How It Works; Air Pressure Switch; High Limit; Boiler Circulator - Weil-McLain GOLD CGt Manual

GOLD CGt Gas-Fired Water Boiler — Boiler Manual

How it works . . .

①
Control module
The control module responds to signals from the room thermo-
stat, tankless heater low limit, air pressure switch and boiler limit
circuit to operate the boiler circulator, pilot burner, gas valve and
inducer. When room thermostat calls for heat, the control module
starts the system circulator and inducer.
The control module runs the inducer long enough to purge the
boiler flue passages, then opens the pilot valve and activates pilot
ignition spark.
The control module allows up to 15 seconds to establish pilot
flame. If flame is not sensed within 15 seconds, the control module
will turn off the gas valve, flash the Flame light, and then enter a
15-second postpurge. The control module will then start a new
cycle. This will continue indefinitely until pilot flame is established
or power is interrupted. Once pilot flame is proven, the control
module opens the gas valve to allow main burner flame.
When the room thermostat is satisfied, the control module turns
off the gas valve, operates the inducer for a 15-second postpurge
and waits for the next heat call.
The control module indicator lights show normal sequence when
the lights are on steady. When a problem occurs, the control
module flashes combinations of lights to indicate the most likely
reason for the problem (see page 47).
②
Transformer
The control transformer reduces line voltage to 4 volts for the
gas valve circuit.
③
Inducer
The inducer pulls flue gases through the boiler, causing air to be
pulled in through the boiler air openings. The inducer pushes the
flue gases through the vent pipe as well. The inducer is shipped
with gasket and 4 nuts inside a carton located inside the crate. See
Figure 36 on page 59 for proper installation of inducer.
④

Air pressure switch

The air pressure switch signals the control module, telling the
control module whether the inducer is working correctly or the
vent is blocked.
⑤

High limit

The high limit turns off the gas valve if the temperature in the
boiler goes above its setting. (The circulator will continue to run
as long as there is a call for heat.)
⑥

Boiler circulator

The boiler circulator circulates water through the external (system)
piping. The circulator is shipped loose, and
Other boiler components:
a supply to system
b return from system
c stainless steel burners
d flue outlet
e gas valve
f pressure/temperature gauge

⑦
⑧
⑨
must be mounted
g relief valve
h air vent connection
i flame rollout thermal fuse element (TFE)
j burner holding bracket
k pilot burner and bracket
l gas manifold
on the boiler return piping
control module provides a pump exercising routine. If the
boiler is not operated for 30 days, the control module will
power the circulator for 30 seconds, then turn off.
Tankless heater low limit control
This control provides domestic priority by diverting all
available heat to domestic water heating whenever it
senses water temperature below its setting.
3-Way valve
If the tankless heater low limit control senses boiler water
is too cool to provide domestic water from the coil, the 3-
way valve diverts all of the hot water flow from the boiler
back to the return, dedicating all available heat for domes-
tic water. The 3-way valve is shipped inside the inducer
carton. You must install this valve and fittings as
shown. See pages 21 and 64 for details
Make sure the valve body is in the correct position as
shown on page 3 and Figure 39, page 6. Valve port "A"
must connect to boiler supply piping. Valve port "AB"
must connect to boiler return piping. Valve port "B" must
be used for the system return connection. This allows
water to flow normally from port "B" to port "AB" dur-
ing a space heating cycle. The valve stops space heating
circuit flow and switches to full recirculation (flow from
port "A" to port "AB") when the tankless heat low limit
control closes.
Tankless heater
The tankless heater uses hot boiler water to heat domestic
water.
Wires to ambient temp. switch
Install the switch and bracket supplied with the boiler on
the wall closest to the boiler, within 5 inches of the enclo-
sure ceiling. This switch senses the ambient temperature
in the boiler space. Should boiler room temperature rise
too high due to insufficient ventilation air, the switch will
cycle the boiler off when the temperature at the switch
reaches 135°F.
m cast iron boiler sections
n flue collector
o junction box
p drain valve
q burner shield
r expansion tank line connection
Part Number 550-110-290/0107
NOTE
as shown. — The