Functional Testing and Phase Sequence

<h2>Functional testing</h2>
<p>After all dead and live tests are complete, functional testing verifies that switchgear, controls, interlocks, and equipment operate correctly. This is the final check before the installation is handed over.</p>

<h2>What to check</h2>
<ul>
<li><strong>Main switch</strong> — operates correctly and isolates all live conductors</li>
<li><strong>RCDs</strong> — test button operates the trip mechanism</li>
<li><strong>MCBs and fuses</strong> — operate and reset correctly</li>
<li><strong>Interlocks</strong> — verify they prevent unsafe conditions</li>
<li><strong>Emergency stops</strong> — operate and latch correctly where fitted</li>
<li><strong>Time switches and programmers</strong> — advance through settings and switch correctly</li>
<li><strong>Luminaires and controls</strong> — light, dim, switch as intended</li>
</ul>

<h2>Phase sequence testing</h2>
<p>Three-phase installations require verification that phases are connected in the correct sequence (L1, L2, L3 — clockwise rotation). Incorrect phase sequence causes:</p>
<ul>
<li>Three-phase motors to run in reverse</li>
<li>Equipment damage</li>
<li>Interlock failures</li>
</ul>
<p>A phase sequence indicator (or MFT with phase rotation function) is connected to the three line conductors. The result is displayed as clockwise (correct) or anticlockwise (incorrect). If incorrect, swap any two phase conductors at the supply point.</p>

<h2>Key exam points</h2>
<ul>
<li>Functional testing is the LAST stage of initial verification</li>
<li>RCD test button tests mechanism only — not electronic sensitivity</li>
<li>Phase sequence: clockwise = correct. Anticlockwise = swap any two phases.</li>
<li>Record all functional test results on the Schedule of Test Results</li>
</ul>