Continuing with my series on “Back to Basics” and concentrating on why Proper Start-up Procedures are necessary to assure proper running equipment, the next thing we need to examine is setting up PROPER AIR FLOW for both residential and commercial equipment.
As I have been “preaching” in this whole series, too many contractors still think equipment is “plug & play”! What they feel is that the unit comes from the factory set for the proper CFM for the tonnage or heating capacity of the unit. What they do not realize is, again, the manufacturer sets the unit up for a “nominal” CFM but they do not know the application or job duct work or job static pressure.
On residential furnaces, a lot of manufacturers are shipping the heating speed of the fan on HIGH (this moves the cooling speed to a “medium” setting). They are doing this in “self-defense” to keep units from tripping on limits. Now, the home owner complaint is the air feels too cold at the register. This is , at least, better that shortening the life of the furnace due to over heating” and usually causes the contractor to move the wires on the board to adjust the fan speed. Hopefully when they do this, they take the time to properly set it up based on the TEMPERATURE RISE through the furnace. (see Heating Season — Temperature Rise post).
Commercial units are probably the most “abused” when it comes to the idea of being set & run equipment. The contractor feels, since he is replacing a unit with the “same size” unit, all he has to do is pipe and wire and leave. What he forgets is that someone had to set up the original unit to work properly on that application. Now he has added a curb adapter, not even considering the added static pressure that causes, and never sets the CFM.
That alone is a problem, but, since most commercial units are belt drive blowers, was the belt tension ever checked? Was the pulley alignment ever checked to see if it moved in shipping? Are all the pulleys tight on their respective shafts? Is the drive pulley adjustment set screw tight? So, does the contactor take the time to set his new unit up to meet the job specification for both heating and cooling CFM?
Now, add in the use of FREQ DRIVES to meet some of the latest standards in the industry, matching CFM to heating stages and cooling stages, and there is no way that unit is “plug & play” anymore.
It is coming down to the fact that INSTALLERS either need to be trained to perform the proper start-up or the contractor needs to figure in his quote having a qualified/trained SERVICE TECH perform the start-up. Think of it a new car dealer prep. We all know this is part of a car’s selling price and it should be part of any new piece of heating or cooling or packaged equipment. Once we all realize this fact , then the necessity for proper start-up of any piece of equipment will become an integral part of any job.