Basic Roof Top Unit — Proper Stat-ups


Concluding my series on Basics – Proper Start-ups – I am ending with a post on Commercial Equipment Start-ups. A lot of this applies to residential equipment also and should be looked at with that also.  The best suggestion that I can make is it USE THE START-UP SHEETS that almost every manufacturer ships with their equipment, again, bot commercial and residential. This way you won’t miss anything and it will set a “base line” in case there are any warranty issues.

It has been proven that a well performed start-up (1) instills confidence in your customers, (2)identifies installation and application problems, and (3) reduces call backs and consumer complaints.

Too often, contractors just set a roof top unit and walk away without setting the unit up properly.  They think that the “factory” has done all of that for them.  You need to keep in mind that most manufacturers do “run test” all units before shipping but they do not know the specific job site requirements.  They do not know the duct system static pressure.  They do not know the inlet gas pressure. They do not know the actual voltage at the site.  Yes the unit has run at the factory, but it still needs to be set up for the  individual application that the units is being “applied” to.

When a unit is “started”, all the operating data should be recorded on a start-up sheet. Most manufacturers include a start-up sheet with their equipment or have them available on their website.  It is good to use these as it will help you remember what to check and what information to record.  The following is a very general check list of things to be checked when setting and starting a packaged roof top unit.

  • Check power supply to make sure it matches the unit name plate. If the    unit is a 208/230-volt unit, and the measured power is 208 volts, move the tap on the transformer to the 208-volt tap.
  • Check all electrical connections for proper tightness.
  • If the unit has a scroll compressor, check for proper rotation of compressor on 3 phase units. (On small units, blower is single phase so it could be turning correctly and the compressor could be running backwards.  On larger units with 3-phase blower motors, the compressor and motor are phased at the factory.)
  • Make sure all shipping braces and straps are removed.  Check the compressor for “tie downs” and mounting bolts.
  • Check incoming gas pressure. If “high pressure” gas; be sure reducing regulator is installed.  Be sure the reducing regulator has a proper vent installed on it to prevent water from getting in to it.
  • Make sure the air intake and vent hoods are properly installed with the top lip inside the cabinet to prevent water getting in behind the hood.
  • If the unit has an economizer, make sure the hoods are properly installed.  Check all the linkage for proper tightness.
  • Check and adjust settings for economizer operation and minimum position if the unit is so equipped.
  • Check belts for proper tension or blower speed.
  • Turn on the heat and check for proper manifold pressure to the burners and adjust as necessary.
  • Check temperature rise over heat exchanger, or use blower CFM charts provided by the manufacturer to make sure there is proper airflow.
  • Make sure trap is installed and primed  if they are needed.
  • Check refrigerant charge on each system.  Even in winter, it can be run for as few minutes just to make sure that it is working.
  • Replace all panels that were removed and be sure ALL screws are replaced in the doors.

This whole check out procedure should take approximately about an hour to complete on simple packaged units.  If this is properly performed, it will save many hours of warranty problems and possible re-calls on the job site.

As I stated at the start of this posting — a well performed start-up (1) instills confidence in your customers, (2) identifies installation and application problems, and (3) reduces call backs and consumer complaints.  Packaged units, as well as any HVAC equipment today, are not “plug and play”.  Each application is different and the unit needs to be set up for that application so it functions properly and provides the comfort to your end-user that it was designed to do.

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About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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