Pure Humidifier GX Series User manual

TM
READ AND SAVE THESE INSTRUCTIONS
Standard Water
GX Series
Gas Fired Exchanger Humidifier
Installation Instructions
Operation and Maintenance Manual
FOR YOUR SAFETY:
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other
appliance.
WARNING:
Improper installation, adjustment, alteration, service or maintenance can cause injury or property
damage. Refer to this manual. For assistance or additonal information consult a qualified installer,
service agency, or the gas supplier.
WARNING:
If the information in this manual is not followed exactly, a fire or explosion may result, causing property
damage, personal injury, or loss of life.
WHAT TO DO IF YOU SMELL GAS:
Do not try to light any appliance.
Do not touch any electrical switch; do not use any telephone in your building.
Immediately call your gas supplier from a neighbor’s telephone.
Follow the gas supplier’s instructions. If you cannot reach your gas supplier, call the fire department.
IMPORTANT: Read and save this guide for future reference. This
guide to be left with equipment owner.
ETL/ETLC Listed #43438 To “IAS 12-94 Gas Fired Humidifier”
Our results are comforting
PURE HUMIDIFIER® and INTAC® are registered trademarks of PURE Humidifier Co.
Form No: GXOM-6-2023

TM
To the User of PURE Humidifier Co.’s
GX Series Humidifiers
We at PURE Humidifier Co. thank you for choosing one of our quality products. PURE Humidifier Co. GX Series humidifiers
are models of simplicity to install, operate and maintain. However, they must be maintained to provide maximum operating
efficiency.
PLEASE READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY. PROPER OPERATION AND HUMIDITY CONTROL
IS POSSIBLE ONLY WITH PROPER INSTALLATION AND MAINTENANCE.
The GX Series Humidifier utilizes a Tri-Probe conductive type water control system, which is designed for use with standard
(hard or soft) tap water. Use of demineralized, deionized or reverse osmosis water will cause a failure of the water level
control system and void the warranty. PURE Humidifier Co.’s GXDDR Series should be installed on applications that require
demineralized, deionized or reverse osmosis water.
High chloride content in feed water can cause chloride stress cracking and chloride pitting in stainless components. Chloride
stress corrosion cracking (CSCC) and chloride pitting of stainless steel components is not covered by warranty. Do not use
hydrochloric acid descalers or bleach to clean the tank. Consult the factory if you are unsure about which chemical descaler
to use.
To ensure proper installation of this product, it must be installed by qualified HVAC and electrical contractors, and must be
in compliance with local, state, federal, and governing codes. If installed improperly this product may cause damage to
property, severe personal injury, or death as a result of electric shock, burns, and/or fire.
Do not adjust any components inside humidifier control box without consulting the factory.
For indoor installation in conditioned paces only unless supplied with an outdoor enclosure.

TM
Table of Contents
TM
Introduction
Warnings ……………………………………………………………………………………….....
Overview
Features ………………………………………………………………………………………......
Capacities, Electrical & Weights ………………………………………………………………..
GX-3, GX-4 Dimensions & Layout ……………………………………………………………...
GX-8 Dimensions & Layout …………………………………………………………................
GX-12 Dimensions & Layout ..…………………………………………………………………..
Installation
Installation & Location …………………………………………………………………….…......
Drain Pan Mounting ……………………………………………………………………….….....
Electrical, Combustion & Ventilation Air ……………………………………………………….
Gas Piping Installation ……………………………………………………………………….….
Venting …………………………………………………………………….................................
Sealed Combustion ………………………………………………………………….….............
GX-8 Exhaust Manifold ……………………………………………………………….…….......
GX-12 Exhaust Manifold …………………………………………………………………….…..
Water Supply & Drain Piping ……………………………………………………………………
Supply Piping Examples …………………………………………………………………….…..
Operation
Modulating Control Operation …..……..………………………………………………….…....
GX Pre-Startup Checklist …………………………………………………………………….….
GX Startup Procedure…..……..………………………………………………….….................
GX Burner Startup Procedure ……………………………………………………….……........
Troubleshooting ……………………………………………………………………………….....
Burner Troubleshooting & Maintenance …..……..…………………………………………….
Burner Flame Controller Troubleshooting …..……..…………………………………………..
Maintenance
Tool Requirements and Torque List ………………………………………….…………….......
GX Maintenance ………………………………………………………….………….................
Exchanger Gasket Replacement ………………………………….……….............................
Cover Gasket Replacement Instructions ……………………………………….…………......
Maintenance Notes ……………………………………………………………….…………......
Spare Parts
GX-3 & GX-4 Exploded Parts Drawing ……………………………………………….……….
GX-3 & GX-4 Parts List …………………………………………………………………….…...
GX-8 Exploded Parts Drawing ……………………………………………….………..............
GX-8 Parts List …………………………………………………………………….…................
GX-12 Exploded Parts Drawing ……………………………………………….………............
GX-12 Parts List …………………………………………………………………….…..............
Modulating Burner Exploded View ……………………………………………….………........
Modulating Burner Gun Assembly Exploded View …………………………………………...
Modulating Burner Parts List ..............................................................................................
On/OffBurner Exploded View ……………………………………………….………...............
On/OffBurner Gun Assembly Exploded View …………………………………………...........
On/OffBurner Parts List .....................................................................................................
Warranty ……………………………………………………………………………………….…………....
1-2
3
4
5
6
7
8
9
10
11-12
13-15
16
17
18
19
20
21-22
23
24
25-26
27
28
29
30
31
32
33
34-35
36
37
38
39
40
41
42
43
44
45
46
47
48

