system". This allows you to draw air from outside and heating it with the the exhaust gasses from the furnace in a heat exchanger. This is different from combustion air from outside. If you need moisture a humidifier can be added.

    If you do a search on "comfort chart" you'll find a renge of temps and humidities that a certain percentage of people are comfortable in. So, creature comfort is one reason for humidity control.

    Your health is another.

    The wood in you house does not like it to be extremely dry.

  3. #3
    Join Date
    Oct 2006
    Location
    Midwest
    Posts
    282
    Thanks for your input. I understand the humidity considerations & the HRV setup you describe, since I did some HVAC design years ago. I should have mentioned that I already have a humidifier with a "percent humidity" control for the heating season.
    Here in South Dakota, I'm not sure that the average humidity in the summer is high enough to warrant the price of additional humidity control these systems provide.
    If infiltration doesn't provide enough fresh air (in a really "tight" building) an HRV would be worth considering, although it would offset most or all of the efficiency gains of a new system. Decisions, decisions. Thanks again.

  4. #4
    The HRV would increase efficiency of the system.

    Not sure what you mean by "although it [HRV] would offset most or all of the efficiency gains of a new system.".

  5. #5
    Join Date
    Oct 2006
    Location
    Midwest
    Posts
    282
    Sorry, I think you're right. Thanks again.

  6. #6
    Let's look at your speed issue again. Higher speeds are usually used for AC because of the evaporative cooling effect of the airflow on people. Cold air is also heavier and requires a higher hoursepower to move it. If you move air fast across an AC coil less moisture will be removed hence you can control humidity somewhat by controlling fan speed.

    You would like a house to be quiet. High fan speeds contrubute to duct noise which could be objectionable. A variable speed blower with an excellent control like the Infinity allows the use of the lowest fan speed that would achieve the comfort desired. A variable speed motor with an appropriate control will be most helpfull for air conditioning, becuse the higher speeds create the most duct noise and you don't want the higher speeds because of the noise. The Infinity system is quiet. Both inside and outside the house.

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