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  1. #1

    Honeywell Vision Pro IAQ Questions

    I am having a Honeywell Vision Pro IAQ installed as a retrofit on a 12 year old Trane 3 Ton 13 SEER single stage airconditioning condenser by a licensed HVAC friend of my father-in-law. I am an engineer, so naturally I want to understand the system and maximize performance. I recently finished the basement, but have not cut in the return duct yet, so the basement is much colder than the rest of the house. My house is an open foyer design that is approximately 2300 ft 2 without the basement and temperature equality on the 1st and 2nd floors has always been the biggest problem with my system as supplied by the builder. Last year before the changes, I had a 7 degree difference from the 1st to 2nd floor and had to run the A/C at 68 degrees to have the upstairs at 75 degrees when we slept. Last summer I installed a 20 watt solar attic fan that lowered the air temperature in my attic by over 25 degrees removing a lot of heat load on the upstairs ceiling. We also had the blower motor changed from 1/3HP to 3/4HP in cooling mode, which really helped move more air to my upstairs ducts. Now my house has only a 2 degree difference between the 1st and 2nd floors maximum and I have been able to run my current thermostat at 75 both day and night which has cut almost 700kWh off my 1800kWh June bill from last year. My biggest problem now is that when it is really hot outside, the system runs plenty long enough and the house is very comfortable at 75, however when it is humid and only in the lower 80's, the system does not cycle enough and the humidity rises, so it in not comfortable at 75.

    My friend is going to cut in the return duct in the basement and install the IAQ with my assistance. He recommended that unit and I hope to use the dehumidifying control in the IAQ and fan operation modes to solve the humidity problem and even out the temperature a bit more including the basement in an energy efficient manner. I also have a honeywell humidifier for winter that I would like to control from the unit. I also know that my Trane is coming down the homestretch on life and I will look to move to install a 14 SEER heat pump to replace with N.G. fossil fuel backup for a hybrid system, which will require a good controller like the IAQ anyway.

    My questions are:

    1. Is there any advantage to installing the outside air temperature sensor now, even though I do not have a heat pump running in dual fuel mode yet. I will probably install it anyway to get ready for the future, but would like to know what features it is required for.

    2. My blower motor is a Rescue fractional HP blower motor and I do not have variable speed control. Is there a lot of advantage to lowering the speed of the blower down in humidity control mode to improve the moisture removal. I read elsewhere on this forum that 300 CFM per ton was a good target. Is there an easy way retrofit multispeed capability (not variable speed) to an older single speed air handler? A possible solution might be to drop back down to 1/3 HP during a humidity control cycle as I know the airflow would drop some, especially upstairs, but not sure if this is worth it or the right way to do it.

    3. What I really wanted to do is install a remote indoor temperature sensor upstais in the master bed room and have the system control to that temperature only during the sleep cycle, but I called Honeywell and they confirmed that the unit could not do that. It looks like if you install an additional thermister you can either controll off of that one only or do an average and control to the average. I think that may actually hurt me (especially during winter as it is hotter upstairs) overall as I only need it a bit cooler at night in the upstairs bedrooms. I am hoping that the humidity control and fan circulation options may lessen the need to lower the downstairs setting much at night. Any advice? I am pretty sure that the house probably should have been designed with zone control from the beginning, but with the basement finished it is too late for that kind of change.

    Any advice appreciated.

  2. #2
    Join Date
    Jul 2008
    Location
    Middle TN
    Posts
    24
    What I know, which is not much - but I do have an IAQ and outdoor sensor .

    The outdoor sensor is used for heat pump lockout or dual fuel choice and also if you have a humidifier to prevent frost on the windows in the winter. It is pretty cheap and the hardest part of the install is probably running the wires, but it does not buy you anything to hook it up now. If you DO NOT have the sensor then the display always shows current temp, set point temp, and current humidity. With the sensor installed it replaces humidity with outdoor temp, and you have to hit the "more" button a time or two to see the humidity level.

    Lowering the blower speed to remove more moisture is the reason there are variable speed blowers. Most drop to 80 to 85% of full speed when in d-hum mode and (I am told) it really helps. If you don't have a speed control, then the t-stat will just remove humidity by overcooling. You can set it in the IAQ to 3 levels from 1 to 3* with 3* being the default.

    The IAQ indoor sensors have to be installed in certain numbers - 1, 4, and 9. You can set the IAQ to use the temps from the indoor sensors (averaged) or the t-stat temp and the indoor sensors (averaged). So you could put the t-stat on one level and one sensor on the other and average the temps.

    Sounds to me like you need to get a contractor to come out and look things over. I would bet a whole house dehumidifier and / or a simple zone system would make you a lot happier than the IAQ will just added to your current system.

    But what do I know ?

    Dennis

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,307
    The outdoor sensor is also used for freeze protection when the IAQ controls a humidifier.

    You tech can install a relay to use a slower speed on your PSC motor during dehumidify calls.

    You could install the IAQ stat in your bedroom. And teh remote sensor where your current stat is. Then(PITA part) you could set it to use teh stat during the night while your in sleeping, and then reset it to use the remote sensor during the day.
    But to do it you have to go into intsller set up each time. Which I recomend against doing.

    Easier way, if you like your temp cooler at night while sleeping. Just program the sleep program to drop the temp an extra degree or 2.
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  4. #4

    re

    Thanks for the responses. That is what I thought on the temperature sensors after reading the manual. Do you think there is any advantage to averaging the two floor temperatures? I am worried that in the winter the first floor maybe a little too cold as the average is pulled up by the upper floor temps. I was hoping to balance the temps more through extra circulation running of the fan. I am not interested in a whole home dehumidifier due to the extra energy and would just like to optimize the current A/C system to help. The system is already 10 times better than last year and the problem I am running into is just because I am pushing the setpoints way up while still trying to keep it comfortable. I am finding that humidity is a bigger factor in comfort in the summer than even the temperature alone. Would the humidity control system or the fan programming system be the most useful to improve comfort when the delta T between inside and outside drops down to around 5 degrees and the system does not cycle much. I am guessing from your posts that lowering the speed of the blower fan with a relay is a very good thing to do when in the humidity control cycle?

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,307
    Slowing the blower will help reduce the humidity during the milder outdoor temp days.
    Which is what the stat does with a system with a VS blower. So it will help on your also.

    Constant, or using fan circ, will help even temps between the two levels.
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