TM
Warnings
PLEASE READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY. PROPER OPERATION AND HUMIDITY CONTROL
IS POSSIBLE ONLY WITH PROPER INSTALLATION AND MAINTENANCE.
Improper installation, adjustment, alterations, service, maintenance, or use can cause carbon monoxide poisoning, an
explosion, fire, electrical shock, or other conditions which may cause property damage, personal injury or loss of life.
Consult a qualified installer, service agency, local gas supplier, or your distributor or branch for information or assistance.
The qualified installer or agency must use only factory authorized and listed kits or accessories when modifying this product.
A failure to follow this warning can cause electrical shock, fire, personal injury, or loss of life.
WARNINGS
RECEIVING
Inspect humidifier and accessories upon arrival for damaged, missing, or improper parts. If there is a problem, call PURE
Humidifier Co.
SERVICING
Disconnect main power before servicing or maintaining humidifier.
The humidifier system including the humidifier tank, steam supply piping, condensate piping and steam distribution grid can
be extremely hot and can cause burns if touched.
Do not use hydrochloric acid descalers or bleach to clean the tank. Consult the factory if you are unsure about which
chemical descaler to use.
ELECTRICAL
Electrical work should be done by qualified electrical contractors and must be in compliance with local, state, federal, and
governing codes.
PLUMBING
Plumbing and pressurized steam work should be done by qualified installers and must be in compliance with local, state,
federal, and governing codes.
Drain and overflow water can be 212°F (100°C). If you are not using a DCT-927 Drain Tempering Kit, allow the water to cool
before draining tank.
This humidifier produces steam at atmospheric pressure. Do not install any components between humidifier tank and steam
distribution grid which can block or restrict steam flow.
LOCATION
Do not mount on hot surfaces.
Do not mount on vibrating surfaces.
MAKEUP WATER
High chloride content in feed water can cause chloride stress cracking and chloride pitting in stainless components. Chloride
stress corrosion cracking (CSCC) and chloride pitting of stainless steel components is not covered by warranty.
Use of mineralized (hard or soft) tap water will cause fill valve failure and void the warranty. PURE Humidifier Co.’s GX
Series should be installed on applications that require tap water.
Do not adjust any components inside humidifier control box without consulting the factory.
For indoor use only unless supplied with an Outdoor Enclosure.
1

TM
GAS
Application of this humidifier should have special attention given to vent sizing and material, gas input rate, and unit sizing.
Improper installation or misapplication of the humidifier can require excessive servicing or cause permanent component
failure.
The installation must conform to the requirements of the authority having jurisdiction, or in the absence of such requirements,
to the National Fuel Gas Code, ANSI Z223.1 (latest edition). In Canada, the installation of this unit must comply with
local plumbing or waste water codes and other applicable codes and with the current code CAN/CGS-B149.1 “Installation
Code for Natural Gas Burning Appliances and Equipment or CAN/CGA-B149.2 “Installation Code for Propane Burning
Applications and equipment.”
Do not install in potentially explosive or flammable atmospheres laden with grain dust, sawdust, or similar airborne materials.
Installation of humidifier in high humidity or salt water atmospheres will cause accelerated corrosion, resulting in a reduction
of the normal lifespan of the unit.
Humidifier must be located in a conditioned space.
To prevent premature heat exchanger failure, do not locate ANY GX unit in areas where chlorinated, halogenated or acid
vapors are present in the atmosphere.
Locate the humidifier in an area clear of combustible materials, gasoline, and other flammable vapors and liquids.
When working on equipment, observe precautions in this literature, tags, and labels attached to or shipped with the unit,
and other safety precautions that may apply. Have fire extinguisher available during startup, adjustment procedures,
and service calls.
Do not use this appliance if any part has been under water. Immediately call a qualified service technician to inspect the
appliance and to replace any part of the control system and any gas control which has been under water.
Do not lift humidifier by gas controls or gas manifold.
Should overheating occur, or the gas supply fail to shut off, shut offthe manual gas valve to the appliance before shutting
offthe electrical supply.
Do not locate units in tightly sealed rooms or small compartments without provision for adequate combustion air and
venting. Combustion air must be supplied to the confined space through a minimum of two permanent openings in the
enclosure, with at least one near the bottom. They should provide a free area of one square inch per 1000 BTU per hour
input rating of the unit with a minimum of 100 square inches for each opening, whichever is greater. Refer to Venting
Installation information on pages 8 & 9.
Warnings (Con’t)
TM
2

