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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.
