Heating System Service Checks - Lennox EL195UHE Unit Information

IV−HEATING SYSTEM SERVICE CHECKS
A−C.S.A. Certification
All units are C.S.A. design certified without modifications.
Refer to the EL195UHE Operation and Installation Instruc-
tion Manual Information.
B−Gas Piping
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet. The flexible connector can then
be added between the black iron pipe and the gas
supply line.
Gas supply piping should not allow more than 0.5" W.C.
drop in pressure between gas meter and unit. Supply gas
pipe must not be smaller than unit gas connection.
Compounds used on gas piping threaded joints should be
resistant to action of liquefied petroleum gases.
C−Testing Gas Piping
IMPORTANT
In case emergency shutdown is required, turn off
the main shut-off valve and disconnect the main
power to unit. These controls should be properly
labeled by the installer.
When pressure testing gas lines, the gas valve must be dis-
connected and isolated. Gas valves can be damaged if
subjected to more than 0.5 psig (14" W.C.). See figure 57.
MANUAL MAIN SHUT−OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
FIGURE 57
When checking piping connections for gas leaks, use pre-
ferred means. Kitchen detergents can cause harmful corro-
sion on various metals used in gas piping. Use of a specialty
Gas Leak Detector is strongly recommended. It is available
through Lennox under part number 31B2001. See Corp.
8411−L10, for further details.
WARNING
Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.
CAP
FURNACE
ISOLATE
GAS VALVE
Page 43
D−Testing Gas Supply Pressure
Gas Flow (Approximate)
TABLE 16
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
EL195
Unit 1 cu ft
Dial
−045 80
−070 55
−090 41
−110 33
−135 27
Natural−1000 btu/cu ft
Furnace should operate at least 5 minutes before check-
ing gas flow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures a
more accurate time.) Divide by two and compare to time
in table 16. If manifold pressure matches table 17 and rate
is incorrect, check gas orifices for proper size and re-
striction. Remove temporary gas meter if installed.
NOTE − To obtain accurate reading, shut off all other gas
appliances connected to meter.
Supply Pressure Measurement
When testing supply gas pressure, use the 1/8" N.P.T.
plugged tap located on the gas valve to facilitate test gauge
connection. See figure 7. Check gas line pressure with unit
firing at maximum rate. Low pressure may result in erratic
operation or underfire. High pressure can result in perma-
nent damage to gas valve or overfire.
On multiple unit installations, each unit should be checked
separately, with and without other units operating. Supply
pressure must fall within range listed in table 17.
Manifold Pressure Measurement
1 − Remove the threaded plug from the outlet side of the
gas valve and install a field−provided barbed fitting.
Connect to a manometer to measure manifold pres-
sure.
2 − Start unit and allow 5 minutes for unit to reach steady
state.
3 − While waiting for the unit to stabilize, observe the
flame. Flame should be stable and should not lift from
burner. Natural gas should burn blue.
4 − After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in table
17.
NOTE − Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed fitting and replace threaded plug.
TABLE 17
Supply Line and Manifold Pressure (inches w.c.)
Unit Fuel
All Nat
All LP/Propane
LP
2 cu ft 1 cu ft 2 cu ft
Dial Dial DIAL
160 200 400
110 136 272
82 102 204
66 82 164
54 68 136
LP−2500 btu/cu ft
Manifold
Supply Line
Pressure
3.5 4.5 − 10.5
10.0 11.0 − 13.0