TM
Features
1. Tri-Probe Sensor
2. 1/4”-NPT Water Inlet & Strainer
3. Over Temperature Cut-Out Switch
4. Flusher & Overflow Piping
5. 3/4” Motorized Drain Valve
6. Control Panel
7. INTAC®PLC Controller
8. Support Legs
9. Burner Assembly
10. Exhaust Connection
11. Steam Outlet Connection
FEATURES
1
2
3
4
5
6
7
8
9
10
11
3

TM
Capacities, Electrical & Weights
This humidifier is a forced combustion type that can be used with natural gas or liquid propane. The burner can be easily
removed to access the side entry exchanger(s) for cleaning. It is designed to work with low-pressure gas between 5” W.C.
up to 14” W.C.
Standard Water
Unit Model No.
Steam Capacity
lbs/hr (kg/hr)
No. of
Burners *BTU Input
#Exhaust
Manifold
Vent Size
(cm)
Shipping Weight Operating Weight
(kg)
120 Volt, 60 Hz
Full Load
Amps
GX-3 110 (49.9) 1 150,000 4” (10.2) 201 lbs (91.2) 420 lbs (190.5) 5.0
GX-4 300 (136.1) 1 400,000 4” (10.2) 390 lbs (176.9) 710 lbs (322.1) 5.0
GX-8 600 (272.2) 2 800,000 6” (15.2) 827 lbs (375.1) 1391 lbs (630.9) 10.0
GX-12 900 (408.2) 3 1,200,000 8” (20.3) 1125 lbs (510.3) 2072 lbs (939.9) 15.0
† Actual humidifier capacity may vary due to the heat loss from the humidifier reservoir. The ambient air temperature,
air velocity and injection tube system will affect the rate of heat loss from the reservoir.
* Altitude adjustment:
100% up to 2000’
Over 2000’, 4% de-rate per 1000’
# Vent Size is larger than connection size.
Standard Water
Unit Model No.
Water Volume in
Gallons (Liters)
GX-3 22 (83.3)
GX-4 48 (181.7)
GX-8 94 (355.8)
GX-12 143 (541.3)
Unit Capacities in Pounds per Hour (Kg/Hr) †
Weights in lbs (kg) and Electrical Specification
Reservoir Water Volume in Gallons (Liters)
4

TM
Dimensions
GX-3 & GX-4
Required Clearance:
For recommended service and maintenance purposes
the following clearances should be maintained:
Right side, see Top View for required clearance
Front side, NEC requires 36” clearance to
control cabinet
Left side, 6” for access
Rear, 6” for access
Top, 12” for cover and Tri-Probe removal
Heat exchangers have a top and bottom. There is a break (crease) on the bottom side of the heat exchanger. Do not install heat
exchanger upside-down.
All dimensions are approximate and subject to change at manufacturer’s discretion.
Standard Water
Unit Model No. Dim. “A” Dim. “B” Dim. “C” Dim. “D” Dim. “E” Dim. “F” Dim. “G” Dim. “H”
GX-3 34.18” (86.8) 20.46” (52.0) 13.84” (35.2) 24.0” (60.9) 45.9” (116.5) 3/4”-NPT 3.0” (7.62) 50.0” (127.0)
GX-4 54.0” (137.2) 30.1” (76.5) 13.84” (35.2) 24.0” (60.9) 54.7” (138.9) 3/4”-NPT 3.0” (7.62) 66” (167.6)
Unit Dimensions in Inches (cm)
7.8”
(19.8)
“A”
8.0”
(20.3)
“B”
“E”
“H”
Clearance required for
exchanger removal
“F”
Gas Inlet
“G”
Exhaust
Connection
2.8”
(7.1)
“C”
“D”
Steam Outlet Connection
(Size and Qty. will vary with
application)
Top View
Right Side ViewFront View
5

