268894-UIM-A-0407
Unitary Products Group
19
Multi-story or common venting systems are permitted and must be
installed in accordance with the National Fuel Gas Code, ANSI Z223.1/
NFPA 54 and / or the CSA B149.1, Natural Gas and Propane Installa-
tion Codes, local codes, and the manufacturer's instructions.
Vent connectors serving Category I furnaces shall not be connected
into any portion of mechanical draft systems operating under positive
pressure.
Horizontal portions of the venting system shall be supported to prevent
sagging using hangers or perforated straps and must slope upwards
not less than 1/4" per foot (0.635 cm/m) from the furnace to the vent ter-
minal.
It is recommended that you follow the venting safety procedure below.
This procedure is designed to detect an inadequate ventilation system
that can cause the appliances in the area to operate improperly causing
unsafe levels of Carbon Monoxide or an unsafe condition to occur.
SECTION VIII: SAFETY CONTROLS
CONTROL CIRCUIT FUSE
A 3-amp fuse is provided on the control circuit board to protect the 24-
volt transformer from overload caused by control circuit wiring errors.
This is an ATO 3, automotive type fuse and is located on the control
board.
BLOWER DOOR SAFETY SWITCH
This unit is equipped with an electrical interlock switch mounted in the
blower compartment. This switch interrupts all power at the unit when
the panel covering the blower compartment is removed.
Electrical supply to this unit is dependent upon the panel that covers the
blower compartment being in place and properly positioned.
ROLLOUT SWITCH CONTROLS
These controls are mounted on the burner assembly. If the temperature
around the burners exceed the set point, the ignition control and the
gas valve are de-energized. The operation of this control indicates a
malfunction in the combustion air blower, heat exchanger or a blocked
vent pipe connection. Corrective action is required. These are manual
reset controls that must be reset before operation can continue.
PRESSURE SWITCHES
This furnace is supplied with a pressure switch which monitors the flow
through the combustion air/vent piping system. This switch de-ener-
gizes the ignition control module and the gas valve if any of the follow-
ing conditions are present. Refer to Figure 26 for tubing connections.
1.
Blockage of vent piping or terminal.
2.
Failure of combustion air blower motor.
LIMIT CONTROLS
There is a high temperature limit control located on the furnace vesti-
bule panel near the gas valve. This is an automatic reset control that
provides over temperature protection due to reduced airflow. This may
be caused by:
1.
Dirty filter.
2.
If the indoor fan motor should fail.
3.
Too many supply or return registers closed or blocked off.
The control module will lockout if the limit trips five (5) consecutive
times. Control will reset and try again after one 1 hour.
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each appliance connected to the venting system being placed into operation could result in carbon
monoxide poisoning or death.
The following steps shall be followed for each appliance connected to the venting system being placed into operation, while all other appliances
connected to the venting system are not in operation:
1. Seal any unused openings in the venting system.
2. Inspect the venting system for proper size and horizontal pitch, as required in the National Fuel Gas Code, ANSI Z223.1/NFPA 54 or the
CSA B149.1, Natural Gas and Propane Installation Code and these instructions. Determine that there is not blockage or restriction, leak-
age, corrosion and other deficiencies which could cause an unsafe condition.
3. As far as practical, close all building doors and windows and all doors between the space in which the appliance(s) connected to the vent-
ing system are located and other spaces of the building.
4. Close fireplace dampers.
5. Turn on clothes dryers and any appliance not connected to the venting system. Turn on any exhaust fans, such as range hoods and bath-
room exhausts, so they are operating at maximum speed. Do not operate a summer exhaust fan.
6. Follow the lighting instructions. Place the appliance being inspected into operation. Adjust the thermostat so appliance is operating contin-
uously.
7. Test for spillage from draft hood equipped appliances at the draft hood relief opening after 5 minutes of main burner operation. Use the
flame of a match or candle.
8. If improper venting is observed during any of the above tests, the venting system must be corrected in accordance with the National Fuel
Gas Code, ANSI Z223.1/NFPA 54 and/or CSA B149.1, Natural Gas and Propane Installation Code.
9. After it has been determined that each appliance connected to the venting system properly vents when tested as outlined above, return
doors, windows, exhaust fans, fireplace dampers and any other gas-fired burning appliance to their previous conditions of use.
Main power to the unit must still be interrupted at the main power
disconnect switch before any service or repair work is to be done to
the unit. Do not rely upon the interlock switch as a main power dis-
connect.
Blower and burner must never be operated without the blower
panel in place.
FIGURE 26:
Pressure Switch Tubing Routing
