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mranswer, HVAC Mechanic
Category: HVAC
Satisfied Customers: 6160
Experience:  20 years experience running my own business
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my ac runs constantly during the day. thermostat

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my ac runs constantly during the day. thermostat set to 76 but thermostat temperature keeps going up to around 88. I have a new air handler and condenser
Figure the temperature difference between the air at the return air grille and a supply register- you should have 15-20 degrees. IF you do, then the ac is too small for the job and that is why it runs and does not drop the temp. IF NOT, then you have a refrigeration issue that the installer needs to rectify as you should not have any issues with properly installed and sized new equipment. I do not know if the evaporator coil is part of your new air handler or not- if it is old it may be dirty and needs a cleaning.
Customer: replied 4 years ago.

"then the ac is too small..." Do you mean the air handler or the condensing unit. I have a 1400 under air sized home. The condensing unit is a Goodman GSC13 and the air handler is Goodman ARUF14/ARPT14.

The house cools at night and I can feel cool air coming out of the vents during the day, but the system continues to run...

The whole system must match in capacity- you cannot replace just one component here if this is an undersized system.

Customer: replied 4 years ago.

how do you determine the correct size? Please answer in lay terms.

A proper heat load calculation needs to be done by an a/c professional to get the right size system. An average size needed is one ton (12,000 btu) per 500 sq. ft. of cooled space.


The type of construction, exposure, insulation, etc all affect how much heat gets into your house and unless it's calculated properly then you are throwing money away on exorbitant utility bills.

Customer: replied 4 years ago.

They are both 3 ton units, and as previously stated 1400 sqft under air. Is there anything else that can be looked at? Thermostats?

No- just do what I first said and that will give you the answer to the issue you have. It is of no help to speculate here- find the problem first then address it.
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