First we should understand   -  -  How a Heat Pump operates.

 

     A heat pump is like an air conditioner that runs back wards  -  Well sort of  -  The initial heating portion of a heat pump system is contained inside the condenser and from a distance of three feet it looks just like an air conditioner.  Inside a heat pump condenser there are extra controls, valves and switches which permits the refrigerant to flow in opposite directions, depending on the mode of operation set on the thermostat.  Heat Pump thermostats have three settings, Heat, Cool, Emergency Heat (More about this emergency thing later). Plus the settings for fan on and fan auto.  If your system was installed properly, and no one has incorrectly changed out the thermostat or the outside condenser, the best way for the average homeowner to tell if they have a heat pump is by the thermostat.

 

    In the air conditioning mode , the compressor pumps HOT refrigerant gas, (a compressor only pumps gas it doesn't like liquid), into the Condenser coils (the outside unit).  Here the gas is literally condensed into a liquid, with the help of the condenser fan.  This hot liquid refrigerant continues under high pressure through the copper lines to the Evaporator Coil (inside unit).  Here, at the evaporator coil entrance is a "metering device", there are several types.  The metering device separates the system into high pressure (Condenser) and low pressure (Evaporator).  This metering device restricts the flow of the high pressure liquid so that it sort of 'squirts' into the evaporator coils, which is actually low pressure, and as pressure drops so does temperature.  The refrigerant in this coil literally evaporates back into a gas. This low pressure evaporation results in the coil getting cold, the fan (Blower) in the heater compartment blows through this coil, blowing cool air through the duct system and into your home, -  cool. 

The cool gas continues back outside to the compressor to start the cycle over again.

 

    In the Heat Pump mode, when the thermostat is set to the heating, where we want to heat the home, the controls in the condenser shift to permit the refrigerant to flow in the opposite direction. (The compressor still pumps in the same direction, it's the valve after it that causes the change of refrigerant direction).  Now we have the hot refrigerant gas being pumped into the inside coil which becomes the condenser coils, the metering device is bypassed and the hot gas is condensed into a hot liquid with the aid of the furnace fan. The fan / blower distributes the hot air through the same ducts that supplied cool into the home,  - heat.

The hot liquid continues back outside to the "condenser" which now contains the evaporator coil, it must first pass through a metering device, the same as it did inside in the cool mode, we have the same pressure drop with a similar temperature drop where the liquid refrigerant is evaporated into a gas to continue on to the compressor.

 

    There is a simple test that anyone can perform to get an idea of the heat generated by an air conditioning / heat pump system.  Now this is just an idea. Wait till a warm day when the air conditioner is running, just go outside and place your hand about one foot over the top of the condenser - don't touch it.  You will notice that the discharge air from the condenser fan is warmer than the ambient air, actually about 25 degrees warmer.  The refrigerant that is condensed into a liquid gives off heat, the same thing happens inside when the refrigerant flow is reversed.

 

    With this understanding we can appreciate the convenience, effectiveness and cost savings as compared to a regular heat / cool air conditioning system only after understanding how a conventional electric heater functions.

 

    Most older heating systems have one heat setting mode that is automatic, you don't even know it's happening.  When the thermostat calls for heat, all the heat strips are energized, the fan blows at full heat setting speed and the home gets warm.  Newer systems may have two heat capability called 'staged heat', where the thermostat calls for heat and just some of the heat strips are energized, if there is not enough heat (the thermostat automatically controls this) then the rest of the heat strips energize until the thermostat is satisfied. 

 

    Now lets talk costs.  All heat strips that are single phase (very rare to find anything other than single phase in a residential community) require approximately 20 amps of electric power to energize - now that's 20 amps per heat strip, and the voltage required is 240 volts.  The calculation for energy consumption is Volts x Amperage = Watts, and that is how we pay our bill - in watt hours.  Generally all systems 3 1/2 ton and above have 4 heat strips so that's 4 x 20 = 80 amps x 240 volts = 19,200 watts.  An air conditioner / heat pump condenser requires approximately 20 amps to energize.  Here in our Texas area, a heat pump system is the best investment for an all electric home, we are able to heat our home for most of our winter with 20 amps x 240 volts = 4,800 watts. 

 

    A heat pump system, properly installed and set up, there will have 3 stages of heat:

1) heat pump heating. 

2) heat pump with 1 or 2 heat strips (called auxiliary heat).

3) Heat Pump de-energized and two stages of heat available, which will only happen when the outside temperature drops below 40 degrees.  -  -  And how often does that happen here?

 

EMERGENCY HEAT SETTING - - Using this setting on your thermostat does NOT constitute and emergency!!!!!!!

     The Dumbotts that named it EMERGENCY should go to the back of the class with a long pointed hat on his head and miss recess forever! What this setting does; is remove the heat pump (condenser) from the circuit and now your heater will operate as a standard heater with an air conditioner.

 

    This is a somewhat simplified explanation of a heat pump system, your technician can further explain the advantages and operation of an out door thermostat, fan speed settings, multi speed condensers, variable speed heaters air flow and so on.

 

THINGS TO BE AWARE OF: BUT PLEASE CALL US WITH YOUR CONCERNS.

   1.  EFFICIENCY - The heat pump (outside condenser) is the first stage of heat and it will stay energized as long as the thermostat in your home is calling for heat, even if it is not heating your home sufficiently and the heat strips are all energized. - - That is unless you have an OUTDOOR THERMOSTAT installed.  This 'thermostat' is something that should be installed by the original contractor, unfortunately most contractors working new construction do not include this relatively inexpensive switch.  Without this switch, the outside unit will run continuously using an additional   20 Amps of power and actually the condenser is adding cool to your home.  Utility bills could rise an additional $100.00 without this thermostat, especially if we see damp weather with temperatures below 37 degrees.

   2.  FIRE  -  The outside unit is smoking and on fire!    -   PROBABLY NOT  - ( If you don't smell smoke or burning electric wires). Remember the outside coil acts as the evaporator coil in the heat pump mode, also remember that this coil is low pressure and is cooler than the surrounding air.  The heat pump is equipped with a device to permit the outside coil to defrost the ice that is accumulated during cold, especially damp weather.  When the system is in defrost mode, the outside fan will stop, and the system actually reverses into cool mode in order to heat the outside coils and defrost.  The "smoke" you see is actually steam created in cold temperatures when the ice is melting.

   3.  My condenser is making a weird noise.   I don't know how to describe this sound,  -  swooshing? - growling? -  It is the noise made when the reversing valve shifts to permit the heat pump to go into the defrost mode, or back to heat pump after defrost  -  -  It is normal.

   4.  There is a lot of water around my condenser.  -  This is the water created from the melting ice when the system is defrosting  -  It is normal.

 

 

 

Wayne