Service manual

44
TWO--STAGE 25HNB/24ANB
Application Guidelines
Carrier designed and tested the two--stage air conditioner and heat
pump products with Puron refrigerant to operate at a minimum
outdoor operating ambient in cooling mode at 55_F without low
ambient cooling enabled and the maximum outdoor operating
ambient in cooling is 125_F/51.6_C. On Infinity communicating
systems, only low ambient cooling is available to 0_F/--17.8_C.
The maximum outdoor operating ambient in heating mode is
66_F/18.8_C on all heat pumps. Continuous operation in heating
mode is approved to --30_F/--34.4_C. Thermostat options for the
two stage units are as follows:
S A,B,C,D four--wire connections for Infinity User
Interface.
S R,C,W,Y1,Y2, and O wire connections for standard,
non--communicating thermostat.
25HNB6, 25HNB9, 24ANB7, and 24ANB1 units can run, and are
matched with, User Interface (UI) communicating and
non--communicating indoor fan coils and furnaces. Only unit
combinations listed in the two--stage Product Data are
recommended.
Line sets for two stage units are similar to the single stage units.
However, some restrictions may apply to specific combinations in
long line applications. Refer to the Long Line Guideline for further
information.
The Tennessee Valley Authority (TVA) requires that electric strip
heat have a lockout feature. This is achieved through Carrier
thermostats required per above and must be used on all TVA
approved units.
The new control board in the two stage units with Puron refrigerant
has dip switches for defrost timing. The Infinity controls provide
these two stage units with high stage latching and Hybrid Heatt
(dual fuel) capabilities. The standard Hybrid Heatt (duel fuel)
thermostat can be used on two stage units with Bristol
reciprocating compressors only.
Model Plug
Each control board contains a model plug. The correct model plug
must be installed in order for the system to operate properly. (See
Table 13.)
The model plug is used to identify the type and size of unit to the
control. On 25HNB6 models, the model plug is also used to
determine the start sequence timing for each individual model.
On new units, the model and serial numbers are inputted into the
board’s memory at the factory. If a model plug is lost or missing at
initial installation, the unit will operate according to the
information input at the factory and the appropriate error code will
flash temporarily. An RCD replacement board contains no model
and serial information. If the factory control board fails, the model
plug must be transferred from the original board to the replacement
board for the unit to operate.
NOTE: The model plug takes priority over factory model
information input at the factory. If the model plug is removed after
initial power up, the unit will operate according to the last valid
model plug installed, and flash the appropriate fault code
temporarily.
Table 13—Model Plug Information
MODEL
NUMBER
MODEL
PLUG
NUMBER
PIN RESISTANCE
( K --- o h m s )
P i n s 1 --- 4 P i n s 2 --- 3
25HNB624 HK70EZ041 18 91
25HNB636 HK70EZ043 18 150
25HNB648 HK70EZ045 18 220
25HNB660 HK70EZ047 18 360
25HN9624 HK70EZ010 5.1 120
25HNB936 HK70EZ012 5.1 180
25HNB948 HK70EZ014 5.1 270
25HNB960 HK70EZ016 11 5.1
24ANB124 HK70EZ009 5.1 91
24ANB136 HK70EZ011 5.1 150
24ANB148 HK70EZ013 5.1 220
24ANB160 HK70EZ015 5.1 360
24ANB724 HK70EZ040 18 75
24ANB736 HK70EZ042 18 120
24ANB748 HK70EZ044 18 180
24ANB760 HK70EZ046 18 270