TM
Dimensions
GX-8
Required Clearance:
For recommended service and maintenance purposes
the following clearances should be maintained:
Right side, see Top View for required clearance
Front side, NEC requires 36” clearance to
control cabinet
Left side, 6” for access
Rear, 6” for access
Top, 12” for cover and Tri-Probe removal
Heat exchangers have a top and bottom. There is a break (crease) on the bottom side of the heat exchanger. Do not install heat
exchanger upside-down.
All dimensions are approximate and subject to change at manufacturer’s discretion.
Standard Water
Unit Model No. Dim. “A” Dim. “B” Dim. “C” Dim. “D” Dim. “E” Dim. “F” Dim. “G” Dim. “H”
GX-8 54.0” (137.2) 30.1” (76.5) 32.5” (82.6) 24.0” (60.9) 54.7” (138.9) 1”-NPT 3.0” (7.6) 66.0” (167.6)
Unit Dimensions in Inches (cm)
7.8”
(19.8)
“A”
9.0”
(22.9)
“H”
Clearance required for
exchanger removal Top View
“B”
“E”
“F”
Gas Inlet
“G”
Exhaust
Connection
Right Side View
5.6”
(14.2)
“C”
“D”
Steam Outlet Connection
(Size and Qty. will vary with
application)
Front View
6

TM
Dimensions
GX-12
Heat exchangers have a top and bottom. There is a break (crease) on the bottom side of the heat exchanger. Do not install heat
exchanger upside-down.
All dimensions are approximate and subject to change at manufacturer’s discretion.
Unit Dimensions in Inches (cm)
Standard Water
Unit Model No. Dim. “A” Dim. “B” Dim. “C” Dim. “D” Dim. “E” Dim. “F” Dim. “G” Dim. “H”
GX-12 54.0” (137.2) 30.1” (76.5) 43.5” (110.5) 24.0” (60.9) 55.8” (141.1) 1-1/4”-NPT 3.0” (7.6) 66.0” (167.6)
“D”
“C”
5.6”
(14.2)
Steam Outlet Connection
(Size and Qty. will vary with
application)
Front View
“F”
Gas Inlet
“G”
Exhaust
Connection
Right Side View
Required Clearance:
For recommended service and maintenance purposes
the following clearances should be maintained:
Right side, see Top View for required clearance
Front side, NEC requires 36” clearance to
control cabinet
Left side, 6” for access
Rear, 6” for access
Top, 12” for cover and Tri-Probe removal
7.8”
(19.8)
“A”
9.0”
(22.9)
“H”
Clearance required for
exchanger removal Top View
“B”
“E”
7

TM
Installation & Location
Important: Remove all shipping brackets and materials
before operating the humidi¿er. Humidi¿er Àue gases
must be vented to the outside atmosphere. Power
supply disconnect switch must be in the oႇposition while
making wiring connections to prevent electrical shock
and equipment damage. All units must be wired in strict
accordance with wiring diagram furnished with this unit.
Turn oႇall gas while installing the supply gas piping and
¿eld installed manual gas shut-oႇvalve for the humidi¿er.
Location
The location selected must provide for electrical service,
cold or hot water supply, and sanitary drain.
When selecting a location, try to keep the humidi¿er within
10 feet (305 cm) of the duct to avoid unnecessary heat
losses and condensation within the steam supply line.
Visible “fog” will saturate and condense when it contacts
objects such as turning vanes, ¿lters, fans, elbows or take-
oႇs. The warmer the air, the more easily it will dissipate
the visible steam. The most active and warmest portion of
the duct will provide better mixing of the steam and air. The
injection tube should be mounted a minimum of 2 feet (61
cm) downstream from an elbow or other turbulent air Àow
area.
Avoid mounting single style injection tube(s) closer than
8-10 feet (244-305 cm) upstream of objects that could
become saturated and condense the steam (reference
the paragraph above). If the duct layout does not provide
a straight unobstructed run of 8-10 feet (244-305 cm), a
multiple injection tube system should be considered to
reduce the visible steam travel distance.
For Fast-Pac and Insty-Pac multiple tube assemblies
please consult factory for job speci¿c non-wetting
distances.
Reference Fast-Pac or Insty-Pac O&Ms for full installation
details.
CAUTION: Do not humidify upstream of ¿lters. Consult
factory.
CAUTION: Smoke detectors should not be located
downstream of injection tube assemblies.
Location of Controls
It is important to avoid mounting any controls within the
visible steam. The controls should be mounted a minimum
of 8-10 feet (244-305 cm) downstream from the humidi¿er
injection tube. Due to the temperature rise that exists
within the visible steam dissipation area, thermostats
should not be mounted near the injection tube.
High-limit humidistats should be installed before any duct
obstruction to make sure the humidi¿er is interrupted
before saturation can occur on the object. The high-limit
should be mounted a minimum of 8-10 feet (244-305 cm)
downstream from the injection tube. Installing the high-limit
closer than 8 feet (244 cm) from the humidi¿er may cause
erratic control.
8

