Weil-McLain GV90+ - How it works...

Part number 550-142-903/1016
2
GV90+ Series 2 GAS-FIRED WATER BOILER — Boiler Manual
 )NTEGRATEDBOILERCONTROL
The integrated boiler control (IBC) responds to signals from the room thermostat, air
pressure switch, inlet water sensor, boiler water temperature sensor and boiler limit circuit
to operate the circulators, gas valve, igniter and blower. When a room thermostat calls
for heat, the IBC starts the system circulator and blower.
The IBC runs the blower to purge the boiler flue passages, then turns on the igniter and
lets it warm up.
After igniter warm-up, the IBC opens the gas valve, turns the igniter off, and checks for
flame. The flame must come on within 4 seconds or the IBC will shut down and try the
full cycle again.
When the room thermostat is satisfied, the IBC turns off the boiler components and
waits for the next heat call.
The IBC indicator lights show normal sequence when the lights are on steady. When a
problem occurs, the IBC flashes combinations of lights which indicate the most likely
reason for the problem.
While attempting to satisfy the heat demand, the control module monitors the boiler
temperature changes via the temperature sensors and determines whether or not the
available hot water will satisfy the demand, only running the circulator. If additional
heat is needed, the sequence continues. When DHW (if used) calls for heat, sequence
above is bypassed.
 4RANSFORMER
The control transformer reduces line voltage to 24 volts for the gas valve and limit circuit.
 "LOWER
The blower pulls in air and mixes it with gas from the gas valve. The blower forces this
mixture into the burner for combustion inside the boiler chamber.
 2ECUPERATOR
The recuperator is a stainless steel heat exchanger that increases boiler efficiency by ex-
tracting additional heat from the flue gases. Return water passes through the recuperator
before entering the boiler.
 7ATERTEMPERATURESENSOR
The water temperature sensor provides a signal to the control module to turn
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.)
 3YSTEMCIRCULATOR
The system circulator circulates water through the external (system) piping. The flow
rate of the circulator is controlled by the IBC, depending on the temperature of the water
entering the boiler sections. Pump must remain on boiler — do not remove.
 "YPASSCIRCULATOR
The IBC operates the bypass circulator to mix hot water from the boiler outlet with
colder return water from the system as needed to prevent condensation of flue gases in
the cast iron heat exchanger.
When the water returning to the boiler is below 140°F, the IBC regulates the bypass cir-
culator and system circulator flow rates to raise the return water temperature up to 140°F
before it enters the cast iron sections. By balancing these flow rates, the IBC can protect
against condensation in the cast iron heat exchanger even if return water is as low as 60°F.
Pump must remain on boiler — do not remove.
 !IRPRESSURESWITCH
The air pressure switch signals the IBC, telling the control whether air is moving through
the blower.
 2ETURNWATERTEMPERATURESENSOR
The water temperature sensor monitors the temperature of the water entering the boiler
sections. The sensor sends this information to the IBC. The IBC determines how much
to adjust the circulator flow rates to provide at least 140°F water to the cast iron heat
exchanger.
How it works . . .
LEGEND
A Supply to system, 1” NPT
B Return from system, 1” NPT
C Combustion air inlet fitting —
3” PVC connection
D Flue outlet — 3” PVC connection
E Gas valve — negative pressure
regulated gas control
F Pressure/temperature gauge
G Flueway inspection port cover
H Sensor hose trap
I Manual air vent
J Relief valve
K Thermal fuse — a one-time fuse
device that shuts boiler off if flue
temperature exceeds its setpoint
M Condensate trap line — shipped
loose with boiler, field installed
N Condensate drain connection —
½” PVC female
O On/off power switch
This boiler uses a negative-pressure-
regulated gas valve, set for an outlet
pressure approximately –0.20” water
column.
$/./4 set the outlet pressure higher
than factory setting.