Thomas & Betts HEEDU, EEDU User Manual
Installation and Operation........................ 1-26.......................... 1-20
Check Installation and Start-Up .............. 27 ............................. 21
Service/Maintenance/Troubleshooting..... 28-33........................ 22-24
Index by Page Number
Air Flow Requirements ................................. 13
Blower Connections ..................................... 14
Burner Air Adjustment.................................. 2 1
Burner Rack Removal .................................. 22
Burners .......................................................... 21
Bypass Duct.................................................. 13
Carryover System ......................................... 21
Check Installation and Start-Up................... 21
CHLORINES.................................................. 5
Cleaning Pilot and Main Burners................. 22
Cleaning the Heat Exchanger....................... 23
Clearances ...................................................... 4
Combustion Air ............................................... 4
Combustion Air Proving Switch .................. 15
Condensate Drain, Option CS1.................... 13
INSTALLATION FORM RGM 421 (Version A)
APPLIES TO: Installation/Operation/Service
Table of Contents
Paragraph No. Page No.
Coupling Two, Three, Four or Five
Furnaces ..................................................... 7
Dimensional Data ........................................... 3
Disconnect Switch........................................ 15
Duct Connections ......................................... 12
Operating Sequence ...................................... 16
Optional Ductstat ......................................... 19
Electrical Supply and Connections .............. 15
Optional Electronic Modulation .................. 20
Fan Control (Optional) ................................. 18
Gas Piping and Pressures ............................... 8
GENERAL...................................................... 1
HAZARD INTENSITY LEVELS .................. 2
Installation Codes ........................................... 2
Limit Switch ................................................. 17
MAINTENANCE ......................................... 22
Model EEDU
and HEEDU
Indoor/Power-Vented
Duct Furnaces
Mounting the Furnace .................................... 6
Pilot and Ignition Systems ........................... 20
Reversing Air Flow ........................................ 6
SERVICE...................................................... 22
Start-Up ........................................................ 21
Suspending the Furnace ................................. 6
Thermostat.................................................... 15
Troubleshooting...................................... 23, 24
Optional Two-Stage Operation..................... 19
Uncrating ........................................................ 4
Valve ............................................................. 19
Venter ............................................................ 23
Venting ........................................................... 9
Warranty ......................................................... 2
Wiring Diagrams ..................................... 16-17
Reference: Replacement Parts Form, RGM 735
FOR YOUR SAFETY
If you smell gas:
1. Open windows.
2. Don't touch electrical switches.
3. Extinguish any open flame.
4. Immediately call your gas supplier.
WARNING: Gas-fired appliances are not
designed for use in hazardous atmospheres
containing flammable vapors or combustible
dust, in atmospheres containing chlorinated
or halogenated hydrocarbons, or in
applications with airborne silicone substances.
See Hazard Levels, Page 2.
GENERAL
Installation should be done by a qualified agency in accordance
with the instructions in this manual and in compliance with all
codes and requirements of authorities having jurisdiction. The
instructions in this manual apply to the duct furnace models
shown on the right.
FOR YOUR SAFETY
The use and storage of gasoline or other
flammable vapors and liquids in open
containers in the vicinity of this appliance is
hazardous.
W ARNING: Improper installation, adjustment,
alteration, service, or maintenance can cause
property damage, injury or death. Read the
installation, operation, and maintenance
instructions thoroughly before installing or
servicing this equipment.
Model Characteristics
EEDU
HEE DU
Ind oor, Power-Vented, Standard CF M, 80%
T h ermal Eff icient
Indoor, Power-Vented, High CFM, 80%
T h ermal Eff icient
RGM Form 421, Mfg No. 150492, Page 1
HAZARD INTENSITY LEVELS
1. DANGER:
Failure to comply will result in severe personal injury or death and/or property damage.
2. WARNING: Failure to comply could result in severe personal injury or death and/or property damage.
3. CAUTION: Failure to comply could result in minor personal injury and/or property damage.
2. Warranty
1. Installation Codes
The duct furnaces covered in this manual are design-certified by the
American Gas Association and approved by the Canadian Gas Association for use with either natural or propane gas. The type of gas for
which the furnace is equipped and the correct firing rate are shown on
the rating plate attached to the unit. Electrical characteristics are shown
on both the motor nameplate and the unit rating plate.
