Installing a 2nd aircon compressor in your HDB flat can improve cooling performance, reduce system strain, and allow better zoning between rooms.
But here’s what many homeowners get wrong:
⚠️ Most HDB Owners Get This Wrong
Many people assume they can install a second compressor as long as there is space.
In reality:
- 30A flats require HDB approval
- Electrical limits can cause constant power trips
- Wrong setup can lead to costly rework
👉 This is why checking your electrical loading first is critical.
⚡ Understanding HDB Electrical Loading
Most HDB flats fall into two categories:
30 Amp (Older / Non-Upgraded Flats)
- Approximate capacity: 6.9 kW
- Typically designed for one aircon system and basic appliances
- Limited ability to support multiple heavy electrical loads
40 Amp (Newer / Upgraded Flats)
- Approximate capacity: 9.2 kW
- Suitable for multiple aircon systems and modern appliances running at the same time.
🏢 Which HDB Flats Have 40A?
You are more likely to have 40A electrical loading if your flat:
- Was built after 1 January 1994
- Has undergone upgrading programmes such as MUP or HIP
More info:
https://www.hdb.gov.sg
🔍 Check Your Electrical Loading (Official HDB Tool)
Before installing a second compressor, always verify your flat’s electrical loading using the official HDB tool:
https://services2.hdb.gov.sg/webapp/BN31AWERRCMobile/BN31SElectrical?loadAction=electrical
This allows you to:
- Check if your block has higher electrical loading
- Estimate whether your setup is within safe limits
⚠️ Do You Need HDB Approval?
This is the most misunderstood part.
For 40A flats (upgraded):
- No permit is generally required
- Must still follow HDB guidelines
For 30A flats (non-upgraded):
👉 Installing a second compressor requires HDB approval.
This is not optional.
💡 Why Electrical Loading Matters
A typical aircon compressor uses about 1,500W to 3,000W, with higher draw during startup.
Example:
- Compressor 1: 2,500W
- Compressor 2: 2,500W
- Water heater: 3,000W
Total: 8,000W
👉 This exceeds a 30A flat’s capacity (~6,900W)
Result: power trips, unstable system, poor performance.
🔧 Installing a 2nd Compressor in a 40A Flat
If your flat has 40A supply, installation is straightforward:
- Confirm electrical capacity
- Install a dedicated isolator for each compressor
- Balance load across systems
- Follow HDB-approved installation guidelines
👉 When properly done, this setup is safe and reliable.
🔧 Installing a 2nd Compressor in a 30A Flat
For non-upgraded flats, this is an approval-based process.
Step 1: Check electrical loading
Step 2: Apply for HDB approval
Step 3: Conduct load assessment
Step 4: Plan system properly
Step 5: Follow HDB installation guidelines
👉 Skipping any of these can lead to failure or rejection.
🚫 Common Mistakes to Avoid
- Installing without checking electrical loading
- Assuming all HDB flats can support 2 compressors
- Skipping HDB approval for 30A flats
- Using undersized wiring
- Hiring unlicensed installers
📊 Quick Comparison
30A Flat
- Capacity: ~6.9 kW
- 2nd Compressor: Possible with approval
- Risk: High if not planned properly
40A Flat
- Capacity: ~9.2 kW
- 2nd Compressor: Yes
- Risk: Low when installed correctly
📞 Thinking of Installing a 2nd Aircon Compressor?
Don’t risk costly mistakes.
At Lion City Aircon, we help you:
- Check your electrical loading
- Advise if HDB approval is required
- Design a safe and compliant system
- Handle full installation
👉 Contact us today for a proper site assessment before you proceed.
📞 Call or WhatsApp: +65 8818 5781
🌐 Visit: https://lioncityaircon.sg
❓ Frequently Asked Questions
Can I install a second aircon compressor in HDB?
Yes, but it depends on your electrical loading. 30A flats require HDB approval.
Do I need HDB approval?
Yes, for non-upgraded 30A flats.
What happens if I install without checking?
You may face power trips, system issues, or compliance problems.
