Bryant R-22 service manual High Superheat with Normal or High Suction Pressure, Hunting Superheat

High Superheat with Normal or High Suction Pressure

NOTE: Normal to High suction pressure is considered

for R-22: > ∼65 psig, Puron: > ∼110 psig. An application issue or other system component failure typically causes this condition.

15.Check airflow, sensing bulb tightness, orientation on vapor tube and ensure bulb is properly wrapped.

SIf OK proceed to Step 16

16.R-410A Systems: Make sure proper valve is used (Not R-22)

SIf OK proceed to Step 17

17.Check for even temperature distribution at outlet of each circuit of evaporator

SIf OK proceed to Step 18

18.Check for high evaporator load: Return Air Leaks, high indoor wet bulb and/or dry bulb temp, undersized system, etc.

SIf OK proceed to Step 19

19.Check that compressor is pumping properly

SLoose Rule of Thumb: Is discharge saturated ∼20°F higher than ambient temperature? Is discharge superheat between 15_F and 50_F?

Hunting Superheat

NOTE: Hunting is when the valve superheat swings more than 10°F Superheat in repetition. This is typically an application issue.

20.Check for obvious kinked or pinched distributor (capillary) tubes causing imbalance to the circuiting.

SIf OK proceed to Step 21

21.Check that proper size valve is used per Product Literature.

SIf OK proceed to Step 22

22.Check airflow, sensing bulb tightness, orientation on vapor tube and ensure bulb is properly wrapped.

SIf OK proceed to Step 23

23.Check for even temperature distribution (±5° difference) at outlet of each circuit of evaporator and for even air distribution over all evaporator slabs

SIf OK proceed to Step 24.

24.Move sensing bulb further down suction line.

SIf problem not corrected, replace valve

Pseudo Evaporator Superheat Instructions

The Pseudo Evaporator Superheat calculates the superheat at the outlet of the evaporator with known and available information. Because there generally is not a pressure port on the vapor line at the indoor coil, this procedure allows the service personnel to evaluate the evaporator superheat with the vapor pressure port at the outdoor unit.

The method requires the following information:

SSuction line temperature at the outlet of the evaporator (°F).

SSuction line pressure at the outdoor unit (psig). S Outdoor nominal unit size (btuh).

S Suction line equivalent line length (ft).

SSuction line pressure drop from tables (Table 6 and Table 7).

SPressure-Temperature relationship for refrigerant used (P-T Chart).

If system uses a vapor line the same size as vapor service valve fitting or larger AND the line set equivalent length is 80 feet or less, the pressure drop in vapor line of line set can be ignored.

1.Take suction line temperature at outlet of evaporator at indoor unit.

2.Take suction service valve pressure at OD unit.

3.Determine lineset vapor line equivalent length and tube diameter.

4.Determine suction line pressure drop from Table 6 (Puron) or Table 7 (R-22).

5.Calculate Pseudo Evaporator Superheat.

SAdd the suction line pressure drop to the pressure reading obtained at suction service valve.

NOTE: For nominal and larger diameter vapor lines with standard length linesets (vapor line same size as service valve fitting size and larger with equivalent length less than 80 ft) the pressure drop can be ignored – use vapor service valve pressure and evaporator outlet temperature to calculate superheat

SDetermine saturated evaporator temperature from a refrigerant pressure temperature relationship chart (PT chart).

SSubtract saturated evaporator from evaporator suction line temperature to obtain evaporator superheat.

	90° STD
	90° LONG RAD	45° STD
			A01058
	Fig. 32 – Tube Fitting Geometry
	Table 5—Fitting Losses in Equivalent Feet
TUBE SIZE OD	90° STD (A)	90° LONG RAD (B)	45° STD (C)
(IN.)
1/2	1.2	0.8	0.6
5/8	1.6	1.0	0.8
3/4	1.8	1.2	0.9
7/8	2.0	1.4	1.0
1---1/8	2.6	1.7	1.3

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