Everything About Semi-Hermetic Compressors
Semi-Hermetic compressors are one of the most popular compressor types currently available. They differ in several key ways from the other compressor types which makes them a more viable option for certain situations.
Semi-Hermetic compressors are compressor types that house the motor alongside the compressor but have an accessible chamber that can be opened for repairs and routine maintenance. A Semi-Hermetic compressor can be thought of as the step between an open compressor, in which the motor is not located with the compressor, and a Hermetic compressor, where the motor and compressor are both sealed in a chamber and impossible to access.
This guide will focus on the different semi-hermetic compressor types and the ways that they are utilized. This information can help you better understand the benefits of a Semi-Hermetic compressor over the Open and Hermetic types.
Difference Between Open, Hermetic, and Semi-Hermetic Compressors
The difference between open, hermetic, and semi-hermetic compressors refers to the way that the engine is housed in the compressor. With an open compressor, the engine and compressor are not housed together, meaning that both are easily serviceable.
As this guide will indicate, a semi-hermetic compressor has an accessible chamber that houses the engine within the compressor, allowing for easy access for repairs and maintenance. This is the most common type of compressor, as it is the preferred design for more situations.
A hermetic compressor has the engine components completely sealed within the compressor. This means that you will not be able to access these components for service or repairs. This will cause you to have to replace your entire compressor if an issue arises with the engine.
All three of the compressor types can be found in five build varieties that will be detailed later in this guide.
Ultimately, the best choice will depend on your situation. You can use the information in this guide to find out more about the different types of compressors and how you can benefit from using a semi-hermetic compressor type.
Semi-Hermetic Compressor Types
The five main types of Semi-Hermetic compressor types are reciprocating, rotary, centrifugal, screw, and scroll. All of these compressor types can be found in Semi-Hermetic styles and have their own unique designs.
These designs will be detailed in the section below. You can use this information to better understand the different types of Semi-Hermetic compressors and the different ways that they function.
Reciprocating
A reciprocating compressor operates by a reciprocating function involving the piston within the cylinder. The piston works to compress the refrigerant as the piston works its way down to create a vacuum. This will cause the pressure to rise above the intake valve which will force it to open and suck the refrigerant into the cylinder.
Once the piston reaches the bottom, it will begin to move upward again, causing the intake valve to close. This will trap refrigerant inside the cylinder and cause it to compress. The pressure will then begin to rise and then be expelled through the exhaust valve of the cylinder.
Rotary
A rotary compressor uses a roller to compress the refrigerant by rotating within the cylinder. As the roller rotates around the shaft, it will remain in contact with the wall of the cylinder. This process will cause the refrigerant to become compressed as the space inside the cylinder is reduced.
Once the exhaust valve becomes exposed after coming into contact with the roller, the high pressure will be released through the exhaust valve. Rotary compressors are extremely efficient as the process of taking in refrigerant and compression happen simultaneously.
Centrifugal
A centrifugal compressor uses an impeller wheel that rotates to create centrifugal force to apply to the refrigerant. The refrigerant is sucked into the impeller wheel by a wide circular intake flowing between the impellers.
This will cause the refrigerant to become more pressurized as it is forced against the sides of the chamber. This is one of the most common ways to utilize compressed gas as there are few moving components and little room for error in the internals of the compressor.
Screw
A screw compressor uses two offset spiral disks to compress refrigerants. The disks that are located in the uppermost position will remain stationary while the bottom disk circles around continuously. This motion will cause sealed spaces to appear in the chamber.
The refrigerant will be forced into these sealed spaces and compressed until finally it is discharged through the center of the disks.
Scroll
Scroll compressors use an orbiting scroll to compress gas and refrigerants. The orbiting scroll is powered by an electric motor that rotates a shaft within the chamber. This will cause the gas to be captured between the fixed and orbiting scroll. Scroll compressors are considered the quietest and smoothest operating machines out of the five main types of compressors.
Semi-Hermetic Compressor Price
You can purchase a 5HP Semi-Hermetic for anywhere between $1800 to $5200, depending on the type of compressor you purchase. You can expect to pay much more for a Semi-Hermetic compressor with more HP.
A semi-hermetic compressor is a good investment, as it can be easily serviced and repaired. With the proper maintenance, your purchase could last you up to 15 years. You should shop around different dealers to ensure that you get the best price for your semi-hermetic compressor.
The table below contains the average prices for each type of Semi-Hermetic Compressor for the 5HP model.
You can expect the price to scale appropriately when purchasing compressors with higher HP. This information can help ensure that you are paying the average price for a semi-hermetic compressor.
| Semi-Hermetic Compressor Type | Avg. Cost (5HP) |
| Reciprocating | $1800 |
| Rotary | $3600 |
| Centrifugal | $4800 |
| Screw | $3200 |
| Scroll | $2800 |
Semi-Hermetic Compressor Uses
Semi-Hermetic compresses are best used in commercial or industry settings, such as a large warehouse or storefront. They are also well suited for large air condition systems that cover a very wide range such as a whole business or shopping mall.
Hermetic compressors on the other hand are more suited for domestic uses, such as refrigeration and home air conditioning systems. Semi-Hermetic compressors are better suited for large-scale use because they are much easier to access for repairs and routine maintenance.
Because of this, you will likely come across many more semi-hermetic compressors being used while you are out. They are commonly used to provide air conditioning for storefronts and businesses as well as provide compressed air for large warehouses and work areas.
