Installation
RT-SVX26R-EN
29
during compressor starts. Oil foaming occurs when
refrigerant condenses in the compressor and mixes with
the oil. In lower ambient conditions, refrigerant migration
to the compressor could increase.
When the compressor starts, the sudden reduction in
crankcase pressure causes the liquid refrigerant to boil
rapidly causing the oil to foam. This condition could
damage compressor bearings due to reduced lubrication
and could cause compressor mechanical failures.
Before starting the unit in the “Cooling” mode, set the
system switch to the “Off” position and turn the main
power disconnect to the “On” position and allow the
crankcase heater to operate a minimum of 8 hours.
Before closing the main power disconnect switch, insure
that the “System”selection switch is in the “Off” position
and the “Fan” selection switch is in the “Auto” position.
Close the main power disconnect switch and the unit
mounted disconnect switch, if applicable.
ReliaTel Controls
Upon power initialization, the RTRM performs self-
diagnostic checks to insure that all internal controls are
functional. It also checks the configuration parameters
against the components connected to the system.
The Liteport LED located on the RTRM module is turned
“On” within one second of power-up if internal operation
is okay.
Use one of the following “Test” procedure to bypass some
time delays and to start the unit at the control panel.
Each step of unit operation can be activated individually by
temporarily shorting across the “Test” terminals for two to
three seconds. The Liteport LED located on the RTRM
module will blink when the test mode has been initiated.
The unit can be left in any “Test” step for up to one hour
before it will automatically terminate, or it can be
terminated by opening the main power disconnect switch.
Once the test mode has been terminated, the Liteport LED
will glow continuously and the unit will revert to the
“System” control.
Three Stage Cooling
T/YH*150, 180, 210, and 240 models have the ability to
utilize three stages of cooling when the unit is controlled
by a zone sensor. To enable three stages of cooling,
connect wires 36BY and 36BZ.
Important:
This is only intended for HIGH EFFICIENCY,
SHORT-ORIFICE UNITS. Disconnecting
these wires will disable three-stage cooling.
4 Stages of Cooling (25 Tons)
25 tons high efficiency units have 4 stages of cooling with
a single compressor and tandem set (similar to variable
speed).
Modulating Gas Heat 2.5:1 Turndown
(Optional)
The set-up required for equipment ordered with
modulating gas heat varies based on the control system
utilized. Zone sensors, LonTalk, and Comm3/4 do not
require additional set-up.
24 volt control systems (thermostats) require setting the
desired leaving air temperature. The heat exchanger will
modulate to maintain this temperature. Use the following
procedure for set-up:
1. Locate the RTOM
2. Locate the “Discharge Air SP” or “OA CFM SP”
3. Adjust the variable resistor to match the desired
leaving temperature
a. Range = 50°F–150°F
i. Clockwise—Increase Temperature
ii. Counterclockwise—Decrease Temperature
