MRCOOL® DIY 18K Hyper Heat 5th Gen Mini Split System
Summary
The MRCOOL® DIYHH-18 Hyper Heat 18K Mini Split System is a 5th Generation Hyper Heat bundle engineered for cold-climate performance down to -22°F with genuine DIY installation. This complete system delivers 18,000 BTU heating and cooling for spaces up to 800 sq. ft., combining professional capability with homeowner-friendly setup.
Featuring the DIYHH-18-HP-C-230D25-O outdoor condenser and DIY-18-HP-WMAH-230D25-O wall-mounted air handler, this system uses factory-sealed QuickConnect® pre-charged line sets with R-454B refrigerant—eliminating the need for vacuum pumps, gauges, or HVAC certification. With efficiency ratings of 21.2 SEER2 and 11 HSPF2-4, smart controls via the MRCOOL SmartHVAC App, and Alexa/Google compatibility, it’s a strong fit for garages, additions, workshops, and larger rooms.
Highlights
Up to 800 sq. ft.
208/230V
25A max
Down to -22°F
- 2025 5th Generation Hyper Heat: Enhanced cold-climate heating performance down to -22°F.
- True DIY installation: Pre-charged QuickConnect® line set requires no vacuum pump, gauges, or refrigerant handling.
- Premium efficiency: 21.2 SEER2 and 11 HSPF2-4 ratings for reduced energy use.
- Smart connectivity: MRCOOL SmartHVAC App + Alexa/Google Assistant + included remote.
- Quiet indoor operation: Indoor sound levels as low as 19 dB.
What's Included
- Outdoor Condenser: MRCOOL® DIYHH-18 Hyper Heat Condenser (DIYHH-18-HP-C-230D25-O)
- Indoor Unit: MRCOOL® DIY-18 Wall Mount Air Handler (DIY-18-HP-WMAH-230D25-O)
- Line Set: 25 ft Pre-Charged QuickConnect® Line Set (DIY25-1412)
- DIYPRO® Communication Cable
- Wireless Remote Control
- Complete mounting hardware & template
- Installation and user manuals
Warranty
- 7-Year Compressor Warranty (registration required)
- 5-Year Parts Warranty (registration required)
- Extended limited lifetime coverage with MRCOOL® Care
Important: Warranty benefits require product registration. Refer to MRCOOL warranty documentation for full terms and conditions.
Technical Information
Outdoor Model: DIYHH-18-HP-C-230D25-O
| Brand | MRCOOL |
| Series | DIY Hyper Heat 5th Gen |
| Model | DIYHH-18-HP-C-230D25-O |
| Unit Type | Mini-Split |
| Equipment Type | Condenser |
| Short Description | 18K Hyper Heat 230V Condenser with QuickConnect® |
| Cooling Capacity (BTU) | 18,000 |
| Heating Capacity (BTU) | 18,000 |
| SEER2 | 21.2 |
| EER2 | 12.5 |
| HSPF2-4 | 11 |
| HSPF2-5 | 8.5 |
| Voltage | 208/230 |
| Phase | 1 |
| Cycle | 60 Hz |
| Min Circuit Ampacity (A) | 19 |
| Max Fuse / Breaker (A) | 25 |
| Min Ambient Heat (°F) | -22°F |
| Max Ambient Cool (°F) | 122°F |
| CFM | 1765.8 |
| Compressor Type | Inverter Rotary |
| Metering Device | Electronic Expansion Valve (EEV) |
| Refrigerant Type | R-454B |
| Refrigerant Volume (oz) | 52.21 oz |
| Line Set Included | Yes |
| Line Set Length | 25 ft |
| Max Lineset Length (ft) | 75 ft |
| Liquid Line Size | 1/4" |
| Suction Line Size | 1/2" |
| Decibel Rating High (dBA) | 58 |
| Net Width (in) | 35.04 |
| Net Height (in) | 26.5 |
| Net Depth (in) | 13.46 |
| Net Weight (lbs) | 99.87 |
Indoor Model: DIY-18-HP-WMAH-230D25-O
| Brand | MRCOOL |
| Series | DIY 5th Gen |
| Model | DIY-18-HP-WMAH-230D25-O |
| Unit Type | Mini-Split |
| Equipment Type | Air Handler |
| Short Description | 18K 230V Wall Mount Air Handler |
| Cooling Capacity (BTU) | 18,000 |
| Heating Capacity (BTU) | 18,000 |
| Max Coverage Area | 800 sq. ft. |
| Mount Type | Wall |
| Fan Speeds | 5-Speed |
| Quiet Mode | Yes |
| Decibel Rating Low (dBA) | 19 |
| Decibel Rating High (dBA) | 54.5 |
| Net Width (in) | 42.52 |
| Net Height (in) | 13.19 |
| Net Depth (in) | 8.9 |
| Net Weight (lbs) | 35.49 |
| Smart Features | MRCOOL SmartHVAC App, Alexa, Google Assistant, Wireless Remote |
Frequently Asked Questions
Is this system really DIY-friendly?
Yes. The pre-charged, factory-sealed QuickConnect® line set eliminates the most complex steps of traditional mini-split installation. No vacuum pump, gauges, or refrigerant handling is required.
How low of a temperature can it heat?
This Hyper Heat system is engineered to provide effective heating down to -22°F outdoor temperature.
What electrical requirements are needed?
A dedicated 208/230V circuit is required with a 25A breaker (19A minimum circuit ampacity).
Is the line set included?
Yes, a 25 ft pre-charged QuickConnect® line set (DIY25-1412) is included. Extended lengths may be available.
Does it come with smart controls?
Yes. The system is WiFi-enabled for the MRCOOL SmartHVAC App and supports voice control with Amazon Alexa and Google Assistant.
