The humble thermostat
The California Energy Code has targeted smart control systems for many years. It’s one of the most effective ways to reduce energy use in buildings, but many projects miss or under-utilize their smart control options.
Across all occupancies, Section 110.2(b) and 110.2(c) are the mandatory requirements for space conditioning equipment thermostats. Per 110.2(c), at the most basic, the thermostat must be able to schedule the heating and/or cooling set points for at least four periods over 24 hours. Obvious, right? On in the morning, setback when you go to work, on in the evening, setback when you go to bed. It doesn’t need to be a “smart” thermostat, but it must be programmable for four times. Surprisingly, many professionals miss this Section when contractors leave thermostats unprogrammed.
There are a handful of exempt system types, including non-central electric heaters, room air conditioners, gravity gas floor or wall heaters, wood stoves, and fireplaces or decorative gas appliances. Other than that, new heaters and/or air conditioners require a programmable thermostat.
“Zonal Control” Credit
In performance-based Title 24 compliance, there is a credit for additional zonal control. A credit here makes sense: if the designer or builder adds more zones, each with its own thermostat, there is a potential for energy savings. To meet the credit, there are eligibility and installation requirements, such as the number of habitable rooms, temperature sensors and a limit on the area of non-closeable openings (meaning, the zones cannot be too interconnected).
Extra Requirements for Heat Pumps with supplemental heaters
110.2(b) is specific to Heat Pumps with supplementary Electric Resistance Heaters. The controls must prevent supplementary heater operation when the heating load can be met by the heat pump mode alone. Additionally, the cut-on temperature for heat pump heating needs to be higher than the cut-on temperature for supplementary heating, and reverse as well (heat pump cut off > supplementary heat).
Residential Alterations – What triggers a thermostat upgrade?
Regardless of the project’s alteration scope, whenever an existing refrigerant containing component is added or replaced, the thermostat must be upgraded to a digital setback type that meets the mandatory requirements of Section 110.2(c).
Similarities, and differences, with Multi-Family
Per Section 160.3(a), Multi-Family has similarities to Single Family, such as the requirements of Section 110.2(c) and 110.2(b) which would still apply.
However, a multi-family project has the option to be controlled by a central energy management control system (EMCS) if it complies with all applicable requirements for each thermostatic control.
The thermostatic control requirements dictate capabilities of being set to 55F or lower, 85F or higher, and a temperature range dead band of at least 5F.
If more than one piece of heating and/or cooling equipment is installed in a dwelling unit, the setback thermostat requirement can be met by controlling all heating or cooling units with one thermostat or with a separate thermostat for each unit.
Whether you’re making sure a project’s controls meets the energy code, or taking advantage of increased energy savings by multiple zones or central EMCS, the humble thermostat is a small but important tool for achieving compliance and energy savings.