I spent much of this week with clients reviewing winter ventilation details and evaluating temperature logs from recorders placed in barns earlier this month. In every instance, I found mistakes in controller settings that cost producers a lot of money.
The most common mistake I saw was incorrect furnace temperature settings. The goal of furnace settings in the controllers is to turn off the furnace at a point relative to the controller settings so the variable speed fan(s) on stage 1 doesn’t increase speed as a result of the temperature probes delayed reaction to the furnace heat.
If the controller speeds up variable speed fans at 0.1F above the set point, the furnace should turn off about 2F below the controller set point. This week I saw controllers where the off temperature setting for the furnace was at or even above set point in this type of controller. This guarantees that every time the furnace operates, the fan(s) will speed up and unnecessarily remove some of the added heat. I have a temperature plot for 1 facility with pigs near market weight that indicates furnace operation, something that should never happen with a facility full of market weight pigs, especially at this time of year.
If the controller has a different set point relative to the controller set point for when stage 1 variable speed fans increase speed, the furnace should be set to turn off at 2F below this set point.