More on why your heat pump may need repair
There are numerous reasons why your heat pump stopped working. But without over complicating things, in the simplest form, the causes can be split up into 2 problems.
The first is electrical. The second is mechanical.
On the electrical side of things, each system has a electrical power side and a controls side. The power side is what is coming from your electric panel. In homes, this is the 120 or 208 volts AC that powers your outdoor and indoor units.
The electrical controls primarily consist of a lower voltage (typically 24 volts AC). Control signals can also be in the form of milliamps and volts DC. Special meters are required to read these signals.
On the mechanical side of things, are all of the moving parts including the physical components and refrigerant system. These are your fans, compressors, refrigerant piping, burners, valves, etc.
Electrical issues are caused by tripped, blown, or bad breakers or fuses. They are also caused by other faulty electrical wiring or parts such as transformers, circuit boards, capacitors, contactors, safety switches, etc.
Mechanical issues can be caused by usual wear and tear or wear caused by an abnormal condition. For example, fan motors can go bad because they are just old and have reached the end of their life. On the other hand, fan motors can go bad in a few years from repeat on and off cycles or because another part the motor relies on is going bad. In the latter case, the motor is forced to run without the help of the other part and therefore it runs under more extreme conditions. The worst enemies to a motor are excessive heat, dirt, and electrical surges and shorts.
LOW ON REFRIGERANT
Heat pumps can stop running because they are low on refrigerant. If the system lacks the proper amount of refrigerant then the low pressure switch can open the electrical controls circuit and thereby prevent the compressor from running. On the opposite side of that equation, if a condition is causing the refrigerant pressure to escalate when the system is running, the high pressure switch will stop the unit from heating or cooling.
BAD SAFETY SWITCHES
Sometimes one of those pressure switches goes bad and sticks in the open position preventing the system from running despite having sufficient refrigerant. Sometimes the refrigerant levels are good, the switches are fine, but the compressor itself is bad. The compressor can be bad because the motor in the compressor is dead. This could be caused by bad electrical windings due to a short to ground or between its own windings. More often, the compressor is fine, but a part it relies on is bad or is weakening. This part could be a capacitor, a contactor, a circuit board.
Compressors can also go bad or stop running due to refrigerant piping or refrigerant flow problems. For example, if a refrigerant pipe developed a blockage from either a kink in the copper piping or on the inside of the piping, then the compressor would not be properly cooled by the returning refrigerant and could be cycling off on high temperature protection. A metering device in the indoor coil could get blocked and this would cause a lack of refrigerant to the evaporator. In cooling mode, this would result in an overly superheated gas back to the compressor. The compressor would start overheating, and motors do not like excessive heat. The oil inside the system can break down and form acid. This acid can also destroy the compressor and system components.
More on Why your Furnace may need repair
Not to beat the same drum again, but furnace issues can be split into the same 2 problems as heat pumps. The only difference here is you are not dealing with refrigerant, but a fuel.
Its important to note that furnaces come in 3 main varieties based on the fuel they consume – natural gas, propane, and oil.
While the biggest difference lies between gas and oil, each system has similar protections due to the potential dangers involved with igniting and burning a fuel.
The furnace has what is known as a combustion cycle. This cycle involves the process of introducing, igniting, and safely operating while heating. The cycle has safety switches built into the process that will open the control circuit should the combustion of the fuel deviate from normal parameters. Included in this is proper air flows, proper temperature ranges, proper response signals, proper flame detection, a lack of flame roll out, etc. As soon as a safety switch senses an abnormal reading, it will act to shut of the gas valve or oil pump, ignitor spark to prevent the furnace from operating outside of safe limits.
The pressure switch confirms that the combustion fan motor is running to expel hot combustion gases outside. This prevents overheating the heat exchanger and putting harmful gases and carbon monoxide into the home.
The limit switches make sure the furnace doesn’t get too hot and start potentially causing a fire hazard.
The flame sensor senses that there is actually a flame. If it fails to sense a flame, its signal (or lack of a signal) will shut the gas valve off and prevent gas from being disbursed into the home.
The flame rollout switch senses when the flame is not being properly pulled into the heat exchanger. When the flames “roll out” and dance up the wall of the furnace, then the rollout switch will shut down the furnace.
Cracked heat exchangers can cause flame rollout. This can be witnessed when the main air blower turns on and the flame begins to dance out of the heat exchanger openings. The main airstream is causing back pressure in the combustion side of the heat exchanger. This force can cause the flame to be pushed back into the burner chamber.
On furnaces in particular, ignition control boards and transformers can go bad as well. This prevents the furnace from sending and receiving proper signals to bring on the furnace fan or combustion cycle.