25HCS
Quiet Shift
Quiet shift is a field selectable defrost mode (factory set to OFF), which will eliminate occasional noise that could be heard at the start of defrost cycle and restarting of heating cycle. It is selected by placing DIP switch 3 on defrost board (see Fig. 9) in the ON position.
When Quiet Shift switch is placed in ON position, and a defrost is initiated, the following sequence of operation will occur. Reversing valve will energize, compressor will turn off for 30 seconds, and then turn back on to complete defrost. At the start of heating after conclusion of defrost, reversing valve will
Defrost
The defrost control is a time/temperature control which has field selectable settings of 30, 60, 90, or 120 minutes, factory set to 90 minutes. These settings represent the amount of time that must pass after closure of the defrost thermostat before the defrost sequence begins.
The defrost thermostat senses coil temperature throughout the heating cycle. When the coil temperature reaches the defrost thermostat setting of approximately 32 _F, it will close, which energizes the DFT terminal and begins the defrost timing sequence. When the DFT has been energized for the selected time, the defrost cycle begins. Defrost cycle is terminated when defrost thermostat opens, or automatically after 10 minutes.
Defrost Speedup
To initiate a forced defrost, speedup pins (J1) must be shorted with a flat head screwdriver for 5 seconds and RELEASED. If the defrost thermostat is open, a short defrost cycle will be observed (actual length depends on Quiet Shift switch position). When Quiet Shift is off, only a short 30 second defrost cycle is observed. With Quiet Shift ON, the speedup sequence is one minute; 30 second compressor off period followed by 30 seconds of defrost with compressor operation. When returning to heating mode, the compressor will turn off for an additional 30 seconds and the fan for 40 seconds.
If the defrost thermostat is closed, a complete defrost cycle is initiated. If the Quiet Shift switch is turned on, the compressor will be turned off for two 30 second intervals as explained previously.
O | T2 C C O | DFT |
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R | T1 |
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W |
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Y |
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C | Y |
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SPEEDUP | P1 |
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J1 | P3 | INTERVALTIMER | 90 | 60 30 | 30 60 | 120 |
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| QUIET SHIFT | ON | HK32EA003 |
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| Speedup |
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| Quiet | Defrost interval |
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| Shift | DIP switches |
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| A05378 |
Fig. 9 - Defrost Control
Table 3 – Defrost Control Speedup-Timing Sequence
PARAMETER | MINIMUM | MAXIMUM | SPEEDUP | |
(MINUTES) | (MINUTES) | (NOMINAL) | ||
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27 | 33 | 7 sec | ||
45 | 55 | 12 sec | ||
81 | 99 | 21 sec | ||
9 | 11 | 2 sec | ||
5 minutes | 4.5 | 5.5 | 1 sec |
Check Charge
Factory charge amount and desired subcooling are shown on unit rating plate. Charging method is shown on information plate inside unit. To properly check or adjust charge, conditions must be favorable for subcooling charging. Favorable conditions exist when the outdoor temperature is between 70_F and 100_F (21.11_C and 37.78_C), and the indoor temperature is between 70_F and 80_F (21.11_C and 26.67_C). Follow the procedure below:
Unit is factory charged for 15ft (4.57 m) of lineset. Adjust charge by adding or removing 0.6 oz/ft of 3/8 liquid line above or below 15ft (4.57 m) respectively.
For standard refrigerant line lengths (80 ft/24.38 m or less), allow system to operate in cooling mode at least 15 minutes. If conditions are favorable, check system charge by subcooling method. If any adjustment is necessary, adjust charge slowly and allow system to operate for 15 minutes to stabilize before declaring a properly charged system.
If the indoor temperature is above 80_F (26.67_C), and the outdoor temperature is in the favorable range, adjust system charge by weight based on line length and allow the indoor temperature to drop to 80_F (26.67_C) before attempting to check system charge by subcooling method as described above.
If the indoor temperature is below 70_F (21.11_C), or the outdoor temperature is not in the favorable range, adjust charge for line set length above or below 15ft (4.57 m) only. Charge level should then be appropriate for the system to achieve rated capacity. The charge level could then be checked at another time when the both indoor and outdoor temperatures are in a more favorable range.
NOTE: If line length is beyond 80 ft (24.38 m) or greater than 20 ft (6.10 m) vertical separation, See Long Line Guideline for special charging requirements.
Heating Check Chart Procedure
To check system operation during heating cycle, refer to the Heating Check Chart on outdoor unit. This chart indicates whether a correct relationship exists between system operating pressure and air temperature entering indoor and outdoor units. If pressure and temperature do not match on chart, system refrigerant charge may not be correct. Do not use chart to adjust refrigerant charge.
Final Checks
IMPORTANT: Before leaving job, be sure to do the following:
1.Ensure that all wiring is routed away from tubing and sheet metal edges to prevent
2.Ensure that all wiring and tubing is secure in unit before adding panels and covers. Securely fasten all panels and covers.
3.Tighten service valve stem caps to
4.Leave Owner’s Manual with owner. Explain system operation and periodic maintenance requirements outlined in manual.
5.Fill out Dealer Installation Checklist and place in customer file.
CARE AND MAINTENANCE
For continuing high performance and to minimize possible equipment failure, periodic maintenance must be performed on this equipment.
Frequency of maintenance may vary depending upon geographic areas, such as coastal applications. See Users Manual for information.
Copyright 2008 Carrier Corp. S 7310 W. Morris St. S Indianapolis, IN 46231 | Printed in U.S.A. | Edition Date: 04/08 | Catalog No: |
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Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations. | Replaces: NEW | ||
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