ALERTS AND DELTA T DIAGNOSTICS WITH THE PRESTIGE® 2.0 IAQ THERMOSTAT
Automation and Control Solutions
Honeywell International Inc.
1985 Douglas Drive North
Golden Valley, MN 55422
customer.honeywell.com
® U.S. Registered Trademark
© 2011 Honeywell International Inc.
69-2678EFS—03 M.S. Rev. 10-11
Printed in United States
4.
When setting the run time, select a setting based
on when Delta T began to stabilize during the
equipment test. In the example shown in Fig. 17
and 19, Delta T began to stabilize in about 10-11
minutes.
5.
Set the limits and run time for all stages of cooling
using steps 1–4 above.
6.
Repeat steps 1–5 above for Heating.
After Delta T Diagnostics Setup is
Complete
The thermostat will measure Delta T after the specified
run time, and compare Delta T to the minimum and
maximum limits for each valid cycle. If the system
operates below the minimum limit or above the maximum
limit multiple times (see Table 1), an alert is recorded in
the Alerts Log. If configured to do so, an alert is displayed
to the user (Display Delta T Alerts to User, ISU 13190).
The user is alerted by default. For example, if 10 of the
last 15 cycles have the same fault, an alert is logged and
the user is alerted.
Advanced Options for Delta T
Diagnostics
To set Advanced Options for Delta T Diagnostics, select
Yes at ISU 13015.Then the following advanced options
are displayed:
• Delta T Alert Sensitivity (ISU 13180
; Default: 3
)
• Display Delta T Alerts to User (ISU 13190
; Default:
Yes
)
• Allow Delta T Diagnostics:
— during humidification (ISU 13020; Default: Yes)
— during dehumidification (ISU 13030; Default:
Yes*)
— during ventilation (ISU 13040; Default: Yes)
— only when indoor temperature is within a certain
range (ISUs 13050, 13090, 13130; Default:
Always)
— only when indoor humidity is within a certain
range (ISUs 13060,13100, 13140; Default:
Always)
— only when outdoor temperature is within a certain
range (ISUs 13070, 13110, 13150; Default:
Always)
— only when outdoor humidity is within a certain
range (ISUs 13080, 13120, 13160; Default:
Always)
* Default is Yes for Dehumidifiers and A/C with High
Speed Fan. The thermostat does NOT allow Delta T
diagnostics during dehumidification if it is setup for A/C
with Low Speed Fan, Hot Gas Bypass, or Reheat.
The Delta T Alert Sensitivity is set on a scale of 1–5 at
ISU 13180 (1 is the least sensitive; 5 is the most
sensitive):
Table 1. Delta T Alert Sensitivity (ISU 13180).
Setting
Alert is logged and user is alerted if
1
10 of the last 15 valid cycles have the same fault, or
25 of the last 30 valid cycles have the same fault.
2
10 of the last 15 valid cycles have the same fault, or
20 of the last 30 valid cycles have the same fault.
3
(Default)
5 of the last 5 valid cycles have the same fault, or
10 of the last 15 valid cycles have the same fault, or
15 of the last 30 valid cycles have the same fault.
4
5 of the last 5 valid cycles have the same fault, or
8 of the last 15 valid cycles have the same fault, or
15 of the last 30 valid cycles have the same fault.
5
3 of the last 5 valid cycles have the same fault, or
8 of the last 15 valid cycles have the same fault, or
10 of the last 30 valid cycles have the same fault.
