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This is a result of zone air flow sizing. The zone air flow is 0.170368 m3/s and the coil load at this time is 1554.202 W which gives a flow to capacity ratio of 1.093E-4. This ratio is too high for DX coils at about 800 cfm/ton or twice the normal flow rate. Nominal flow to capacity ratio is 5.0E-5. To correct this, adjust the supply air temperatures in the Sizing:Zone object so that zone air flow decreases. For cooling, a lower supply air temperature will lower zone cooling air flow and a higher heating supply air temperature will lower zone heating air flow. The PTHP uses the greater of these 2 zone flow rates so only one or both may be causing this sizing issue.

This is a result of zone air flow sizing. The zone air flow is 0.170368 m3/s and the coil load at this time is 1554.202 W which gives a flow to capacity ratio of 1.093E-4. This ratio is too high for DX coils at about 800 cfm/ton or twice the normal flow rate. Nominal flow to capacity ratio is 5.0E-5. To correct this, adjust the supply air temperatures in the Sizing:Zone object so that zone air flow decreases. For cooling, a lower supply air temperature will lower zone cooling air flow and a higher heating supply air temperature will lower zone heating air flow. The PTHP uses the greater of these 2 zone flow rates so only one or both may be causing this sizing issue.issue. In your case it looks like the zone cooling air flow rate is causing this warning.

This is a result of zone air flow sizing. The zone air flow is 0.170368 m3/s and the coil load at this time is 1554.202 W which gives a flow to capacity ratio of 1.093E-4. This ratio is too high for DX coils at about 800 cfm/ton or twice the normal flow rate. Nominal flow to capacity ratio is 5.0E-5. To correct this, adjust the supply air temperatures in the Sizing:Zone object so that zone air flow decreases. For cooling, a lower supply air temperature will lower zone cooling air flow and a higher heating supply air temperature will lower zone heating air flow. The PTHP uses the greater of these 2 zone flow rates so only one or both may be causing this sizing issue. In your case it looks like the zone cooling air flow rate is causing this warning.

Sizing:Parameters,
  1.2,                     !- Heating Sizing Factor
  1.2;                     !- Cooling Sizing Factor

 ! <Zone Sizing Information>, Zone Name, Load Type, Calc Des Load {W}, User Des Load {W}, Calc Des Air Flow Rate {m3/s}, User Des Air Flow Rate {m3/s}, Design Day Name, Date/Time of Peak, Temperature at Peak {C}, Humidity Ratio at Peak {kgWater/kgDryAir}, Floor Area {m2}, # Occupants, Calc Outdoor Air Flow Rate {m3/s}, Calc DOAS Heat Addition Rate {W}
 Zone Sizing Information, SPACE1-1, Cooling, 3487.37160, 4184.84592, 0.28446, 0.34135, MIAMI INTL AP ANN CLG .4% CONDNS DB=>MWB, 7/21 15:45:00, 32.89850, 1.71418E-002, 99.16000, 11.00000, 0.10384, 0.00000
 Zone Sizing Information, SPACE1-1, Heating, 1259.72572, 1511.67086, 3.80418E-002, 0.10384, MIAMI INTL AP ANN HTG 99.6% CONDNS DB, 1/21 23:15:00, 8.70000, 6.99118E-003, 99.16000, 11.00000, 0.10384, 0.00000

This is a result of zone air flow sizing. The zone air flow is 0.170368 m3/s and the coil load at this time is 1554.202 W which gives a flow to capacity ratio of 1.093E-4. This ratio is too high for DX coils at about 800 cfm/ton or twice the normal flow rate. Nominal flow to capacity ratio is 5.0E-5. To correct this, adjust the supply air temperatures in the Sizing:Zone object so that zone air flow decreases. For cooling, a lower supply air temperature will lower zone cooling air flow and a higher heating supply air temperature will lower zone heating air flow. The PTHP uses the greater of these 2 zone flow rates so only one or both may be causing this sizing issue. In your case it looks like the zone cooling air flow rate is causing this warning.

Look in the eio file for zone load and air flow sizing information and use this information to guide the adjustments. Note in this example the 0.28446 Calculated Des Air Flow Rate and 0.34135 User Des Air Flow Rate (includes sizing factors from Sizing:Parameters object) for cooling and Calc = 0.0380418 and User = 0.10384 for heating (I'm not sure at this time why the User flow rate (higher than a factor of 1.2 because of the zone OA limit, see 2nd to last value in the eio output for heating is not 1.2 times the Calc). as Calc Outdoor Air Flow Rate). The higher of the User Des flow rates will be used for PTHP air flow sizing. Notice the zone loads also have Calculated and User values where the User values are 1.2 times the Calc values.

Sizing:Parameters,
  1.2,                     !- Heating Sizing Factor
  1.2;                     !- Cooling Sizing Factor

 ! <Zone Sizing Information>, Zone Name, Load Type, Calc Des Load {W}, User Des Load {W}, Calc Des Air Flow Rate {m3/s}, User Des Air Flow Rate {m3/s}, Design Day Name, Date/Time of Peak, Temperature at Peak {C}, Humidity Ratio at Peak {kgWater/kgDryAir}, Floor Area {m2}, # Occupants, Calc Outdoor Air Flow Rate {m3/s}, Calc DOAS Heat Addition Rate {W}
 Zone Sizing Information, SPACE1-1, Cooling, 3487.37160, 4184.84592, 0.28446, 0.34135, MIAMI INTL AP ANN CLG .4% CONDNS DB=>MWB, 7/21 15:45:00, 32.89850, 1.71418E-002, 99.16000, 11.00000, 0.10384, 0.00000
 Zone Sizing Information, SPACE1-1, Heating, 1259.72572, 1511.67086, 3.80418E-002, 0.10384, MIAMI INTL AP ANN HTG 99.6% CONDNS DB, 1/21 23:15:00, 8.70000, 6.99118E-003, 99.16000, 11.00000, 0.10384, 0.00000