RTH2520 69-1867ES—05 03-11 1/8
The RTH2520 programmable thermostat can be used to control:
• a gas, fuel oil or electric furnace -2 or 3 wires
• a central air conditioner - 2 or 3 wires
• a hot water system with or without pump - 2 wires
• a millivolt system - 2 wires
• a central heating and cooling system - 4 or 5 wires
Note: This thermostat is not compatible with heat pumps or multi-
stage systems.
Features
• System operating mode selection: heat, cool or off
• Fan operating mode selection: automatic or on (continuous)
• Programmable heating and cooling cycle lengths: 10, 12, 15, 20
or 30 minutes
• Temperature display in °F or °C
• Backlit display
• Battery replacement indicator
• 7-day programming including:
- Preprogrammed energy-saving schedule
- Early Start
- Temporary bypass
- Time display (12 h or 24 h)
• Filter replacement indicator
• Automatic daylight savings changeover
• Interchangeable faceplates (titanium, charcoal & taupe)
2.1 Removing the Old Thermostat
IN ORDER TO AVOID ANY RISK OF ELECTRIC SHOCK, CUT
POWER TO THE HEATING/COOLING SYSTEM.
Remove the old thermostat to access the wires.
Warning: If the old thermostat was mounted onto an electrical box,
it was probably powered by 120/240 volts. In this case, this thermo-
stat cannot be used.
Identify and label each wire (with the corresponding letter on
the wire terminal) and remove them from the terminals.
If necessary, strip the end of each wire (maximum of 1/4 inch).
Wrap the wires around a pencil to prevent
them from falling into the wall.
If the hole in the wall is too big, insulate it
using a non-flammable material in order to
avoid air draughts behind the thermostat.
2.2 Installing the New Baseplate
For a new installation, choose a location approximately 5 feet
(1.5 m) above the floor and on an inside wall. Avoid draughty
areas (top of staircase, air outlet, etc.), dead air spots (behind
doors), direct sunlight or areas near concealed pipes or chim-
neys.
Remove the thermostat faceplate.
Loosen the locking screw in order to separate the thermostat
from its baseplate (the screw cannot be completely removed).
Gently tilt the thermostat upwards.
Mark and bore the appropriate mounting holes (using a 3/16”
drill bit) or use the existing holes. Insert the plastic anchors.
Pass the wires through the opening of the baseplate and fix the
baseplate to the wall using the screws provided.
2.3 Connecting the Thermostat
Refer to the following table for matching the wire labels with the
thermostat terminals.
Note: Do not connect wires identified as C, X or B. Wrap the bare
end of these wires with electrical tape.
Important: The red jumper wire between Rh and Rc terminals must
be removed in a 5-wire installation.
1. Introduction
2. Installation
RTH2520
Programmable Thermostat
Installation and User Guide
Adjustment
buttons
Display
System operating
mode selector
Fan operating
mode selector
Backlight
button
Programming
buttons
RTH2520 terminals Description Wire labels
Rh Heating power supply Rh, R, 4, V
Rc Cooling power supply Rc, R
W Heating signal W, W1, H
Y Cooling signal Y, Y1, M
GFan G, F
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