Bryant 580J*04--12 Manual de instalación descargar pdf (Pagina 24)

Filter Status

Filter status may be configured on any unused binary input

channel. A typical application is a differential pressure

switch that senses the pressure drop across a filter bank.

When the pressure across the filter bank exceeds the setpoint

of the differential pressure switch, the Filter status is

displayed as Dirty on the controller graphic. An alarm

indicates a dirty filter.

Door Switch

A Door Contact may be configured on any unused binary

input. A typical application is an occupancy sensor

mounted within the space served by a single zone rooftop.

Door Contact disables mechanical cooling and electric or

gas heating, when active. Economizer cooling, if

available, continues to operate. A configurable Door

Alarm Delay is provided to prevent immediate action. The

default is set to 60 seconds.

Remote Occupancy

Remote occupancy may be configured on any unused

binary input channel. A typical application is a remote

contact, controlled by a third party, or an occupancy

sensor to set the controller’s occupied mode. The Remote

Occupancy function requires both an input configured for

Remote Occupancy, and Occupancy Source set to Remote

Occ Input to operate. Once configured, the controller will

operate in the occupied or unoccupied mode, as

determined by the state of the Remote Occupancy input.

TROUBLESHOOTING

General

The RTU Open controller acts as an intelligent imbedded

thermostat to the rooftop unit, but can be monitored and

controlled from a 3rd party network. This causes the

system as a whole to be troubleshot from three points of

view. The three parts to the system are the rooftop unit,

the Open controller, and the network connected.

Determining which part needs to be troubleshot is the first

step.

The Open controller can be used to troubleshoot the rooftop

unit and/or itself with service test, communicating LED’s,

and built in alarms. Disconnecting the RTU Open from the

network may also help troubleshooting the controller and

rooftop unit. Third Party Network troubleshooting may also

be required. For base unit troubleshooting, refer to specific

base unit Service Maintenance manual.

There is an on--board battery that is used for RAM and

clock back--up (see Fig. 1). It is a 3--volt lithium battery

(CR2032). The average life is 7 years with a minimum of

10,000 hours of back--up. When the RTU Open board is

powered up, the battery is not being used. If power is lost,

the battery backs up the time clock.

Replacing the RTU Open’s Battery

To determine when to replace the battery, remove and

measure the voltage. If the voltage is below 2.9 volts,

replace the battery.

UNIT OPERATION HAZARD

Power must be ON to the RTU Open when replacing

the battery or date, time, and trend data will be lost.

CAUTION

1. Remove the battery from the controller, making

note of the battery’s polarity.

2. Insert the new battery, matching the battery’s polarity

with the polarity indicated on the RTU Open .

Thermistor Troubleshooting

RTU Open uses thermistors to sense temperatures for

control operation of the unit. Resistances at various

temperatures are listed in Table 2. Thermistor pin

connections are shown in Table 1. Thermistors are used

for supply air temperature (SAT), outdoor air temperature

(OAT), and space temperature (SPT) and all must be a 10

kilo-ohm type II sensor.

To check accuracy, use a high quality digital

volt-ohmmeter. Connect the meter to the thermistor leads

to obtain a resistance value. Use Table 2 to convert that

resistance to a temperature. Next step is to measure

temperature at probe location with an accurate

thermocouple-type temperature-measuring instrument.

Temperature measured by thermocouple and temperature

determined from thermistor voltage reading should be

close, within 5_F if care was taken in applying

thermocouple and taking readings. If a sensor must be

corrected, use the RTU Open’s calibration function to

offset the temperature reading.

Table 2 – Thermistor Resistance vs Temperature Values

for Space Temperature Sensor, Supply Air Temperature

Sensor, and Outdoor Air Temperature Sensor

TEMP

(C)

TEMP

(F)

RESISTANCE

(Ohms)

--- 4 0 --- 4 0 335,651

--- 3 5 --- 3 1 242,195

--- 3 0 --- 2 2 176,683

--- 2 5 --- 1 3 130,243

--- 2 0 --- 4 96,974

--- 1 5 5 72,895

--- 1 0 14 55,298

--- 5 23 42,315

0 32 32,651

5 41 25,395

10 50 19,903

15 59 15,714

20 68 12,494

25 77 10,000

30 86 8,056

35 95 6,530

40 104 5,325

45 113 4,367

50 122 3,601

55 131 2,985

60 140 2,487

65 149 2,082

70 158 1,752

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Bryant 580J*04--12 Manual de instalación Pagina 24

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