Head pressure hvac

Here are the details: 3 loops 156 feet. 1 loop of 140 feet. 3/4-inch copper feed to manifold 60 feet feed and 60 feet return with seven elbows in each run and flowchecks. I am not sure of the ID of the tubing: it is flexible black rubber. The OD is around 3/4-inch.

Head pressure hvac. As a ballpark & it depends on a lot of factors, suction should be in the range of 60 to 80 & head should be in the range of 150 to 300. I've got a 2.5 ton heatpump, @ 90 degrees in heat mode the suction should be @ 74 and the head should be @ 255. Reply. 05-28-2005, 07:33 PM #6. david2641.

I was working on a water source heat pump Trane serial number# W04C11546 MN# GEVB02411J0110TL. The unit is an upflow with the compressor compartment being on the bottom and the fan and coil on top. The problem is that the unit will run for about one minute in cooling mode then goes off on high head (400 psi r-22). …

Allow condenser to equal ambient temp. Then read pressure of condenser. Read pressure on PT chart. If no non condensables exist the pressure will be equal to what PT chart reads at that temp. Example: r 410a 80° f ambient refrigerant press should be 236 psig. If I read 290 psig my system has non condesables.Various experts and professionals claim that head pressure for a 410A system should be 400 to 418 PSIG on the high side while 120 to 130 PSI on the lower side. Anything more than this range is considered high head pressure. This value may vary a little bit depending on the weather and other external conditions.Jan 6, 2014 · To replace a defective low-ambient control valve with a pressurized dome charge, follow the steps below: 1. Recover the refrigeration system’s refrigerant; 2. Cut the process tube on the valve’s charged dome to remove the pressure charge (wear safety glasses); 3. With a torch, heat the valve until the solder melts; 4. What Is Head Pressure In HVAC? Head pressure is the pressure that is created by the gas compressor within the air conditioning unit. This is something that is typically measured when there is believed to be a refrigerant issue. Head pressure that is within a reasonable range is no cause for concern. High head pressure creates problems for the ...Are you looking to enhance your skills in the HVAC industry without breaking the bank? Look no further. In this article, we will explore the best free HVAC classes available to hel...Apr 17, 2022 ... HVACR Service Call: Water Source Refrigerator With High Head Pressure Tripping On Pressure Control. Jumper man Tech•6.1K views · 11:06. Go to ...Head pressure in HVAC systems is a critical factor for efficient operation, reflecting the pressure at which the refrigerant is condensed into a liquid. Properly managing head pressure ensures the longevity and efficiency of your HVAC system, reducing the likelihood of breakdowns and energy waste.Mar 1, 2022 · Head pressure is generated by your gas compressor and can be too high or too low depending on the weather, condensing temperature range, and other factors. Learn how to detect, prevent, and repair high head pressure in your HVAC unit with tips from Home Inspection Geeks.

Oct 29, 2004 · A 30 degree reduction in condensing temperature (110 degrees to 80 degrees) will reduce the current draw to 37.5 amps. While a 6.75-percent reduction is significant, it's only part of the story. The typical supermarket compressor rack will run a reasonably constant suction pressure, regardless of head pressure. Country of Origin: US. Condenser fan speed controls regulate refrigeration system pressures by adjusting the fan speed to help prevent low-pressure cutoffs, evaporator freezes, and bogging the compressor with liquid at lower ambient temperatures. They come in either mechanical or electronic versions, depending on the system and the type of ...Typical Low Side Pressure Range for R410A in the field: 115-120 psi. Typical High Side Pressure Range for R410A in the field: 410-420 psi. By 2025, high Global Warming Potential (GWP) refrigerants with a GWP of over 750, will be banned together with the systems using that gas. R410A has a GWP > 2,000.Now on startup, my head pressure at 87 degrees outside was at 225 or so. Suction was around 81 with the indoor temp at 78. After the rainstorm, 77 outdoor, I was at 75/175 with with maybe 74 or 75 indoor temp. Getting tons of condensation and 20* temp drop. Everything seemed good to me except that i thought the head was a little low.Mar 10, 2014 · This video explains what determines head pressure in refrigeration systems. Its explained by a Dunwoody College of Technology staff member Tom Kleinman. Pump head pressure basics, learn why pumps read pressure in height and call it head pressure.Learn more here ️ https://theengineeringmindset.com/pump-head-... Head pressure is the force exerted by a fluid in an HVAC system, which is essential for the fluid (typically a refrigerant) to circulate and enable heating or cooling. Why is it important to monitor head pressure?

I was working on a water source heat pump Trane serial number# W04C11546 MN# GEVB02411J0110TL. The unit is an upflow with the compressor compartment being on the bottom and the fan and coil on top. The problem is that the unit will run for about one minute in cooling mode then goes off on high head (400 psi r-22). …A thermostatic expansion valve (TXV) (see Figure 1) is a refrigeration and air conditioning throttling device that controls the amount of refrigerant liquid injected into a system’s evaporator—based on the …In this HVAC Training Video, I show the R-22 and R-410A Range of Operating Pressures on Air Conditioning Systems! I show why we Measure Pressures and Tempera...Share this Tech Tip: Suction pressure, head pressure, subcooling, superheat, delta T. Taking all five of these calculations into account on every service call is critical. Even if you must do further diagnostic tests to pinpoint the problem, these five factors are the groundwork before more effective diagnostics can be done.Took a reading off one of our units that cool an elevator machine room. It's an old Carrier 10 ton unit, single compressor, water cooled tube in tube condenser. Suction pressure was good at 68 , head pressure went over 300 and was tripping it out. Cleaned the strainer, same thing happens. Brought in a mechanic who says the TEV is bad and …Make your influence uniquely far-reaching. If they pulled a vacuum period, and broke the vacuum with R22, then the problem isn't noncondensables. There simply wouldn't be enough air or nitrogen in the system even at 28-29" vacuum to affect the head pressure. The high head pressure is more likely due to an overcharge.

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Liebert High Head Pressure lockout. Today customer claims Liebert mini-mate has been locking out on high head pressure once or twice a month, sometimes more often, since it was installed approx. 1 year ago. The company that installed it has come out several times to check it out but found no high pressures. I decided to take the high …I have a on going argument, discussion and bet over head pressure. I have two fellow employees, one being a supervisor, that have made the statement numerous times that head pressure was high due to high indoor temperature. They are telling me that at a return temperature of 90 degree F a DX refrigeration system will have a higher head …An oversized condenser means lower head pressure, and reduced electrical consumption. When the actual ambient is below the design ambient, we can take advantage of the now greater condenser …Troubleshooting Refrigerant Charge to Determine a Bad TXV. If your suction pressure is staying the same while adding refrigerant, and your head pressure is shooting up while the suction pressure is staying the same, your TXV valve is probably bad. If you do your homework and suspect that the TXV bulb lost charge, it’s probably a better idea ...I was working on a water source heat pump Trane serial number# W04C11546 MN# GEVB02411J0110TL. The unit is an upflow with the compressor compartment being on the bottom and the fan and coil on top. The problem is that the unit will run for about one minute in cooling mode then goes off on high head (400 psi r-22). Unit runs fine in heat.

If you are wanting to maintain 180 psig. head pressure the controls would be set as follows: Cut-in Cut-out. Fans 1-2 180 psig. 160 psig. Fans 2-4 200 psig 190 psig. As you can see, this causes fluctuation of the head pressure and can result in expansion valve hunting and poor superheat control.The most common liquid line restrictions are clogged filter-driers, metering device inlet screens, a kinked liquid line, or a TXV with an empty bulb. These very rarely cause high head for more than a short period of time. The most common causes of high head pressure include high load, overcharge, and poor heat rejection (such as from …Head pressure, also referred to as discharge pressure, is a vital component of the refrigeration cycle in an HVAC system. It is the pressure exerted by the refrigerant in the condenser as it transforms from a high-pressure gas to a high-pressure liquid, following compression in the compressor.The pressure that’s generated by the gas compressor of your air conditioning unit is known as head pressure. The head pressure is something to measure whenever you suspect a refrigerant issue. While reasonable head pressure is nothing to worry about, it’s high head pressure that’s an issue.Typical Low Side Pressure Range for R410A in the field: 115-120 psi. Typical High Side Pressure Range for R410A in the field: 410-420 psi. By 2025, high Global Warming Potential (GWP) refrigerants with a GWP of over 750, will be banned together with the systems using that gas. R410A has a GWP > 2,000.The pressure that’s generated by the gas compressor of your air conditioning unit is known as head pressure. The head pressure is something to measure whenever you suspect a refrigerant issue. While reasonable head pressure is nothing to worry about, it’s high head pressure that’s an issue.rmosden, hvacmatt123 liked this post. A cold suction line (low superheat) with low suction pressure is a symptom of low evaporator air. A liquid restriction would result high superheat (warm suction line). The high head probably due to the other guys overcharging, trying to get the suction pressure up.Here are the details: 3 loops 156 feet. 1 loop of 140 feet. 3/4-inch copper feed to manifold 60 feet feed and 60 feet return with seven elbows in each run and flowchecks. I am not sure of the ID of the tubing: it is flexible black rubber. The OD is around 3/4-inch.Head just surging from 280 t0 330 about every 10 to 15 seconds. Talking with owner had Company X out on a service contract, he signed up on a year prior. Guess his system was freezing up and tech wrote down he found leak at schraeder core on LL valve. Replaced schraeder and added 2 pound and 3 ounces of NU22.evaporator pressure. The biggest difference between low airflow and low charge is the level of superheat and subcooling. In a poor refrigerant charge scenario, the load is still there, but there is not enough refrigerant to absorb the heat. If signs point to the refrigerant charge being low, charge the system while following proper field procedures or original …Check the Condenser Fan. The condenser fan generates airflow through the condenser coil. If the condenser fan doesn’t spin, then the condenser coil won’t reject heat properly and your AC high pressure switch will trip. Check the condenser fan to make sure that it spins when the condensing unit kicks on.

Fluctuating head pressure, R22, Piston. Looks like non condensables. Noncondensibles for sure, possibly moisture. -Recover all refrigerant. -If you can change the oil in the compressor might be worth it. -Replace Filter drier. -Triple evac If you have the time. -Charge by weight, then check superheat and add what’s needed.

Typical Low Side Pressure Range for R410A in the field: 115-120 psi. Typical High Side Pressure Range for R410A in the field: 410-420 psi. By 2025, high Global Warming Potential (GWP) refrigerants with a GWP of over 750, will be banned together with the systems using that gas. R410A has a GWP > 2,000.To replace a defective low-ambient control valve with a pressurized dome charge, follow the steps below: 1. Recover the refrigeration system’s refrigerant; 2. Cut the process tube on the valve’s charged dome to remove the pressure charge (wear safety glasses); 3. With a torch, heat the valve until the solder melts; 4.Most technicians in the HVAC field know the normal range of operation for the low-pressure side of an air conditioning system. This tends to be around 60 PSI to 85 PSI for R-22 and 105 PSI to 143 PSI for R-410A and is dependent upon operating conditions. On the high-pressure side of the system, there is a wide variation in …2 posts · Joined 2013. #1 · Jul 22, 2013. So I go to the job the other day and I have a older bryant ac system not working. So I check and find out that I had a bad dual capicatior so I replaced it and now I have a high head pressure and high suction pressure and the head pressure is jumping up and down and at first I thought that this is bc ...HVAC Static Pressure - Main Duct Must Reduce in Size. HVAC static pressure is maintained in your home by making the main supply duct get smaller the farther away it is from the furnace. Tim Carter. HVAC static pressure needs to be maintained equally in all ducts for you to be comfortable in your home.When the temperature and pressure of the bulb’s charge rises, the powerhead provides the force to open the TXV. When the temperature and pressure of the bulb charge decreases, the TXV closes. As you can see, the sensing bulb determines if a TXV opens or closes. The powerhead is simply there to relay the pressure from the bulb and provide the ...The pressure that’s generated by the gas compressor of your air conditioning unit is known as head pressure. The head pressure is something to measure whenever you suspect a refrigerant issue. While reasonable head pressure is nothing to worry about, it’s high head pressure that’s an issue.

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I settled on an Aspen Coil that was 20" tall, 4 row coil with the higher fin count of the two they offered. It's just a rental, so we stayed with the fixed orifice to save cost. It's got a .080 piston in it. The 3.5 ton we took out was a .078 but it was 10 seer. Now on startup, my head pressure at 87 degrees outside was at 225 or so.Jan 27, 2024 · Head pressure in HVAC refers to the pressure exerted by the refrigerant within the condenser unit. It is a critical factor in the functionality and efficiency of an HVAC system. Understanding head pressure is essential for maintaining a well-functioning HVAC unit. Watch on. Compression ratio is the ratio of head pressure to suction pressure in an HVAC/R unit. Generally, compression ratios approach 2.5:1 on high-efficiency, 16+ SEER A/C systems. The highest compression ratio in A/C compressors is typically 11:1. Refrigeration compression ratios tend to be quite a bit higher (up to 26:1).P215PR. P215PR direct-mount single phase condenser fan speed controllers are pressure-actuated to vary the speed of single-phase motors. Speed variation of the fan on an air-cooled condenser controls the refrigeration system’s head pressure, for optimum performance year-round. These controllers can be used with non-corrosive refrigerants.Jun 21, 2021 · Compression ratio is the ratio of head pressure to suction pressure in an HVAC/R unit. Generally, compression ratios approach 2.5:1 on high-efficiency, 16+ SEER A/C systems. The highest compression ratio in A/C compressors is typically 11:1. Refrigeration compression ratios tend to be quite a bit higher (up to 26:1). The SC might be normal , but the normal head for a r410 system w/ a 68* ambient should be closer to 300psi and the normal suction press should be closer to 110psi w/70* IDB. Those p/t's sound more like r22. kdean1, buttwheat liked this post. As others have said it sounds like a TXV and maybe low on juice. Pressure vs. Head (6) can be transformed to: Δ h = (p 2 - p 1) / γ (7) Δ h express head - the height difference of a column of fluid of specific weight - γ - required to give a pressure difference Δp = p 2 - p 1. Example - Pressure vs. Head. A pressure difference of 5 psi (lb f /in 2) is equivalent to head in water The fan speed controller keeps the condensing pressure at a steady level by regulating the speed of the fan motors. When pressure is declining, the controller decreases the output voltage, changing the speed of fan motor. The proportional band is a non-adjustable pressure difference between max. and min. pressure where the regulation occurs ... The Two Condenser Head Pressure II Module is designed to work stand-alone by using its OPTIONS dip switch to adjust the Head Pressure setpoint. The Two Condenser Head Pressure II Module is directly connected to the VCM-X Modular E-BUS, VCM-X WSHP E-BUS or SA E-BUS Controller, allowing the Module(s) to receive setpoints from the Controller. When ... If, for example, the discharge temperature were 210° with a 150 PSI head pressure and a 10 PSI suction with a 50° outdoor temperature, this would show an extreme undercharge. You can still …Head pressure 190 Suction Pressure 90 Suction line temp 54 inside temp 75 wetbulb 69 So ive been thru this problem b4 with the low head high suction so i assume piston or a-coil . I open up the duct and the other hvac guy has put in a 3ton acoil . I told the neighbor that he should replace the acoil with a 2 1/2 ton . ….

Suction fluctuating pressure was 70 - 74 PSIG. Fluctuation is immediately following start up. Superheat was low about 7F. Subcooling was high like 35F. My first impression was maybe it was overcharged so I recovered about 1 and 1/2 pounds. It brought the head pressure down to a fluctuation of 195 -> 225. Suction pressure to 69 …Head pressure is the pressure generated by the gas compressor of your air conditioning system. It can be high or low depending on various factors, such a…Three indications that your HVAC system make have high static pressure are: Uneven Heating and Cooling. Higher Energy Bills. A Noisy System. Before we go any further, we’ll note that these symptoms aren’t exclusive to this problem. But, if you’re noticing all three, then this could be what’s causing them.Jan 28, 2023 · Restriction in the Refrigerant Flow. Another cause of low suction pressure high head pressure can be a restriction in the refrigerant flow. This can be caused by a blockage in the refrigerant lines or a problem with the compressor, and can lead to low suction pressure and high head pressure. 3. Faulty Compressor. Bryan with HVAC School goes over AC pressures, subcooling, and superheat in his troubleshooting mindset presentation from the BTrained HVAC training event in...Jan 5, 2001 · The Cost of High Head Pressure. January 5, 2001. Table 1. Based on recopricating compressor operating at 30 psig suction, °0 superheat, °10 subcooling, 92% motor efficiency, year-round operation. Figure 1. The effect of rising head pressure. I was working on a water source heat pump Trane serial number# W04C11546 MN# GEVB02411J0110TL. The unit is an upflow with the compressor compartment being on the bottom and the fan and coil on top. The problem is that the unit will run for about one minute in cooling mode then goes off on high head (400 psi r-22). Unit runs fine in heat.I have a on going argument, discussion and bet over head pressure. I have two fellow employees, one being a supervisor, that have made the statement numerous times that head pressure was high due to high indoor temperature. They are telling me that at a return temperature of 90 degree F a DX refrigeration system will have a higher head …Are you interested in pursuing a career in the HVAC industry? With the convenience of online learning, you can now take HVAC courses from the comfort of your own home. However, wit... Head pressure hvac, The most common liquid line restrictions are clogged filter-driers, metering device inlet screens, a kinked liquid line, or a TXV with an empty bulb. These very rarely cause high head for more than a short period of time. The most common causes of high head pressure include high load, overcharge, and poor heat rejection (such as from …, rmosden, hvacmatt123 liked this post. A cold suction line (low superheat) with low suction pressure is a symptom of low evaporator air. A liquid restriction would result high superheat (warm suction line). The high head probably due to the other guys overcharging, trying to get the suction pressure up., Various experts and professionals claim that head pressure for a 410A system should be 400 to 418 PSIG on the high side while 120 to 130 PSI on the lower side. Anything more than this range is considered high head pressure. This value may vary a little bit depending on the weather and other external conditions. What causes high head pressure HVAC., Jul 5, 2019 ... ... pressure range of what a R410A air conditioner pressures should be. Note that in order to handle or work with refrigerant you need to be ..., The most common liquid line restrictions are clogged filter-driers, metering device inlet screens, a kinked liquid line, or a TXV with an empty bulb. These very rarely cause high head for more than a short period of time. The most common causes of high head pressure include high load, overcharge, and poor heat rejection (such as from dirty or ..., When it comes to finding the right HVAC system for your home or business, there are many factors to consider. With so many options available on the market, it can be overwhelming t..., Understanding Head Pressure in HVAC Systems Force Exertion. Head pressure in an HVAC system is the force that refrigerant exerts within the compressor. It’s a key player in moving refrigerant through the system, including head pressure controls. Think of it as pushing a fluid through a pipe at home; more pressure control means faster movement., The fan speed controller keeps the condensing pressure at a steady level by regulating the speed of the fan motors. When pressure is declining, the controller decreases the output voltage, changing the speed of fan motor. The proportional band is a non-adjustable pressure difference between max. and min. pressure where the regulation occurs ..., Share this Tech Tip: Suction pressure, head pressure, subcooling, superheat, delta T. Taking all five of these calculations into account on every service call is critical. Even if you must do further diagnostic tests to pinpoint the problem, these five factors are the groundwork before more effective diagnostics can be done., The Two Condenser Head Pressure II Module is designed to work stand-alone by using its OPTIONS dip switch to adjust the Head Pressure setpoint. The Two Condenser Head Pressure II Module is directly connected to the VCM-X Modular E-BUS, VCM-X WSHP E-BUS or SA E-BUS Controller, allowing the Module(s) to receive setpoints from the …, The fan speed controller keeps the condensing pressure at a steady level by regulating the speed of the fan motors. When pressure is declining, the controller decreases the output voltage, changing the speed of fan motor. The proportional band is a non-adjustable pressure difference between max. and min. pressure where the regulation occurs ..., The most common system configuration used for HVAC systems is closed-loop. In this application, static elevation is not accounted for in head pressure calculations and the system should not lose water. In a closed-loop system, water is circulated through an air handler coil that cools or heats the incoming air. In some applications, the air ..., How