These units must be installed in accordance with local building codes.
In the absence of local codes, in the United States, the unit must be
installed in accordance with the National Fuel Gas Code Z223.1a (latest edition). A Canadian installation must be in accordance with the
CAN/CGA B149.1 and B149.2 Installation Code for Gas Burning Appliances and Equipment. These codes are available from CSA Information Services, 1-800-463-6727. Local authorities having jurisdiction should be consulted before installation is made to verify local codes
and installation procedure requirements.
Clearances from the heater and vent to construction or material in storage must conform with the National Fuel Gas Code ANSI Z223.1a
(latest edition) pertaining to gas-burning devices, and such material
must not attain a temperature over 160
heater.
Special Installations (Aircraft Hangars/
Garages)
Installations in aircraft hangars should be in accordance with ANSI/
NFPA No. 409 (latest edition), Standard for Aircraft Hangars; in public garages in accordance with ANSI/NFPA No. 88A (latest edition),
Standard for Parking Structures; and for repair garages in accordance
with ANSI/NFPA No. 88B (latest edition), Standard for Repair Garages. ANSI/NFP A-88 (latest edition) specifies overhead heaters must
be installed at least eight feet above the floor. In Canada, installations
in aircraft hangars should be in accordance with the requirements of
the enforcing authorities, and in public garages in accordance with CAN/
CGA B149 codes.
o
F by continued operation of the
Refer to limited warranty information on the warranty card in the
"Owner's Envelope".
WARRANTY: Warranty is void if......
a. Furnaces are used in atmospheres containing flammable
vapors or atmospheres containing chlorinated or halogenated hydrocarbons or any contaminant (silicone, aluminium oxide, etc.) that adheres to the spark ignition flame
sensing probe.
b. Wiring is not in accordance with the diagram furnished
with the heater.
c. Unit is installed without proper clearances to combustible
materials or located in a confined space without proper
ventilation and air for combustion. (See Paragraph 5.)
d. Furnace air throughput is not adjusted within the range
specified on the rating plate.
Form 421, Page 2
3. Dimensions
Figure 1
D
(centerline of hangers)
M
J
(Duct width)
Front View
Limit
3/4" (19mm)
3/4" (19mm)
Combustion
Air Opening
4" (102mm)
Minimum unit
spacing
6-3/4"
(171mm)
18"
A
(457mm)
8-1/8"
(206mm)
5"
(127mm)
Side View
(406mm)
(660mm)
16"
26"
C
Airflow
K
Keep
clear for
service
29"
(737mm)
View
port
(both
sides)
L
F
3-1/2"
(89mm)
Electric Supply
E
B
Rear View
Dimensions (inches)
Size A B C D E F G H J K L M
Nat Pro
75, 100
125, 140
170
200
225
250
300
350
400
34-3/8 14-1/4 35-11/16 14-5/8 4-3/8 3-15/16 1/2 1/2 5/8 12-1/2 7-1/4 7-7/16 4-5/8
34-3/8 17 35-11/16 17-3/8 4-3/8 3-15/16 1/2 1/2 5/8 15-1/4 7-1/4 7-7/16 6
34-3/8 19-3/4 35-11/16 20-1/8 4-3 /8 3-15/16 1/2 1/2 5/8 18 7-1/4 7-7/16 7-3/8
34-3/8 22-1/2 35-11/16 22-7/8 4-3/8 3-15/16 1/2 1/2 5/8 20-3/4 7-1/4 7-7/16 8-3/4
34-3/8 25-1/4 35-11/16 25-5/8 4-3/8 4-15/16 1/2 1/2 1-3/8 23-1/2 7-1/4 7-7/16 10-1/8
34-3/8 28 35-11/16 28-3/8 7-1/8 4-15/16 1/2 1/2 1-3/8 26-1/4 7-1/4 7-7/16 11-1/2
34-3/8 33-1/2 38-1/8 33-7/8 9-7/8 5-15/16 3/4 1/2 1-3/8 31-3/4 9-9/16 7-5/8 13-7/8
34-3/8 39 38-1/8 39-3/8 12-5/8 5-15/16 3/4 1/2 1-3/8 37-1/4 9-9/16 7-5/8 16-5/8
34-3/8 44-1/2 38-1/8 44-7/8 15-3/8 5-15/16 3/4 1/2 1-3/8 42-3/4 9-9/16 7-5/8 19-3/8
H
Combustion
Air Opening
G = Gas
Connection
(not supply line)
