Superheat Problem I had an aircondition installed yesterday by a technician and today I did some measurements and found something that I do not understand. The system is using R407C refrigerant and is 18000 BTU. I found the following: Suction Pressure (70 psig) Suction Line Temperature (93 degrees Fahrenheit) Evaporator Temperature (43 degrees Fahrenheit) Outdoor Temperature (100 degrees Fahrenheit) Does the above mean that i have Superheat 50 degrees? Is this normal?

Sounds like you need another opinion from another AC man. If you are in an apartment complex, it has been my experience most apartment techs have limited knowledge of what to check. Try this
1. With the unit on, go to you air filter and check for proper air flow. If you are using pleated filters, stop. Use what is called 30 day throwaway filters. Pleated filters block 35 % of the air flow and can cause evaporators to freeze over. Ace hardware still stocks the ones with the blue mesh with cardboard edges. I have used the same filters for over 2 years. All I do is use my vacuum cleaner and clean the dust bunnies collected every 30 days.
2. Perform an sight inspection of your duct system. I have had several customers whose duct have fallen off and they were air conditioning the attic space and/or crawl space.
3. Have your AC man determine your superheat and subcooling value for your airconditioning unit. If your AC man does not know what these are then he really isn't an AC man. A typical value for most superheat (SH) and subcool (SC) is 12 to 15 degrees. These values are typically normal values but can change due to design criteria established among manufactures. If your AC man does not know what these are or can not measure these you need to get someone that know how to obtain them. These values are typical value for a normally charged equipment and does not vary from refrigerant to refrigerant.
Hope this helps.

You need to to determine the superheat and subcooling to check for the proper operation of your system when the compressor is running. I ran into a case just yesterday, the breaker kept tripping. Unit had the same readings as yours. This one had a subcooling of >25 degrees and 0 degrees superheat indicating unit was overcharged. I took an extra 8 pounds of r22 out of the system. During the investigation I also determined the filter/drier was blocking the refrigerant flow causing the technician to overcharge the unit. To check filter/drier performance all you need to do is measure the upstream and downstream temperature. The difference should be less than 2 degrees. This one was 7 degrees indicating it was metering flow. If your compressor stops operating before determining superheat and subcooling, you can get a professional tech to recover and weigh out the refrigerant in your system. You can look on the nameplate data on the side of the outside unit and see the ounces of refrigerant it is charged. If the compressor is operable go ahead and adjust charge by recovering the excess refrigerant into a recovery container for that refrigerant. Normal superheat and subcooling is normally around 10 - 15 degrees.
Hope this helps

the model says that this is a cooler/freezer combination unit. super heat has to be measured on each section separately. As a general rule: Freezers run around 6-8 degrees and coolers are 8-10. I have seen freezers go as low as 4 degrees right before they hit set point temp and shut off.

Low ice production has multiple causes. First check condensing coil to see if they are dirty and not passing air. This is the most probable cause for low ice production. Next, measure freeze cycle time and harvest time. Freeze time is typically 20 to 30 minutes and harvest time is normally 1.5 to 3 minutes. If freeze time is long (> 35 minutes), first check water valve shuts after reservoir is full. If it does not shut off the water solenoid operated valve needs replaced. Second, find the harvest solenoid operated valve which branches off the compressor discharge and port high temperature gas into evaporator during harvest and see that evaporator side of harvest valve cools down to surrounding temperature in a few minutes 8 - 10 after freeze cycle starts and harvest time stops. If it does not cool off the valve is leaking by its seat and will require a technician to replace. Lastly, if long freeze cycle could be due to low refrigerant and will require and tech to charge properly. Ice machine are critically charged and a tech will know how to charge the right amount. Again, it is possible the metering device is not passing enough refrigerant and a technician can determine this by checking the superheat and subcool. Low subcooling <3 and a high superheat >20 typically indicate an txv (metering devise) needs replaced and will require a tech to replace.

superheat is the difference of line temperture at suction of the compressor to the pressure converted to temperture for freon used in system. subcooling is the difference of temperture measured on liquid line compared to pressure measured at discharge line converted to temperture for the freon used in system.