to diagnose high head pressures at the air conditioning or heat pump compressor: What are the causes of high head pressure at an air conditioner or heat pump compressor motor? This article lists twelve …, Head pressure is the force that refrigerant exerts in the condenser section of your HVAC unit, affecting the cooling performance and efficiency. Learn how outdoor temperature, dirty coils, overcharged refrigerant and other factors influence head pressure and how to maintain optimal levels., Physical Properties Of R22. In parallel to using the R22 PT chart, professionals will usually need to know some of the following R22 physical properties: R22 liquid density at -69°C: 1.49 g/cm 3. R22 gas density at 15°C: 3.66 kg/m 3. Triple point temperature: -115.76K. Critical pressure: 49.36 bar. Heat capacity ratio at 86°F: 1.178253., May 25, 2017 ... In this HVAC Video, I go over how to Calculate a Refrigerant Charge on an Air Conditioning Condenser by Measuring Temperature and Pressure ..., Pump head pressure basics, learn why pumps read pressure in height and call it head pressure.Learn more here ️ https://theengineeringmindset.com/pump-head-..., Apr 17, 2022 ... HVACR Service Call: Water Source Refrigerator With High Head Pressure Tripping On Pressure Control. Jumper man Tech•6.1K views · 11:06. Go to ..., normal suction low head pressure. im in the field 3 years now and this is the first time ive come across this. residential split system 1.5 tons and i had a good suction pressure but my head pressure was super low, only 150-160. the strange thing is operations seemed pretty normal. cold suction line, warm liquid line, condenser was …, Hissing. The most common cause of a heat pump hissing noise is a refrigerant leak. As the refrigerant escapes through a small opening created by the leak, it transitions from a high-pressure liquid to a lower-pressure gas, resulting in a distinct hissing sound. Your heat pump won’t run efficiently or provide proper levels of heating …, Troubleshooting Refrigerant Charge to Determine a Bad TXV. If your suction pressure is staying the same while adding refrigerant, and your head pressure is shooting up while the suction pressure is staying the same, your TXV valve is probably bad. If you do your homework and suspect that the TXV bulb lost charge, it’s probably a better idea ..., 145 °F. 571.7 psig. 150 °F. 607.6 psig. 155 °F. 645.2 psig. You can see that this R410A pressure chart includes high and low side pressures at temperatures ranging from -60 °F to 155 °F. Higher temperature equates to higher pressure. Here are 4 examples of how you can use this chart:, Refrigerant Pressure Temperature Chart - PT Chart for R-410A, R-134A, and R-22. These are currently the three most widely used refrigerants on the market today for HVAC applications in residential and commercial use. R-22 refrigerant is the king and used widely in the residential and commercial markets followed by R-134A which is used in ..., 7. install liquid line oversize burn out drier. 8. complete leak testing and evacuation and charge refrigerant. 9. complete system start up and testing let unit run for 4 to 24 hours. 10. use acid oil test to see if oil is acceptable. 11. if clean recover refrigerant and remove suction line filter driers. 12. if not, replace suction and liquid ..., Here are some of the symptoms of this system: • Higher than normal discharge temperatures; • Low condensing (head) pressures and temperatures; • Normal to high condenser subcooling; • Normal to high superheats; • High evaporator (suction) pressures; and. • Low amp draw. Higher than normal discharge temperatures:A …, May 5, 2016 · The SC might be normal , but the normal head for a r410 system w/ a 68* ambient should be closer to 300psi and the normal suction press should be closer to 110psi w/70* IDB. Those p/t's sound more like r22. kdean1, buttwheat liked this post. As others have said it sounds like a TXV and maybe low on juice. , Various experts and professionals claim that head pressure for a 410A system should be 400 to 418 PSIG on the high side while 120 to 130 PSI on the lower side. Anything more than this range is considered high head pressure. This value may vary a little bit depending on the weather and other external conditions., 2 stage Carrier 48TJE12-High Head Pressure. Hi! Working on a Carrier roof top 48TJE12 2 stage... Everything turns on for a call for cooling. The head pressures goes to 400 and the internal pressure valve on both compressors kicks in. The suction is at 85 and drops a little., An HVAC technician taking a static pressure measurement. STEP 2: Drill test ports using a 3/8′ drill bit with a metal piercing tip. A bullet-tip drill makes a clean round port. So make sure to use your drill bit sheath (described above) to help prevent you from drilling into the coil., 2 posts · Joined 2013. #1 · Jul 22, 2013. So I go to the job the other day and I have a older bryant ac system not working. So I check and find out that I had a bad dual capicatior so I replaced it and now I have a high head pressure and high suction pressure and the head pressure is jumping up and down and at first I thought that this is bc ..., Method 4: Check the Radiator. You need to make sure that the radiator is not blocked. A blocked radiator can cause the engine to overheat, leading to high head pressure. If the radiator is still blocked, you may need to flush it out. To do this, remove the radiator hose and flush it out with a garden hose., The fan speed controller keeps the condensing pressure at a steady level by regulating the speed of the fan motors. When pressure is declining, the controller decreases the output voltage, changing the speed of fan motor. The proportional band is a non-adjustable pressure difference between max. and min. pressure where the regulation occurs ..., I was working on a water source heat pump Trane serial number# W04C11546 MN# GEVB02411J0110TL. The unit is an upflow with the compressor compartment being on the bottom and the fan and coil on top. The problem is that the unit will run for about one minute in cooling mode then goes off on high head (400 psi r-22). …