79
20. Service Relay
20.1. Service Relay Operation
The M3 unit controller Service Relay output (A55_P298-8) default operation indicates that service is required.
If the default operation is not required, the Service Relay output may be used as a control output. Use parameter 186 to
choose the input which will trigger the Service Relay output. The formula X + (32
x
Y) + (16
x
Z) is used to select the option.
If parameter 186 input sources 7-9 are used, the set point and dead-band must be set with parameter 187, parameter
188, parameter 189, parameters 190, 191 and 192.
20.2. System Relative Humidity Options
Table 52. System Relative Humidity Options
Option
Description
0 - Hysteresis
ON when relative humidity is equal to or greater than parameter 188 setting.
OFF when relative humidity is less than parameter 188 setting minus parameter 191.
1 - Window
ON when relative humidity is within range.
Parameter 188 plus parameter 191
NOTE
: Fixed 3% relative humidity hysteresis on options 1 - 3
2 - Delayed ON
Only ON when relative humidity is greater than parameter 188. Otherwise service delay will be OFF.
3 - Delayed OFF
When relative humidity falls below parameter 188 the service delay is turned OFF once parameter 193 setting
(seconds) is reached.
20.3. System Indoor Air Quality / Carbon Dioxide Options
Table 53. System IAQ / Carbon Dioxide Options
Option
Description
0 - Hysteresis
ON when indoor air quality/carbon dioxide is greater than parameter 187 setting.
OFF when indoor air quality/carbon dioxide is less than parameter 187 minus parameter 190 setting.
1 - Window
ON when indoor air quality/CO2 within range.
Parameter 187 (SRV OUTPT SP CO2) plus parameter 190 .
2 - Delayed ON
ON when indoor air quality/CO2 is greater than parameter 187. Otherwise service delay will be OFF.
3 - Delayed OFF
When indoor air quality/CO2 falls below parameter 187 the service delay is turned OFF once parameter 193 setting
(seconds) is reached.
20.4. System Outdoor Air Temperature Operation
Table 54. System Outdoor Air Temperature Operation Options
Option
Description
0 - Hysteresis
ON when outdoor air temperature is greater parameter 189 setting.
OFF when outdoor air temperature is less than parameter 189 setting.
1 - Window
ON when outdoor air temperature is within range.
Parameter 189 plus parameter 192.
2 - Delayed ON
ON when outdoor air temperature is greater than parameter 189 setting. Otherwise service delay will be OFF.
3 - Delayed OFF
When outdoor air temperature falls below parameter 189 the service delay is turned off once parameter 193 setting
(seconds) is reached.
Example 1
: Use the Service output to energize a dehumidifier at 60% relative humidity and turn off at 55% relative
humidity. (Refer to figure 24.)