When technicians take an air conditioning course, one of the first things they learn is to use superheat to charge a fixed orifice air conditioning system.

Superheat is not hard to deal with, but the technician needs to take four good measurements.

To get the actual superheat, the technician measures suction line pressure and suction line temperature. When he reads suction line pressure, he reads the *F scale on his gauge. That's the boiling point of that refrigerant at that pressure. To get actual superheat, subtract the suction line boiling point temperature from the measured temperature of the suction line.

To read get the required superheat from the most common A/C manufacturer's superheat charts, the technician measures indoor "wet bulb" temperature and outdoor air temperature ("dry bulb"). Using these two temperatures the technician can look up the required superheat on most A/C manufacturers' superheat charts. Required superheat's can vary from 5 *F to over 45*F depending on the conditions (indoor wet bulb and out door dry bulb). The higher the load, the higher the required superheat.
The technician adds or subtracts refrigerant to decrease or increase the actual superheat to match the required superheat.

Superheat is the temperature difference between the boiling point of the refrigerant in the evaporator and the actual temperature of the refrigerant gas after the evaporator. It is the "extra" temperature (or temperature rise) the refrigerant picks up in the evaporator after it boils.

When charging the system, the technician adds as much refrigerant as he can. But if he adds too much (overcharge), he risks flooding the compressor with liquid refrigerant.

The biggest risk of flooding is under low load conditions: low outside temperatures and low indoor wet bulb temperatures. The refrigerant boils off late in the evaporator. To make sure the refrigerant is all boiled off before the end of the evaporator, the the A/C manufacturer's required superheat chart directs the technician to stop adding refrigerant when the suction line temperature gets down to within a few degrees of the boiling point inside the evaporator. The "few degrees" is the superheat. At low load conditions, the superheat is often specified as five or six degrees. It's a safety factor to make sure no liquid gets to the compressor.

At other load conditions, as determined by outdoor air and indoor wet bulb temperatures, the required superheat is given by a the superheat chart supplied by the A/C manufacturer. The higher the temperatures, the higher the load and the higher the required superheat.

Doing a superheat analysis is the best way to insure that an air conditioner has the proper charge.

Hello, in order to find if the sytem is operating correvtly you should measure the outdoor dry bulb temp and indoor wet bulb temps, this will givenyou a target superheat. Pressures will vary always use superheat. If superheat is higher than target add refrigerant if it is lower remove refrigerant.

Check your room thermostat sensor. Replace it.

You are still low on freon. Charging AC by superheat and subcool
First charging a unit by superheat, this is only for Acs with an orifice or capillary tube.
Optimum superheat is 12° to 15° at the compressor or suction line outside the unit.
Hook up your gages and put a thermometer on suction line (large line), start the AC. Measure the temperature of the suction line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant, (you can also use a temperature pressure chart), now read the thermometer, let’s say the suction temperature( the thermometer) is 67° and the saturation temperature (the gages or temp. press. Chart), is 55°, subtract the saturation temperature from the suction temperature, 67°- 55° = 12° superheat.
Charging by Subcooling, this is for Acs with a thermostatic expansion valve, it’s common to see a sight glass on the liquid line (on these units with a sight glass just clear it, when, indoor room is at approximate set point of the thermostat). Optimum sub cooling is 12° to 15° at the outdoor unit.
Hook up your gages and put a thermometer on liquid line (small line), start the AC. Measure the temperature of the liquid line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant,(you can also use a temperature pressure chart), now read the thermometer, let’s say the liquid temperature( the thermometer) is 100° and the saturation temperature (the gages or temp. press. Chart), is 114°, subtract the liquid temperature from the saturation temperature, 114°- 100° = 14° subcool.