The first thing you should do before changing the thermostat is to select
the proper thermostat for your system. If you are retired or if someone is at home
most of the time during the day you most likely do not need a programmable
thermostat. If this is the case the only benefit you will get from a
programmable is at night.
Once you have made the selection you can proceed to the next step.
Thermostat Installation Advisory: If you decide
to install your own thermostat you do so at your own risk. There are
many incidences where the homeowner installed their own thermostat
and were successful. There are also many incidences were the homeowner
was unsuccessful. The ones that were unsuccessful wasted part of their
day, ruined a thermostat or two, and caused the malfunction of an integral
part of their system. That is not mentioning the fact that they ended up
calling a professional HVAC Technician to fix the problems caused by
improperly installing a thermostat. The ones that are unsuccessful end up paying
three to four times what they would have paid had they called a professional
in the first place. Factor this in to your decision and if there is
any doubt call a professional to install the new thermostat.
- Get the tools
together that you will need to do the job right. You will need:
- A small straight-slot (or flathead) screw driver
- A small phillips screw driver
- A pair of needle nose pliers
- A utility knife or wire strippers (for small wire)
- Plastic wall anchors (sometimes provided with the thermostat)
- A drill with a bit to make the holes for the plastic wall anchors
- A small level
- Two pencils or pens
- A small paper bag and some masking tape (tape the bag
below the area where the thermostat is so that any trash or dust
will fall into the bag and not onto the floor) - Some touch up paint
- Clean hands (don't do a great job changing the thermostat and
leave all those prints all over the wall) - Plenty of light
- Turn the power off to the unit at the circuit
breaker or the emergency cutoff switch. After doing that make sure
the power is off by turning the thermostat to the on position
and going to the unit to make sure it is not on. Not all circuit
breakers are labeled correctly and not all emergency switches are
hooked up. Just make double sure that you have killed power to the
unit not only for your safety but also to keep from blowing the
transformer.
- Pull the cover off the front of the thermostat.
If it is a mechanical thermostat there should be a little adjuster tab
in the center of it. This is your heat anticipator. It should have
numbers ranging from 1.5 to .1. Take note of this setting and remember
to set the new thermostat to this same setting if you are replacing a
mechanical thermostat with another mechanical thermostat. You probably
want to do this now before you proceed further. If you are replacing
a mechanical with a digital, the digital should set itself automatically.
If not read the instructions on the new thermostat for instructions on
how to set the anticipator. This is very important. An improperly set
anticipator will cause your heater to run improperly. The thermostat
is also equipped with a cooling anticipator. Cooling anticipators are
most often on the sub-base and are non-adjustable.
- Unscrew the thermostat from the sub-base. Take
note of each wire. The following list should match the wires and terminals
on your thermostat.
- Red to the RH or RC terminal with a jumper wire
between RH and RC. Or Red to the R terminal which is shared with both
the heating and cooling. It has an internal jumper built in to the
sub-base. The red wire is the hot wire. All other wires are common wires. - Green to the G terminal. This is for the fan.
- Yellow to the Y terminal. This is for air conditioning.
- White to the W terminal. This is for heating.
These are the four wires that
you need to control the heat, cooling and the fan. If
the colors of the wires do not match the colors described here
make sure you mark the wires with masking tape. If there are more
wires that are not hooked up don't worry. This is common. Thermostat wire
comes in many different varieties and the contractor who installed the
system probably used 5 wire or 8 wire thermostat wire. They used what
they needed and simply twisted or cut the other wires off.
- Red to the RH or RC terminal with a jumper wire
- Remove the wires from the terminals on the sub-base.
The power should be off so you shouldn't have to worry about being shocked.
Be careful not to let the wires fall back into the wall. Sometimes there
is just enough wire to reach the terminals and that's it. Try pulling the
wires a bit to see if there is more wire behind the wall. Most of the time
there is some slack and you can pull the wire out more. Unscrew the sub-base
from the wall while holding the wires. When you get the sub-base off wrap the wires
around the pencil or pen. This will keep the wires from falling back into the wall.
- Get the new sub-base and compare it to the old one.
Hold it up to the wall in the position you want it. Is the old paint
that was covered by the old sub-base going to be covered by the new
sub-base? If any of the old paint is going to show you may want to make
some touch ups now. After finishing with that, put the new sub-base back
on the wall in the position you want it. Make sure it is as level as possible.
You can use a level to do this.
(This is very important especially for mechanical
thermostats. It must be level or the mercury switch will not keep the
proper temperature settings in the house. Make sure it is level.)
Mark the new holes through the sub-base where the screws will go into the
wall to fasten the sub-base.
- It is important in this step to have the proper drill bit
size for the size of wall anchors you have. Some wall anchor kits come with
a bit in them. We recommend the wall anchor kits with the bits in them
because it is the perfect size drill bit for the anchors. The bit should be
slightly smaller than the anchor. If the bit is bigger the wall anchor will
not hold and the possibility exists that the thermostat will fall off the wall.
Drill the mounting holes you made for mounting the sub-base. Insert the wall anchors
and push them hard with your thumb. Approximately 1/16th of an inch on the lip of
the anchor will remain sticking out of the hole. If it is more than that use the
butt-end of the screw driver and push it in until just the lip of the anchor
remains visible.
- Undo the wires from the pencil or pen and run them through
the center of the sub-base. Insert the screws and screw them only snug tight.
Get the level and make sure the sub-base is level. When you are sure
that it is level, tighten the screws. Be careful not to allow the sub-base
to move when you are tightening the screws.
- Using the color code of the wires (or if they didn't match,
the color markings you made with masking tape), attach each wire to their proper
terminal. Some people like to loop the wire around the terminal screws. This is
not necessary. What is necessary is that the wires are attached to the terminals
and they are tight. Additionally, make sure that none of the bare wire is touching
anything except the terminal. Once the wires are attached you are almost finished
completing the task of installing the thermostat. The hard part is over!
- Attach the thermostat to the sub-base. The screws for this
are built in the the thermostat. Tighten these screws and check to make sure the
heat anticipator is set to the same setting as the old anticipator setting.
- Attach the front cover to the thermostat and restore power.
Start and check the heating, air conditioning, and with the heating and air
conditioning off, the fan only sequence. All systems should be working properly
at this time (if you did the task properly) and you are the proud owner of a brand
new, properly installed thermostat.
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