Last updated: 19 Dec 2025
Source: Factory investigation (FG Thailand) – Kono
Applies to: AOTH30KBTA (T002472)
Known production example: 2024/04/08 (use unit serial/production date to confirm applicability)

1) Issue Summary

Some outdoor units may present abnormal vibration and noise when butyl rubber adhered to the discharge pipe makes contact with the dividing panel, creating resonance and panel vibration.


2) Symptoms (Customer Report / Technician Observation)

  • Outdoor unit produces abnormal vibration, rattle, or resonant noise

  • Noise may be intermittent or worsen under load (compressor operating / higher discharge temperature)

  • Noise can reduce/stop when cabinet pressure is applied (hand pressure test) or when pipe position shifts slightly

3) Root Cause

  • Butyl rubber protrusion / bonding position on the discharge pipe can reduce clearance.

  • If the discharge pipe + butyl rubber contacts the dividing panel, it can transmit vibration into the cabinet, resulting in abnormal noise.

Factory note: While workers are instructed on the bonding procedure, historically there was no downstream inspection focused on detecting butyl rubber protruding in a way that reduces clearance.

4) Inspection / Diagnosis (On-Site)

  1. Confirm symptom with unit operating (if safe and appropriate).

  2. Remove panels as required and visually inspect the discharge pipe area:

    • Look for butyl rubber on the discharge pipe contacting or very close to the dividing panel.

  3. Check clearance requirement:

    • General regulation: minimum 10 mm clearance between piping and dividing panel.

    • This model’s design clearance is typically ~20 mm, so a unit near 10 mm may be more susceptible.

  4. If contact marks exist (rub marks / witness marks on panel or butyl), treat as confirmed.



5) Resolution (Field Fix)

Corrective action: Move/reposition the discharge pipe to ensure the butyl rubber is separated from the dividing panel.

Acceptance criteria after adjustment

  • Clearance between butyl rubber (on discharge pipe) and dividing panel is ≥ 10 mm

  • Butyl rubber is pressed firmly with no gaps

  • Butyl rubber bonding position is correct (not protruding into the panel clearance zone)

  • Abnormal vibration/noise stops and unit operation returns to normal

Important: Do not create strain on brazed joints or introduce pipe stress. Repositioning must maintain safe pipe routing and support.

6) Preventative / Process Actions (Factory Countermeasure)

As of production from 9 Dec 2025, factory instructed operators to confirm during the first visual inspection:

  • Clearance ≥ 10 mm between butyl rubber on discharge pipe and dividing panel

  • Butyl rubber fully pressed with no gaps

  • Correct bonding position

This countermeasure is to be applied to other chassis where similar part-contact noise risk exists.



7) What to Capture in the Ticket (Mandatory)

When logging/escalating:

  • Model: AOTH30KBTA (T002472)

  • Serial number + production date (photo of nameplate)

  • Short video/audio of noise (before/after if possible)

  • Photos showing:

    • Butyl rubber placement on discharge pipe

    • Clearance to dividing panel (measure shown if possible)

    • Any witness marks/contact points

  • Confirmation of final clearance (≥10 mm) after adjustment

  • Outcome: noise eliminated / reduced / unchanged