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Dual Zone Furnance Heating & Cooling

Hello Melvin,Zoned units have their own rules to be obeyed.Like sizing of the ducts is differant than regular AC&H.Like the need for a dump zone/trunk/damper.Now,with a repeat call I do not understand why the system can not looked at in pretty much any ambient.Freezing of the evaporator coil can be caused by lot's of stuff.You need to check a few things.With an unfrozen/unfrosted evap coil;1st floor calling for cooling,fan switch in auto;2nd fl OFF,fan in auto.With pad& pencil,record the air flow out of both zones supply registers.Then reverse the t'stat settings and record again.I'm not asking for cfm readings,just ,can you feel the air moving several feet away.On the mechanic's pressure gauges the temp gauge should be around 40* on a73*-75* day.


  • Melvin
    Melvin Member Posts: 1
    Dual Zone Furnance Heating and Cooling

    I recently purchased a brand new three level single family home in Maryland. The house has an American Dual Zone Furnance supporting the heating/cooling requirements. The heating works well, but the cooling not so good. The problem we are having is with the cooling system. We have had to two repairman come out and inspect the system--both came on cool days--go figure. The second repair notice that the furnance had frozen up completely. So instructed us to turn off the furnance for a week in order to allow the furnance to thaw out. He came back on a cool day and stated that he needed to return on a hot day to figure out if the coolant was correct. Well, low and behold, we hit two 90 degree temperature days and the upstairs was a blazing 80 degrees while the downstairs was a 74. We had both thermostates (upstairs & downstairs) on 66 degrees. I have no experience and very little confidence in dual zone cooling systems. How do I fix the problem? Very little air is coming from the upstairs vents. I have replaced the filters and done all I can do. Is there a supplemental system that i can purchase? Please help...
  • don_205
    don_205 Member Posts: 66
    being rnc

    Being a new home I could only assume that the system has not been started/charge and check for proper operation.

    That mean checking airflow,refrigerant and a capacity test on the system.And yes..often times it best to charge a system when you have a good load inside and out.

    Often time I find people that are confuse as to how their ac system should work.They like many assume that if they lower the tstat that it should drop the temps to where they have it set.Whew! Not the case.

    If your system is rated or pick on a 95 degree outdoor temps and a 80 degree indoor temp with a 67% wetbulb temp then when, and if you meet or exceed this you will see no change in the indoor temperture as far as dropping that is.

    In your case you have issue.Could be as simple as not enough refrigerant or even worse, not enough airflow.

    Watch the weather report..when you see 70 degree and sunny coming up in the future call and make an appointment to get it checkout.

    If you still want to spend some money on that new house give me a call.i'm sure I can find away to help you do so.
    LOL.Just kidding please to not take that to heart.

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