Most non-electrical HVAC/R problems are charge related. Many systems in operation are undercharged or overcharged. This can cause decreased efficiency and compressor failure. The higher the efficiency of a system, the more critical it is that it is charged properly.
The Fieldpiece Superheat and Subcooling for Air Conditioning and Refrigeration meter, model SSX34, measures suction line, or low side, line temperature and pressure. It then calculates actual superheat in real time using built in P/T charts. It also measures liquid line, or high side, line temperature and pressure, and calculates actual subcooling. Use it to get actual superheat on R-22, R-410A, R-134A, and R-404A fixed orifice systems and actual subcooling on TXV / TEV regulated systems.
Use the “T” fitting to charge to actual superheat or subcooling by putting the SSX34 in-line between your refrigerant bottle and the system. Use it to monitor superheat and subcooling when recovering too.
How Does it Work?
Finding actual superheat or subcooling is easy with the SSX34. Simply hook it up to the system, let the system stabilize, and get your actual superheat or subcooling reading in real time. No charts, no calculations. It’s all done for you in the instrument.
It has a 1/4” industry standard fitting and for actual pressure with a “T” to use in line when charging or recovering to actual superheat or subcooling. An advanced pipe clamp k-type thermocouple model ATC1 is included for actual line temperature. Connect the SSX34 directly to the A/C or refrigeration system using a standard 1/4” EPA approved refrigerant hose using the pressure port at the top of the meter. Connect the pipe clamp T/C to the meter as close to the condenser or evaporator as possible. Select R22, R410A, R134A or R404A. Select English or Metric units and test.
It features a rugged rubber boot for durability and magnetic hanger for easy use. Hang the magnetic hanger over a corner to minimize slip and work hands free. The SSX34 will display superheat or subcooling in real time.
Connect the thermocouple pipe clamp and refrigerant hose to the meter.
Calibrate if needed (see Field calibration).
Select °C or °F by holding down the °C or °F button while turning on the SSX34.
Hand tighten 1/4” flare to suction line or liquid line as close to the evaporator or condenser as possible using an EPA approved service hose (not included).
Select proper pressure units (english psi or metric KPa) by pressing the UNIT button.
Select refrigerant (R22, R410A, R134A, or R404A) by pressing the TYPE button and observing the arrow at the bottom of the LCD.
Connect the pipe clamp to the suction (superheat) or liquid (subcooling) line near the compressor and slide it under the insulation for best accuracy isolating the pipe clamp from the ambient air.
Select temperature to display (superheat, subcooling, or refrigerant temperature). Temperature being displayed is designated by the arrows along the right side of the LCD “K” is the direct temperature from the thermocouple (actual refrigerant temperature). “SH” is superheat and “SC” is subcooling. Pressure is constantly displayed in lower right.
You must wait until the system you are testing has stabilized.
Once you have the superheat or subcooling reading follow the manufacturer of the air conditioner’s specifications to properly charge or diagnose the system.
Measuring Actual Superheat and Subcooling.
Superheat is the difference between the actual temperature of the refrigerant (gas) as it leaves the evaporator and the boiling point temperature of the refrigerant in the evaporator coil. After boiling, the refrigerant continues to warm up. The number of degrees it “warmed up” after boiling is called the superheat. Under worst case conditions (low load for fixed orifice systems), the refrigerant in the evaporator boils off near the end of the evaporator coil. To make sure liquid doesn’t enter the compressor under the worst case condition (low load), the AC manufacturers publish charts indicating what the superheat should be at a given indoor wet bulb measurement and outdoor air temperature.
Measuring superheat is your best indication on a fixed orifice system of the proper refrigerant charge and operating conditions. If everything else is working properly and the actual superheat is too high, add refrigerant. If it’s too low, remove refrigerant.
Subcooling is the difference between the boiling point of the refrigerant in the condenser and the actual temperature of the refrigerant as it leaves the condenser. The number of degrees the refrigerant “cools down” below the boiling point is the subcooling. Under worst case scenario (low load for TXV) the subcooling will continue to rise. If the subcooling rises to high, liquid may be backed into the compressor causing damage and catastrophic failure. On TXV systems, subcooling is the best indication of the state of charge in the refrigerant system since these systems are designed to maintain constant superheat.
Properly charging a system ensures maximum efficiency and longer equipment life.
When charging, the hose must have a Schrader valve depressor on one end to release the refrigerant from the suction or liquid line. This is the same type of hose available with most pressure gauge sets. We suggest EPA sanctioned “no leak” hoses. Exercise caution whenever working with any electricity and high pressure liquid or gas. Follow all instructions provided with equipment being serviced or installed.
Target Superheat and Subcooling.
Heed all equipment manufacturer’s specifications, warnings and suggestions above anything found in this manual. To determine the target superheat (fixed orifice system) or subcooling (charts vary dramatically from one system to another), you will typically need three things. Outdoor dry bulb (outdoor air temperature), indoor wet bulb, and the manufacturers target superheat chart or subcooling chart. You can use the ARH4 accessory head or the SRH2 Diagnostic Psychrometer for both indoor wet bulb and outdoor dry bulb. In fact, the SRH2 calculates target superheat and target evaporator exit temperature automatically based on psychometric measurements. Or you can use any Fieldpiece meter that has a temperature function along with an ATWB1 wet bulb thermocouple. Below is a diagram of the SSX34 on a split-system residential A/C unit.
Battery Check Function.
The SSX34 allows the user to check the battery charge at any time during use, simply by holding down the UNIT button for over one second. The approximate percentage of battery charge will be displayed on the main display for three seconds before returning to its reading prior to performing the battery check.
When the pressure/vacuum is near zero, the unit shown on the display may fluctuate between vacuum and pressure. This is to a classical gauge face as shown. Below zero is vacuum (inHg or cmHG), above 0 is pressure (psi or kPa). There is nothing wrong if this happens. The appropriate units will be displayed when a pressure/vacuum measurement is taken.
Many AC system analyzers include PT charts you don’t want or need. The SSX34 gives you actual superheat and subcooling in real time like the expensive analyzers do in a rugged, compact design. The SSX34 constantly displays refrigerant line pressure, toggles between line temp actual superheat, and actual subcooling for four of the most common refrigerants found in HVAC/R field service. If need you need more refrigerants in your daily work, check out the HVAC GUIDE® System Analyzer, model HG1 or HG2, and the ASX14 for a system analyzer and then some. P/T charts for 12 of the most common refrigerants you use in HVAC/R are included, as well as the software and firmware to generate for printable work orders for customers. For even easier refrigeration testing take a look at the ATC1R pipe clamp especially designed to fit smaller refrigerant lines.
Recommended Accessories and Replacement Parts.
Technicians who like the SC77 may also enjoy these instruments and accessories: