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. This article sets out what the three terms mean, which temperature ranges they correspond to, and where to read them on the datasheet.
One idea underneath all three: evaporating temperature
Embraco associates the three markings with the level of evaporating temperature the compressor is applied at. “Back pressure” means suction pressure:
- LBP: low back pressure; low evaporating temperatures
- MBP: medium back pressure; medium evaporating temperatures
- HBP: high back pressure; high evaporating temperatures
According to Embraco, freezers work with low evaporator temperatures between −35 °C and −25 °C, while dehumidifiers remain above 0 °C.
Temperature ranges and where each is used
According to Embraco, the classes are used as follows.
| Class | Typical applications |
|---|---|
| LBP | Freezers, refrigerators, storage cabinets |
| MBP | Beverage and self service display cabinets |
| HBP | Coolers, dehumidifiers, air dryers |
The exact temperature range is stated in the datasheet for the individual model. Embraco also notes that this naming depends on the compressor manufacturer and may change, and that models combining two classes (such as L/MBP) are very common.
Even under the same class name the range differs from model to model. In the Cubigel datasheets in our catalogue, LBP models are given the following ranges:
- −40 °C to −10 °C: Cubigel NUT 55 CA, NUT 60 CA, NPY 14 LAa and NST 34 LA-T
- −35 °C to −15 °C: Cubigel GL 55 AA and HYE 131 MHUa
- −35 °C to −10 °C: Cubigel HYE 125 MHU
LMBP (low-medium back pressure) is an intermediate class that appears in Cubigel datasheets with a range of −40 °C to 0 °C (for example the NUF 45 NA). For HBP models, the GU 60 TG datasheet gives −15 °C to +10 °C. So not every catalogue will contain exactly three classes.
The boundaries differ for another manufacturer too: the table in Tecumseh’s service handbook gives the low temperature range (high torque motor) 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
The Tecumseh hermetic compressor service handbook puts it this way:
Hermetic compressors are designed for a particular evaporator temperature range and a specific refrigerant. Compressors that are operating outside their design evaporator temperature range can be expected to have poor pumping efficiency and experience motor problems.
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”. The original datasheet of a model opens from the datasheet link on its 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 beside the capacity figures, and the evaporating temperature there (−23.3 °C or +7.2 °C, for instance) tells you which operating point that capacity was quoted for.
The COP (capacity / input power) of a model can be calculated from its capacity and input power tables, and it changes with evaporating temperature. In the Zingfa QL3-74 datasheet, at 45 °C condensing, −25 °C evaporating gives 3,653 W / 2,075 W = 1.76 and −15 °C evaporating gives 6,542 W / 2,923 W = 2.24 (the calculation is ours).
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 GL 55 AA R134a | LBP | −35 °C to −15 °C |
| Cubigel HYE 125 MHU R600a | LBP | −35 °C to −10 °C |
| Cubigel HYE 131 MHUa R600a | LBP | −35 °C to −15 °C |
| 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
The class and the capacity are separate pieces of information:
- The class (LBP / MBP / HBP) shows the evaporating temperature range the compressor is designed for.
- The capacity (HP or watts) shows the cooling power quoted under specific test conditions.
The capacity tables in the datasheets are built that way: 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. According to Embraco it is associated with low evaporating temperatures and used in freezers, refrigerators and storage cabinets.
- What is the difference between MBP and HBP? According to Embraco, MBP suits medium evaporating temperatures (beverage and self service display cabinets); HBP suits high evaporating temperatures (coolers, dehumidifiers, air dryers).
- Can I use an MBP compressor in a freezer? According to Tecumseh’s service handbook, compressors operated outside their design evaporator temperature range can be expected to have poor pumping efficiency and motor problems. Check the class of the model in its datasheet.
- Where is this stated on the datasheet? In Zingfa and Cubigel datasheets, in the “Application” line on the first page.
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. For product information, contact TURA Soğutma.