Now that cold weather has settled in on most of us, are you finding that your head pressures on some of your refrigeration equipment have gone south?

Here in the Technical Support department at ICOR, when the weather cools down, some of the calls we receive on refrigerant related issues will ultimately end up being a head pressure problem on an air cooled condenser. It may take us a few minutes to come to this conclusion, but after some persistent questioning we’re usually discussing a head pressure issue. When the ambient drops below design temperature of the condenser, head pressure will usually drop with it. When head pressure is too low, the results are typically the same on most equipment. You can see both run-cycle and off-cycle problems. Liquid line pressures can be low enough to cause insufficient feed to the evaporator. Low head pressure can also cause problems on equipment that is designed with hot gas defrost.

There are a few ways to compensate for this problem, and trust me, just about all of them can fail or break. The most common components to control head pressure are condenser fan cycling controls, ORI, ORD, and OROA valves. If a technician is not familiar with these components, and one of them is not working correctly, then his or her work day just got a little more interesting.

A condenser fan cycling control is probably the easiest of these components to trouble shoot, especially on a single condensing unit system with one or two fans. If you walk up to this type of system when it’s 30deg. outside and the condenser fan or fans are running continuously, then look at the fan control. More than likely it is broken, stuck, or not adjusted correctly. Easy enough to troubleshoot and repair.

The ORI, ORD, and the OROA valves can be a little more difficult to troubleshoot when they aren’t working correctly, especially if you’re not familiar with how they operate or what their function is. My purpose is not to explain how each one of these components operate, but to make you aware that they can fail and cause head pressure problems. If you’re working on a system and suspect one of these components not working correctly, give us a call on our Tech to Tech line. We’ll be glad to help if you’re not sure what’s going on.

One of the more common mistakes a technician will make when finding a system with low head pressure is to add refrigerant. This will inevitably cause more problems, now that the system has been overcharged. Once the head pressure control is found to be the problem, remember to recover the excess gas from the system. If you don’t do it while you’re there, you’ll be back to do it when the weather warms up.

The bottom line here is to get to know the equipment you’re working on and understand what all the components are designed to do. Head pressure is important in every system. Knowing how to control it is just as important.

This is a dialogue, so if you have any questions, don't hesitate to e-mail me at
DCallender@icorinternational.com. Till next time,

Dave