Dimensions (mm)
Size A B C D E F G H J K L M
Nat Pro
75, 100
125, 140
170
200
225
250
300
350
400
873 362 906 371 111 100 13 13 16 318 184 189 117
873 432 906 441 111 100 13 13 16 387 184 189 152
873 502 906 511 111 100 13 13 16 457 184 189 187
873 572 906 581 111 100 13 13 16 527 184 189 222
873 641 906 651 111 125 13 13 35 597 184 189 257
873 711 906 721 181 125 13 13 35 667 184 189 292
873 851 968 860 251 151 19 13 35 806 243 194 352
873 991 968 1000 321 151 19 13 35 946 243 194 422
873 1130 968 1140 391 151 19 13 35 1086 243 194 492
RGM Form 421, Mfg No. 150492, Page 3
4. Uncrating and Preparation
This furnace was test operated and inspected at the factory prior to
crating and was in operating condition. If the furnace has incurred any
damage in shipment, file a claim with the transporting agency.
CAUTION: Remove the panel from the bottom rear of the
furnace (See Paragraph 28) and check the burner rack assembly. The burner rack "drawer" should be setting level with
each side on a support rail. Check to assure that EXCESSIVE shipping vibration has not caused the burner rack assembly to "drop off" the support rails into the bottom pan. If
the burner rack assembly is positioned properly, close the
back panel. If the burner rack has fallen, remove the screws
holding the burner rack assembly and pull out the burner rack
"drawer". Re-assemble by sliding the burner rack "drawer"
into the heater, being sure that both sides are resting on the
support rails. Re-attach to the support brackets underneath
the burners. Re-insert the burner rack screws and close the
back panel.
Check the rating plate for the gas specifications and electrical characteristics of the furnace to be sure that they are compatible with the gas
and electric supplies at the installation site. Read this booklet and become familiar with the installation requirements of your particular furnace. If you do not have knowledge of local requirements, check with
the local gas company or any other local agencies who might have
requirements concerning this installation. Before beginning, make
preparations for necessary supplies, tools, and manpower.
Check to see if there are any field-installed options that need to be
assembled to the furnace prior to installation.
Option Parts -- Some gas control options will have parts either shipped
loose with the heater or shipped separately. If your unit is equipped
with any of the following gas control options, be sure these parts are
available at the job site.
Heati n g -- Gas O ption AG7
Control Option
Makeup Air -- O ption AG3
Gas C ontrol
Options
(All of these Opti o n AG8
options al s o
re quire a
shippedseparate fan Option AG9
con t rol, Opt
CQ1 (P/N
57960), which
should be
at the job Option AG15 or AG16
site.
Amplifier, P/N 48035
Thermost at , P/N 48033
Control Switch, P/N 29054
Gasket, P /N 7726
Gasket R et ainer Plate, P/N 7727
Temperature Sensor, P/N 480 41
Amplifier, P/N 48037
Control Switch, P/N 29054
Remote Temperature Selector, P/N 48 042
Temperature Sensor, P/N 480 41
Amplifier, P/N 48035
Control Switch, P/N 29054
Remote Temperature Selector, P/N 11 5848
Stage Adder M odule, P/N 115849
Control Switch, P/N 29054
Transformer 115 to 24V, P/N 103055 or
208/230 to 24V, P/N 103497; and 1/2" locknut ,
P/N 16222 (for transformer)
Display M odule, P/N 115852
(AG16 only)
5. Location, Clearances, and
Combustion Air
Unit must be installed so that the following clearances are provided for
combustion air space, service and inspection, and for proper spacing
from combustible construction.
