Outdoor Reset v Setback Thermostats

For years the Department of Energy has promoted the programmable setback thermostat as a means of saving energy.  In 2005 several field studies by the Department of Energy determined that in most cases the introduction of a programmable thermostat didn’t conserve energy and in some cases actually increased usage.  The biggest problem they found was that the thermostats either were not programmed correctly or in some cases were not programmed  at all.

Now along comes outdoor reset which adjusts the water temperature based on the outdoor temperature in an attempt to match the heat loss.  When coupled with a programmable thermostat it can be a recipe for customer discomfort.  As the water temperature is reduced the BTU’s into the space are reduced as well since the heat loss is less, the goal is to only put into the space what is leaving.  However if a setback thermostat is in play and not only are we trying to match the heat loss but raise the space temperature 10 degrees it could take a few hours.  To combat this many thermostat manufacturers have added to logic in their thermostat to learn a systems response time and come on a few hours earlier.

If a customer is setting their thermostat back at night to save energy they are better off to just set it and forget it and allow outdoor reset to manage the system.  The long run time to heat the house back up will offset any energy savings.

Or take a look at the next step in the energy saving evolution indoor feedback, with indoor feedback a system can tailor the water temperature to the actual heat loss, synchronize the zones to eliminate short cycling and ramp the water temperature up for those times when it has been setback or turned off.

Article by George Carey about Indoor feedback
Tekmar House Controls