Mercury PR0091 - Manual (Page 11)

Mercury 6-5 Stat – Installation & User Guide
Over-ride Operation
The 5 Channel Thermostat can operate either from its internal channel time settings or from a network Data
Manager GP Timer channel (P70 sets the mode either local or remote). If the 5 Channel Thermostat is set up
to use the remote timing channels it reverts to local mode if network communications are lost for more than 5
minutes. An over-ride occurs when a resistor is switched in across the input which has to be overridden,
however when the over-ride signal is removed the channel returns too normal operation.
Thermostat Over-ride: -
When a channel is configured for thermostat operation the following will occur when an over-ride is present on
the channel input. In the example below channel 1 is set as a thermostat in a heating application, the relay
inverse feature is disabled, the controller timer is set to local operation and is off. When the timer is in the off
period the channel will not be enabled for heating and the thermostat relay remains off, providing the probe
temperature is not below the frost detect set point. As shown in the diagram an over-ride is applied to channel
1, this will enable the channel. The thermostat relay does not immediately turn on, it only does so when the
temperature drops below the cut-in set point. The controller will continue normal temperature control until the
over-ride is removed or the next scheduled off occurs in the local timer schedule. When the timer is in the on
period, the over-ride has no effect. Note:- An over-ride should be removed as soon as it is not required on an
input.
Cut-in Set
Point
Frost
Detect
Time
Relay
State
On
Off
Over-ride
Activated
Thermostat Relay Status
Ch 1 Probe Temperature
Tempera
ture
Diff
Ensure that all power is
switched off before
installing or maintaining
this product
Revision 1.2 Page 11 of 21