NOTE: See Figure 5 for service clearance illustration.
REQUIRED CLEARANCES
Front Top Flue Connector Sides Bottom Rear
6" 6" 6" 6" 12" 29"
152mm 152mm 152mm 152mm 305mm 737mm
CAUTION: Do not locate heater where it may
be exposed to liquid spray, rain or dripping
water.
These duct furnaces are designed to take combustion air from the space
in which the furnace is installed. The air that enters into the combustion process is vented to the outdoors. Sufficient air must enter the
equipment location to replace the air exhausted through the vent system. Modern construction methods involve the greater use of insulation, improved vapor barriers and weather-stripping, with the result
that buildings generally are much tighter structurally than they have
been in the past. The combustion air supply for gas-fired equipment
can be affected by these construction conditions because infiltration
that would have existed in the past may not be adequate. Extensive use
of exhaust fans aggravates the situation. In the past the filtration of
outside air assumed in heat loss calculations (one air change per hour)
was assumed to be sufficient. However, current construction methods
may now require the introduction of outside air through wall openings
or ducts.
W ARNING: These furnaces ar e designed to take
combustion air from the space in which the unit
is installed and are not designed for connection
to outside combustion air intake ducts. Use of
outside air ducts voids the warranty and could
cause hazardous operation. (See Hazard Levels,
page 2.)
Requirements for combustion air and ventilation air depend upon
whether the unit is located in a confined or unconfined space. An "unconfined space" is defined as a space whose volume is not less than 50
cubic feet per 1000 BTUH of the installed appliance. Under all conditions, enough air must be provided to ensure there will not be a negative pressure condition within the equipment room or space. A positive seal must be made in all return-air connections and ducts. Even a
slight leak can create a negative pressure condition in a confined space
and affect combustion.
Installation in a Confined Space
Figure 2 Confined Space: A
space whose volume
is less than 50 cubic
feet per 1000 BTUH
of the installed
appliance input
rating
Other shipped-separate options could include a gas shutoff valve, a
condensate drain fitting, a thermostat, a hanger kit, a coupling kit, a fan
control, or high temperature sealing tape.
Form 421, Page 4
Do not install a unit in a confined space without providing wall open-
ings leading to and from the space. Provide openings near the floor
and ceiling for ventilation and air for combustion as shown in Figure
2, depending on the combustion air source as noted in Items 1, 2, and
3 below the illustration.
Add total BTUH of all appliances in the confined space and divide by
figures below for square inch free area size of each (top and bottom)
opening.
1. Air from inside the building -- openings 1 square inch free area per
1000 BTUH. Never less than 100 square inches free area for each opening. See (1) in Figure 2.
2. Air from outside through duct -- openings 1 square inch free area
per 2000 BTUH. See (2) in Figure 2.
3. Air direct from outside -- openings 1 square inch free area per 4000
BTUH. See (3) in Figure 2.
NOTE: For further details on supplying combustion air to a confined
space, see the National Fuel Gas Code ANSI Z223.1a (latest edition ).
Hazards of Chlorines
The presence of chlorine vapors in the combustion air of gas-fired heating equipment presents a potential corrosion hazard. Chlorine will,
when exposed to flame, precipitate from the compound, usually freon
or degreaser vapors, and go into solution with any condensation that is
present in the heat exchanger or associated parts. The result is hydrochloric acid which readily attacks all metals including 300 grade stainless steel.
Care should be taken to separate these vapors from the combustion
process. This may be done by wise location of the furnace with regard
to exhausters or prevailing wind direction. Remember, chlorine is
heavier than air. This fact should be kept in mind when determining
installation locations of heating equipment and building exhaust systems.
Figure 3A - Limit Control Location - When r eversing
air flow, the limit control must be re-located. The
limit control MUST be on the discharge end of the
heat exchanger
Location of
the
factoryinstalled
Limit
Control
Bracket on
a Furnace
with
Standard
Air Flow
Direction
NOTE: Actual gas valve
may not be as illustrated.
