What a good RTU startup report includes

A startup report has one job: prove the unit was started the way its manufacturer says, and that it is running right. Checkmarks say the steps were done. Readings prove the result. A good rooftop unit report has both, and puts the readings first.

Here is what a commissioning provider looks for in an RTU startup report, part by part, and why each part is there.

1. Who, what and where

Project, unit tag, location on the roof, manufacturer, model and serial number, the technician's name and the date. It sounds obvious, but a report that says "RTU" with no tag can't be matched to a unit, and a report with no date can't be matched to the schedule.

A photo of the nameplate settles more questions than anything else on the sheet.

2. Nameplate data

Copy these from the unit, not from the submittal:

• Voltage and phase
• Minimum circuit ampacity (MCA) and maximum fuse or breaker size (MOCP)
• Compressor RLA and LRA
• Supply fan motor FLA and horsepower
• Refrigerant type and factory charge

Running amps mean nothing without the nameplate numbers on the same page. Neither do pressures without the refrigerant type.

3. Pre-start checks

These are the checklist items. They matter, but they back up the readings rather than replace them.

• Unit set level on the curb, curb sealed
• Shipping brackets and blocks removed
• Electrical connections tight, unit grounded, disconnect installed
• Filters installed
• Condensate trap installed and primed
• Belt tension and alignment checked
• Crankcase heater energized for as long as the manufacturer calls for before the compressor runs
• Gas piping leak tested, drip leg installed
• Fan rotation correct

4. Electrical readings

With the unit running, record supply voltage on all three legs (L1 to L2, L2 to L3, L1 to L3) and work out the voltage imbalance: the largest difference from the average, divided by the average. Most manufacturers want it under 2 percent. Then record running amps for each compressor and the supply fan motor, and compare them to the nameplate RLA and FLA.

5. Cooling readings

This is the heart of the report. Record, after the unit has run long enough to settle:

• Outdoor air temperature
• Entering and leaving air temperature at the unit, and where each was measured
• Suction pressure and suction line temperature, which give superheat
• Liquid (or discharge) pressure and liquid line temperature, which give subcooling

Write down the pressures and temperatures, not only the superheat and subcooling. With only the results, nobody can check the math. Our guide to superheat and subcooling in plain words walks through how to take them.

6. Heating readings

For gas heat: inlet gas pressure, manifold pressure, and the temperature rise across the heat exchanger, which should fall inside the range printed on the unit's rating plate. Add flue gas readings if the project specification asks for them. For electric heat: amps on each stage. For a heat pump: the heating mode pressures and temperatures, as the manufacturer lists them.

7. Controls and economizer

Thermostat or building automation connection working, setpoints entered, economizer dampers stroking through their full range with the minimum outside air position set, and safeties tested: high and low pressure switches, limits, and the smoke detector shutdown if one is installed.

8. Notes, photos and sign-off

Anything that wasn't right and what was done about it. Photos of the nameplate and the gauges. A signature with a printed name and the date. A deficiency written down at the unit is worth ten remembered later.

The three gaps that send reports back

The gap	Why it comes back
Pressures with no conditions	No outdoor or entering air temperature, so the pressures can't be judged.
Results with no readings	"Superheat 10" with no pressure or line temperature behind it can't be checked.
Checkmarks with no numbers	Every box ticked and no readings. It shows steps were done, not that the unit runs right.