First of all, lets quickly define a "slip-in". A Slip-in or under-the-hooder, what ever other nick name you have for it, is a straight forward unit replacement, nothing fancy, take one out, put a new one in and be on your way as quickly as possible. Little to no duct modifications or transitions, return drop lines right up, and electric and venting is just as easy. Crank up (or down) the thermostat and let'r rip!. For decades we loved them, and made good money at it. However, the way we were able to get away with not commissioning the new system properly, is now biting us in the rear. 

I would also like for us all to realize that, there is no equipment manufacture out there, purposely building junk equipment. They cant afford too. Everyone of them wants, and needs market share, and they do not want to go bankrupt or out of business. They will however, try to cut costs in manufacturing. Which can lead to some failed small parts here and there or even thinner sheet metal. Never the less, they still have safety standards, efficiency standards and rules of science that they must follow. All confirmed usually by third party testing and verification. 

As Jim Bergmann put it, Our industry is "bound-by-physics". 

Equipment is changing, and changing frequently. The tolerances are getting tighter (as they should be), and because of that, we as technicians are now forced to be held accountable for what we do. We also must become better at what we do. This means that we truly need to "Commission" or "Set-up" the equipment we service or install.  

Did you know that, although some manufactures are test-firing every piece of equipment on the line, they do not make an adjustment to the gas pressure? 40 years ago maybe, but this has not been done by any manufacture that I am aware of in quite some time. All they do is make sure it starts up and shuts off, that's it. It is up to us to properly adjust and set. Its in the manual even. 

Airflow is another thing we had little concern with back in the day. If a customers furnace hit limit, we only then, checked the gas pressure and related it to a dirty, or too restrictive filter. Sometimes we would even be lucky enough to work on a furnace that had an adjustable limit. To "fix" the issue, we just cranked it up!, and then said, "it must be getting old".  We never really diagnosed or tested anything. If the filter change helped, we billed them and left. We got away with this because we got lucky, and the units back then could handle the abuse. We didn't need to measure airflow back then, why? "because the curtain is moving, and the toilet paper is blowing off the roll, the airflow has to be good!.... And look, we gained 4 degrees in 2 minutes, without hitting limit man...... this furnace works great!!" 

With tighter tolerances, efficiency and customer comfort in mind, as well as our reputation as a company, we really must start commission the equipment properly. Actual start-up sheets or reports, equipment sizing, measuring airflow, external static pressure, adjusting gas pressure, checking flue temperatures, vent lengths and sizes, clocking gas meters, checking super-heat and sub-cooling, motor and compressor amp draws, verifying electrical connections and systems. All the things.

We don't "need" 200 degree air to keep us or the home warm, realistically, 120 degree air is all we need. We don't "need" ice cold AC to keep the house cool, or us comfortable in the summer.

Just imagine the number of call-backs we could eliminate, or even the impact we would have on the energy grids if we just started doing it right. Just imagine if we had been doing this all along. Just because we got away with it, doesn't make it right, or "Good".   

And that is your Marksman Minute.