What to Do if My Heat Pump isn’t Defrosting Itself

Is your heat pump not defrosting? Did you even know it should automatically defrost itself? Maybe your home heating just seems inefficient and you don’t know why. If it’s in the midst of a few cold winter days and nights in a row, the defrost mode could be worth checking out or contacting an expert to look at.

Nearly every heat pump or cooling system will have a time when it gets snow and ice on its components. As the ice buildup normally impacts the performance of the device, the heat pump automatically goes into a mode specifically designed for melting the ice, a mode known as defrosting. If that mode isn’t working, the system will have reduced efficiency, then get to the point of failure.

Here we are going to review what you need to understand when the heat pump is not warming, itself, why it is so important, and how you can fix it.

What’s the Defrost Mode?

As the heat pump runs, in very cold weather, it’s a normal part of the process for ice to build on the exterior coils. As soon as this happens, the system’s defrost setting should start. The thermostat senses the low temperature. The reversing valve, well, reverses. The unit’s evaporator becomes the condenser for a short time.

A heat pump needs to defrost frequently when icing is taking place repeatedly. The defrost mode is efficient enough to thaw the ice, yet runs for a short period of time to prevent wasted energy and wasted time from heating the home. The defrost mode will cycle on about every 30 minutes. The mode should stay on 5-10 minutes, but no longer. The reversed valve and the heated evaporator should thaw the frozen components of the unit very fast. After the defrost setting stops, the heat pump should resume normal heating.

Older heat pump also have the defrost setting, but rather than thermostats or sensing units, they may make use of timers that run the mode for a set period of time. One issue with the older models is the unit will certainly run the defrost cycle no matter if ice is present or not, this wastes energy and time heating the house.

How Does a Heat Pump Defrost?

• Temperature difference from outside to inside

When the thermostat or sensing unit located under of the exterior coil reads a very low temperature compared to the outside temperature, the defrost mode starts. This could occur with temperatures as high as 60 depending on the system’s settings. Once the thermostat on the bottom of the coil reaches a temperature close to the outdoor temperature, the defrost cycle quits and the coil is free of frost.

• Air pressure

When the coil is frozen, the area between the coils narrows and air flow is restricted. The defrost cycle can activate when the air pressure is too high, then cut off once the pressure is closer to normal.

• Timer and thermostat

Sometimes, the device can have a thermostat/sensor with a timer at the same time. This is a great deal much more reliable than any one of the previous ones alone. It just focuses on gauging the temperature level every 90 mins approximately as well as relying on what the thermostats or sensors say; the tool will figure out whether to transform the defrost mode ON or not.

Also in summer, these systems need to function efficiently. However, often this doesn’t take place which brings about the frozen heat pumps. If any of these previous approaches don’t take place, likely you will certainly have to look better for the root cause of your heat pump not functioning.

• Relay

The defrost relay supervises to turn the compressor on, change the reversing valve and stop the fan from rotating.

Causes and Signs of a Heat Pump not Defrosting

When the evaporator or condenser thaws, the refrigerant, which is actually hot right now, is rerouted into the coil while the outside fan quits working to speed up the system. The compressor is the part which moves the refrigerant and warms the temperature. The process is followed by the humming sound of the compressor running, “whooshing” noise when the defrost cycle ends and thick steam coming out of the top of the machine.

Even when it looks like this process is running effectively, it might be working partially or in need of repair. If any step in the system is inefficient, it could be hurting the overall ability of the heat pump.

Causes and symptoms are:

• Leaking on the heat pump

When water is dripping on the heat pump evaporator or condenser, the ice build-up happens faster.

• Lack of water drainage

When the heating unit is located in a place with poor drainage, or a blockage, water will be stored inside the pump, lowering the temperature and developing blocks of ice.

• Poor refrigerant levels

If there’s insufficient refrigerant in the heat pump, you will get iced and frozen parts. The refrigerant is what heats the components in defrost mode. Leaks might trigger coolant to work slower and to decrease with time.

• Bad installation

When there is no air movement, poor drainage, lack of circulation inside the heat pump, a poor set-up on the ground or property, or poor construction leading to refrigerant not running through the system as it should, any of this can lead to a defrost setting malfunctioning or being inefficient.

• A busted reversing valve

When the valve that reverses heating to cooling doesn’t work, the defrost mode won’t work.

• Issues with wiring

If wires are worn or installed poorly, some components won’t work. If wires have become damaged, defrost or other functions might not work.

• Damaged exterior coil

When the outdoor coil does not work correctly, air can’t travel through the device effectively, and after that the ice freezes faster. This could also make how the defrost mode starts and stops inefficient.

At South End Heating and Air we specialize in HVAC and furnace repair, call us for a free consult. We’ll evaluate your system and help make recommendations for optimum value. After all, we want to keep you cool all summer long and warm in the winter. Just schedule a visit with one of our technicians to talk about how we can help with your heating needs. Would you like to learn more options our techs can help you with? Give us a call 704-684-5339.