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Old 12-23-2009, 04:29 PM   #1
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Goodman air handler adjustment

I have a Goodman HVAC question.
A little background....
A 2 ton/16 SEER R410a Goodman system is the SSZ16024 Heat Pump coupled with the AEPF303616 Air Handler.
Goodman states that the typical design air flow in HVAC sustems is 400 to 450 cfm per for two tons you need 800 to 900 cfm.
The AEPF303616 is the handler specified for 2 to 5 ton systems.
Air flow is controlled by dipswitch adjustments on the control board. The dipswitches basically control voltage sent to the motor.
This motor will operate at 30% output during "Fan Only Operation".
The Installation/Operating Manual gives the dipswitch settings for heating and cooling.
Only problem is that the lowest air flow shown in the manual is for a 2 1/2 ton system (by using the trim adjustment dipswitchs #s 7 and 8 gives you 1020 cfm), even though Goodman couples this Handler with a 2 ton system.
I notice that some other adjustments to the blower (for a humidistat or for staged electric heat) can be made by cutting jumpers on the control board.
It would seem that this is how you would lower the blower output.
My question is: how do you lower the air flow to the 2 ton requirement of 800 to 900 cfm?
I greatly appreciate any help you can offer.
Best regards and very Happy Holidays,
John Gregus


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Old 12-23-2009, 09:39 PM   #2
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AEPF Operating Instructions page 10:

Setting dip switch 7 and 8 to OFF ON will decrease blower CFM by 15% and get you where you want the system to be.

CFM Switch 7 Switch 8
+10% ON OFF

-15% OFF ON

Table 10
Emergency (Electric) Heat:
1020 x 15% = 153 ****** 1020 - 153 = 867 CFM

Heat Pump w/Back up Heat:
1070 x 15% = 161 ****** 1070 -161 = 909 CFM

Table 11
Nominal Cooling Tonnage 2.5:
1020 x 15% = 153 ****** 1020 - 153 = 867 CFM


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Old 12-24-2009, 02:32 PM   #3
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The answer is....

The 1020 cfm listed in Table 10 for heating service is with the 7/8 dipswitches already trimming the output of 1200 cfm to 1020,
In cooling, you can also only trim to 1020.
I have the answer from Goodman to my installer.
For a 2 ton system, to get 800 cfm, you have to fool the board into believing you have a 2 stage system which has a stage 1 blower output equal to 2/3 of rated output.
So you use Y1 input to the board instead of Y/Y2 and you bypass the board with the yellow wire. You connect yellow from the condenser directly to yellow from the thermostat with a third yellow going to the Y1 terminal on the thermostat section. You set dipswitches for 1200 cfm (3 ton) and turn dipswitch #4 to OFF.
First stage will now tell the blower to output 2/3 of 1200 = 800 cfm.
Goodman should put this in the I/O Manual instead of having to call their Tech Department to get the info.
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