Figure 3B - Model EEDU has a top and bottom
support assembly and individual baffles.
6. Instructions for Reversing Air Flow
by Changing Directional Air Baffles
in the Heat Exchanger
Duct furnaces are equipped with directional air baffles between the
heat exchanger tubes. Facing the control compartment of the furnace,
the standard direction of air flow is from the rear of the furnace (gas
valve location) toward the front of the furnace. If the installation site
requires air flow from the front to the rear, the unit may be field adapted
by re-locating the limit control and reversing the position of the directional air baffles.
Instructions:
NOTE: If the unit has optional outer side panels, locate the limit con-
trol and remove the outer panel on that side of the furnace.
All Models - Refer to Figure 3A. Remove the screws attaching the
1.
limit control bracket to the side of the furnace. Carefully pull the bracket/
control assembly through the hole. (Do not disconnect wires.)
2. All EEDU Models (see below for high CFM HEEDU Models) -
Refer to Figure 3B and follow Steps a)-d) below to reverse the direction of the baffles.
a) Remove Screws "A". Individually lift each baffle slightly and slide
forward. Remove all baffles completely from the heat exchanger .
b) Remove Screws B and the top baffle support assembly . Re-position
the assembly on the opposite send of the heat exchanger and attach.
c) Remove Screws C and the assembled bottom baffle support and
brackets. Plug the holes in the heat exchanger bottom by re-inserting the screws in the holes. Position the assembly on the opposite
end of the heat exchanger and attach using field-supplied sheet metal
screws.
d) Re-install all of the individual baffles by reversing procedure in
Step a) above.
All HEEDU Models (see above for EEDU Models) - Refer to
Figure 3C and follow Steps a) and b) below to move the top
baffle to the entering air end of the heater exchanger .
a) Remove screws B and the baffle.
b) Re-position the baffle on the "entering air" end of the heat exchanger
and attach.
RGM Form 421, Mfg No. 150492, Page 5
6. Instructions for Reversing Air
Flow (cont'd)
Figure 4A - Suspending a Single Furnace
7/16" Diameter
Threaded Rod
Figure 3C - Model
HEEDU has only a
top rear heat
exchanger baffle.
3. All Models - Relocate the limit control.
a) At the discharge end on the same side of the heat exchanger, mea-
sure down 4-1/2" and in 1-11/16". Using that point as the center,
punch a 2-1/4" diameter hole in the side panel.
NOTE: It may be necessary to move cable connections. Re-insert
screws to plug all holes in the side panel. After the limit control is
installed, the cable connections may be re-attached using field-supplied sheet metal screws.
b) With the limit control on the heat exchanger side of the bracket,
slide the limit control/bracket assembly into the hole. Attach the
bracket with two sheet metal screws.
c) Cover all of the original factory-made limit control holes with a
field-supplied sheet metal plate. Do not leave any open holes in the
side panel or the heat exchanger bottom.
4. The furnace is now ready for installation with the air flow from front
to rear (gas valve side).
7. Suspending or Mounting the
Furnace
Before installing the furnace, check the supporting structure to be used
to verify that it has sufficient load-carrying capacity to support the weight
of the unit.
Net Weight
Size 75 100 125 140 170 200 225 250 300 350 400
Lbs 104 104 126 128 150 172 194 216 262 306 328
15/32"
(12mm)
Diameter
16"
(406
mm)
Size "A"
75-100 14-5/8" 371mm
125-140 17-3/8" 371mm
170 20-1/8" 371mm
200 22-7/8" 371mm
225 25-5/8" 371mm
250 28-3/8" 371mm
300 33-7/8" 860mm
350 39-3/8" 1000m m
400 44-7/8" 1140m m
Hole
Figure 4B - Option
CK3 Hanger Kit (P/N
57959) with four
threaded sockets
Centerline of hangers
Nut for 7/16" Rod
15/32" (12mm)
Diameter Hole
Hanger
Split Ring Lockwasher
Nut for 7/16" Rod
A
Free-turning
threaded
socket
(1" pipe)
Mounting the Furnace
Change position of the hanger bracket as shown in Figure 5. When the
furnace is mounted on combustible material, a minimum clearance of
12" is required.
