What is the first thing a technician needs to know about the system he is trying to troubleshoot?
How the system is supposed to operate.
What are eight pieces of information needed to diagnose a system problem?
1. Ambient temperature entering the condenser
2. Condenser temperature
3. Condenser split
4. Condenser subcooling
5. Refrigerated space temperatures entering the evaporator
6. Evaporator temperature
7. Evaporator TD
8. Evaporator superheat
If warm product is added to a box how do the evaporator temperature and pressure respond?
The temperature and pressure rise.
Why does raising the temperature of refrigerant raise its pressure?
The added heat makes the refrigerant boil faster.
If the evaporator is covered in frost, dirt, or the fan motor stops how do the evaporator temperature and pressure respond?
The evaporator temperature and pressure fall.
If warm product is added to a box how do the condensing temperature and pressure respond? Why?
The condensing temperature and pressure rise because the evaporator heat causes the condensing pressure to rise more than normal to reject the additional heat.
If the evaporator is covered in frost, dirt, or the fan motor stops how do the condensing temperature and pressure respond? Why?
The condensing temperature and pressure both fall, because there is little or no heat being picked up from the evaporator.
What is the pressure drop across a metering device using R404A if the condensing temperature is 110� and the evaporator temperature is 25�?
210 PSIG
If the ambient temperature entering the condenser increases from 70� to 90�, will the condensing temperature increase? Why or why not?
Yes. The condenser split is a constant value, therefore an increase in ambient increases the condensing temperature.