TM
Drain Pan Mounting
Drain Pan Mounting
A drain pan is an additional safety feature which may be required to be supplied in the field. In a proper humidifier installation,
a drain pan is not required. However, if the humidifier and injection tube are located in an area that contains valuable
equipment or is a water sensitive area, PURE Humidifier Co. recommends the addition of a drain pan under the humidifier
and under the injection tube. The drain pan should extend past all edges of the humidifier and if installed in the duct, it should
extend a minimum of 3 feet (91 cm) downstream from the injection tube. The pan should be of a size which is capable of
draining at a rate of 3 gpm for units with a capacity of up 200 lbs/hr, and 5 gpm for units with a capacity over 200 lbs/hr. The
pan should be drained to a sanitary drain.
Drain Pan Humidifier Reservoir
Injection Tube Duct/AHU
Airflow
Drain Pan
Humidifier Reservoir and Injection Tube Plan View
9

TM
Electrical, Combustion & Ventilation Air
Electrical
WARNING:
The cabinet must have an uninterrupted or unbroken
ground according to National Electrical Code, ANSI/NFPA
70 and Canadian Electrical Code, CSA C22.1, or local codes
to minimize personal injury if an electrical fault should occur.
This may consist of electrical wire or conduit approved for
electrical ground when installed in accordance with existing
electrical codes. Do not use gas piping as an electrical
ground.
Connect copper ground wire to cabinet ground lug.
Humidifiers should be supplied with 120-volt AC, 60 Hz,
15-amp separately fused electrical service. The humidifier is
equipped with a transformer to step down the voltage to 24
VAC control voltage.
When installed, the humidifier must be electrically
grounded in accordance with local codes, or in the absence
of local codes, with the National Electrical Code ANSI/NFPA
No. 70-1987. The electrical conductors shall be a minimum
Type MTW (105°C) AWG #14 wire for line voltage (120V),
with BLACK WIRE for HOT; WHITE WIRE for NEUTRAL,
GREEN WIRE for GROUND; and minimum #18 gauge for
control wiring. All electrical components and wiring must be
protected from mechanical damage and water. The control
system requires an earth ground for proper operation.
The humidifier is adjusted for correct performance. Do
not alter fan or operate motors at reduced speed.
The current characteristics, and capacity requirements
should be checked against the nameplates. All wiring must
be in accordance with all governing codes, and with wiring
diagram located inside the control cabinet.
See separate publication for the INTAC®controller
furnished with this humidifier.
Combustion & Ventilation Air
CAUTION:
Air for combustion must not be contaminated by halogen
compounds, which include fluoride, chloride, bromide
and iodide. These elements are found in aerosol sprays,
detergents, bleaches, cleaning solvents, salts, air
fresheners, and other household products.
CAUTION:
The operation of exhaust fans, kitchen ventilation fans,
clothes dryers, or fireplaces could create a negative
pressure condition at the humidifier. Make-up air must
be provided for the ventilation devices, in addition to
that required by the humidifier.
All fuel burning equipment must be supplied with air for
combustion of the fuel. Sufficient air MUST be provided to
ensure there will not be a negative pressure in the equipment
room or space.
Provisions for adequate combustion and ventilation air
must be provided in accordance with Section 5.3, Air for
Combustion and Ventilation, of the National Fuel Gas Code
ANSI Z223.1 1-1988, or applicable provisions of the local
building codes. Canadian installations must be installed in
accordance with sections 7.2, 7.3, and 7.4 of the CAN/CGA.
B149 Installation Codes, and all authorities having
jurisdiction.
10

