🔍 Key Concepts

• Evaporator pressure regulating (EPR) valve purpose in multi-box systems • Relationship between evaporator pressure, saturation temperature, and box temperature • Why different-temperature boxes can share one compressor without overloading it

💭 Think About

• Think about what would happen to the suction pressure and compressor load if the warmest box were allowed to run at very low pressure. • In a multi-temperature system, which coil (warmer or colder box) naturally wants to operate at higher evaporating pressure for its required temperature? • Is the purpose of the valve to protect the warmer coil from getting too cold, or to protect the colder coil/whole system from too much pressure and load?

✅ Before You Answer

• Identify which box (warmer vs colder) will normally have higher evaporator pressure for its set temperature. • Recall that an EPR valve is typically set to maintain a minimum evaporator pressure (and therefore a minimum temperature) for a given box. • Confirm whether the question is asking about minimum vs maximum pressure control and which evaporator group (warmer or colder) is being controlled.