Weil-McLain GV90+ User Manual download pdf (Page 10)

Part number 550-142-055/0411

GV90+ gas-fired water boiler — User’s Information Manual

1 Integrated boiler control

The integrated boiler control (IBC) responds to signals from the room thermostat, air

pressure switch, inlet water 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.

2 Transformer

The control transformer reduces line voltage to 24 volts for the gas valve and limit circuit.

3 Blower

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.

4 Recuperator

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.

5 Water temperature limit switch

The water temperature limit switch turns off the gas valve if the temperature in the

boiler goes above its setting. (The circulators will continue to run as long as there is a

call for heat.)

6 System 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.

7 Bypass 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

circulator 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 even if return water is as low as 60°F.

Pump must remain on boiler — do not remove.

8 Air pressure switch

The air pressure switch signals the IBC, telling the control whether air is moving through

the blower.

9 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

This boiler uses a negative-pressure-

regulated gas valve, set for an outlet

pressure approximately –0.20” water

column.

DO NOT set the outlet pressure higher

than factory setting.

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Weil-McLain GV90+ User Manual Page 10

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