TM
Gas Piping Installation
CAUTION:
Gas pressure to humidifier controls must never exceed
14” W.C. (1/2 psi).
Contact your local gas service company to ensure that
adequate gas service is available, and to review applicable
installation codes for your area. All gas piping installations
must be in accordance with codes, and ANSI Z233.1,
“National Fuel Gas Code,” or CAN/CGA-B149 in Canada.
Do not use flexible connectors.
Piping to units should conform with local and national
requirements for type, volume, gas handled, and pressure
drop allowed in the line. Refer to tables 1 and 2 to determine
the cubic feet per hour (cfh) for the type of gas and size of
unit to be installed. Using this value and the length of pipe
necessary, determine the pipe diameter. Where several units
are served by the same main, the total capacity, gas flow
(cfh), and length of main must be considered. The figures
shown are for straight lengths of pipe at 0.2” w.c. pressure
drop, which is considered normal for low-pressure systems.
Note that fittings such as elbows and tees will add to the pipe
pressure drop.
After threading and reaming the ends, inspect piping and
remove loose dirt and chips.
Support piping so that no strains are imposed on unit or
controls.
Use two wrenches when connecting piping to unit controls.
Provide a drip pocket before each unit and in the line where
low spots cannot be avoided.
Take-offto unit should come from top or side of main to avoid
trapping condensate.
Piping subject to wide temperature variations should be
insulated.
Pitch piping up toward unit at least 1/4” per 15’ of horizontal
run.
Compounds used on threaded joints of gas piping must be
resistant to the harmful action of liquefied petroleum gases.
Purge air before lighting unit by disconnecting piping at gas
control. In no case should the line be purged into heat
exchanger.
Install pressure regulator directly upstream of main automatic
gas valve(s) and fit drip leg main gas cock upstream of
regulator or automatic valve(s).
Install vent lines from main gas regulator (if used) and
diaphragm gas valve where applicable. Vent lines should
be run to the outside of the building, terminating clear of
windows or fresh air intakes. Outside termination of vent
should have a screen to prevent insects from building nests
in vent pipe.
Install a ground joint union and a manual gas shut-
offvalve immediately upstream of the unit including
a 1/8” NPT plugged tapping accessible for test gauge
connection.
Allow at least 5 feet of piping between any high pressure
regulator and unit pipe connection.
11

TM
Gas Piping Installation (Con’t)
Gas Leak Testing
When testing the gas supply piping system, the humidifier and its gas shut-offvalve must be disconnected during any
pressure testing in excess of 14” W.C. (1/2 psi). The humidifier must be isolated from the gas supply piping system by
closing its field-installed manual shut-offvalve during any pressure testing equal to or greater than 14” W.C. (1/2 psi).
Test gas lines for leaks using a soap solution. Your local gas service company may wish to execute or witness this test.
CAUTION: Gas pressure above 14” W.C. may damage the standard diaphragm gas shut-offvalve. Do not exceed this value
when pressure testing lines unless you cap-offline upstream of main gas cock and pilot take-off.
Check gas supply pressure with all burners running at inlet pressure tap of gas control. The recommended supply pressure
should be 7” W.C. on natural gas or 11” W.C. on LP gas. Purging of gas piping should be performed as described in ANSI
Z223.1 (latest edition), or in Canada in CAN/CGA-B149 codes.
Minimum supply pressure. Natural - 5” W.C. LP - 5” W.C.
Gas valves outlet pressure (manifold) shall be factory set. This pressure can be checked at the 3/4” tee after the orifice.
See humidifier label for correct pressure rating.
Model Max BTU/hr
Input
Max CFH
(Nat. Gas)
Max CFH
(Propane)
GX-3 150,000 150 60
GX-4 400,000 400 160
GX-8 800,000 800 320
GX-12 1,200,000 1,200 480
EQUIVALENT LENGTH OF STRAIGHT PIPE IN FEET
20 30 40 20 60 80 100 150 200
CFH GAS WITH .2” PRESSURE DROP
Pipe Size in Inches
3/4” 152 120 105 93 84 73 66 54 45
1” 300 250 210 190 180 150 135 110 75
1 1/4” 520 425 360 325 300 260 230 190 165
1 1/2” 800 690 560 500 480 410 370 300 260
2” 1700 1400 1200 1100 1000 850 750 600 540
2 1/2” 3000 2500 2100 1900 1800 1550 1375 1100 950
EQUIVALENT LENGTHS OF STANDARD PIPE IN FEET FOR LISTED FITTINGS
Fitting Type 3/4 1 1 1/4 1 1/2 2 2 1/2 Nominal
Std. Tee 2.4 5.5 7.5 9 12 13.5 Pipe Size
Std. Elbow 4.4 2.7 3.7 4.5 5.5 6.1 in Inches
Table 2 - Gas Piping Pressure Drop Data
Table 1 - Gas Input CFH for GX Series Humidifiers
12

