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k_mcgonigal@yahoo.com

new member

0 post(s)
posted on 7/10/2007
Hi,  Hope someone on this forum can give advice on my problem.  First let me give you a little history about what has been done to this point and what issues I am having.  We built a new home that was completed not quite a year ago.  The original system would never adequately cool the house.  The system was a 4ton unit with three zones.  The original contractor went out of business before completion so we had 2 other contractors evaluate the system.  One of the contractors took a copy of house plans and calculated the load.  He determined we needed a 5ton unit.  We went with his advice and replaced the 4ton with a 5.  We now have 2 zones that seem to be working fine, however the third zone will not reach the temperature set on the thermostat.  The  temp seems to hang out at 81 degrees while the thermostat is set at 76 and the compressor will not shut off.  At this rate, I will not be able to afford the electric bill.  Let me try to explain the design.  The house is a 1 1/2 story approx.  2200 square feet.  The furnace and coil are in the attic, 1 zone feeds the upstairs bath and 2 upstairs bedrooms,  another zone feeds the master suite (master bedroom, bath and closet),  the final zone feeds the kitchen, 2 living areas, powder bath and laundry.  There is a mechanical chaise that has 2 - 12" ducts running down beneath the slab (1 for each downstairs zones).  Not sure what size the duct work is under the slab.  I know some is 12" and reduces down.  We have 3 returns:  1 (14x24 & 12" duct) in kithen/living area, 1 (14x17 & 12" duct) outside master suite and 1 (14x24 & 12" duct) outside upstairs bedrooms.  It has been suggested the returns are not adequate but the contractor who did the load calculation disaggrees and says that they are sufficient.  The temperature in the small living area is approx. 75 degrees with ceiling fan running however just 15 feet away at the thermostat was verified with pocket thermometer at 81 degrees.  The temperature out of closest supply vent is reading 60 degrees.  Any advice would be greatly appreciated.
 
 
Replies [ post reply ]
cplangelo@yahoo.com

junior member

7 post(s)
replied on 7/19/2007

RETURNS ARE NOT YOUR PROBLEM. IT APPEARS AS IF YOU HAVE A 
COUPLE IF THINGS GOING ON HERE. FIRST THING IS TO ENSURE 
YOU HAVE 1 TO 2 SUPPLY VENTS TOWARD EACH UNCONDITIONED WALL.
1 TO 2 WILL DEPEND ON LENGTH OF WALLS. ( TYPICAL TO INSTALL 
1 VENT BY EACH WINDOW.) SECOND PROBLEM COULD BE WITH THE BY-PASS
DUCT ON THE RETURN. THIRD COULD ALSO BE THERMOSTAT CALIBRATION
AND/OR THERMOSTAT LOCATION. MORE THAN LIKELY IT WILL BE SUPPLY
DUCT ISSUES. HOPE THIS HELPS IN YOUR DIAGNOSES. IF NOT E-MAIL ME BACK.



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