New Install Doesn't Work: Commissioning Fault Tree

Why this matters

A brand-new install that will not run is a different animal from a service call on an old system. The component is almost never the problem - a new part is the least likely thing to be defective. The fault is almost always in how it was installed, connected, configured, or supplied. Diagnose a commissioning failure by suspecting the install first and the equipment last, and you find it fast.

Start here: think install, not failure

On an existing system that quit, parts wear out and you suspect them. On a new install, flip that instinct. Out-of-box failures happen, but they are rare. Work the install errors before you condemn new equipment, because returning good parts and re-ordering wastes days you do not have.

Confirm one thing first: was the install ever finished? A missed final step, an unmade connection, a setting never configured, will look exactly like a dead unit.

Step 1: is it getting what it needs to run

Every device needs supply - power, water, fuel, air, signal, whatever feeds it. Confirm the supply reaches the unit before anything else.

• If the supply is absent at the unit, trace back to the source. A breaker not turned on, a valve left closed, a disconnect open, a fuse pulled for the install and never replaced. This is the single most common new-install no-start.
• If the supply is present but wrong - low voltage, low pressure, wrong phase, reversed polarity - the install tapped the wrong source or wired it wrong. Compare the supply against the unit's nameplate requirement.

Step 2: are the connections right

New installs fail on connection errors more than any other cause.

• If wiring or piping is reversed, swapped, or mislanded, the unit may sit dead, run backward, or trip immediately. Verify every connection against the install diagram, terminal by terminal. Reversed polarity, swapped legs, crossed control wires, and supply/return reversed are the usual suspects.
• If a connection is loose or not fully made, it will read open or intermittent. Re-check seating and torque on everything that was landed during the install.
• If a required connection was simply never made, find it. A control wire left off, a ground not landed, a line not coupled.

Step 3: is it configured for this application

Modern equipment ships with settings, jumpers, dip switches, or programming that must match the job.

• If the unit is on default settings, it may be configured for a different application than the one it is installed in. Confirm the configuration matches what this install requires.
• If a required setup step was skipped - addressing, pairing, calibration, a sizing selection - the unit cannot operate correctly even though every connection is right.

Step 4: is the install mechanically correct

• If orientation, mounting, or clearance is wrong, the unit may refuse to start by design (a safety interlock) or fail under load. Confirm it is mounted, leveled, and clearanced per the install instructions.
• If a protective interlock is open because something is not in place (a panel, a guard, a sensor not in position), the unit will not run until the install satisfies it.

Step 5: only now, suspect the equipment

If supply is correct, connections are verified, configuration matches, and the install is mechanically sound, then and only then treat the unit as possibly defective. Test it the same way you would any component - against its nameplate, isolated if needed. Before you condemn it, swap in a known-good unit if you can; a clean swap that works proves the original was bad and clears your install.

Document the commissioning

Record the as-left readings - supply values, settings, performance numbers. This commissioning sheet becomes the baseline for every future service call on this system and turns later callbacks into fast comparisons.

References

• Manufacturer installation and commissioning instructions
• Trade-standard startup and acceptance-test procedures
• See related: Baseline vs Faulty Comparison Diagnosis Method
• See related: Callback: The Fix Didn't Hold