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.
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We will prepare your order within 24 hours if it’s received on a weekday (before noon). Orders are shipped in one to two business days. Transit time is between 3 to 6 business days, although exceptions apply. We email tracking information once your purchase is shipped.
Delivery Map
IMPORTANT DELIVERY INFORMATION: Please be kindly informed that this air conditioner, due to its weight and shipping restrictions, is shipped palletized with an arranged freight service and requires an appointment for delivery. To AVOID delays, please check if the provided phone number in the order details is a current number where you can be reached. You can also contact the carrier directly and refer to your tracking number to set up a date and time for your appointment. It is your responsibility to ensure a safe and secure environment for delivery. Please note that we cannot be held liable for any packages that are stolen or lost after delivery has been confirmed. PLEASE verify your shipping address, as changes to the address after freight has shipped can result in an additional 15% or higher fee depending on freight weight and dimensions.
SMALLWARES INFORMATION: Please be informed that for smaller items, such as Installation Kits, Smart Connectivity Dongles, and TTW Sleeves, when these items are ordered individually, they may be shipped via FedEx without a signature requirement. It is your responsibility to ensure a safe and secure environment for delivery. Please note that we cannot be held liable for any packages that are stolen or lost after delivery has been confirmed. Thank you for your understanding and cooperation.
INSPECT YOUR MERCHANDISE BEFORE SIGNING: Please inspect your boxes thoroughly when you receive them. They should arrive shrink-wrapped and on a pallet. If you notice any damages or imperfections (e.g. crushed box or forklift hole), please write comments on the receipt before signing for delivery, no matter how small damages seem. Contact us immediately to assist you.
Shipping & Delivery
We will prepare your order within 24–48 hours if it’s received on a weekday (before noon). Orders are shipped in one to two business days. Transit time is between 3 to 6 business days, although exceptions apply. We email tracking information once your purchase is shipped.
Delivery Map
IMPORTANT DELIVERY INFORMATION
Please be informed that this air conditioner, due to its weight and shipping restrictions, is shipped palletized with an arranged freight service and requires an appointment for delivery.
To AVOID delays, please make sure the phone number in your order details is accurate and one where you can be reached. You may also contact the carrier directly using your tracking number to schedule your delivery.
It is your responsibility to ensure a safe and secure delivery environment. We are not liable for any packages that are stolen or lost after delivery is confirmed.
Please verify your shipping address carefully. Changes to your shipping address after the freight has been shipped may result in additional fees of 15% or more, depending on freight weight and dimensions.
SMALLWARES INFORMATION
Smaller items such as Installation Kits, Smart Connectivity Dongles, and TTW Sleeves may be shipped via FedEx without a signature requirement if ordered individually.
It is your responsibility to ensure a safe delivery location. We are not liable for packages lost or stolen after delivery confirmation. Thank you for your understanding and cooperation.
INSPECT YOUR MERCHANDISE BEFORE SIGNING
Please inspect your boxes carefully upon delivery. Shipments should arrive shrink-wrapped and on a pallet. If you notice any damage or signs of mishandling (such as a crushed box or forklift puncture), write comments on the delivery receipt before signing, even if the damage appears minor.
Contact us immediately if any issues arise so we can assist you promptly.
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