Carrier HS070-160 manual Troubleshooting, Schd

TROUBLESHOOTING

If necessary, review the Flotronic Plus Control System, Control Sequence, and Controls Operation sections found in this book. Tables 5 and 6 show how to use the keyboard/display module to access functions and sub- functions. (These procedures are also explained in the 3OHR,HS Installation, Start-Upand Service Instructions along with examples and details on using the control features. A copy of the installation instructions should be kept handy while troubleshooting.)

Checking Display Codes - To determine how the machine has been programmed to operate, check the

diagnostic information (	and	operating
mode displays (	If no display	appears,

follow the procedures in Troubleshooting, Modules, page 23. If the display is working, continue as follows:

1. Note all the alarm codes displayed (

2 . Note all the operating mode codes displayed

(ppq).

3.Note the leaving chilled water temperature set point in effect and the current leaving water temperature

If the machine is running, compare the “in effect” leaving water temperature set point with the current water temperature. Remember that if reset is in effect, they may be different because the machine is operating to the modified chilled water set point. If the current temperature is equal to the set point but the set point is not the one desired, recall that if dual set point has been selected in the schedule function, there are 2 set points to which the machine can be operating. Check the programming of the schedule function to see if the occupied or unoccupied set point should be in effect.

OPERATING MODE CODES - Following is an explanation of the operating mode codes:

Temperature Reset (21) ~ In this mode, the unit is using temperature reset to adjust the set point, and the unit is controlling to the modified set point. This means that the leaving water temperature may not equal the chilled water set point. The set point can be modified based on return water, outside air temperature or space temperature.

Demand Limit (22) - This indicates that the capacity of the unit is being limited by the demand limit control option. The unit may not be able to produce the desired leaving water temperature because the unit may not load to full capacity.

Pulldown Control (24) -- If this option is in effect and the cooler water temperature is warm, extra stages will not be added if the water temperature leaving the cooler is decreasing faster than I0 F (0.6 C) per minute.

Standby (26) ~ The unit is being held in the standby mode either because the RUN /STANDBY switch is onen or a set of relay contacts in series with the KUN/ STANDBY switch is open (contacts wired between terminals TBl-13 and TBI-14).

Unoccupied Mode (27) - In dual set point schedule, this mode means the machine is operating to the unoccupied set point. In single set point schedule, this mode shuts down the unit in the same manner as “Unit Standby.”

If the schedule is holding the machine off when it is needed, set the schedule for inactive mode until the schedule can be properly reprogrammed. (See the Sched- ule Function section of the Installation, Start-Up and Service Instructions.) The override feature can also -be used to temporarily place the unit in occupied mode.

Enter	SCHD	, then the number of hours to override
	c	l

(1 to 4), then press EWR . If the unit is in override and 0

you wish to cancel it, enter zero hours in the same manner. Run Mode (28)

To enter the MODES subfunction, depress p-j Fj

and use the 4 key to determine if more than one

mode applies.

Do not attempt to bypass, short or modify the control circuit or electronic boards in any way to correct a problem. This could result in component failures or a hazardous operating condition.

ALARM CODES - The following is a detailed descrip- tion of each alarm code error and the possible cause. Manual reset of an alarm is accomplished by moving the RUN/STANDBY switch to STANDBY, then back to RUN.

Codes 5 l-54, Compressor Failure - If the DSIO relay module relay or control relay feedback switch opens during operation of a compressor, the microprocessor will detect this and will stop the compressor, energize the alarm light, and display a code of 5 1 to 54, depending on the compressor. The compressor will be locked off; to reset, use the manual reset method.

If the lead compressor in a circuit is shut down, all the other compressors in the circuit will be stopped and locked off. Only the alarm code for the lead compressor will be displayed,

The microprocessor has also been programmed to indicate a compressor failure if the feedback terminal on

the 253 terminal strip receives voltage when the com- pressor is not supposed to be on.

Following are possible causes for this failure:

High-Pressure Switch Open - The high-pressure switch for each compressor is wired in series with the 24-volt power that energizes the compressor control relay. If the high-pressure switch opens during operation the com- pressor will stop and this will be detected by the micro- processor through the feedback terminals.

Discharge Gas Thermostat ~ The discharge gas thermo- stat switch in each compressor is also wired in series with the 24-volt power that energizes the control relay (CR). If the switch opens during operation of the compressor, the compressor will be stopped and the failure will be detected through the feedback terminals.

DSIO Module Failure ~ If a DSIO relay module relay fails open or closed, the microprocessor will detect this and lock the compressor off and indicate an error.

Wiring Errors - If a wiring error exists causing the CR or feedback switch not to function properly, the micro-

nrocessor will indicate an error.

1

Processor (PSIO) Failure - I f t h e h a r d w a r e t h a t monitors the feedback switch fails or the processor fails to energize the relay module relay to ON, an error may be indicated.

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t.,

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