Figure 5 - Base Mounted Furnace
As shipped location of hanger
support angle
Limit
Control
Suspending the Furnace
The furnace is provided with four 15/32" diameter holes to provide
four-point suspension. To suspend the unit, cut lengths of 7/16"-16
threaded rod to provide unit height. See Figure 4A for details. NOTE:
A hanger adapter kit Option CK3 is available to facilitate suspension.
See Figure 4B.
WARNING: Units must be level for proper
operation. Do not place or add additional weight
to the suspended furnace. See Hazard Levels,
page 2.
Form 421, Page 6
Combustion
Air Inlet
6" (152mm)
minimum
clearance
Access
Panel
10"
(254
mm)
Airflow
Direction
Access
Panel
Combustion Air Inlet
Keep clean and maintain 29"
6"
(737mm) clearance for burner
rack service
12" (305mm)
Hanger Support Angle
8. Coupling Two, Three, Four or Five Furnaces using Optional Coupling Kits
Refer to illustrations and follow the instructions below.
Coupling Kit, Option CR1 (P/N
57963), fo r Two Furnaces
Qty P /N Descrip tion
2 57964 Filler Plate
1 5 7965 Tie Plate
2 9557 Threaded Socket Assembly
2 5095 3/8-16 x 1-1/4" lg Hex
Head Bolts
2 5197 Split Ring Lock Washer
20 11813 #10 x 1/2" lg Sheetmetal
Screws
Additional Kits
3 Furnaces - Option CR2 (P/N 82654)
4 Furnaces - Option CR3 (P/N 82655)
5 Furnaces - Option CR4 (P/N 82656)
:
Figure 6A - Coupling Furnaces
Instructions for Coupling Furnaces (Refer to Figures 6A,
6B, 6C and 6D)
1. Attach the tie plate to the first furnace using threaded socket assemblies. Tie plate must be positioned below the hanger angles. Secure
fasteners firmly.
2. Move the second furnace into position next to the first furnace. Tie
plate must be below the hanger angle. Secure the tie plate to the
hanger angle using the 3/8-16 bolts, the washers, and the spotweld
nuts on the tie plate.
Figure 6B - Installing Coupling Kit
Tie Plate
4"
1
2
Unit
1
3
6
Unit
2
5
7
7
Item Description
1 Socket Assembly
2 Bolt
3 Lockwasher
5 Spotweld Nut
6 Tie Plate
7 Hanger Angles
3. Position the filler plates to furnaces as shown in Figure 6A. Using a
filler plate as a template, drill 1/8" diameter holes. Attach filler plates
using the sheet metal screws provided. Offset of filler plate allows
alignment with unit duct flanges. See Figure 6C.
4. Coupled units require access panels in the top or bottom of the
outlet duct for limit control service. See Figure 6D and Paragraph
11.
Figure 6C - Front View of Coupled Furnaces
A
Limit
Control
Size "A"
75-100 14-5/8" 371mm
125-140 17-3/8" 371mm
170 20-1/8" 371mm
200 22-7/8" 371mm
225 25-5/8" 371mm
250 28-3/8" 371mm
300 33-7/8" 860mm
350 39-3/8" 1000m m
400 44-7/8" 1140m m
A + 2"
(51mm)
Limit
Control
Figure 6D - Top View of Coupled Furnaces (NOTE:
Access panel may be in top or bottom of ductwork.)
Limit Control
Access panel for
limit control
service and
observation of
coupled unit
Discharge Duct
RGM Form 421, Mfg No. 150492, Page 7
9. Gas Piping and Pressures
WARNING: This appliance is equipped for a
maximum gas supply pressure of 1/2 pound, 8
ounces, or 14 inches water column. Supply
pressure higher than 1/2 pound requires
installation of an additional service regulator
external to the unit.
PRESSURE TESTING SUPPLY PIPING
T est Pressures Above 1/2 PSI: Disconnect the heater and manual valve
from the gas supply line which is to be tested. Cap or plug the supply
line.
