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How it Works

FanHandler FAC/HP controls work by means of Phase Modulation to control blower motor speed in direct relation to delivered air temperature, as measured in the supply plenum or duct.  No special motor is required (see A Word About Motors).

Here's how it works:  The FAC/HP consists of the control circuit and two temperature sensors, one for heating and one for cooling.  These sensors are mounted in the supply plenum or duct, where they can get an accurate measurement of the air temperature being delivered into the home.

IN BETWEEN HEATING OR COOLING CYCLES:  The FanHandler is designed to operate the blower 24/7.  When neither heating nor cooling is called for, the blower runs at a minimum speed, typically 35% to 40% of full speed (adjustable at installation).  This provides constant, gentle air circulation which balances temperatures throughout the house.  It also keeps filters, EACs and UV lights working full time instead of part time.  These devices attain peak performance in the FanHandler environment because of the reduced airflow.

COOLING CYCLE:  The thermostat calls for cooling and the compressor starts.  The blower is already running at minimum speed.  It is not going to speed up until the cooling sensor detects cool air.  This allows the coil to get very cold almost instantly, right down to design temperature.  The cold coil grabs onto the latent load and begins collecting water to its maximum design capability.  Because the coil is very cold, the air moving across it is also cooled, reducing the delivered air temp, causing the FanHandler to instantly increase blower speed.  The colder the air, the faster the blower, until delivered air temp reaches 50^o, at which point the blower is at full speed.  HERE IS WHAT MAKES THE FANHANDLER SO GREAT:  Removing latent heat uses part of the compressor's cooling capacity.  The higher the latent load, the less capacity is left to reduce the sensible load and thus speed up the blower.  If RH is high, the fan will ramp up slowly as the latent load is reduced.  If RH is low, the blower will ramp up to full speed very quickly.  The FanHandler actually fine-tunes your system according to what is happening in your house at this minute.

(Tech note:  The cooling sensor begins to increase blower speed at about 65^o delivered air temp and reaches max speed at about 50^o.  See the diagram)

EQUALIZATION CYCLE:  When the thermostat is satisfied, the compressor shuts down.  The coil begins to warm and the blower smoothly and instantly begins to slow.   Liquid refrigerant moves from high pressure (at the compressor) to low pressure (in the coil) providing additional cooling even after the compressor has stopped running.  As the pressure slowly equalizes (this usually takes 5 to 10 minutes) the coil gradually warms and the fan slows toward its minimum speed.  During this equalization cycle the coil remains cool and continues to drain water.  WATER IS NOT BLOWN OFF THE COIL INTO THE SUPPLY DUCTS, AND THERE IS NO RE-EVAPORATION. See Humidity Control & A/C

HEATING CYCLE:  The stat calls for heat.  The blower is already at minimum speed, and won't begin to speed up until the delivered air temp reaches about 85^o.  No more cold drafts while you wait for heat, especially with electric strips or heat pumps.  The reduced blower speed allows the heat source to get up to temperature rapidly.  From that point on, the warmer the air, the faster the blower speed.  With electric heat strips, instead of lukewarm air blasting out of the grilles you will get much warmer air flowing gently from the grilles, a real increase in comfort.

SPECIAL NOTE FOR HEAT PUMPS:  Heat pumps are notorious for blowing cold air during heating season.  The high-speed blower inhibits the coil from reaching the warm temperature it was designed for.  The FanHandler will keep the speed low at first, raising the speed as the air temp rises.  No more waiting for heat!  No more cold drafts!

(Tech Note: The heating sensor begins to increase blower speed at about 85^o.  Maximum speed is reached at 139^o for electric and fuel furnaces, 105^o for heat pumps.  (See diagram)

 How it Works    Installation    FAQs    Read Humidity and Air Conditioning by Richard Peters, PE, CM 

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