Fusible Unk Control
This control is mounted in the burner compartment. If the
temperature in the burner compartment exceeds 306°F, the
cir?ui.t to the ig.niter control and the gas valve is de-energized.
Th1s 1s·a one-t1me fusible link type control. Before the furnace
can operate again, the control must
be
replaced. The operation
of this control indicates a possible burner flame r<?ltout. condi
tion. The combustion air blower and the combustion a1r pres
sure switch should be checked for proper operation.
Pressure Switches
This furnacels supplied with pressure switches which monitor
the flow through ths-combustion air/vent
system. These
switches de-energize the ignition control
and the gas
valve if any of the following conditions are present.
1. Blockage of combustion air piping or terminal.
2.
Blockage of vent piping or terminal.
3. Failure of combustion air blower motor.
4.
Blockage of condensate drain piping.
START-UP AND ADJUSTMENTS
The initial start-up of the furnace requires the following addi
tional procedures:
1. When the gas supply is' initially connected to the furnace,
the gas piping may be full of air. In order to purge this air,
it is recommended that the ground union be loosened until
the odor of gas is detected. When gas is detected, imme
diately retighten the union and check for leaks. Allow five
minutes for any gas to dissipate before continuing with the
start-up procedure.
WARNING:
Be sure proper ventilation is available to dilute and
carry away any vented gas.
2.
The condensate trap must
be
filled with water before
putting the furnace into operation. The recommended
procedure is as follows:
a Disconnect the condensate drain hose from the con
densate drain outlet fitting (see Figure 10 for location
of this hose connection).
b. Elevate this hose above trap level and fill with water
using a funnel. Drain excess water into a container.
c. Replace the condensate drain hose and clamps.
3.
All electrical 'connections made in the field and in the
factory should
bEi
checked for proper tightness.
IGNITION SYSTEM CHECKOUT/ADJUSTMENT
1. Tum gas supply OFF at external gas valve or main gas
valve (see F.igure
12).
Turnelectrical power
ON.
Check
that
24
volts is available across terminal C and
R
on the
transformer.
2. Check ignition module operation as follows:
a. Set the thermostat to "heat". Tum thermostat setting
above room temperature to call for hea1.
b .. Through burner box observation ports watch-for the hot
surface igniter to begin glowing.
c. If glow is seen, turn the thermostat down (below room
temperature). Hot surface igniter should stop glowing.
3. Tum the gas supply ON at external valve and main gas valve.
4.
Set the-thermostat above room temperature to call for h
ea
t
.
5
.
.
SystE)m �tart-Lip will occur
as
follows:
Unitary Producls Group
650 65-N2
a. Venter motor will
start and
come up to speed. Sh ortly
after venter
start-up, the hot suriace igniter will glow
for
about
45
seconds.
b. After warm-up
cycle, ignition m
od
u
le will energize
(open) the
ma1n gas
valve for four seconds.
At the same
t
i
m
e power
to
the igniter is shut otf .
NOTE:
Burner ignition may not be satisfactory on first start-up
due to residual air in gas line, or until gas pressure
{mani
fold} or burner air shutters are adjusted.
6. With furnace in operation, paint the
pipe joints
and valve
gasket lines with a rich soap
and
water··solution. Bubble
indicate a gas leak. Take appropriate steps to
stop
the
leaks. If the leak persists, replace the co
mp
on
e
n:
.
WARNING:
DO NOT omit this test!
NEVER
use
a flame
to
check for gas leaks.
ADJUSTMENT OF MANIFOLD
G
AS P RESS
URE
1.
Tum gas off at main gas valve. Remove 1/8" plug in the main
gas valve body and install proper manometer tube adapter
fitting. Connect line
from
gas valve tap to manometer
2.
Refer to Figure 12 for location of pressure regulator adjust
ment cap and screw on main gas valve.
Inlet
Wrench
Wiring
Terminals
Jumper
Boss
Manual Gas
Press. Reg.
Control Knob Under Cover
Screw
FIGURE
12- GAS VALVE
Outlet
Pressure
Tap
NOTE:
The screw-off
cap
for the pressure regulator must
be
re
moved
entirely to gain access to
the
adjustment
screw
Loosc:n
ing or tifjltening the
cap cbes
not adjust the
flow
of gas.
3.
Turn gas and electrical supplies
ON.
Start furnace and
observe manifold pressure on manometer.
4.
Adjust manifold pressure by adjusting gas valve reg'u.!ator
screw: for natural gas, set at 3.5" W.C.; for propane
{LP)
gas, set at 10.0" W.C.
If gas valve regulator is turned in, or clockwise, manifold
pressure is increased. If screw is turned out, or counter
clockwise, manifold pressure will decrease.
Natural Gas
3.5" w.c.
10.0" w.c.
WARNING:
If manifold pressure is too high, an over-fire con-
_,
dition exists which could cause heat exchanger failure. If
the manifold pressure is too low, sooting and eventual
clogging of the heat exchanger could occur.
WARNING:
Once the correct gas pressure to the burners has
been established, tum the gas valve knob to OFF and turn
the electrical supply switch to OFF; then remove the-
·
pressure tap at the gas valve and re-install the plug, using
a compound
{
on the threads) resistant to the action of
LP
gases.
11
