Honeywell RTHL3550 User manual

Owner’s Manual
Read and save these
instructions.
For help please visit
yourhome.honeywell.com
RTHL3550
Non-Programmable
Digital Thermostat
Installation is Easy
1. Label wires and remove your old thermostat
2. Install and wire your new thermostat
3. Set your new thermostat to match your heating/cooling system
• It is preset for the most common system
Do you need assistance? We are here to help.
Call 1-800-468-1502 for wiring assistance before returning
the thermostat to the store.
This thermostat works on 24 volt or 750 mV systems. It
will NOT work on 120/240 Volt systems.

2
NOTICE: To avoid possible compressor damage, do not run air
conditioner if the outside temperature drops below 50°F (10°C).
ATTENTION: MERCURY RECYCLING NOTICE
This product does not contain mercury. However,
this product may replace a product that contains
mercury. Mercury and products containing
mercury should not be discarded in household
trash.
For more information on how and where to
properly recycle a thermostat containing
mercury in the United States, please refer to the
Thermostat Recycling Corporation at
www.thermostat-recycle.org.
For mercury thermostat recycling in Canada,
please refer to Switch the Stat at
www.switchthestat.ca
NO MERCUR
Y
NO BOTE
MERCURIO
Hg
MCR32585
Customer assistance
For assistance with this product, please visit
http://yourhome.honeywell.com.
Or call Honeywell Customer Care toll-free at
1-800-468-1502.
To save time, please note your model number
and date code before calling.
Remove battery holder; model number is on
the battery holder.
® U.S. Registered Trademark. Patents pending.
US Patent No. D542,677; 7,832,652; 7,641,126 and other patents pending.

3
Installation
Installation............................................3
Advanced Installation.........................10
About your new thermostat
Controls and Home screen
quick reference...................................12
Compressor protection.......................14
Replace batteries ...............................14
Appendices
Troubleshooting..................................15
Limited warranty.................................16
Table of contents
1 Turn Off Power to Heating/Cooling System
or
M31535
Circuit breaker
box Heating/cooling system power switch
2 Remove Old Thermostat
Remove old thermostat but leave wallplate with wires attached.
Do not remove wallplate yet
C
C
MCR33823
Terminal
designation
If you have an older thermostat with a
sealed mercury tube, turn to page 2
for proper disposal instructions.

4
3 Label Wires with Tags
Label the wires using the supplied wire labels as you disconnect them.
M28100
4 Separate Wallplate from New Thermostat
Remove wallplate from the new thermostat and mount onto wall.
M28343
Wallplate
Wire Labels
Terminal designation
C
C
MCR31537

5
5 Mount Wallplate
Mount the new wallplate using the included screws and anchors.
Drill 3/16-in. holes for drywall
Drill 3/32-in. holes for plaster
M28345
Remove metal
jumper if you
have both Rand
Rc wires.
MCR31270A
W2 G
G
W
W
Y
Y
R
R
RcY2
We are here to help. Call 1-800-468-1502 for wiring assistance.
6 Connect Wires
Simply match wire labels.
If labels do not match letters on the thermostat, check “Alternate Wiring
(Conventional Systems)” on page 6 and connect to terminal as shown (see
notes, below).

6
If wires will be connected to both Rand Rc terminals, remove metal
jumper.
Do not use C, X or B. Wrap bare end of wire with electrical tape.
If Eand Aux do not each have a wire connected, use a small piece of wire to
connect them to each other.
MCR31274B
Y2C
Y2 W2 GW YR
R
4M
V
RHY1
H
W1
B
XF
RYW
GR
c
Rc
W2
Wiring—Heat Pump
MCR31276A
Aux
O/BLG
Y
GO
YR
R
Rc
Aux
E
Alternate Wiring (Conventional Systems)
If labels do not match terminals, connect wires as shown here (see notes,
below).

7
Alternate Wiring (Heat Pump Only)
5
Leave metal jumper in place, connecting Rand Rc terminals.
If your old thermostat had both Vand VR wires, stop now and contact a
qualified contractor for help.
If your old thermostat had separate Oand Bwires, wrap the Bwire in
electrical tape and do not connect.
If your old thermostat had Y1, W1 and W2 wires, stop now and contact a
qualified contractor for help.
If there were seperate wires on Eand Aux, place both wires in the Aux/E
terminal.
If labels do not match letters on the thermostat, check the chart below and
connect to terminal as shown here (see notes, below).
MCR31275B
E
5
4
2
AUX
XWFH
B
W1
W2
X2
LOG
F
L
C
YR
R
VRM
VY1
B
X
R
YR
c
RcG O/B
Aux
E

8
M28346
Back of thermostat
7 Install Batteries
Install two AA alkaline batteries.
8 Install Thermostat
onto Wallplate
Install thermostat onto the wallplate
on the wall.
MCR32613
M31544
or
Circuit breaker box Heating/cooling system
power switch
9 Turn Power Back On
Turn the power back on to the
heating/cooling system.

9
10 If your system type is...
If your system type is:
qSingle Stage Heat and Cool
Congratulations, you’re done!
If your system type is:
qMultistage Heat and Cool
qHeat Pump* without Backup Heat
qHeat Pump* with Backup Heat
qHeat Only
qCool Only
Continue with Advanced Installation to match your thermostat to your system
type.
*Heat Pump—an air conditioner that provides cooling in the summer, and also
runs in reverse in the winter to provide heating.
If you are not sure of your system type or if you have other
questions, call us toll-free at 1-800-468-1502.
This thermostat works on 24 volt or 750 mV systems. It will NOT work on
120/240 Volt systems.

10
Function
Description
Press the sor tbutton to Setting
1 select the type of system you
have in your home
0 Heating & cooling: Gas, oil or electric heating with
central air conditioning.
1 Heat pump: Outside compressor provides both heating
and cooling without backup or auxiliary heat.
2 Heating only: Gas, oil or electric heating without central
air conditioning.
3 Heating only with fan: Gas, oil or electric heating
without central air conditioning. (Use this setting if you
could turn the fan on and off with a fan switch on your
old thermostat.)
4 Cool only: Central air conditioning only.
5 Heat pump: Outside compressor provides both heating
and cooling with backup or auxiliary heating.
6 Heat/Cool Multiple Stages: Two heat stages (wires on
W and W2), two cooling stages (wires on Y and Y2).
7 Heat/Cool Multiple Stages: Two heat stages (wires on
W and W2), one cooling stage (wire on Y).
8 Heat/Cool Multiple Stages: One heat stage (wire on
W), two cooling stages (wires on Y and Y2).
2 select whether your
changeover valve is used in
heating or cooling
0 Cooling changeover valve: Use this setting if you
connected a wire labeled “O” to the O/B W wire terminal.
1 Heating changeover valve: Use this setting if you
connected a wire labeled “B” to the O/B W wire terminal.
MCR3337
7
Function Setting
MCR32600
Done Next
Advanced Installation
Enter System Setup
To enter system setup, press and hold
both the sand FAN buttons until the
display changes (approximately 5
seconds).
Changing Settings
1. Press the sor tbutton to change
the setting.
2. Press NEXT to advance to the next
function.
3. Press DONE to exit and save settings.