Form I-RDF, P/N 148384 (Rev 1), Page 17
These direct-fired makeup air systems are designed to operate on a natural gas
supply differential pressure range of a minimum of 4.3-5.0" w.c. plus the mani-
fold pressure drop. Maximum supply pressure depends on specific unit firing
rate and manifold selection; see below. If the natural gas supply pressure is
above the maximum allowed, it is necessary to install a field-supplied step-
down gas regulator in the supply line. Order and install the appropriate Gas
Regulator Kit, Option CZ1 (1") or CZ2 (1-1/2"). These kits include spring-
loaded, lockup type regulators that comply with national and local codes speci-
fying that type of regulator. Follow the instructions provided with the kit. Mea-
sure the gas pressure between the step-down regulator and the unit.
Maximum Supply Pressure by Manifold
Manifold Option BM75, BM76, BM77 - 1/2 psi
Manifold Option BM78, BM79 - 2 psi
Manifold Option BM80, BM81 - 5 psi
Supply Pressure
Requirement by
Manifold Option
WARNING: All
components of the gas
supply system must be
leak tested prior to
placing equipment in
service. NEVER TEST
FOR LEAKS WITH AN
OPEN FLAME.
Pilot Supply
Pressure
These systems are designed to operate on a natural gas pilot supply pressure of
3.5" w.c. or propane gas of 6.0" w.c. Measure both operating pressure and
pilot supply pressure with the blower in operation.
Manifold pressure is defined as the gas pressure as measured at the burner
pressure tap. Measure manifold gas pressure with the blowers operating. Mini-
mum gas pressure at the burner is typically 4.3" w.c. for natural gas or typi-
cally 1.5" w.c. for propane gas.
FIGURE 23 - Pressure Tap
Locations for Measuring
Manifold and Pilot Pressure
Manifold Pressure
Minimum Supply Gas Pressure ("w.c.) for Full Fire
Manifold Option
with Gas Control
Option
Manifold Size
MBH
Nat
Pro
Nat
Pro
Nat
Pro
Nat
Pro
Nat
Pro
Nat
Pro
Nat
Pro
Nat
Pro
250
4.0
1.4
4.0
N/A
4.1
1.6
4.3
1.5
4.4
1.6
4.6
1.6
4.5
1.6
5.1
1.8
500
5.3
1.9
5.0
N/A
5.8
2.3
6.2
2.2
6.0
2.3
5.2
1.9
5.0
1.7
5.3
1.9
750
7.5
2.7
6.8
N/A
8.5
3.3
9.5
3.3
8.4
3.3
6.1
2.3
5.7
2.0
5.5
1.9
1000
12.4
4.7
11.7
4.6
7.4
2.8
6.7
2.4
5.8
2.1
1250
9.1
3.5
8.0
2.9
6.2
2.2
1500
11.2
4.3
9.6
3.5
6.6
2.4
1750
13.6
5.3
11.5
4.2
7.2
2.6
2000
16.5
6.3
13.7
5.0
7.8
2.8
2500
23.3
8.9
18.9
7.0
9.4
3.4
3000
11.3
4.1
BM80
BM81
BM79
AG 30, 31, 32, 33, 35, 36, 37, 47, 48, or 51
1-1/4"
2"
1"
1"
1"
1"
AG1
BM75
1"
1-1/4"
AG3
AG 30, 31, 32, 33,
36, 37, 47, 48, or 51
BM76
BM78
AG50
BM77
Inlet Pressure Tap
Valve
Valve
Regulator
Manifold Pressure Tap
Gas
Supply
Pilot
Regulator
Pilot Solenoid Valve
Pilot Pressure Tap
