Carrier 58MVP 170 Series Troubleshooting Manual page 26

STEP
Turn power on and depress door switch. Use a piece of
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45 Jumper R and W/W1 thermostat terminals.
46 Does status code 33 occur during low heat?
Clean or replace filter if necessary, then recycle furnace
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Observe furnace operation for 25 minutes or until status
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Is furnace considerably overfired (10or more)? Clock input
50 rate. Do not use manifold pressure method unless using
Ensure gas inlet pressure and burner orifices (natural or
propane) are correct. Then adjust gas valve to proper rate
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per Installation, Start-Up, and Operating Instructions. If it
cannot be adjusted to proper rate, replace gas valve.
52 Is temperature rise within rise range?
Does the installation have a bypass humidifier or zoning
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Turn power off and install a temperature probe in front of
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Turn power on and cycle unit. Does limit switch open at a
temperature at least 10 deg. F below temperature setpoint
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for limit switch? (EXAMPLE: The setpoint is 220 deg F, but
the switch opens at a temperature below 210 deg F.)
The problem may be related to poor air distribution or ex-
cessive pressure drop across filter. Check filter and return-
56 air grilles for blockage. Add turning vanes, more supply
openings, or more return-air openings. Use Appendix D to
57 While the unit is operating in low heat jumper R and W2.
With blower access panel in place record temperature rise
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across return air duct before and after the bypass.
59 Is temperature rise from bypass greater than 15 deg. F?
The bypass is oversized. Adjust damper or replace with
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61 Does installation have modulating zone dampers?
Disable modulating zone damper system with all dampers
in open position except bypass damper. If installation is
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equipped with a bypass damper, it should be in the closed
Turn power off and disconnect jumper from the R thermo-
stat terminal. Turn power back on and reconnect jumper to
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R thermostat terminal. Observe for 15 minutes with the
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The problem is caused by the modulating zone damper sys-
65 tem. Check the zoning system manufacturer's Installation
and Troubleshooting guide for corrective action.
Turn power off and install a temperature probe in front of
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Turn power on and cycle unit. Does limit switch open at a
temperature at least 10 deg. F below temperature setpoint
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for limit switch? (EXAMPLE: The setpoint is 220 deg F, but
the switch opens at a temperature below 210 deg F.)
Adjust the blower airflow using dip switch SW1-3 and
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SW1-4 to get the temperature rise within the rise range.
ACTION
tape to hold switch closed.
after limit resets.
code 33 starts flashing.
Does status code 33 occur?
propane.
system bypass?
limit switch button.
evaluate external static pressure.
properly sized bypass.
position.
blower access panel in place.
Does status code 33 flash?
limit switch button.
YES
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