By Alec Johnson May 25, 2019. Environmentally acceptable replacement compounds are therefore needed for use in existing medium and low temperature refrigeration applications. Used 1/6 - 1/5 can of 12oz r134a. check out the. The low-side should be near 30 PSI at 90 degrees Fahrenheit or less. R-134a is the most common refrigerant found in automobiles today. Also, what causes high suction pressure r22? You can use those numbers to calculate superheat and get a clearer picture of what’s going on. I've been reading through these comments wondering where this one was. Especially on these little refrigerators. There is absolutely a restriction, most likely cap tube/strainer. We're using 12 oz cans of R134a. If it's in vacuum, then the superheat is high due to the evaporator being starved. Then look for a leak if you have one. No this is aimed at hvac / appliance techs. After I added more to get it to 0, the suction line is now covered in frost. Most refrigerators built after 1995 typically uses the R134a refrigerant. The system should be recovered, vacuumed (min 20 minutes) and charged. I vacuumed the system down and went to charge, but found only a low pressure port. This chart details how ambient temperature correlates with the system refrigerant charge pressure, and how it affects high and low side psi readings. The boiling temp of R134A is -15 degrees F at 1 bar absolute pressure. I'd keep slowly adding refrigerant an ounce at a time until the freezer stabilizes at a nice low temperature with a reasonable superheat. Many servicemen experience service calls where the compressor has both a low head pressure and a high suction pressure. High and low side pressures are pretty close to R134a vapor pressure for temps of the lines … With 134a, a low-side pressure of 0 PSIG means your boiling liquid is at -15F. Suction or, as it is also known, low side pressure, is one of the critical variants in the operation and diagnostic processes of air conditioning and refrigeration. R134a Refrigerant Running Pressure Normal Refrigerators. If you didn’t properly weigh in the charge you’re going to have no idea how much volume you actually have in the system. Similarly, at the highest temperature, 60−20 = 40 degrees Fahrenheit, the coil should run at 57 psi. Of course, your system is leaking and will not stay functional in the long run unless you find and fix the leak - at which point you get to weigh in a proper full charge and don't have to guess at it. High pressure side is high, low pressure side (suction pressure) is low: Discharge pressure is very high after turning on the A/C switch, and bubbles are seen in the sight glass (if charge valve is located after R/D, discharge pressure is unknown)-----Choking between compressor and R/D: Remove clogged materials, or replace condenser Suction pressure or Back pressure of R 134a is 0 to 5 lbs psig. That way, you can use evaporator superheat as low as possible, and total superheat as required by Bitzer. Get shopping advice from experts, friends and the community! This is a likely explanation for the problem. I totally missed this interpretation of the situation, but it's very likely correct. Table 1: R134a Saturation Properties pressure table (Reference: www.chemours.com) Back to the problem at hand. R134a Refrigerant mostly use for Refrigerators. Especially when pulling down from almost room temp. In that case shut it off for a day and see if the oil will migrate back to the compressor. If it's not leaking, it's restricted. That being said, there are still millions of cars on the road that use R-134a and there will be continue to be for at least another … Suction pressure low - Low superheat at evaporator outlet. I would advise (if it is possible) to install suction line heat exchanger in order to increase subcooling and total superheat. With 134a, a low-side pressure of 0 PSIG means your boiling liquid is at -15F. You need to find and repair the leak before you charge it. The most common cause of low condenser air flow is a dirty coil. If your freezer is stable at -2F, the evap coil should be only a few degrees cooler than that, so your low side pressure should really be something like 2-6 PSIG. Checked today and it’s at -10 (freezer at -2 woohoo, fridge at 40, even though I set it to 34). With too little flow through the metering device, the refrigerant will all get condensed and stored in the high side of the system and suction pressure will go low no matter what the freezer temp or charge level is. Use the hex-head wrench to turn the piercing valve, found in the center of the top half of the saddle … The pressure for an ordinarily operating R134a is between 22 and 57 pounds per square inch (PSI). As a result of marginally higher discharge pressure and lower suction pressure for R134a, the frictional losses in the R134a are marginally higher, as shown in Fig. This condition could also be caused by bad motor bearings, defective capacitor, and shrubs or other obstructions around the unit. Press question mark to learn the rest of the keyboard shortcuts, ‍ Deep Fried Condenser (Commercial Tech). Did it drop because the system got cold? After compressor disengagement, the rise in suction side pressure will usually be very slow. Told the fridge to keep the freezer at -12 but it’s holding -2f (using a thermometer). When compressor is at room temperature then stand by pressure is 50 to 60 lbs psig. 2(d). Suction pressure is a term used to describe the pressure of a refrigerant gas at the intake point of a refrigerator or air conditioner compressor. I would throw it in the trash to be honest but if you insisted on fixing it. Remember, there are two sides to the chart; we have the low and the high. It seems that it's still under-charged. If the designer of the unit wanted to achieve -10F in the freezer case, they would design for 2 or 3 PSIG on the suction side at that cabinet temperature. Therefore in a normal R134a, the low-pressure side is 90 degrees or less, and the PSI should be close to 30. Poor distribution of refrigerant thru the evaporator nozzle and circuits. this is the pressure in the air conditioner's refrigerant suction line (low side pressure during compressor operation) and this will be a relatively low number, often less than 100 psi. So I refilled from -28 to 0 yesterday. Iso butane is R600a, when you compare the change of temperature with pressure the change is drastic in the case of iso butane than in R134a. Readings that are higher or lower indicate an overcharged system. But for real throw it in the trash. For a high pressure gauge when the high pressure reading is 200 to 225 psi for R12 or 225 to 250 psi for 134a, the system is fully charged. These calls are tough to handle because the compressor is still cooling, but not cooling to its rated capacity. We have an ice maker that uses 134A gas. Remember that as the freezer temp drops well below zero, the suction pressure will go into vacuum and this is expected. It should never be negative. Filled to 0 psi and waited overnight. For any refrigeration cycle/AC unit there are two operating pressures: suction pressure and discharging pressure, high and low settings for each pressure line determined by the manufacturer will stop the unit. Having gone through all the above details, you are still wondering, Also, you gain in capacity with higher subcooling. Pull a good deep vacuum and then weigh in charge. EDIT: u/chefjeff1982 correctly notes that this may be a restriction on the high side, like a clogged cap tube, rather than being under-charged at all. Fridge section stayed at 38 but freezer was 62. Pressure that is too much lower or higher shows there is a problem. Production of chlorofluorocarbons (CFCs) has been phased out. So as your fridge cools down, some pressure drop is expected. The R134a is a popular refrigerant used in a variety of modern refrigeration and air conditioning applications. As a low-pressure refrigerant system, the R134a is used in most home refrigerators as it is very effective and convenient for high-temperature applications. Please contact the moderators of this subreddit if you have any questions or concerns. R-134a TEMPERATURE PRESSURE CHART (Tabla de Temperaturas y Lecturas) Ambient Temperature °F / °C (Temperatura Ambiental) Low-Pressure Gauge (Puerto de Servicio del Lado de Baja Presion) High-Pressure Gauge (Puerto de Servicio del Lado de Lado de Alta Presion) 65°F (18°C) 25-35 psi / 172-241 kPa: 135-155 psi / 931-1069 kPa: 70°F (21°C) Headpressure is 150 to 185 lbs psig. Piercing valves are never supposed to be left on a system and they most definitely leak. If you have the equipment that is. But the low air problem would result in high head pressure in the heat cycle. Moisture in the refrigeration system, problems, and remedy. A restricted orifice will usually show as very low suction side pressure and lower than normal high side pressure. Light load conditions. It has been in use since the early 1990’s and now, in 2019, we are beginning to see it’s popularity wane with the rise of the new HFO refrigerant known as R-1234yf. I would recover the charge the try to free the restriction with a heavy charge of rx-11 and nitrogen. I had to fix a leak and thus started with an empty system. You do not have enough refrigerant in the system with r134a at 0 psi. kenmore model #253.23024102 serial #wb40836697 hot gas coil in condensate collector was leaking repaired leak evacuated system but had no way to weigh 6.5 oz charge .unit is at 13 degrees with suction line icing up I am retired hvac tech but am not familiar with r134a 2(a) and 2(c) also show that R134a has a higher final discharge pressure and temperature. It looks like this is a post about a domestic appliance - you would be better off asking this question in r/Appliances! Your suction pressure will drop as the load does. What is the lowest normal operating suction pressure that is acceptable on R134a chiller running water with no glycol or other low temp additives? The table below shows the comparison between temperature and pressure for R134a. do a pressure test with nitrogen for at least a couple hours. It's the difference between freezer temp and boiling refrigerant temp (from the PT chart) which gives you some information about how much liquid is in the evap. It can be used for recharging refrigerant, or to diagnose an a/c system based on pressure readings from your gauges. If you can fix the leak great, but dont forget a new spun driver. Minimum normal suction pressure for R134a chiller, http://www.funke.de/files/funke_shell_tube_he_e.pdf, If this is your first visit, be sure to But initially running -28 psig seems very, very low. The gauges readings will depend on the ambient temperature. The high pressure