Background/Info
GMVC951155 furnace. 2 Stage Variable speed heat, single stage cooling. 4 Ton compressor, 5 Ton A coil
I had to replace the original PCBKF101S main board in this unit with an updated White Rodgers PCBKF103 (50C51-707) . This board is a tad different than the original from 2010. The original is no longer available and this is the superseded replacement. I am having trouble understanding why the cooling speed is coming up as 15...makes no sense. I have tried a jumper between Y1 Y2 O, this does kick on C2 high but CFM displayed doesnt correspond to anything i can point my finger to. Previous Board/Thermostat would just say HI for single stage cooking.
Furnace Board Settings
Heating Speed Tap D = 1922 High, 1335 Low, Heating Airflow "D" S4 ( dip switch 3 & 4), Ramping Profile "D" S4 (dip switch 1 & 2)
Cooling Speed Tap D = 1800 High, 1170 Low, Cooling Airflow "D" S3 (dip switch 1 & 2),
Trim % = -5% S3 (dip switch 3&4)
Actual CFM from furnace in heat mode all makes sense and fits the needs on heating but not on cooling. LCD indicates: Heat Low = 13 or (1335 x .95 = 1268), Heat High = 18 or (1922 x .95 = 1826), Cooling (shows C2) and max blower speed =15...there is no 15 on the specs for this furnace or anywhere near this. As you can see above its 1800 (18) or 1170 (12) should be displayed on the LCD. Does anyone have any insight on this? I cannot tell if this is a NEST issue or the control board. Nest shows equipment is correct. As far as I can tell the only thing that seems to make sense is the board is taking the high and low, adding together and averaging them. (1800+1170/ 2 = 1485 (15). Additional info, prior to the board and nest replacement the furnace never showed a C1 or C2 when in cooling mode. It used to display HI then 18, which is not the correct speed for this home. Bad install, installer took the 5 ton coil as a reference vs 4 Ton compressor, or he figured 450 CFM/Ton.
It is very hard to correlate the new boards manual PCBKF103 vs the original installation instructions/manual for the furnace. For instance the new board S3 dip switch 3 and 4 shows +5,-5,+10,-10 yet the original manual shows normal,10, -10, normal. This is slightly different. This is negligible for what i am trying to achieve (see below), just an example of maybe i am missing something but I don't think so...
What I am trying to achieve is 1600 CFM so I can get closer to 400BTUs per Ton for this home. Right now even though 15 is displayed on the LCD I have no way to tell if I am between 1549 or 1451 because the value displayed does not seem to correlate to any of the Taps I selected and the furnace LCD rounds to the nearest number. Something seems wrong.
I uploaded the manuals if that helps. I am lost, cant get this one correct for cooling, in fact can never get it over 15 unless i trim the % but that seems to trim the heat as well. Static pressure isnt correct if i run the system higher than 18.
GMVC951155 furnace. 2 Stage Variable speed heat, single stage cooling. 4 Ton compressor, 5 Ton A coil
I had to replace the original PCBKF101S main board in this unit with an updated White Rodgers PCBKF103 (50C51-707) . This board is a tad different than the original from 2010. The original is no longer available and this is the superseded replacement. I am having trouble understanding why the cooling speed is coming up as 15...makes no sense. I have tried a jumper between Y1 Y2 O, this does kick on C2 high but CFM displayed doesnt correspond to anything i can point my finger to. Previous Board/Thermostat would just say HI for single stage cooking.
Furnace Board Settings
Heating Speed Tap D = 1922 High, 1335 Low, Heating Airflow "D" S4 ( dip switch 3 & 4), Ramping Profile "D" S4 (dip switch 1 & 2)
Cooling Speed Tap D = 1800 High, 1170 Low, Cooling Airflow "D" S3 (dip switch 1 & 2),
Trim % = -5% S3 (dip switch 3&4)
Actual CFM from furnace in heat mode all makes sense and fits the needs on heating but not on cooling. LCD indicates: Heat Low = 13 or (1335 x .95 = 1268), Heat High = 18 or (1922 x .95 = 1826), Cooling (shows C2) and max blower speed =15...there is no 15 on the specs for this furnace or anywhere near this. As you can see above its 1800 (18) or 1170 (12) should be displayed on the LCD. Does anyone have any insight on this? I cannot tell if this is a NEST issue or the control board. Nest shows equipment is correct. As far as I can tell the only thing that seems to make sense is the board is taking the high and low, adding together and averaging them. (1800+1170/ 2 = 1485 (15). Additional info, prior to the board and nest replacement the furnace never showed a C1 or C2 when in cooling mode. It used to display HI then 18, which is not the correct speed for this home. Bad install, installer took the 5 ton coil as a reference vs 4 Ton compressor, or he figured 450 CFM/Ton.
It is very hard to correlate the new boards manual PCBKF103 vs the original installation instructions/manual for the furnace. For instance the new board S3 dip switch 3 and 4 shows +5,-5,+10,-10 yet the original manual shows normal,10, -10, normal. This is slightly different. This is negligible for what i am trying to achieve (see below), just an example of maybe i am missing something but I don't think so...
What I am trying to achieve is 1600 CFM so I can get closer to 400BTUs per Ton for this home. Right now even though 15 is displayed on the LCD I have no way to tell if I am between 1549 or 1451 because the value displayed does not seem to correlate to any of the Taps I selected and the furnace LCD rounds to the nearest number. Something seems wrong.
I uploaded the manuals if that helps. I am lost, cant get this one correct for cooling, in fact can never get it over 15 unless i trim the % but that seems to trim the heat as well. Static pressure isnt correct if i run the system higher than 18.
source https://hvac-talk.com/vbb/showthread.php?2224011-Goodman-Amana-Furnace-Cooling-Speed-Tap&goto=newpost
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