TM
Venting Installation
For proper and safe operation this appliance needs air for
combustion and ventilation. DO NOT block or obstruct air
openings on the appliance, spaces around the appliance, or
air openings communicating with the appliance area.
DO NOT block the flow of combustion and ventilation air.
To provide for necessary oxygen for proper combustion,
opening must be provided to allow outside air to enter the
space in which the heater is located. Enclosed spaces,
such as equipment rooms, must be vented at the blower for
combustion air. The size of air openings must be based on
all gas-burning equipment installed in the space involved.
Provisions for adequate combustion and ventilation air
in accordance with Section 5.3, Air for Combustion and
Ventilation, of the National Fuel Gas Code, ANSI Z223.1, or
Sections 7.2, 7.3 or 7.4 of the CAN/CGA B149 Installation
Codes, or applicable provisions of the local building codes.
The burner should be initially set up and serviced at regular
intervals (preferably at the beginning of and mid-way through
high use period) by a trained serviceman using the proper test
instruments. Failure to maintain the correct burner settings
may result in inefficient gas consumption, premature wear of
burner components, or explosion hazard.
Venting
The GX Series Humidifiers are a Category 3 Appliance.
The purpose of venting the gas humidifier is to completely
remove all products of combustion and ventilation gases to
the outside air, without condensation in the stack.
When connecting the humidifier to a gas vent or chimney,
the installation shall be in accordance with Part 7, Venting
of Equipment, of the National Fuel Gas Code, ANSI Z223.1,
or Section 7, Venting Systems and Air Supply Appliances,
of the CAN/CGA-B149 Installation Codes, the local building
codes, and the vent manufacturer’s instructions.
Do not reduce the vent diameter, and avoid short turns in
the vent piping. Use the exhaust manifold vent size shown
on page 15.
Allow for removal of air intake and exhaust connections for
heat exchanger cleaning and regular maintenance. Maintain
a 1/4-inch-per-foot pitch for horizontal runs. Maintain proper
support of vent connections and joints. Observe clearances
(in accordance with applicable codes) from all combustible
materials, and obtain an approved cap for the stack outlet.
The bottom of the cap must be one stack diameter above the
top of the stack.
Inspect for proper and tight construction. Any restrictions
or obstructions must be removed. An existing chimney may
require cleaning.
Chimney or vent must extend at least 3 feet above its
passage through a roof and at least 2 feet above any ridge
within 10 feet of the chimney (local codes apply).
Minimum clearance from the vent connector to combustible
material is 6 inches unless the combustible materials are
protected in accordance with applicable codes.
PURE Humidifier requires humidifiers be connected to vent
systems sufficient for use with Category 3 Appliances (listed
to UL Standard 1738 or ULC-S636). Any condensate formed
is acidic and could cause corrosion of the vent materials.
This humidifier must not be connected to a chimney flue
servicing a separate appliance designed to burn solid fuel.
If condensation is noticed in the field, a condensate trap
should be installed in the venting system.
Never connect this humidifier to a chimney.
Venting into an unlined masonry or concrete chimney is
prohibited by code.
Insulation must be added to any vent connector which will be
exposed to ambient temperatures of 30°F or less.
Do not insulate vent pipe exposed to outdoor weather
conditions (i.e. above roof lines).
Installation of the vent pipe should be as direct as possible,
with a minimum number of turns or elbows.
Rigidly support the vent pipe every 5 feet or less with
hangers or straps to ensure that there will be no movement
or sagging after installation. The humidifier vent box should
not be supporting the weight of the vent piping.
13

TM
Venting Installation (Con’t)
No portion of the vent system shall extend into, or pass
through, any circulation air duct or plenum.
The vent system shall terminate above the roof surface
per the National Fuel Gas Code or CAN/CGA.B149
requirements, and shall include a UL or CUL listed vent cap
or roof assembly, unless prohibited by local codes.
All vent pipe passing through floors, ceilings, and walls must
be installed with the proper clearances from combustible
material, and be fire-stopped according to the National Fuel
Gas Code requirements and Canadian Standards CAN/
CGA.B149.
In replacement installation, where an existing vent system
may be used, the vent system must be inspected for
condition, size, type of vent material, and height to meet the
requirements in these instructions. If the existing vent system
is too large, condensation could occur, causing corrosion of
the vent system. Installing a replacement vent system may
be required.
Horizontally Vented Humidifier
Maintain a minimum upward slope of 1/4-inch per linear
foot on all horizontal vent pipe runs. If condensate in venting
is noticed, a condensate trap must be installed.
Rigidly support the vent pipe at intervals no longer than
five feet with hangers or straps to ensure there will be
no movement after installation. The humidifier exhaust
termination should not be supporting the weight of the vent
piping.
Distances from the vent terminal adjacent public walk ways,
buildings, and openable windows and building openings
should be consistent with the National Fuel Gas Code, ANSI
Z223.1, and/or CAN/CGA.B149 Installation Codes.
The vent terminal location must be at sufficient height above
ground level to prevent blocking by expected snowfall.
Building materials should be protected from degradation by
flue gases.
A minimum horizontal clearance of 4 feet (1.22m) from
electric meters, gas meters, regulators, and relief equipment
must be maintained.
Venting Requirements
100’ maximum equivalent length of vent pipe.
90° Elbow = 10’
45° Elbow = 5’
Maximum of 4 elbows.
Vent pipe is to be rated for Category 3 Appliances listed to
UL Standard 1738 or ULC-S636 (AL29 4C).
Allow for removal of air intake and exhaust connections for
heat exchanger cleaning and regular maintenance.
Inspect for proper and tight construction. Any restrictions
or obstructions must be removed. An existing chimney may
require cleaning.
Chimney or vent must extend at least 3 feet above its
passage through a roof and at least 2 feet above any ridge
within 10 feet of the chimney (local codes apply).
Minimum clearance from the vent connector to combustible
material is 6 inches unless the combustible materials are
protected in accordance with applicable codes.
PURE Humidifier requires humidifiers be connected to vent
systems sufficient for use with Category 3 Appliances (listed
to UL Standard 1738 or ULC-S636). Any condensate formed
is acidic and could cause corrosion of the vent materials.
This humidifier must not be connected to a chimney flue
servicing a separate appliance designed to burn solid fuel.
If condensation is noticed in the field, a condensate trap
should be installed in the venting system.
Never connect this humidifier to a chimney.
Venting into an unlined masonry or concrete chimney is
prohibited by code.
Insulation must be added to any vent connector which will be
exposed to ambient temperatures of 30°F or less.
Do not insulate vent pipe exposed to outdoor weather
conditions (i.e. above roof lines).
Installation of the vent pipe should be as direct as possible,
with a minimum number of turns or elbows.
14

