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  1. #14
    Join Date
    Nov 2019
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    Thread Starter
    Quote Originally Posted by sammyray View Post
    I think Bosch is design to be install on a standard air handler with standard thermostat. The Trane XV unit with Tam 9 unit is design to modulate blower air flow and compressor speeds to control temperature and humidity.
    I don't know about the Bosch, but yes, that's what was explained to me.

    That is exactly the reason I have questions about the way my system seems to be operating. Maybe it's normal, I don't know?!

  2. #15
    Join Date
    Jan 2019
    Location
    Vero Beach, Florida
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    With it being grossly oversized it will never run at 100% and will have oil return issues for the compressor. Sweating issues the list will go on and on.

    My company is dealing with a issue like this now. A previous sales tech sold a customer 2 XVs, total of 7tons of cooling on a 2200sq ft house. He told them the same thing you were told. Guess what both units are sweating like whores in church because the ductwork is not sized for the equipment that was installed. Multiple problems and the units are not even a year old. Already had to replace two ECM motors. Both units are running 1.03” WC We are going to rip them out and and install the proper sized units

    What was the final total external static pressure?
    Why didn’t the installing contractor do a load calc
    Why didn’t the installing contractor do a commissioning report?
    These are all questions you need to ask your installing contractor!!!

    I’m willing to bet you could have had a 3 or 4 ton XV installed and be fine.

  3. #16
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
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    What do we know about
    your BUILDING THERMAL ENVELOPE?

    3,000 Sq Feet
    8" MIN FOAM __ Ceiling
    It has good windows

    _________________

    What we do Not know?

    Location: 36'N or 63'N Latitude / presume Western Hemisphere
    ______ ZIP _ _ _ _ _
    __ Current control and equipment sizing issue is not specifically defined as Cooling or Only Heating

    __ Elevation: 1,200' or 12,000'

    __ Built in 1980 or 2010 ?

    R- _ # _ Walls ( ? 5" Foam )
    R- _ # _ Floor

    One or two story with or without basement ?
    IF basement, is it totally underground?


    " Good " Windows:
    … presume in the BALL PARK of U-factor 0.3, S.H.G.C. < 0.40
    … Perhaps, triple Pane & Argon filled __ ?

    < ~ 500 Sq Feet of Glass ?
    Window Area per Orientation
    N
    S
    E
    West
    __________________

    Equipment:

    TRANE XV20i with TAM9060 ____ 5-Ton A/C
    ________ Furnace: ?

    Frequent Start & Stop recently

    Heating source is NOT known.
    Is heating the primary issue?
    i.e. Location South of 29'N or North of 46'N latitude

    Natural Gas, Liquid Propane, Electric Strips

    Equipment Location:
    1. Basement, Attic, Garage, Mechanical Closet on 1st Floor
    2. Conditioned Space ?

    Air Distribution:

    Measured E.S.P.
    Total Air flow rate is not stated.
    ______
    Last edited by dan sw fl; 12-03-2019 at 07:46 AM.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  4. #17
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
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    Quote Originally Posted by wolfewl View Post
    They did not.

    They did change
    the box on the outlet of the air handler from a sweep elbow to a 90 degree box.. .

    The impression I was given in regards to oversize is that this system
    can adjust from 2-ton to 5-ton depending on demand.

    I was told that would eliminate an oversize unit.
    That's one reason I chose this system.

    I have been told in the past I didn't need a 5-ton.

    What you say about the duct work makes sense to me,
    but wouldn't I have had high back pressure/less airflow with my old system?

    He also verified charge and said it is right where it needs to be.

    90 degree Box
    could create 8 times more local pressure drop
    than a proper Sweep Elbow.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  5. #18
    Join Date
    Jun 2006
    Location
    Victoria, Texas
    Posts
    631
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    Quote Originally Posted by Deathpunch0311 View Post
    With it being grossly oversized it will never run at 100% and will have oil return issues for the compressor. Sweating issues the list will go on and on.

    My company is dealing with a issue like this now. A previous sales tech sold a customer 2 XVs, total of 7tons of cooling on a 2200sq ft house. He told them the same thing you were told. Guess what both units are sweating like whores in church because the ductwork is not sized for the equipment that was installed. Multiple problems and the units are not even a year old. Already had to replace two ECM motors. Both units are running 1.03” WC We are going to rip them out and and install the proper sized units

    What was the final total external static pressure?
    Why didn’t the installing contractor do a load calc
    Why didn’t the installing contractor do a commissioning report?
    These are all questions you need to ask your installing contractor!!!

    I’m willing to bet you could have had a 3 or 4 ton XV installed and be fine.
    I agree with you. With the right load and duct design a XV units work great.

  6. #19
    Join Date
    Nov 2019
    Posts
    38
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    Thread Starter
    Well... Unfortunately most of you are speaking in terms I'm struggling to understand. Not to mention my disappointment as all of the comments point to my dealer putting in an over sized unit.

    With that said, I do understand a 5-ton unit is more than I need. But, I was given the impression this system will modulate down and provide exactly what is needed and if extra cooling/heating is needed it will have the capability to overcome if that situation occurs.

    I assumed it would run at very low output 95% of the time and didn't think that would be an issue. I have an appointment coming up with the dealer to discuss everything that has been brought up here. Unfortunately it's a week out. I'll follow up and let you know what resolution(s) are offered.

