26
Part Number 550-142-320/0720
GWA
Series 3
Gas-Fired Water Boilers –
Boiler Manual
9 Department of Energy – Compliance
10 Sequence of operation
Follow all procedures given in this manual
and operating instructions when oper-
ating the boiler. Failure to do so could
result in severe personal injury, death or
substantial property damage.
1.
Standby:
With no call for heat, the vent damper and
circulator are de-energized. No gas flows to pilot or
main gas valve.
2.
Call for heat
(thermostat circuit closes):
a. While attempting to satisfy the heat demand, the
control module monitors the boiler temperature
changes via the temperature sensor and deter-
mines whether or not the available hot water will
satisfy the demand, only running the circulator. If
additional heat is needed, the sequence contin-
ues. When DHW (if used) calls for heat, sequence
above is bypassed.
b. Vent damper and circulator energized if pilot status
acceptable. Vent damper drives open. When vent
damper end switch makes circuit, ignition control
begins pilot ignition attempt.
c. Ignition control checks for false flame signal: If igni-
tion control senses pilot signal when no pilot gas
should be present, control will lockout, requiring
reset procedure as given in
Figure 20, page 26.
3.
Pilot ignition:
Control module sparks the pilot and
opens pilot valve in main gas valve.
a. If pilot does light and control module senses flame
current, spark generator is turned off and main valve
opens.
b.
Natural Gas -
If pilot does not light within 15 sec-
onds, pilot valve is closed and spark generator is
turned off. Control module waits 5 minutes, then at-
tempts to ignite pilot again. This cycle will continue
indefinitely if pilot ignition control does not sense pilot
flame.
c.
Propane Gas -
If pilot does not light within 15
seconds, pilot valve is closed and spark generator
is turned off. Control module waits 1 minute then
attempts to ignite pilot again. After first failed ignition
retry attempt, control module will attempt to ignite
pilot 2 more times with a 5 minute wait period after the
second try and a 60 minute wait period after the third
try. If the ignition control does not sense pilot flame
during these trials, it will lock out the boiler and require
a manual reset procedure to allow further attempts.
Manual Reset Procedure for Propane Gas Lockout ––
Unburned propane gas may have accumulated
in combustion chamber. Provide adequate
ventilation to completely remove any accu-
mulated LP gas from boiler and adjacent area
before attempting to reset and light boiler.
Failure to do so will cause severe personal
injury, death or substantial property damage.
This boiler is equipped with a control system that automatically adjusts a time delay period to turn on the boiler
during a call for heat. This is accomplished by circulating available hot water in the system while measuring
water boiler water temperature changes. The control calculates a suitable delay based on temperature measure-
ments and turns the boiler on only after it determines that the demand for heat cannot be satisfied with the
available hot water,
Due to the wide variety of controls used in boiler installations, this control is also equipped with an adjustment
for the calculated time delay period (ECONOMY ADJUST). In the MIN position, the time delay is zero and the
IMPORTANT notice below must be observed:
IMPORTANT
In accordance with Section 325 (f) (3) of the Energy Policy and Conservation Act, this boiler is equipped with
a feature that saves energy by reducing the boiler water temperature as the heating load decreases. This feature
is equipped with an override which is provided primarily to permit the use of an external energy management
system that serves the same function.
THIS OVERRIDE MUST NOT BE USED UNLESS AT LEAST ONE OF THE FOLLOWING CONDITIONS IS TRUE:
• An external energy management system is installed that reduces the boiler water temperature as the heating load
decreases.
• This boiler is part of a modular or multiple boiler system having a total input of 300,000 BTU/hr or greater.
• This boiler is equipped with a tankless coil.