TM
Venting Installation (Con’t)
Rigidly support the vent pipe every 5 feet or less with
hangers or straps to ensure that there will be no movement
or sagging after installation. The humidifier vent box should
not be supporting the weight of the vent piping.
No portion of the vent system shall extend into, or pass
through, any circulation air duct or plenum.
The vent system shall terminate above the roof surface
per the National Fuel Gas Code or CAN/CGA.B149
requirements, and shall include a UL or CUL listed vent cap
or roof assembly, unless prohibited by local codes.
All vent pipe passing through floors, ceilings, and walls must
be installed with the proper clearances from combustible
material, and be fire-stopped according to the National Fuel
Gas Code requirements and Canadian Standards CAN/
CGA.B149.
In replacement installation, where an existing vent system
may be used, the vent system must be inspected for
condition, size, type of vent material, and height to meet the
requirements in these instructions. If the existing vent system
is too large, condensation could occur, causing corrosion of
the vent system. Installing a replacement vent system may
be required.
Horizontally Vented Humidifier
Maintain a minimum upward slope of 1/4-inch per linear
foot on all horizontal vent pipe runs. If condensate in venting
is noticed, a condensate trap must be installed.
Rigidly support the vent pipe at intervals no longer than
five feet with hangers or straps to ensure there will be
no movement after installation. The humidifier exhaust
termination should not be supporting the weight of the vent
piping.
Distances from the vent terminal adjacent public walk ways,
buildings, and openable windows and building openings
should be consistent with the National Fuel Gas Code, ANSI
Z223.1, and/or CAN/CGA.B149 Installation Codes.
The vent terminal location must be at sufficient height above
ground level to prevent blocking by expected snowfall.
Building materials should be protected from degradation by
flue gases.
A minimum horizontal clearance of 4 feet (1.22m) from
electric meters, gas meters, regulators, and relief equipment
must be maintained.
Venting Requirements
100’ maximum equivalent length of vent pipe.
90° Elbow = 10’
45° Elbow = 5’
Maximum of 4 elbows.
Vent pipe is to be rated for Category 3 Appliances listed to
UL Standard 1738 or ULC-S636 (AL29 4C).
Allow for removal of air intake and exhaust connections for
heat exchanger cleaning and regular maintenance.
15

TM
Sealed Combustion
Sealed Combustion Air Kit
Consists of a 6” round stainless steel adaptor to connect to field installed combustion air piping. Use of this kit will allow the
burner to intake combustion air from outside instead of using room air. When using sealed combustion with multiple burners
use separate exhaust pipes or separate makeup air pipes so exhaust gas does not recirculate if one blower malfunctions.
Benefits:
Sealed combustion burners can save energy because they don’t steal heated or cooled indoor air.
Sealed combustion burners reduce space heating costs and noise while eliminating problems associated with power-vented
combustion.
16

TM
GX-8 Exhaust Manifold
Reference pages 8 & 9 for venting installaton instructions
All exhaust connections and piping to be Category 3 Appliance Listed to UL Standard 1738 or ULC-S636
Typical GX-8
Humidifier
Adaptor by others
Heat-fab p/n 9301AMTK
Increaser by others
Heat-fab p/n 9374
6ӯ Manifold
by others
Conduit Tee
by others
Heat-fab p/n
9616X4
Tee Cover w/
Drain Fitting
by others
Heat-fab p/n
9617D
17