What Do LBP, MBP and HBP Mean on a Compressor?
Open the datasheet for any compressor and, right beside the model and refrigerant, you will find a three letter marking: LBP, MBP or HBP. It tells you which refrigeration application the compressor was built for, and in selecting the right model it matters as much as capacity does. This article sets out what the three terms mean, which temperature ranges they correspond to, and how to tell which one suits your system.
One idea underneath all three: evaporating temperature
All three markings describe the same thing: the evaporating temperature range the compressor is designed to work in. Refrigerant evaporates in the evaporator and returns to the compressor, and the lower the temperature at that point, the lower the suction pressure. That is where the term “back pressure” comes from:
- LBP is low back pressure
- MBP is medium back pressure
- HBP is high back pressure
A freezer runs at a low evaporating temperature and therefore falls into the LBP class, while a dehumidifier runs at a far higher temperature and falls into HBP.
Temperature ranges and where each is used
Broadly, the classes are used as follows.
| Class | Typical applications |
|---|---|
| LBP | Freezers, refrigerators, storage cabinets |
| MBP | Bottle coolers, self service display cabinets |
| HBP | Coolers, dehumidifiers, air dryers |
The exact temperature range is stated in the datasheet for the individual model, because manufacturers do not define these boundaries identically. Embraco notes in its own technical writing that the naming can vary from one manufacturer to another.
As an example, the approved evaporating temperature ranges given in the datasheets for the Cubigel and Huayi models in our catalogue are as follows.
- LBP models: −40 °C to −10 °C
- LMBP models: −40 °C to 0 °C
- HBP models: −15 °C to +10 °C
LMBP (low-medium back pressure) here is an intermediate class used by some manufacturers, covering both the low and the medium range. So not every catalogue will contain exactly three classes.
The boundaries shift a little with a different manufacturer. The table in Tecumseh’s service handbook gives the low temperature range as −40 °F to +10 °F (roughly −40 °C to −12 °C) and the medium temperature range as −10 °F to +30 °F (roughly −23 °C to −1 °C).
Why it matters
A compressor is designed to run most efficiently within a particular temperature range. Tecumseh’s hermetic compressor service handbook makes the point directly:
A hermetic compressor is designed for a specific evaporator temperature range and a specific refrigerant. Run one outside its design evaporator temperature range and poor pumping efficiency and motor problems can be expected.
In practice that means using an MBP class compressor in a freezing application can leave the system never reaching the target temperature, with the compressor running continuously and the motor under strain. Even where the capacity (HP) is right, the wrong class means the system will not behave as expected.
How to find the class of your own compressor
The most dependable source is the datasheet for that model. In Zingfa and Huayi/Cubigel datasheets it appears on the first page in the “Application” line, written as, for example, “Low back pressure” or “Medium/high back pressure”.
On the TURA Soğutma website, the original manufacturer datasheet (PDF) is downloadable from every product page.
Reading the “Application” line alone is not always enough: the performance data shows the conditions under which it was measured. Datasheets carry a test condition table beneath the capacity figures, and the evaporating temperature there (−23.3 °C or +7.2 °C, for instance) tells you which operating range that capacity was quoted for. Models measured at a low evaporating temperature show a markedly lower COP. Where you are unsure, ask our sales team.
Examples from our catalogue
The information below is taken from the datasheet published by each manufacturer.
| Model | Class | Evaporating temperature (from the datasheet) |
|---|---|---|
| Cubigel NPY 14 LAa R290 | LBP | −40 °C to −10 °C |
| Cubigel NST 34 LA-T R290 | LBP | −40 °C to −10 °C |
| Cubigel NUT 55 CA R290 | LBP | −40 °C to −10 °C |
| Cubigel NUT 60 CA R290 | LBP | −40 °C to −10 °C |
| Cubigel HYE 125 MHU R600a | LBP | −23.3 °C (test condition) |
| Cubigel HYE 131 MHUa R600a | LBP | −23.3 °C (test condition) |
| Cubigel NUF 45 NA R290 | LMBP | −40 °C to 0 °C |
| Cubigel NUF 70 NA R290 | LMBP | −40 °C to 0 °C |
| Cubigel NUF 80 NA R290 | LMBP | −40 °C to 0 °C |
| Cubigel NUY 120 NAa R290 | LMBP | −40 °C to 0 °C |
| Cubigel GU 60 TG R134a | HBP | −15 °C to +10 °C |
For any other model, open the datasheet on the relevant Cubigel or Zingfa product page and read the “Application” line.
Do not confuse it with capacity
A common mix up is treating the LBP/MBP/HBP class as the same thing as capacity. They are two separate decisions:
- The class (LBP / MBP / HBP) sets the temperature range the system will run in.
- The capacity (HP or watts) sets how much cooling is delivered at that temperature.
The right selection weighs both together. The capacity tables in the datasheets are built on exactly that logic: at a given condensing temperature, separate wattages are quoted for a range of evaporating temperatures.
Frequently asked questions
- What does LBP stand for? Low back pressure. It describes compressors built for freezing applications running at a low evaporating temperature.
- What is the difference between MBP and HBP? MBP is for medium temperature applications (bottle coolers, self service display cabinets); HBP is for applications running at higher evaporating temperatures (coolers, dehumidifiers, air dryers).
- Can I use an MBP compressor in a freezer? Manufacturers do not recommend running a compressor outside its design range: efficiency drops and motor problems can follow. Choose a model in the class that matches the application.
- Where is this stated on the datasheet? Usually in the basic specifications section on the first page, in the “Application” line.
For the other fundamentals of compressor selection, see our guide to hermetic compressors. For reading model and series codes, see the Cubigel compressor guide and the Zingfa selection guide.
TURA Soğutma holds deep stock of Cubigel and Zingfa compressors with technical support. If you are unsure which class and capacity suit your application, send us the details of the system.