T est Pr essures Below 1/2 PSI: Before testing, close the manual valve
on the heater.
All piping must be in accordance with requirements outlined in the
National Fuel Gas Code ANSI/Z223.1a (latest edition), published by
the American Gas Association or CAN/CGA-B149.1 and B149.2, published by the Canadian Gas Association (See Paragraph 1). Gas supply
piping installation should conform with good practice and with local
codes.
Duct furnaces for natural gas are orificed for operation with gas having
a heating value of 1000 (+ or - 50) BTUH per cubic ft. If the gas at the
installation does not meet this specification, consult the factory for
proper orificing.
Pipe joint compounds (pipe dope) shall be resistant to the action of
liquefied petroleum gas or any other chemical constituents of the
gas being supplied.
WARNING: All components of a gas supply
system must be leak tested prior to placing
equipment in service. NEVER TEST FOR
LEAKS WITH AN OPEN FLAME. Failure to
comply could result in personal injury , proper ty
damage or death.
Install a ground joint union and manual shut-off valve upstream of the
unit control system, as shown in Figure 7. The 1/8" plugged tapping in
the shut-off valve provides connection for supply line pressure test
gauge. The National Fuel Gas Code requires the installation of a trap
NOTE: To permit
burner removal,
this nipple must
extend beyond
edge of heater.
Figure 7 - Supply Piping Connection
with a minimum 3" drip leg. Local codes may require a minimum drip
leg longer than 3" (typically 6").
Gas connection sizes are included in the Dimensional Tables in Paragraph 3. After all connections are made, disconnect the pilot supply at
the control valve and bleed the system of air. Reconnect the pilot line
and leak-test all connections by brushing on a soap solution.
Gas Connection to Single-Stage Valve
(Not Gas Supply Line Size)
Unit Size 75-250 300-400
Natural Gas 1/2" 3/4"
Propane Gas 1/2" 1/2"
Manifold or Orifice Pressure Settings
Measuring manifold gas pressure cannot be done until the heater is in
operation. It is included in the steps of the "Check-Test-Start" procedure in Paragraph 24. The following warnings and instructions apply.
WARNING: Manifold gas pressure must never
exceed 3.5" w.c. for natural gas and 10" w.c. for
propane gas.
Ca pacity of Piping
Cubic F eet per Hour based on 0.3" w.c. P ressure Drop
Sp ecific Gravity fo r Natural G as -- 0.6 (Nat ural Gas -- 10 00 B TU/Cubic Ft )
Specific G ravit y for Propane Gas -- 1.6 (Propane Gas -- 2550 BTU /Cubic Ft )
Length Diameter of Pipe
of 1/2" 3/4" 1" 1-1/4" 1-1/2" 2"
Pipe N at ural P ropane N at ural P ropane N at ural P ropane N at ural P ropane N at ural P ropane N at ural P ropane
20' 92 56 190 116 350 214 730 445 1100 671 2100 1281
30' 73 45 152 93 285 174 590 360 890 543 1650 1007
40' 63 38 130 79 245 149 500 305 760 464 1450 885
50' 56 34 115 70 215 131 440 268 670 409 1270 775
60' 50 31 105 64 195 119 400 244 610 372 1105 674
70' 46 28 96 59 180 110 370 226 5 60 342 1050 641
80' 43 26 90 55 170 104 350 214 530 323 990 604
90' 40 24 84 51 160 98 320 195 490 299 930 567
100' 38 23 79 48 150 92 305 186 460 281 870 531
125' 34 21 72 44 130 79 275 168 410 250 780 476
150' 31 19 64 39 120 73 250 153 380 232 710 433
175' 28 17 59 36 110 67 225 137 350 214 650 397
200' 26 16 55 34 100 61 210 128 320 195 610 372
No te: Wh e n sizin g s up ply line s, con sid er p o ss ib ilities o f f u ture exp a n sio n an d in cr e ased re q uirements .
Refer to N ational Fuel G as Code for additional information on line siz ing.
Form 421, Page 8
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