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I started writing HVAC (Heating Ventilating Air Conditioning) automation code, wrongly I might add, back in 1988. Your code is likely written wrong today. It wasn’t my fault then and it’s not the fault of new code programmers now. We simply don’t know any better when we begin.

We are set in front of a computer screen to assemble DDC (Direct Digital Code) modules written by a developer with little actual industry experience. Let me give you one example…

A duty cycle module monitors the percentage of heat call. A 50% call runs the heat for six minutes (out of twelve),then the call stops. You check the heat and it’s off but still calling 30%, so you start through the usual paces. Stop… you’re likely in the ‘off’ cycle. Test the heat directly. If it works by jumping R to W, you don’t have to wait.

So here are some facts. Public comfort is different than hospitality comfort. Heat and Cool cycles are the least comfortable times. Electronics (DDC systems) are faster than pneumatics (air systems) and that’s why they fail sooner. Analog control is more comfortable than digital (on/off) control. More economizer control equals more savings and more comfort. And healthy buildings don’t suck.

Here’s some help if you are a young HVAC programmer. Listen and learn from the mechanics, the balancer and the engineer. Look at the plan and notice that slightly more air is made up than exhausted and effort to understand why. Slow down DDC control as much as you can… three cycles per hour is more comfortable and more cost effective than six. Less cycles means longer equipment life.

With proper programming and maintenance you can save tons of money in the spring and the fall. I will provide featured articles that will explain how.

All control problems are finitely discoverable if you consider the disciplines at play. There’s no magic to be afraid of. A single unit can be out of phase with fifty others. A dirty wire nut connection can limit the maximum frequency of a variable frequency drive (VFD). Brown outs cause ghosts. This is my thing.