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  1. #1
    Join Date
    Jun 2005
    Posts
    15
    I'm not sure if this question makes sense but here goes. I have a 2.5 ton carrier condenser and a VS FV003 airhandler.
    After checking the specs on the airhandler I found that the TXV size is 3 tons. The model FV002's TXV size is 2.5t (which the other estimate I had, but didn't go with was going to use.)

    Is this considered a mismatch? Could this be causing my system to cycle on and off to much and not properly controlling the humidity. The company is coming out July 9th for the other repairs and I would like to know if I should bring this up with them.

    Also, does anyone know if the humidisat comes standard with this fan coil or do they need to install it. I had an air cleaner installed with the system and was wondering if there is a separate filter inside the fan coil and if it should be removed?

    Thanks for all your help.

  2. #2
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by nj_ac
    Could this be causing my system to cycle on and off to much and not properly controlling the humidity. The company is coming out July 9th for the other repairs and I would like to know if I should bring this up with them.
    It sounds like your system is oversized. The TXV by itself isn't the problem.

    Did the contractor do a heat gain calculation before choosing the system?

  3. #3
    Join Date
    Mar 2005
    Posts
    41
    It could be short cycling for many reasons.Where is the thermostat installed?Is it too close to a supply duct?I don't think the TXV is the problem.Why are you installing a humidistat on an a/c system anyway?Are you running a humidifier while your using the a/c?

  4. #4
    Join Date
    Mar 2005
    Posts
    41
    I forgot to add a few things.I think your air handler is a variable speed unit.I think it has to be set up properly to match the outdoor unit.There should be some dip switch settings and other set up options inside the unit.Maybe the service tech had put these set up options in the wrong locations.Just ask them to recheck the control board inside the unit.How many square feet is your house?Usually they figure 400 sq.ft.per ton on older homes and 600sq.st per ton on newer homes.This is only a rule of thumb basis. 21/2 ton should do a home approximately 1000 sq.ft if the home is older with little insulation.

  5. #5
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by eagle1154
    21/2 ton should do a home approximately 1000 sq.ft if the home is older with little insulation.
    Of course, if your are in Winnepeg this may be a bit oversized for you.

  6. #6
    Join Date
    Mar 2005
    Posts
    41
    I assumed the origianl poster was from nj...due to the fact his name was nj-ac.You may be right,if in winnepeg it could be oversized.But I think it gets hot even in winnepeg,maybe not for too long,but I'm sure it gets hot and humid.I know it gets hot and humid here in connecticut,and we use 400 sq.ft per ton here.And how do you know his home isn't 5000 sq.ft.He never said how many sq.ft it is.So don't assume he is oversized.

  7. #7
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,184
    I can't believe that frackin (isn't that Payson's term?) so many sq ft per ton keeps coming up. That's as accurate as standing across the street and how many fingers covers the house is how many tons it needs.

    Anyway, a humidistat on a variable speed blower can slow the blower down if the humidity rises above setpoint.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,108
    Originally posted by BaldLoonie
    I can't believe that frackin (isn't that Payson's term?) so many sq ft per ton keeps coming up. That's as accurate as standing across the street and how many fingers covers the house is how many tons it needs.

    Some one some where will always use it.
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  9. #9
    Join Date
    Mar 2005
    Posts
    41
    I was using the 400 sq.ft per ton as a rule of thumb only.It does work most times in our area.I believe the variable speed blower already has that humidistat option built in.Carrier claims that when using the v.s. blower in conjuction with the "thermidistat"the blower will almost stop to lower humidity.Then ramp back up when needed.

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,108
    400 sq ft per ton will cool most houses. It just won't dehumidify them.

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  11. #11
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by eagle1154
    I know it gets hot and humid here in connecticut,and we use 400 sq.ft per ton here.
    http://www.proctoreng.com/articles/bigger.html

  12. #12
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,184
    Great article, Travis. I'm gonna save that sucker.

    Using the Thermidistat or Infinity control can remove more humidity but not an excuse to oversize.

    Either air handler is fine with the 030 unit. The 003 air handler bumps SEER up a hair and increases SENSIBLE (not humidity) capacity some too. So hopefully you have a Thermidistat or Infinity control and the dealer has the blower speed set properly. Don't worry about what TXV is installed. If it wasn't right, it wouldn't be an improved match.

  13. #13
    Join Date
    Jul 2005
    Posts
    4
    "400 sq ft per ton will cool most houses. It just won't dehumidify them."


    Hey, beenthere, are you saying that we should use less than 400 sq. ft. per ton in figuring our a/c size?

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