Gas Valve - Lennox GHR32Q Unit Information

5.Clamshell Heat Exchanger
GHR32 units use an aluminized steel primary and stain-
less steel secondary heat exchanger assembly. Table 30
shows how many heat exchanger clamshells are used
per unit. Heat is transferred to the air stream from all sur-
faces of the heat exchanger. The shape of the heat ex-
changer ensures maximum efficiency.
The combustion air blower pulls fresh air through the air in-
take box. This air is mixed with gas in the burner venturi
and at the corbel orifices. The gas / air mixture is then
burned at the entrance of each clamshell. Combustion
gases are then pulled through the primary and secondary heat
exchangers and exhausted out the exhaust vent pipe.
6.Flame Rollout Switch (S47)
Flame rollout switch S47 is a SPST N.C. high temperature limit
located behind the burner air intake fitting on the burner box
assembly (see figure 25). S47 is wired to the burner ignition
control A3. When S47 senses flame rollout (indicating a
blockage in the combustion air passages), the flame rol-
lout switch trips, and the ignition control immediately
closes the gas valve.
Switch S47 in all GHR32 units is factory preset to open at
320_F + 12_F (160_C + 6.7_C) on a temperature rise. All
flame rollout switches are manually reset.
FLAME ROLLOUT SWITCH (S47)
FIGURE 25
HONEYWELL VR8205 Series Gas Valve
HIGH FIRE ADJUSTMENT
SCREW (UNDER CAP)
LOW FIRE
ADJUSTMENT
SCREW
(UNDER CAP)
VALVE SHOWN IN OFF POSITION
INLET PRESSURE TAP
FIGURE 26
FLAME ROLLOUT
SWITCH (S47)
MANIFOLD
PRESSURE
TAP
Page 34

7.Gas Valve

The GHR32 uses a gas valve manufactured by White
Rodgers or Honeywell. The valve is two-stage internally
redundant to assure safety shut−off. If the gas valve must
be replaced, the same type valve must be used. The
Honeywell valve can be field converted to LP and is adjust-
able on both low and high fire. WhiteRodgers supplies two
seperate valves for natural and LP and is adjustable for
high fire ONLY.
24VAC terminals and gas control knob are located on top of
the valve. Terminals on the gas valve are connected to wires
from the SureLight integrated control and the two−stage con-
trol. 24V applied to the terminals energizes the valve.
Inlet and outlet pressure taps are located on the valve. A regu-
lator adjustment screw is located on the side of the valve. Re-
fer to figures 26, 27 , and 28 for location of valve features.
NOTE−WhiteRodgers valve is not adjustable on low fire.
Do not attempt to regulate low fire manifold pressure.
WHITE RODGERS 36E SERIES GAS VALVE
NATURAL GAS
(LOW HEAT MANIFOLD PRESSURE FACTORY SET.
DO NOT ADJUST.)
FIGURE 27
WHITE RODGERS 36E SERIES GAS VALVE
PROPANE GAS
(LOW HEAT MANIFOLD PRESSURE FACTORY SET.
DO NOT ADJUST.)
P M
HI
FIGURE 28
100% Sealed Combustion
The burner box is completely sealed and operates under
a negative pressure. A pressure hose is connected from the
burner box to the gas valve regulator. The gas valve senses
the pressure in the burner box and changes gas valve outlet
(manifold) pressure based on changes in burner box pres-
sure. The intent is to compensate for different vent con-
figurations which can greatly affect the firing rate of the
unit.
HIGH HEAT
MANIFOLD
PRESSURE
ADJUSTMENT
ON SIDE
(under cap)
MANIFOLD
PRESSURE
OUTLET ON
SIDE
HIGH HEAT
MANIFOLD
PRESSURE
ADJUSTMENT
ON SIDE
C (under cap)
MANIFOLD
PRESSURE
OUTLET ON
SIDE