diff --git a/add_installation.php b/add_installation.php
index 25f3c34..d0ade99 100644
--- a/add_installation.php
+++ b/add_installation.php
@@ -8,9 +8,9 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
     $technician_name = trim($_POST['technician_name'] ?? '');
     $observations = trim($_POST['observations'] ?? '');
     $status = trim($_POST['status'] ?? 'ativo');
-    $voltage = trim($_POST['voltage'] ?? null);
-    $phase_neutral_ground = trim($_POST['phase_neutral_ground'] ?? null);
-    $breaker_output = trim($_POST['breaker_output'] ?? null);
+    $voltage = !empty($_POST['voltage']) ? trim($_POST['voltage']) : null;
+    $phase_neutral_ground = !empty($_POST['phase_neutral_ground']) ? trim($_POST['phase_neutral_ground']) : null;
+    $breaker_output = !empty($_POST['breaker_output']) ? trim($_POST['breaker_output']) : null;
 
     // Validation removed to allow incomplete forms