Trane IntelliPak I - Page 134

134 RT-SVP04F-EN
System Testing & Troubleshooting
Low Air Temperature Limit
Trip(formerly: Freezestat
Trip)
Problem: The Low Air
Temperature Limit has
Tripped. (Units with Steam or
Hot Water heating, or Air
Handlers with Chilled Water
Cooling)
A Low Air Temperature Limit
Trip is detected continuously
for more than one second.
This can occur if the Hydronic
Heat Low Air Temperature
Limit input closes for > 1
second, or if the Chilled Water
Low Air Temperature Limit Trip
input opens for > 1 second.
On units with both Hydronic
Heat and Chilled water, both
Low Air Temperature Limit
inputs are active, and the unit
will respond in the same
manner regardless of which
input is used.
The UCM will initiate the
following actions;
a. An “Open All Water Valves”
request is issued to the
Heat Module function,
causing any Steam, Hot
Water, or Chilled Water
valves on the unit to open.
b. An “All Heat OFF” request
is issued to the Heat
Control function.
c. A “Fan Off” request is sent
to the Supply Fan Control
function and the Return Fan
Control function.
d. A “Close Damper” request is
sent to the Economizer
Actuator Control function.
(PMR) A manual reset is
required after the Low Air
Tem p era ture Li mit Tri p
condition clears. The
Diagnostic can be reset at the
unit mounted Human
Interface, by Tracer, or by
cycling power to the RTM.
Low Pressure Control Open
- Circuit 1
Problem: The Low Pressure
Control (LPC) for Circuit #1 is
open.
Check: State of refrigerant
charge for circuit #1.
The Circuit # 1 LPC input is
detected open as described in
the Compressor Protection
function.
A “Lockout Circuit # 1”
request is issued to the
Compressor Staging Control
function.
(PMR) A manual reset is
required anytime after the
Diagnostic is set. The
Diagnostic can be reset by the
Human Interface or Tracer, or
by cycling power to the RTM.
Low Pressure Control Open
-Circuit 2
Problem: The Low Pressure
Control (LPC) for Circuit #2 is
open.
Check: State of refrigerant
charge for circuit #2.
The Circuit # 2 LPC input is
detected open as described in
the Compressor Protection
function.
A “Lockout Circuit # 2”
request is issued to the
Compressor Staging Control
function.
(PMR) A manual reset is
required anytime after the
Diagnostic is set. The
Diagnostic can be reset by the
Human Interface or Tracer, or
by cycling power to the RTM.
Low Refrigerant Charge
(Ckt1 and/or Ckt2)
Problem: The difference
between entering and leaving
evaporator temperatures is
greater then Evaporator
Temperature Differential
SETPOINT for 10 minutes.
Check: Status of refrigerant
charge and running pressures
on affected circuit.
Low refrigerant Charge (Ckt1
and/or Ckt2). The cooling
circuit has been active for 10
minutes and the difference in
the entering and leaving
evaporator temperatures is
greater than the Evaporator
Temperature Differential
SETPOINT for 10 continuous
minutes.
A "Lockout (Ckt1 and/or
Ckt2)" request is issued to the
compressor Staging Control
Function.
(PMR) A manual reset is
required anytime after the
Diagnostic is set. The
Diagnostic can be reset by the
Human Interface or Tracer, or
by cycling power to the RTM."
DIAGNOSTIC DISPLAYED REASON FOR DIAGNOSTIC UCM’S REACTION RESET REQUIRED