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  1. #14
    Join Date
    Jun 2008
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    Quote Originally Posted by freefall View Post
    the Bosch runs from 25%-120% It only has a single Y call. Basically, the inverter compressor is staged off airflow. It basically sets the inverter speed off suction pressure to maintain a coil temp. The thermostat is predicting runtime and when to come on or off based on what it thinks it knows, but then the bosch changes the capacity. My furnace has a Y1 and Y2 call which further confuses Bosch. The Bosch capacity adjustment confuses the Honeywell. At least thats what i was told at a training and it made sense.

    my furnace also has y1 and y2. I used a spst relay so that when or if the t stat calls for the second stage it keeps the Bosch running while increasing the blower speed of the furnace. It is an easy hookup and works well. I have tested it but so far even in 97 degrees it never needed the second stage. We do not set back our temps so the house never gets hot.

  2. #15
    Join Date
    Dec 2005
    Location
    Indiana
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    Thread Starter
    Im guessing you are oversized then

  3. #16
    Join Date
    Sep 2002
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    It would have to be a pretty small house then - 25% of 36,000 is 9000 BTU's. <g>

    Even if he bought the five ton unit that's only 15,000 BTU's.

    Quote Originally Posted by freefall View Post
    I’m guessing you are oversized then
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  4. #17
    Join Date
    Dec 2005
    Location
    Indiana
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    Thread Starter
    At 90+Deg I would expect a proper sized unit unit to be calling for y2 some portion of the day. Carl what size unit is it. If its a 2-3 ton unit your y2 airflow is too fast. 1250max cfm on those coils. If its a 5 then your air is too low and your superheat is out of spec and needs adjusted

  5. #18
    Join Date
    Sep 2002
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    I have a curiosity about these units / systems.

    If you can set the Bosch OD unit to maintain a 37 saturation temperature - why not just vary indoor air flow to the lowest possible CFM that the duct system will allow?

    Of course in my head I am basically picturing controlling actual motor speeds with a step-controller - but there must be a present-day way of doing it. <g>

    No wait: how about a 'trial & error' method? Just start out with the lowest indoor airflow possible and if the house temperature cannot be maintained at some high level of outdoor ambient - just add 100 CFM at a time to the indoor airflow until it does? Wouldn't that give the best possible RH% reduction?

    PHM
    ---------

    Quote Originally Posted by freefall View Post
    At 90+Deg I would expect a proper sized unit unit to be calling for y2 some portion of the day. Carl what size unit is it. If it’s a 2-3 ton unit your y2 airflow is too fast. 1250max cfm on those coils. If it’s a 5 then your air is too low and your superheat is out of spec and needs adjusted
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  6. #19
    Join Date
    Dec 2005
    Location
    Indiana
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    Thread Starter
    I agree. I think the new Bosch air handler does this. Im not sure. But I basically am doing trial and error. Bosch does not recommend changing airflow. 400 per ton I can understand why because of heating mode. But cooling mode this makes no sense. I see max airflow at 1250 because of water leaving the coil but the Bosch unit doesnt see airflow, only a load. My Bosch loves a y1 call all day long with occasional y2 calls on a 85deg day. Never shuts off and runs less than 1.9 amps on 19hz. My electric bill is cut in half. Works great with zoning not having to use a raywall valve. But Bosch states they want a constant airflow. So I guess I am in a trial period

  7. #20
    Join Date
    Jul 2019
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    My Bosch unit can't maintain at anything above 85ish. Does not dehumidify well when it's not really hot outside. Barely able to get under 50% at 70 when it runs constantly. According to load calc it is slightly over sized. Roughly 30kbtu required at 100.

  8. #21
    Join Date
    Mar 2016
    Location
    Dayton Oh
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    Quote Originally Posted by Cweldy View Post
    My Bosch unit can't maintain at anything above 85ish. Does not dehumidify well when it's not really hot outside. Barely able to get under 50% at 70 when it runs constantly. According to load calc it is slightly over sized. Roughly 30kbtu required at 100.
    If its holding a 37* coil, I dont see how its not pulling the moisture out. Is your fan set correct? is the airflow to fast across the coil to let the moisture condense?

  9. #22
    Join Date
    Sep 2002
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    Post all the operating performance numbers - unless the compressor isn't loading, the problem would seem to be in there.

    PHM
    ---------


    Quote Originally Posted by Cweldy View Post
    My Bosch unit can't maintain at anything above 85ish. Does not dehumidify well when it's not really hot outside. Barely able to get under 50% at 70 when it runs constantly. According to load calc it is slightly over sized. Roughly 30kbtu required at 100.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  10. #23
    Join Date
    Jul 2019
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    I think it's a board issue. When in charge mode it dropped roughly 1 degree every 15 minutes. Normal running conditions only about half the indoor coil sweats. In charge mode the whole thing sweats. I can't remember all the temps and pressures, but they were within factory spec. I believe I have one of the first off of the assembly line. Boards have since been updated.

  11. #24
    Join Date
    Dec 2005
    Location
    Indiana
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    307
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    Thread Starter
    There is a replacement board bulletin if they fall within a certain range. Not sure why you thinks its a board. Sounds like youre guessing without any info

  12. #25
    Join Date
    Jul 2019
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    I was told by one of Bosch's field reps to change the board since it was one of the first units, just because it's in celsius. All settings on unit are factory. A/h is a Bosch unit and blower speed settings are factory.

  13. #26
    Join Date
    Dec 2005
    Location
    Indiana
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    Thread Starter
    Quote Originally Posted by Cweldy View Post
    I was told by one of Bosch's field reps to change the board since it was one of the first units, just because it's in celsius. All settings on unit are factory. A/h is a Bosch unit and blower speed settings are factory.
    is the condenser also factory settings? if so then youre running a 47deg coil.
    Work sucks, lets go skydive

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