Semi-Hermetic Compressor Lifespan
A semi-hermetic compressor will last for around ten years. A well-maintained semi-hermetic compressor can last up to 15 years with the proper care. Because of the ease of maintenance that comes with owning a semi-hermetic compressor, there are many more chances for repair before encountering an issue that will cause you to replace your compressor.
The average lifespan for a hermetic compressor is five years maximum. Because you cannot service the internals of a hermetic compressor efficiently, this will lead to more chances of your compressor breaking down and becoming unserviceable. When this happens, your hermetic compressor will have to be replaced.
This makes semi-hermetic compressors the best option when it comes to longevity. The option to service your compressor will extend its lifetime far beyond that of a hermetic compressor of the same type.
Semi-Hermetic Compressor Vs Scroll
A semi-hermetic scroll compressor is a better option than a hermetic scroll compressor. Since a scroll compressor can be found in both hermetic and semi-hermetic types, choosing the right type for your situation can save you money and hassle.
A semi-hermetic scroll compressor will be cheaper than a hermetic scroll compressor. You can purchase a semi-hermetic scroll compressor for around $2800 for a 5HP model. A hermetic scroll compressor will cost closer to $3600 for a 5 HP unit.
This makes the semi-hermetic scroll compressor the better option when it comes to cost. A semi-hermetic scroll compressor will also last longer due to the ability to repair the internal components using the removable chamber.
That being said, a semi-hermetic scroll compressor is much less compact than a hermetic scroll compressor and is a less viable option for home use. If you are planning on using your scroll compressor for mainly domestic purposes, you will likely do better with a hermetic scroll compressor.
The table below contains detailed comparison information regarding the two types of scroll compressors. You can use this information to help you pick the right scroll compressor type for you.
| Data | Hermetic Scroll Compressor | Semi-Hermetic Scroll Compressor |
| Size | Compact, fit for domestic use | Bulky, not fit for domestic use |
| Seal Type | Weld | Bolt |
| Cost (5HP) | $3600 | $2800 |
| Serviceable | Not Serviceable | Serviceable |
| Lifespan | 5 years | 15 years |
Hermetic Vs Semi Hermetic Compressor
A semi-hermetic compressor is the better choice if you are using your compressor for a large area such as a warehouse or shopping center. If you are using your compressor for mainly domestic purposes, then you will likely be better suited with the hermetic style compressor.
The list below will break down some of the factors that highlight the benefits of both types of compressors so that you can choose which one is right for you.
Hermetic Vs Semi-Hermetic Compressor Price
A semi-hermetic compressor is cheaper than a hermetic compressor. You can generally purchase a 5 HP semi-hermetic compressor for anywhere between $1800 to $5200, depending on the type of compressor.
A hermetic compressor can be purchased for anywhere between $2600 to $7000, depending on the type. This makes a semi-hermetic compressor a much more cost-efficient option to consider. You can use the table below to compare the prices of the different compressor types when purchased in both hermetic and semi-hermetic forms.
| Compressor Type | Avg. Hermetic Type Cost (5HP) | Avg. Semi-Hermetic Type Cost (5HP) |
| Reciprocating | $2600 | $1800 |
| Rotary | $4600 | $3600 |
| Centrifugal | $5800 | $4800 |
| Screw | $4500 | $3200 |
| Scroll | $3600 | $2800 |
Hermetic Vs Semi-Hermetic Compressor Lifespan
A semi-hermetic compressor will also last several years longer than its hermetic counterpart. A well-maintained semi-hermetic compressor can last up to 15 years. This is much longer than the 5 years that a hermetic compressor is expected to last.
Because a hermetic compressor is not serviceable, this makes them much more prone to internal issues that will cause them to be replaced much more frequently. When a semi-hermetic compressor is experiencing internal issues, it can easily be serviced via the accessible chamber that house both the engine and compressor.
Hermetic Vs Semi-Hermetic Compressor Uses
A hermetic compressor is commonly used for domestic purposes such as refrigeration and home air conditioning while a semi-hermetic compressor is best utilized for use in large spaces like warehouses or shopping centers.
Because of the size of hermetic compressors, they are the perfect fit for small-scale compression purposes. Semi-hermetic compressors are most commonly used in large-scale units where serviceability is a priority.
Hermetic Vs Semi-Hermetic Compressor Comparison Table
The table below contains information regarding both types of compressors. You can use this information to compare the different compressor types so that you can make an informed choice when deciding which is right for you.
| Data | Hermetic Compressor | Semi-Hermetic Compressor |
| Size | Compact, fit for domestic use | Bulky, not fit for domestic use |
| Seal Type | Weld | Bolt |
| Cost (5HP) | $2600 to $7000 | $1800 to $5200 |
| Serviceable | Not Serviceable | Serviceable |
| Lifespan | 5 years | 15 years |
| Uses | Home Refrigeration, Home Air Conditioning | Large warehouse refrigeration or air conditioning |
Final Thoughts
This guide has provided you with all of the information you need to better understand the benefits of a semi-hermetic compressor. As this guide indicates, the main difference between a hermetic and semi-hermetic compressor is the accessible chamber that allows access to the internals of the machine.
Having access to both the engine and compressor of your system will allow you to properly maintain and repair your compressor. This will lead to a longer overall lifespan for your compressor as well as ensure that you can maintain it properly to keep it running efficiently.
This guide has also covered all of the five main compressor types that you can find in semi-hermetic form. You can use this information to choose which of the compressor types is right for you.
