T047_F: Inducer Fan 5 Minute Lockout
Status
This fault will occur after multiple "T045_F Inducer Low Pressure Switch Won't Close" or "T057_F Inducer High Pressure Switch Won't Close" faults. It is slightly different for 80+ and 90+ furnaces. This fault indicates the furnace is in a 5 minute delay before retrying.
Description
80+ Furnaces
If the control enters pre-purge with the low pressure switch open and the switch further fails to close within 2-3 seconds of entering pre-purge, the control will log fault "T045_F Inducer Lo Pressure Switch Won't Close" within 5 seconds. The inducer will run at high stage during the next pre-purge cycle in an attempt to close the low pressure switch. If the low pressure switch closes within 14 seconds of the second pre-purge cycle, the inducer will switch to low stage and reset the pre-purge timer back to 34 seconds. After a successful 34 second pre-purge period the control will go into ignition trial. If, however, the low pressure switch fails to close within 14 seconds of the inducer running at high stage, the IFC will go into a 5-min lockout at the end of the cycle (regardless if the low pressure switch remains open or closes later in that cycle). Alert "T047_F Inducer Fan 5 Minute Lockout" will be declared during the lockout.
Moreover, if the low pressure switch unexpectedly opens up for more than 4 seconds with the inducer at low stage, alert "T045_F Inducer Lo Pressure Switch Won't Close" shall be logged within 5 seconds. The inducer will run at high stage in the next cycle in an attempt to close the low pressure switch. If the low pressure switch closes within 14 seconds of high stage inducer operation, the inducer will be staged back to low speed where presumably the pressure switch will remain closed (pre-purge timer will be reset back to 34 seconds and the IFC will go to trial for ignition after a successful 34 second pre-purge period). If, however, the low pressure switch opens up again on low stage inducer speed, the control will repeat the same process in an attempt to close the low pressure switch. The IFC will only allow a maximum of six cycles, in case the low pressure switch keeps failing with the inducer at low stage, before entering a 5-min lockout with fault "T045_F Inducer Lo Pressure Switch Won't Close" and "T047_F Inducer Fan 5 Minute Lockout" declared.
90+ Furnaces
If either/both pressure switches fail to close until 2-3 sec after entering pre-purge or if a pressure switch unexpectedly opens for more than 4 seconds during a pre-purge cycle, alert "T045_F Inducer Lo Pressure Switch Won't Close" and/or "T057_F Inducer Hi Pressure Switch Won't Close" will be logged within 10 seconds, as appropriate. The control will disregard such a pre-purge cycle, although the 34 second period will still be completed before going to the next cycle. The IFC will allow a maximum of 3 cycles for the pressure switch(es) to close. If the pressure switch closes within 2-3 sec from the start of a cycle (or is already closed at the beginning of the cycle), in such a case, the control will complete the 34 seconds pre-purge and will go over to trial for ignition. If the pressure switch(es) fails to close in these three cycles or closes 3 seconds after the start of the third cycle, the control will enter a 5-min lockout with "T045_F Inducer Lo Pressure Switch Won't Close" and/or "T057_F Inducer Hi Pressure Switch Won't Close" declared. Alert "T047_F Inducer Fan 5 Minute Lockout" will also be logged during the lockout.
Cause
1. Blockage or improper termination in either the inlet or exhaust vents.
2. The flue vent length and/or number of elbows exceeds the maximum number specified.
3. Faulty or disconnected inducer.
4. Faulty control board (inducer relay).
5. Loose or faulty wiring.
6. Disconnected, blocked, split or cut pressure switch hoses.
7. Wind gusts (sporadic).
8. Faulty pressure switch.
Solution
1. Check the vent system for blockage and proper termination and repair as necessary.
2. Check the specification sheets and/or installation instructions. Remove excess venting.
3. Repair or replace inducer and/or inducer wiring and/or electrical connections.
4. Replace control board.
5. Check wiring and connections. Replace and/or repair as necessary.
6. Replace hoses as necessary.
7. Insure proper termination and determine if high altitude kit may be necessary
8. Replace the pressure switch.
