Spec Sheet

THX9321 PRESTIGE
®
2.0 AND THX9421 PRESTIGE
®
IAQ WITH EIM
68-0311—07 88
5. For Air-to-Air Heat Pumps, press the up/down
arrows to set the maximum time duration of a
defrost cycle. Default is 10 minutes. Delta T is not
monitored during a defrost cycle. Check the heat
pump documentation for the defrost cycle time.
Fig. 154.
6. When you have completed Installer Setup (see
“Installer Options” beginning on page 21), you will
be asked to finish setting up Diagnostics.
Fig. 155.
7. If you press Set Up Diagnostics, you will enter the
Equipment Test. See “Run a Test for Each Stage”
beginning on page 88.
8. If you press I’ll do it later, you will be reminded to
finish setting up diagnostics the next time you exit
installer setup. You can also finish setting up
diagnostics by following the procedure in “If You
Decide to Set Up Diagnostics Later”.
After Delta T Diagnostics Setup is complete, the
thermostat will detect typical failures such as no heating
or no cooling and performance related issues that are
typically caused by a dirty air filter, blocked registers, loss
of refrigerant, dirty a-coil, frozen a-coil, cracked heat
exchanger, dirty burners, etc.
If You Decide to Set Up Diagnostics Later
When you are ready to set up diagnostics, follow these
steps:
1. From the Home screen, press MENU.
2. Scroll down and press Installer Options.
3. Enter the passcode and press Done (see Note).
NOTE: The passcode is the date code printed on
the back of the thermostat or press
MENU > EQUIPMENT STATUS to find the
date code.
4. Press Set Up Diagnostics.
Fig. 156.
5. Proceed to “Run a Test for Each Stage”.
Run a Test for Each Stage
Follow these steps to run a test for each stage in the HVAC
system.
1. Turn on stage 1.
Fig. 157.
2. For each stage you test, wait until Delta T begins to
stabilize, then turn on the next stage (if present). See
Fig. 158 for an example.
Fig. 158.