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MRCOOL® HyperHeat®

MRCOOL DIY 18K Hyper Heat Mini Split System – 5th Gen, -22°F Heating, 21.2 SEER2, Pre-Charged DIY Line Set

MRCOOL DIY 18K Hyper Heat Mini Split System – 5th Gen, -22°F Heating, 21.2 SEER2, Pre-Charged DIY Line Set

SKUMC-DIY-HH18-WM18-25

TypeSingle Zone Mini Split System

Regular price $3,205.00
Sale price $3,205.00 Regular price $4,006.25
You Save: $801.25
SALE Sold out
Shipping calculated at checkout.

Refrigerant Type: R-454B

Line Set Length
In stock
Ready to ship
Free delivery*
Ships in 1–2 business days
Estimated arrival: Jul 22 – Jul 24
Based on order date & typical delivery times
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PRODUCT DESCRIPTION

MRCOOL DIYHH-18 Hyper Heat 18K Mini Split System with Wall Mount Air Handler

The MRCOOL® DIYHH-18 Hyper Heat 18K Mini Split System is a 5th Generation DIY ductless heat pump designed for homeowners who need reliable heating and cooling in true cold-climate conditions. This complete 18,000 BTU single-zone bundle includes the DIYHH-18 outdoor condenser, the DIY-18-HP-WMAH-230D25-O wall-mounted air handler, a 25 ft QuickConnect® pre-charged line set, and the required DIYPRO® cable.

Built for extreme winter performance, this MRCOOL Hyper Heat system provides dependable heating operation down to -22°F while also delivering efficient cooling for spaces up to 800 sq. ft. It is ideal for garages, bonus rooms, bedrooms, basements, offices, cabins, workshops, detached buildings, and other spaces where standard mini splits may struggle in colder weather.

Unlike traditional ductless mini split systems, the MRCOOL DIY series uses factory-sealed No-Vac® QuickConnect® pre-charged line sets filled with R-454B refrigerant. That means no vacuum pump, no gauges, no nitrogen purge, no refrigerant charging, and no HVAC certification required for the line set connection. Because apparently HVAC finally decided homeowners deserve one system that does not require a tool cart the size of a small moon.

What's Included in This Complete DIY Bundle?

  • DIYHH-18-HP-C-230D25-O – 18K Hyper Heat Outdoor Condenser, 208/230V
  • DIY-18-HP-WMAH-230D25-O – 18K Wall-Mounted Air Handler
  • DIY25-1412 – 25 ft Pre-Charged QuickConnect® Line Set
  • DIYPRO® Cable
  • Wireless Remote
  • Installation Manuals
  • Mounting Hardware

Why Choose the MRCOOL DIYHH-18 Hyper Heat?

  • True cold-climate Hyper Heat performance down to -22°F
  • 18,000 BTU heating and cooling capacity
  • Designed for spaces up to 800 sq. ft.
  • DIY-friendly No-Vac® QuickConnect® installation
  • No vacuum pump, gauges, nitrogen, or refrigerant handling required
  • Factory pre-charged R-454B refrigerant line set included
  • Efficient inverter rotary compressor technology
  • Up to 21.2 SEER2 efficiency
  • Built-in smart control with MRCOOL SmartHVAC App
  • Compatible with Amazon Alexa® and Google Assistant®
  • Quiet indoor operation as low as 19 dBA
  • Excellent choice for garages, cabins, additions, shops, and cold-climate homes

Ideal Applications

  • Garage mini split heating and cooling
  • Detached shop or workshop HVAC
  • Basements and finished lower levels
  • Bonus rooms and room additions
  • Cabins and mountain homes
  • Master bedrooms and large bedrooms
  • Home offices and studios
  • Home gyms
  • Airbnb and rental properties
  • Barndominiums and pole barns
  • Small commercial offices or retail spaces

Line Set Length Information

This system includes a standard 25 ft QuickConnect® pre-charged line set. Extended line set options may add an additional line set, couplers, and a longer control wire for installations requiring more distance between the indoor air handler and outdoor condenser.

Always verify the required line set length before ordering. Excess line set should not be cut. It should be properly coiled and installed according to MRCOOL installation guidelines.

Condenser Performance Specifications

Specification Value
Outdoor Model DIYHH-18-HP-C-230D25-O
System Type Single-Zone Hyper Heat Mini Split
BTU Rating 18,000 BTU Heating & Cooling
Recommended Coverage Area Up to 800 sq. ft.
SEER2 21.2
EER2 12.5
HSPF2-4 11
HSPF2-5 8.5
Minimum Heating Ambient Temperature -22°F
Operating Temperature Range -22°F to 122°F
Compressor Type Inverter Rotary
Airflow 1765.8 CFM
Condenser Noise Level 58 dBA

Condenser Electrical Specifications

Electrical Specification Value
Voltage 208/230V
Phase 1 Phase
Cycle 60Hz
Minimum Circuit Ampacity 19A
Maximum Fuse / Breaker 25A
Dedicated Circuit Required Yes

Refrigeration & Line Set Specifications

Refrigeration Specification Value
Refrigerant R-454B
Factory Charge Volume 52.21 oz
Included Line Set 25 ft Pre-Charged QuickConnect® Line Set
Maximum Supported Line Length 75 ft
Liquid Line Size 1/4 in.
Suction Line Size 1/2 in.
Metering Device Electronic Expansion Valve, EEV
Vacuum Pump Required No
Field Refrigerant Charging Required No

