Weather-Rite XT112 Installation, Operation & Service Manual - page 65
SECTION 19: D
IRECT
FIRED
PROCESS
AIR
HEATERS
59
the process air heater in compliance with:
United States: Refer to NFPA 86 - latest revision,
Ovens and Furnaces /ANSI Z83.25 - latest revision,
Direct Gas-Fired Process Air Heaters.
Canada: Refer to CSA 3.19 - latest revision, Direct
Gas-Fired Process Air Heaters.
19.1 Direct Fired Process Air Heater Models
• 100% Outside Air - Ventilating and Bake Cycle
Mode
• 100% Outside Air - Ventilating with Reduced
Airflow for Bake Cycle Mode
• 100% Outside Air - Ventilating with Recirculation
for Baking Cycle Model (80% Recirculated Air
after the burner and 20% Outside Air)
• 100% Outside Air - Ventilating with Recirculation
for Baking Cycle Model (90% Recirculated Air
across the burner and 10% Outside Air)
Other terms may be used to describe the bake cycle
mode such as; Cure or Cure Time Cycle, Dry or
Drying Cycle, and Flash Kick Cycle. Ventilation air
and the term outside air are also used
interchangeably.
All process heaters come equipped with two High
Limit discharge controllers, one for the ventilation
cycle - maximum 160 °F (71 °C) (automatic reset)
and one for the bake cycle mode - maximum 300 °F
(149 °C) (manual reset). The discharge temperature
controller limits the temperature to a maximum
250 °F (121 °C).
19.2 Installer's Responsibilities
1. All access opening(s) to the heated space,
served by the Process Heater that can be used
by personnel to enter the space, must have
door interlock switch or switches to shut down
the Process Heater if in the bake cycle.
2.
On recirculation Process Heaters, the return air
duct from the served space must have filters
installed to prevent particulate matter from
entering the heater. If not supplied by the Pro-
cess Heater, then the installer must supply
them. These filters must be approved by the
authority having jurisdiction of the installation.
3.
The return air duct system must be installed
with doors, panels or other means for access to
facilitate inspection, maintenance, cleaning
and access to fire protection devices.
4.
Instructions must be provided to require peri-
odic inspection and cleaning of the recircula-
tion air duct. The installer must supply this
information.
5.
The gas piping installer must locate a manual
emergency gas shutoff valve in an appropriate
location that allows access to shut off the flow
of gas to the Process Heater in case of an
emergency.
6.
If a post purge (cool-down) cycle is not sup-
plied with the Process Heater, then the installer
must supply a timing circuit that allows 100%
ventilation air of the space to cool the products
down and purge any airborne contaminants.
7.
It is also suggested that the following Burn
Hazard Warning be installed at all access
opening(s) to the heated space, served by the
Process Heater that can be used by personnel
to enter the space.