Steffes advises caution be used when using room temperature set back with ETS systems. Generally, it is not advisable to do room temperature set back unless the duration of set back is 10-hours or greater.
If doing set back with ETS equipment, it is strongly advised to have the set forward initiated early enough in the off-peak period so the home can be up to temperature prior to going into the On-Peak (control) period. Failure to initiate the set forward well within the off-peak period may cause the heating system to run out of stored heat prior to the arrival of the next off-peak period. As an alternative, a larger size ETS unit can be installed to ensure enough heating capacity for the set forward and On-peak hours.
NOTE: Using room temperature set back will alter how the heater stores heat. Since energy usage will be reduced during the set back time, the ETS heater will think it needs to store a smaller amount of heat.
Room temperature set back does work well in applications where the area being set back will not be used on a regular basis such as a weekend home, cabin, church, school, etc. In applications such as these, room temperature set back can be implemented with the optional time clock module or a telephone transponder.