Reznor R6GP Unit Installation Manual - Manual (Page 16)

16
Verifying & Adjusting Temperature Rise
Verify the temperature rise through the unit is within the
range specified on the unit data label. Temperature rises
outside the specified range could result in premature heat
exchanger failure.
1. Place thermometers in the return and supply air stream
as close to the unit as possible. The thermometer on the
supply air side must be shielded against direct radiation
from the heat exchanger to avoid false readings.
2. Adjust all registers and duct dampers to the desired
position. Run the unit for 10 to 15 minutes before
taking any temperature readings. The temperature
rise is the difference between the supply and return air
temperatures.
NOTE: For typical duct systems, the temperature rise will
fall within the range specified on the data label (with the
blower speed at the factory recommended setting) shown
in Table 16, page 40. If the measured temperature rise falls
outside the specified range, it may be necessary to change
the blower speed. Lowering the blower speed increases
the temperature rise and a higher speed decreases the
temperature rise.
The unit is equipped with a belt driven blower and variable
pitch motor sheave. The selection of a sheave setting
should be based on the desired CFM and the duct system
parameters. Refer to the ACCA’s Manual Q for a complete
description of how to determine these parameters and
Manual N for determination of the commercial load
requirements. The blower performance data can be found
in Tables 5 - 12 (pages 29 - 36).
The integrated control is designed to start the circulating air
blower 40 seconds after the gas valve opens and turn the
blower motor off 150 seconds after the gas valve is closed.
Verifying Burner Operation
WARNING:
Uninsulated live components are exposed when
the louvered control access panel is removed.
1. Remove the louvered control access panel to ensure
there is power to the unit.
2. Set the thermostat above room temperature and observe
the ignition sequence. The burner flame should carry
over immediately between all burners and should extend
from each burner without lifting off, curling, or floating.
The flames should be blue, without yellow tips.
3. After verifying flame characteristics, set the thermostat
below room temperature and verify that the burner flame
extinguishes completely.
Verifying Operation of Over-Temperature
Limit Control
To verify operation of the over-temperature limit control,
make sure the louvered control access panel is in place
and that there is power to the unit.
1. Block the return airflow to the unit by installing a close-
off plate in place of or upstream of the filter.
2. Set the thermostat above room temperature and verify
the unit operates with the correct sequence of operation
(see Operating Sequence).
NOTE: The over-temperature limit control should function
to turn off the gas valve within approximately four minutes
(exact time depends on the efficiency of the close-off when
blocking the return air). The circulating air and combustion
blowers should continue to run when the over-temperature
limit control switch opens.
3. Remove the close-off plate immediately after the over-
temperature limit control opens. If the unit operates
for more than four minutes with no return air, set the
thermostat below room temperature, shut off power to
the unit, and replace the over-temperature limit control.
Verifying & Adjusting Firing Rate
The firing rate must be verified for both HIGH fire and LOW
fire for each installation to prevent over-firing of the unit.
CAUTION:
Do not re-drill the burner orifices. If the orifice
size must be changed, use only new orifices.
IMPOR TANT NOTE: The firing rate must not exceed
the rate shown on the unit data label. At altitudes
above 2,000 ft., it must not exceed that on the data
label less 4% for each 1,000 ft.
Foll ow the steps below to determine the unit firing rate:
• For installations at 2,000 feet and less, the firing rate
is the same as shown on the unit rating label.
• For installations above 2,000 feet, compute the firing
rate as shown in the installation example on page 12.
1. Obtain the gas heating value from the gas supplier
(HHV).
2. Shut off all other gas fired appliances.
3. Turn ON the main gas supply at the manual valve.
4. Start the unit in heating mode and allow it to run for at
least three minutes in HIGH fire mode (Stage 1 & 2).
5. Measure the time (in seconds) required for the gas
meter to complete one revolution.
6. Convert the time per revolution to cubic feet of gas per
hour using Table 17 (page 41).
7. Multiply the gas flow rate in cubic feet per hour by the
heating value of the gas in Btu per cubic foot to obtain
the firing rate in Btu per hour. See Example on page
17:
8. Adjustments to the firing rate can be made by adjusting
the gas manifold pressure. See the High Altitude Deration
section (pages 11 & 12) for additional information of
firing rate at elevations above 2000 ft.
9. Low fire input (Stage 1) must also be verified by repeating
all steps outlined for high fire input rate. Obtain low
fire input values from Table 15 (Page40). If necessary,
follow the manifold pressure adjustment instructions for
the low fire regulator spring to obtain the required input
rate.