auxiliary safety cut-off. The limit switch is supplied with a
manual reset function. If the steam pressure trips the
high limit switch, the limit locks in the off position. The
limit switch will not reset until the manual reset lever is
pressed.
7. Setting The Limit (see diagram below)
This is done using the same procedure as for the
controller. The limit setting will be slightly higher than the
controller's set point.
Low pressure boilers (less than 15 psi): Set the limit
switch 4 psi higher than the controller and 3 psi lower
than the safety valve setting.
High pressure boilers (greater than 15 psi): Set the limit
switch at least 10 psi higher than the controller and 5 psi
lower than the safety valve setting.
8. Night Operating Pressure Switch
A third pressure switch may be supplied as an option.
This switch allows the boiler to operate at low pressure
at night for heating the building. Set the night operating
pressure switch at approximately 10 psi.
9. Example
Boiler with a 100 psi safety valve. Set the controller at 80
psi with an 8 to 1 0 psi differential. Set the limit switch at
90 psi. Turn on the boiler, burner will fire. When the
steam pressure reaches 80 psi, the controller shuts
down the burner. When the pressure drops to 70 to 72
psi the burner restarts. The boiler continues to cycle to
maintain 80 psi. If for some reason the steam pressure
should rise to 90 psi, the limit switch shuts off the boiler.
The manual reset on the limit switch must then be reset
before the boiler will operate again.
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10. More Information
For any additional information on the Honeywell
Pressuretrols, refer to the Honeywell product sheet in
the back of this manual.
0. Start Up of Standard Burners
CAUTION:
All work performed on gas fired equipment
or gas train components must be done by qualified
personnel.
1.
Turn boiler switch OFF
2.
Purge gas line
3.
Turn OFF the main gas supply cock
4.
Turn ON the pilot supply gas cock
5.
Turn boiler switch ON
6.
Burner fan will initiate a pre-purge
sequence followed by ignition of the pilot
7.
Main gas valve will energize and open but
will not fire
8.
Check pilot for adequate flame signal (2.0
mV minimum)
9.
Slowly open main gas cock to allow
main burner to light
10.
If everything is normal, then adjust the
main gas pressure regulator for proper
pressure as shown on the burner "As
Built" specification sheet
11.
Turn OFF boiler switch
12.
Turn ON boiler switch
13.
Check for proper burner ignition
Refer to the burner manufacturer's installation manual
for more specific burner start up instructions.
*For warranty validation, complete start up
check list (included with boiler) and return it to
Lattner. Failure to return check list may void
warranty.
14. Burner Head Pressure
Check gas pressure at burner head. Burner head
pressure should be as specified in the burner manual.
15. Adjust Pressure
If the burner head pressure is not within that range,
adjust the gas pressure regulator. Remove large slotted
cover screw and turn the adjusting screw underneath.
Refer to Maxitrol product sheet for complete
instructions.
