Considering how winter conditions reveal strengths and weaknesses in refrigeration systems.

It’s that time of year again. Later this month ASHRAE will gather in Chicago, and we will hurry from hotel to conference hall or convention center trying to keep out of the cold as best we can. If you have to “winterize” your plant, I hope you have already done so; otherwise, it’s probably too late.

For large industrial systems, this usually involves draining the sumps of evaporative condensers and running them dry. In summertime, this would be a huge energy penalty, but it is a quirk of evaporative cooling that as the air gets cooler its ability to pick up moisture is reduced and so the effect of running a condenser dry in an ambient temperature of 32°F (0°C) is not as extreme as it would be at 95°F (35°C).

The lack of resistance to airflow caused by the removal of the spray water can increase the volume of air pushed through the condenser, resulting in higher fan amps and helping to offset the dry running performance hit. If the condenser doesn’t have a remote sump, then it’s important to check that the makeup water lines and the condenser water pump are properly insulated and trace heated, ensuring that the fuses on the trace heating circuit are sized for the current inrush that will occur on a cold start, for example after a power outage when the heater tapes are all cold.

Aside from evaporative condensers, there are many other elements of industrial systems that need to be ready for winter. Ensure that fan and motor bearings have suitable low temperature grease and other moving parts on the exterior are appropriately prepared, such as air dampers or automatic doors. Make sure that essential water supplies are insulated and trace heated, particularly for emergency showers, sprinkler systems and other utilities that are not often in use. You need them to work when you need them.

Check that all lighting is in good order, especially outdoor areas and parts of the building with natural light. Make sure that emergency lighting is also functional. It’s also a good time to stock up on small spare parts that might be needed to keep the plant running just at the time that deliveries are unreliable, for example fuses, solenoid coils, spare gaskets or O-rings and valve repair kits.

It’s also a good time, although it might seem odd to say so, to take a long hard look at the performance of your defrost system. If the ambient drops below 5°F (-15°C) and stays there for days or weeks then you may not have to defrost at all. If you are running defrosts on a timed schedule then you will be wasting a lot of energy. If you can valve off the hot gas supply to the defrost valve stations, it would be interesting to see how much energy is saved per day. This is a good indication of service work that needs to be scheduled before the warm weather comes back if you are serious about reducing your energy bills.

As I said at the top of the column, if you haven’t already done all this then it’s probably too late. Happy New Year!