Honeywell
Heating & Cooling Appliance Controls
Title: Functional description
S4965A3025
Doc.:
S4965A3025E20
Description Sign.
E.C.N.
Date
Rev.
First issue
M.Matiasko
01-Sep-2015
A
Page
14/22
5.5 - Recommended peripheral devices
Recommended valve: atmospheric VK41xxxxxx
Recommended display: N/A
5.6 - Sensors and actuators
5.6.1 - Safety Cut-off Switch
The safety cut-off switch (also called high limit switch) prevents the system from being damaged by overheat. This switch is
in fact the last stop to the ignition control if the appliance is overheating itself. Overheating can be caused for example by a
bad connected temperature sensor or a low water situation. This switch is normally closed and opens if the overheat
condition occurs. The controller reads continuously the status of the switch and immediately activates the lockout state if the
switch opens due to whatever reason. A manual action is required to release the controller from the lockout state. This can
be done by the integral reset button or by the external communication.
5.6.2 - Alarm/Error Led
When an error condition is reached, the Alarm/Error LED indication output will be used to remote the fault indication
externally (to ELS).
5.6.3 - Error Output to Esys 2
When the lockout error condition is reached (except error 40) the Error output indication will be low. It is used to indication
lockout state to the second Esys.
5.6.4 - Gas Valve
The gas valve which must be connected to the Basic ESYS controller is a CVI-m valve. An example of such a valve is the
VK4115G1005B. There are many other valves which can work together with this ESYS. For more information about gas
valves, please contact the appropriate department or your local Honeywell affiliate.
