When you set your thermostat to both heat and cool at the same time, you're essentially setting conflicting temperature settings, and the thermostat may not be able to satisfy both requirements simultaneously. Depending on the specific thermostat model and system, different things can happen:
HVAC System Confusion: In some cases, the HVAC (Heating, Ventilation, and Air Conditioning) system might get confused by the conflicting settings. This can lead to the system cycling on and off rapidly or continuously, trying to meet both heating and cooling demands, but ultimately not achieving either. It can put unnecessary strain on the system and potentially lead to malfunctions or even damage.
System Shutdown: Some thermostats or HVAC systems have built-in safety features that prevent conflicting settings. In such cases, the thermostat might reject the dual settings and shut down, displaying an error or warning message.
Priority Mode: Certain smart thermostats or advanced HVAC systems might prioritize one setting over the other. For example, if the cooling temperature is set lower than the heating temperature, the system may focus on cooling until it reaches the lower target temperature and then switch to heating.
Manual Override: In some older or basic thermostat models, when you set both heating and cooling at the same time, the last command given may take precedence. For instance, if you set the cooling temperature last, the HVAC system will try to cool the house regardless of the current indoor temperature. If you set the heating temperature last, it will attempt to heat the house, even if it's already warm.
It's essential to avoid setting conflicting heating and cooling temperatures on your thermostat, as it can lead to inefficiency, discomfort, and unnecessary wear on your HVAC system. If you want to switch between heating and cooling modes, it's best to set the thermostat to the desired mode (heat or cool) and adjust the temperature accordingly.
Modern smart thermostats often have "auto" mode, which automatically switches between heating and cooling as needed to maintain the desired temperature range. In this mode, the thermostat intelligently manages both heating and cooling, ensuring energy-efficient operation and a comfortable indoor environment. Always refer to your thermostat's user manual or contact a professional HVAC technician if you have any doubts about how to use your thermostat properly.