Lennox LGH480 User Manual

Page 56
LGH/LCH420, 480, 540, 600
FIGURE 50
MODULATING GAS VALVE (MGV)
GV1
LEFT HEAT
SECTION GAS
VALVE
GV3
RIGHT HEAT
SECTION GAS
VALVE
GV5
RIGHT HEAT SECTION
MODULATING
GAS VALVE
GV4
LEFT HEAT SECTION
MODULATING
GAS VALVE
TO LEFT HEAT
SECTION
TO RIGHT
HEAT SECTION
MANIFOLD
PRESSURE
PORT
MANIFOLD
PRESSURE PORT
GAS
INLET
Optional Modulating Gas Valve (MGV)
Units equipped with optional modulating gas valves (MGV)
contain two modulating gas valves in addition to two
standard gas valves. See figure 50.
Operation
The Unit Controller will control modulating gas valves to
maintain 110°F (default) discharge air during the heating
cycle. The left heat section will operate when 25-50% of
nameplate heat is needed. Both heat sections will operate
when 50-100% of the nameplate heat is needed.
The normally open MGV will allow full heating capacity
should the MGV fail.
Start-Up
1- Operate the unit in heating mode according to the
Heating Start-Up section in this manual.
2- After the unit has operated for 5 minutes, use the Unit
Controller Service - Test menu to run high capacity. The
unit will operate at maximum heating input.
3- Measure the manifold pressure at the gas valves.
Manifold pressures should be:
GV1 & GV3:
Natural - 4.0”w.c. LP - 10.8”w.c.
GV4 & GV5:
Natural - 3.7”w.c. LP - 10.5”w.c.
4- Use the options in the Unit Controller Service Test
menu to run low capacity. The unit will operate at
minimum heating input.
5-Measure the manifold pressure at the gas valves.
Manifold pressures should be:
GV1 & GV3:
Natural - 4.0”w.c. LP - 10.8”w.c.
GV4 & GV5:
Natural - 0.9”w.c. LP - 2.6”w.c.
Unit Controller Output
The Unit Controller 0-10VDC output to the MGVs increases
to modulate valves further closed during a reduced heating
demand. The Unit Controller 0-10VDC output to the MGVs
decreases to modulate valves further open during a higher
heating demand.
Heating
Demand
Reduces
Unit Control
ler Output
To MGVs
Increases
MGVs
Modulate
Further
Closed
Heating
Output
Lowers
Heating
Demand
Increases
Unit Control
ler Output
To MGVs
Reduces
MGVs
Modulate
Further
Open
Heating
Output
Increases

Lennox LGH480 Specifications

General

Brand	Lennox
Model	LGH480
Category	Air Conditioner
Language	English