Condenser Dimensions & Weight

Dimension Value
Net Dimensions 35.04 in. W × 26.5 in. H × 13.46 in. D
Net Weight 99.87 lbs
Gross Dimensions 40.55 in. W × 29.53 in. H × 18.11 in. D
Gross Weight 120.15 lbs

Wall Mount Air Handler Specifications

Indoor Unit Specification Value
Indoor Model DIY-18-HP-WMAH-230D25-O
Indoor Unit Type Wall-Mounted Air Handler
BTU Capacity 18,000 BTU
Coverage Area Up to 800 sq. ft.
Fan Speeds 5-Speed
Quiet Mode Yes
Noise Level 19 dBA Low – 54.5 dBA High
Net Dimensions 42.52 in. W × 13.19 in. H × 8.9 in. D
Net Weight 35.49 lbs
Gross Dimensions 46.73 in. W × 14.29 in. H × 17.68 in. D
Gross Weight 49.6 lbs

Smart Control Features

Smart Feature Included
MRCOOL SmartHVAC App Yes
iOS Compatible Yes
Android Compatible Yes
Amazon Alexa® Voice Control Yes
Google Assistant® Voice Control Yes
Wireless Remote Included Yes

Warranty Coverage

Warranty Item Coverage
Compressor Warranty 7-Year Compressor Warranty with Registration
Parts Warranty 5-Year Parts Warranty with Registration
Extended Warranty Extended Limited Lifetime Coverage Available with MRCOOL Care Registration

Hyper Heat vs Standard DIY Mini Splits

Standard DIY mini split systems are excellent for mild and moderate climates, but they may lose heating output as outdoor temperatures drop. The MRCOOL DIYHH-18 Hyper Heat system is designed for colder regions where winter heating performance matters.

With true low-temperature operation down to -22°F, this system is a better choice for homeowners who need dependable heat in garages, cabins, workshops, basements, additions, and cold-climate living spaces.

Frequently Asked Questions

Can I install the MRCOOL DIYHH-18 myself?

Yes. This system is designed for DIY installation using MRCOOL No-Vac® QuickConnect® pre-charged line set technology. No vacuum pump, gauges, nitrogen purge, or refrigerant charging are required for the line set connection.

Does this system require a dedicated electrical circuit?

Yes. The outdoor condenser requires a dedicated 208/230V electrical circuit with a minimum circuit ampacity of 19A and a maximum fuse or breaker size of 25A.

Will this system heat when it is below freezing?

Yes. The MRCOOL DIYHH-18 Hyper Heat system is engineered for heating operation down to -22°F, making it a strong choice for cold-climate installations.

Do I need to buy refrigerant separately?

No. The included QuickConnect® line set is pre-charged, and the system is designed for installation without field refrigerant charging.

What size space will this 18K Hyper Heat mini split cover?

This 18,000 BTU system is rated for spaces up to approximately 800 sq. ft. Actual sizing depends on insulation, ceiling height, sun exposure, layout, climate zone, and other building conditions.

Is this a good option for a garage or workshop?

Yes. The MRCOOL DIYHH-18 Hyper Heat is an excellent choice for garages, workshops, detached buildings, and other spaces that need both efficient cooling and strong cold-weather heating.

Can I control this system from my phone?

Yes. This system works with the MRCOOL SmartHVAC App and is compatible with iOS, Android, Amazon Alexa®, and Google Assistant®.

Why Buy From MRCOOL DIY Direct?

MRCOOL DIY Direct specializes in MRCOOL DIY systems, parts, bundles, and support. Our team understands these systems and can help verify sizing, electrical requirements, line set selection, and system compatibility before you order.

You are not buying from a random dropshipper copying model numbers into a spreadsheet and hoping the freight truck solves the rest. You are buying from a dedicated MRCOOL dealer focused on helping customers get the correct system the first time.

Rated 4.7 / 5 Stars
4700+ Verified Reviews

Comfort That Speaks for Itself

See why homeowners and pros alike trust MRCOOL DIY systems to deliver comfort, savings, and easy installation.

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

I never thought I’d install my own HVAC system, but MRCOOL made it possible. The instructions were easy, and the pre-charged lines saved me from hiring a tech. Cools my garage workshop perfectly!

Jason R., North Carolina

Our MRCOOL mini-split runs really quiet — you can barely tell it’s on. Our electric bill dropped about 35% this summer. Very impressed with the efficiency

Megan L., Arizona

Installed this in my detached office. Took me a Saturday morning and a friend to lift the outdoor unit. Works flawlessly — heats in winter and cools in summer.

Daniel P., Texas

I swapped my old central unit for two MRCOOL DIY mini-splits. Same comfort, way lower bills. The inverter technology really makes a difference.

Jennifer C., Florida

Had a small question during installation and Vanessa picked up right away. They walked me through it step by step — best customer service I’ve had in years.

Chris B., Ohio

Keeps our sunroom comfortable in 100°F summers and comfy in the winter. The heat pump feature is amazing — one system for both heating and cooling!

Angela K., Kentucky

I’ve remodeled a few homes, and MRCOOL DIY systems are a game-changer. No need for HVAC pros or special tools — everything is plug-and-play.

Brandon S., Tennessee

Why Buy From Us

Why Buy from MRCOOL DIY Direct?

Trusted nationwide for MRCOOL DIY systems, support, and installation guidance.

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Top MRCOOL Dealer

Trusted nationwide for DIY mini split systems.

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DIY System Experts

Specializing in MRCOOL DIY systems and support.

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Fast Shipping

Quick delivery across the lower 48 states.

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Real Support

Help with sizing, compatibility, and installation.

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Family-Owned

Based in Missouri, serving nationwide.

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Complete System Guidance

We help you get everything needed for install.