Thermostats
BASICS

The most basic things about a thermostat are its location and installation:
1. It must be in a frequently occupied room (there are two schools of thought here;
thought we’d jump right in); locating it in a hallway insures slower response time
(because there’s no exposure to the outdoors), and maximizes comfort where no
one lives (and second floor thermostats in hallways respond quite nicely to first
floor temperatures – heat rises, you know). Why someone would want the most
comfortable room to be a hallway escapes us.
2. It must be near a return
or in the path of return air flow (that emphasis is for
the people who want it in the hall, when there’s a central return in the hall).
3. It should be about 60” from an outside wall and must be 60” above the floor;
these are lessons from the “Energy Crunch” of the early 70’s that came out in the
resultant “Emergency Building Temperature Restrictions".
4. It must never be exposed to direct sunlight, heat from appliances, heat or cold
from ducts or pipes in the wall on which it’s mounted, heat from lighting dimmers,
etc.
5. It must not be installed on outside walls, and should not be installed on walls
adjacent to unconditioned spaces.
6. It must not be installed where an air outlet discharges on it (“toward it” might be
OK, but “on it” is definitely not good).
7. It must not be subject to air currents within the wall on which it’s installed; holes
in the wall for wiring must be sealed.
8. There’s probably a lot more; hopefully you get the idea that location affects your
comfort.

ADVANCED

¶503.3.2.3 of the IECC requires heat pumps to have a device to deactivate the
backup heating when the heat pump can meet the heating requirement. This is
accomplished by having the backup controlled as the second stage of heating; the
temperature in the space must drop another degree for the backup to be
energized. That presents a problem for those who are trying to save money by
“setting back” heating temperatures: The backup comes on during warmup,
quickly eating up dollars saved during the setback. See “HEAT PUMPS” for more.

IMPORTANT NOTE: Setting back temperatures in a heat pump system can
actually increase energy usage and energy cost.

That’s not to say you shouldn’t set back if you have a heat pump, just that you have
to be very careful. In fact, you can save money, but as you’ll see, it’s a pain. The
first thing you need is an outdoor temperature sensor or outdoor thermostat (the
latter’s necessary if you’re not working with one of today’s digital thermostats) to
deactivate the resistance heating whenever temperature is above setpoint. This
device is an option on the programmable digital thermostats we’ve seen; the
lowest setting available on mine is only 40º F (it could be as low as 30º to 35º), but
that rules out more than 50% of the hours in our heating season. Here’s the pain:
You have to manually disable the setback anytime outdoor temperature is below
the outdoor sensor setting; many people (yours truly included) opt for a low setting
(68º, we wear sweaters) around the clock during the heating season instead.

Let’s discuss setback in other types of systems.

DINNER PARTY CHIC: “But you lose everything you saved when you warm
everything up again”.

FACT: An eight hour setback of ten degrees saves 10% to 15% (as compared to
constant temperature 24/7); that was proven time and again during the 70’s
energy crunch. Take it to the bank.

Think of it this way: On a 24 hour basis, the average temperature inside is 3-1/3°
lower with the setback; since heating energy is a function of the temperature
difference between indoors and outdoors, less energy is used.

Today’s digital setback thermostats are quite advanced, providing the capability of
two setbacks a day, different schedules on weekends, etc. Lowering the home’s
average temperature 5°
while maintaining comfortable temperatures when
you’re home
is well within reason.

If you have a Zoned System, you may be able to go with longer setbacks,
increasing savings (you're only in your bedroom eight hours or so a day, right?).
Did You Know?

There was actually a
law regulating
temperatures in
public buildings –
EBTR ("Emergency
Building
Temperature
Restrictions"):
Heat 65 and Cool 78.

Occupants were
stressed in the
extreme
This thermostat
was installed in
the second floor
hallway, at the top
of the stairs; yes,
there is a return.

BUT what about
when the unit's
not running?

AND how often is
it going to run in
the winter?

Young viewers,
say
"DUH!"