Adding or Removing Refrigerant

This system uses HFC−410A refrigerant which operates at much higher pressures than HCFC−22. The pre−installed liquid line filter drier is approved for use with HFC−410A only. Do not replace it with components designed for use with HCFC−22.

COOLING MODE INDOOR AIRFLOW CHECK

Check airflow using the Delta−T (DT) process using the illustration in figure 20.

HEATING MODE INDOOR AIRFLOW CHECK

Blower airflow (CFM) may be calculated by energizing electric heat and measuring:

STemperature rise between the return air and supply air temperatures at the indoor coil blower unit,

SMeasuring voltage supplied to the unit,

SMeasuring amperage being drawn by the heat unit(s).

Then, apply the measurements taken in following formula to determine CFM:

Amps x Volts x 3.41

CFM =

1.08 x Temperature rise (F)

AIRFLOWINDOOR COIL			DT
TEMPERATURE OF AIR			DT
TEMPERATURE OF AIR		80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
ENTERING INDOOR COIL ºF		80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
	DRY−BULB	78 23 23 23 22 22 21 21 20 19 18 17 16 15 14
	DRY−BULB	76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
		76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
		74 21 21 21 20 19 19 18 17 16 16 15 14 13 12
A		72 20 20 19 18 17 17 16 15 15 14 13 12 11 10
		70 19 19 18 18 17 17 16 15 15 14 13 12 11 10
WET−BULB ºF			57 58 59 60 61 62 63 64 65 66 67 68 69 70
DRY			B
BULB

C TDROP

53º

19º

AIR FLOW

72º

64º

All temperatures are expressed in ºF

INDOOR COIL

DRY BULB

								WET BULB
Use the following procedure to adjust for optimal air flow across the indoor coil:
1. DETERMINE THE DESIRED DT								TURE USING DRY BULB (A) AND WET BULB (B). DT IS THE INTERSECTING VALUE
OF A AND B IN THE TABLE (SEE TRIANGLE).
2. Find temperature drop across coil								A and C). Temperature Drop Formula:
(TDrop) = A minus C.
3. Determine if fan needs adjustment							ference between the measured TDrop and the desired DT (TDrop–DT) is within +3º, no adjustment
is needed. See example below:
			ASSUME DT = 15 AND A TEMP. = 72º, THESE C TEMPERATURES WOULD NECESSITATE STATED ACTIONS:
Cº	TDROP	–	DT	=	ºF	ACTION		Changing air flow affects all temperatures; recheck temperatures to

53º	19	–	15	=	4	INCREASE THE AIRFLOW		confirm that the temperature drop and DT are within +3º.
58º	14	–	15	=	−1	(WITHIN +3º RANGE) NO CHANGE
62º	10	–	15	=	−5	DECREASE THE AIRFLOW

4.ADJUST THE FAN SPEED

Figure 20. Checking Indoor Airflow over Evaporator Coil using Delta−T Chart Formula

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