What Is High Head Pressure:Types,Causes,Several Facts Around It


What is high head pressure? This question is answered in simple words as below,

Head pressure is the output pressure from the compressor in any system. Extreme high head pressure can cause some problems in the system.

The compressor is necessary equipment in the heat pump, refrigeration and air conditioning system. The high head pressure in this system can cause the failure of the compressor and its components in a period of time.

It ultimately affects the system’s performance, which reduces the cooling capacity or heating capacity.

For proper functioning of the system, all pressures like head pressure and the suction pressure should be designed well as per load calculation.

In earlier days, The problem of the high head pressure was checked by inspecting the condenser fan and condenser coil.

Nowadays, The problem is observed by checking restrictions in the refrigerant lines and the refrigerant charge condition.

High head suction pressure

High suction pressure is a common problem in the cooling systems

It can cause due to improper functioning of the compressor. If the compressor is not delivering sufficient refrigerant to the system, the suction pressure will increase accordingly.

One can understand the high head suction pressure with a better study of the refrigeration cycle. There are two types of pressures significant in the HVAC systems.

  • Suction pressure
  • discharge pressure
What is high head pressure
Pressure Credit Wikipedia

Maintaining both pressures in the specified range is desirable to obtain efficient performance.

If a refrigerant line is leaking at discharge or malfunctioning of a compressor, The evaporator will not receive sufficient refrigerant to provide efficient cooling. With the lack of refrigerant, the temperature and pressure increase at the evaporator outlet; this leads to high suction pressure.

Causes of high head pressure

The pressures of the system should be maintained in the desired range to avoid malfunction.

  • Overcharging of the refrigerant in the system
  • Operating the system at high range than the specified limit
  • Malfunctioning of the condenser fan motor
  • The system is charged with the impurities of non condensing gases
  • The condenser coil is not cleaned well
  • Refrigeration device plugged

In earlier days, The problem of the high head pressure was checked by inspecting the condenser fan and condenser coil.

Nowadays, The problem is observed by checking restrictions in the refrigerant lines and the refrigerant charge condition.

What causes high head pressure in a chiller?

The high head pressure is caused in most of the cooling systems.

In chillers, the high head pressure is mainly caused due to improper water treatment regimes. The clogging of the coils can cause high head pressure in the chiller.

The condenser water loop is open to the atmosphere in the chiller. The dirty particles are concentrated with the working fluid and periodically clog the system. The clogging of the system affect the heat transfer  between the surface and the working fluid. Ultimately, it facilitates heat transfer through the system.

The high head pressure is deteriorating the performance of the chiller. The condenser outside surface is exposed to an open environment in an air-cooled chiller. The dust particles from the atmosphere will stick on the compressor’s effective surface. It will insulate the surface partially and reduce heat transfer.

To avoid such abnormal conditions, one should clean the condenser coil periodically in a proper manner. The cleaning of the condenser can be done with light brushes.

What causes high head pressure in a refrigeration system?

High head pressure is generated because of the following reasons

It can cause rusting on the system’s components and the clogging of the elements like condenser coil, check valve, thermal expansion valve etc.

There are many others reasons like improper charging of the refrigerant, unsuitable operating condition, Improper cooling of the condenser.

Causes of high head pressure low suction pressure

For any HVAC system, The two pressures are to be maintained.

Excessive refrigerant, higher outdoor temperature, improper cleaning of coils are the main reason for both pressures.

Suppose the evaporator is not getting sufficient refrigerant from the compressor. It will not be able to provide proper cooling in the system. This problem can cause low suction pressure in the system. The defective metering device is also the probable reason for low suction pressure.

The outside temperature can also affect the system’s performance. The higher outside temperature can reduce the heat rejection from the system. Ultimately, it raises head pressure in the system. It is desirable to maintain the condensing temperature of the system. The difference of Temp. between the condensing pressure and the outside temperature should be high.

High head pressure in heat mode

The high head pressure in any device deteriorates the performance.

It is difficult to find the high head pressure in the heat pump during heat mode.

If we take a reading in the heating mode, we make sure that the larger diameter pipe is the delivery pressure and the smaller diameter pipe is the liquid pressure.

The pressure will fall below the limit if the flow is restricted from the inside coils. It Will reflect us by measuring pressure between the delivery line and the liquid portion line.

Any heat pump needs to charge it as a specified limit. It is difficult for any technician to charge heat pump during heating mode. The calculation for charging refrigerant is critical in heating mode. The overcharging of the refrigerant leads to many unwanted problems in the system.

One of the primary cause of head pressure  to be high is the overcharging of the refrigerant.

High head pressure on heat pump

The high head pressure in any device deteriorates the performance.

It is difficult to find the fault of high head pressure in the heat pump during heat mode. The system should be adequately designed with specified coil sizes.

If the coil size is not as per design criteria, it is the main reason for the high head pressure in the system.

The airflow through the system should be enough as per requirement. It should be monitored periodically. It can be measured by finding static pressure in the system.

Insufficient airflow or restricted air can cause the problem of inefficient working. Cleaning of the coils is necessary for any systems discussed above. The filters should be cleaned well and replaced if they malfunction.

There are three service ports to measure the pressure. Take the reading of the pressure from all three ports in the system.

If we take a reading in the heating mode, we make sure that the larger diameter pipe is the delivery pressure and the smaller diameter pipe is the liquid pressure.

The pressure will fall below the limit if the flow is restricted from the inside coils. It Will reflect us by measuring pressure between the delivery line and the liquid portion line.

Any heat pump needs to charge it as a specified limit. It is difficult for any technician to assess the heat pump during heating mode. The calculation for charging refrigerant is critical in heating mode. The overcharging of the refrigerant leads to many unwanted problems in the system.

One of the primary cause of head pressure  to be high is the overcharging of the refrigerant.

Deepakkumar Jani

I am Deepak Kumar Jani, Pursuing PhD in Mechanical- Renewable energy. I have five years of teaching and two-year research experience. My subject area of interest are thermal engineering, automobile engineering, Mechanical measurement, Engineering Drawing, Fluid mechanics etc. I have filed a patent on "Hybridization of green energy for power production". I have published 17 research papers and two books. I am glad to be part of Lambdageeks and would like to present some of my expertise in a simplistic way with the readers. Apart from academics and research, I like wandering in nature, capturing nature and creating awareness about nature among people. Let's connect through LinkedIn - https://www.linkedin.com/in/jani-deepak-b0558748/. Also refer my You-tube Channel regarding “Invitation from Nature”

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