  7. #20
    Join Date
    Sep 2008
    Location
    VA
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    The XV20i heat pump can modulate from 25%-100% capacity in 1/10th % increments allowing for a true 750 stage variable capacity. Yes, that means it can go as low as 1.25 tons. The straight cooling AC can go from 30%-100%.
    This unit also encorporates an automatic oil return cycle if low speed is active for extended periods, and also for 1 min upon each start up. If the unit has been disconnected from power, the initial oil return cycle will be 15 minutes upon start up.
    The variable speed blower motor should have constant cfm selected, NOT constant torque mode. They must be configured for 400cfm/ton.

    It sounds to me like the system has not been set up properly. However, like the others have questioned, if it's over-sized for the ducting, it's not going to work as well as it should.

    This is one of the best residential heat pump units on the market. This system can even tell you the calculated static pressure on the digital display of the air handler.

    Does this system have a zoning control? Typically the set up for a non zoned XV is pretty straight forward and easy. Zoned systems can be a bit more challenging especially if the contractor is not familiar with the equipment.
    "The only true wisdom is in knowing you know nothing" Socrates

  8. #21
    Join Date
    Nov 2019
    Posts
    38
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    Thread Starter
    Thanks for using "english"

    My system is not zoned, 1 story 3 bedroom, 3000 sq/ft. Everything you say is more in line with what my dealer told me when I chose the system.

    My gut tells me the 90 degree box they installed is the back pressure issue (biggest part anyway). The new air handler is longer than the original. I have trusses in the attic. The "outlet" ended up in the middle of one of the trusses. Instead of moving the whole air handler 12" one way or the other (and having to redo the intake ducting) they fabricated a new 90 degree box. Again, I base that off of nothing but when I saw it I questioned it...

    Can you help me understand constant cfm vs. torque? I know they changed that during their last visit due to high back pressure. I'm pretty sure they went to torque and said they turned the fan down. What issues will that cause? I guess I'm confused because I don't understand how constant cfm equates to a variable speed blower...? Unless you are saying that for every "1-ton" it will ramp 400cfm (3-ton load the fan will put up 1200 cfm, etc).

    I plan to have them correct the 90 degree box issue on the next visit. I will also ask them to put my settings back to factory settings. If I still experience high back pressure I will look for options from there.

    Thank you for the explanation!

  9. #22
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    Sep 2008
    Location
    VA
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    Constant CFM (cubic feet of air per minute) means the blower will attempt to deliver the proper amount of airflow according to the demand, and will modulate as a variable speed. It will increase torque automatically in attempts to meet the demand.

    Constant Torque allows the blower to operate as a standard type PSC blower or fixed speed Electronic blower. As static pressure increases, the airflow will also decrease. Unlike the variable speed mode which will increase torque as the static increases. Does this cause a higher electrical consumption, yes, but it also helps to deliver the correct amount of air flow.

    In any case, the static pressure issues should be mitigated in order to provide improved performance.

    One other thing. The duty cycle rates can be adjusted on the thermostat. Default, I believe is 3 cycles per hour. If they have it set for 5 or more, you could experience shorter cycle rates, and reduced comfort. Also they have an adjustment for normal or aggressive recovery. If it is set for aggressive, you could experience the issues you've described. These cycle rate settings are in the thermostat.
    "The only true wisdom is in knowing you know nothing" Socrates

  10. #23
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    Nov 2019
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    38
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    Thread Starter
    I assume there's no simple answer, but, is there a number in general I should consider high for back pressure? I would just like an idea to confirm with my installer after the 90 degree box is replaced.

    I have attached a pdf file, but, I'm having trouble interpreting it.
    Attached Images Attached Images

  11. #24
    Join Date
    Jan 2019
    Location
    Vero Beach, Florida
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    That’s telling you how many CFM and watts the motor is producing with what static pressure it’s running at.
    If your installer would have did a commissioning report you would know what static pressure your units is running and know how many CFM the unit is delivering.
    The flashing light is telling you how many CFM the unit is calling for 10blinks 1000CFM

  12. #25
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    Nov 2019
    Posts
    38
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    Thread Starter
    Is there a general number that is considered high for static pressure (above "x")?

  13. #26
    Join Date
    Nov 2004
    Location
    SW FL
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    Quote Originally Posted by wolfewl View Post
    Thanks for using "english"

    My system is not zoned, 1 story 3 bedroom, 3000 sq. ft.
    Everything you say is more in line with what my dealer told me when I chose the system.

    My gut tells me the 90 degree box
    they installed is the back pressure issue (biggest part anyway).

    Thank you for the explanation!
    ZIP _ _ _ _ _ ?
    Year Residence Built _ _ _ _ ? | A.C.H. Natural = 0._ _ ?

    380 Sq Feet Glass total Area ?

    Blower Setting : 370 CFM/ Ton <--- dependent on ZIP.
    [ NOT APPLICABLE IN _ DRY _ REGIONS ]

    Schematic of duct layout & ACCA Manual D calc
    would indicate the necessary changes to reduce E.S.P.

    Max. E.S.P. Target < 0.7"
    Last edited by dan sw fl; 12-05-2019 at 12:06 PM.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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