line coming off the compressor is hot so I guess the compressor is working. The result is lower superheat, high suction pressure, high discharge pressure and lower sub-cooling. Or am I losing refrigerant? Hooked up an envirotech 3226 to it using a supco piercing valve and it was -28psi. I appreciate the nod. We literally haven’t moved it in 5 years so, not sure what would cause it to leak. Waited 24 hours and checked today again by hooking up the envirotech discharge hose to the supco bullet piercing valve and it showed -8psi. The low suction pressure with high evap temperature (excessive superheat) suggests a lack of refrigerant. P.s. If not It may not be worth calling in a professional unless the fridge is worth a couple grand. I am a bot, and this action was performed automatically. Evaporator coil is icing. If your freezer is stable at -2F, the evap coil should be only a few degrees cooler than that, so your low side pressure should really be something like 2-6 PSIG. Your system has a leak. R1234yf is about 18% lower than that of the R134a, as shown in Table 1. I’ve done mini splits but never refrigerators until mine went out. Forane 134a Pressure Temperature Chart Author: Arkema Inc. Subject: Forane 134a Pressure Temperature Chart Keywords: Forane 134a, R-134a, Pressure Temperature Chart, PT Chart, HVAC, refrigeration, air conditioning, refrigerant gas Created Date: 10/4/2012 11:23:04 AM R134a Pressure Gauge Chart. We are operating a 280 ton R134a chiller using a 45 deg F evaporator leaving temperature setpoint. A cold suction line (low superheat) with low suction pressure is a symptom of low evaporator air. What is the lowest normal operating suction pressure that is acceptable on R134a chiller running water with no glycol or other low temp additives? For cooling coil temperature -14 to -16 degree Celsius. Usually the bottom rows of the evaporator will freeze up when this occurs. Compressor oversized and the evaporator is undersized. If you are using a low pressure gauge when the low pressure reading is between 25 psi and 40 psi, the system is fully charged. The high head probably due to the other guys overcharging, trying to get the suction pressure up. and Stand by pressure is 85 to 95 lbs psig . When the compressor kicks in, the suction against the restricted orifice will cause the compressor to quickly cycle out. A liquid restriction would result high superheat (warm suction line). Evaporator starving of refrigerant and … Every Refrigerator have different size of Compressor when we charge Gas then Some Refrigerators Ready on zero (0 PSI) Running Pressure and some refrigerators ready on 15 PSI Running Pressure. There is a pressure drop but even at freezing it should be nowhere near zero. Hello all- Back on this big old boat with another fridge type question. The recommended pressure for a home refrigerator using R134A refrigerant is between 2 psig and 150 psig. If that doesnt work you'll have to cut into the system to put ports in to see what's going on. If I couldnt clear it I would change it. secondly isobutane is a bigger compound. Ambient Temperature (°F) What is suction discharge pressure for r134a? Would recommend pulling refrigerant, brazing in ports high and low. Unlike traditional refrigerants, the R134a is applicable and … During operation refrigerant is returning to the compressor from the cooling (evaporator) coil in this line. Long story short, 15 year old Samsung french door refrigerator. On a properly working system, high-side pressure will be about twice the ambient temperature, plus 50 PSI. The low suction pressure with high evap temperature (excessive superheat) suggests a lack of refrigerant. ~630 gpm chilled water flow with an evaporator inlet temperature of 46-55 degrees depending on the load. An extremely high discharge pressure coupled with an extremely low suction pressure is an indicator of a refrigerant restriction. Remove piercing valve and patch. it's worth noting that this is probably a cap tube system and could very well have a stopped up cap tube. No way anyone can reliably tell you what’s going on without knowing exactly how much refrigerant (in ounces or grams) you put in. We've added 1 and 1/2 cans so far. Any chance you can take a temperature of the suction line and your pressure at the same time. Although the low side pressure should be around 2 psig, at times it can fluctuate from 0 to -3 psig. I always weigh my refrigerant into systems that way I know for sure if it is a leak and not a restriction. Fig. If the low side pressure rises to over 10 psig, the system has too much refrigerant. If you show a vacuum on startup, dump in freon and still show negative pressures, then there is a restriction somewhere. Often, the refrigeration equipment is still running, but the product temperature is suffering about 7 to 10°F. You’re simply stabbing in the dark at this point. This is a good point. New comments cannot be posted and votes cannot be cast, More posts from the refrigeration community, Questions, discussions, and stories related to the Commerical and Industrial Refrigeration industry, Press J to jump to the feed. Could it be leaking from the bullet piercing valve? With the A/C turned OFF - On a cold day the pressure will be low, on a hot day the pressure will be high. This script determines the gas pressure based on temperature of R134a refrigerant.