What's in the box
- MRCOOL® Smart Thermostat MST04 (24V)
- Mounting Kit
- User Manual
- SmartHVAC® App Integration Guide
Free curbside shipping on eligible MRCOOL® systems across the continental U.S. Most products ship in 3–5 business days and arrive in 4–10 days, depending on your location. Freight carriers will call to schedule delivery.
Returns accepted within 30 days on new, unopened items in original packaging. A restocking fee of up to 35% may apply for HVAC equipment — we’ll always confirm before issuing a return authorization.
Each MRCOOL® system is backed by manufacturer warranty coverage as defined by product and model — typically 5–10 years on major components. Register your system after installation to activate full coverage.
Need help with sizing, voltage or compatibility? Email support@coolheatdirect.com — our U.S. team replies within one business day.
Manuals & documents
MODEL: MST04
Smart Comfort Meets Total Control — Wherever You Are
The MRCOOL® Smart Thermostat (Model: MST04) delivers intelligent, intuitive, and energy-efficient control for your home. Designed for easy DIY installation and powered by voice control, touchscreen access, and app-based automation, this 24V thermostat is the ideal upgrade for modern households.
Create the perfect atmosphere with pre-set modes like Home, Away, Sleep, or Vacation, and manage your system from anywhere with the Smart HVAC app. Fine-tune fan speeds, track usage trends, and monitor filter cleaning reminders with ease. Whether you use Alexa, Google Assistant, Siri, or MRCOOL® Link, control is always within reach.
Advanced location-based services automatically adjust your comfort levels when you're arriving or leaving home. Even if the Wi-Fi goes out, you're still in control through the device’s built-in interface. Backed by a 3-Year Warranty, the MST04 puts smart comfort and efficiency right at your fingertips.
Why You’ll Love It
✅ DIY-Friendly Install — No pro needed; set up quickly and easily
✅ Multi-Platform Control — Works with Alexa, Google Assistant, Siri & MRCOOL® Link
✅ Vacation & Smart Modes — Stay energy efficient while you’re away
✅ Location-Based Automation — Adjusts temperature as you come and go
✅ Track & Optimize Usage — Built-in system history and energy monitor
✅ Preset Modes — Home, Away, and Sleep modes tailored to your lifestyle
✅ Works Without Internet — Local touchscreen control always available
✅ One App for All Systems — Control everything in the SmartHVAC® app
✅ Backed by Warranty — 3-Year Parts Warranty for peace of mind
Questions, answered
Everything homeowners ask before buying a MRCOOL® system.
Installation
Do I need an HVAC technician to install this?
No. MRCOOL® DIY systems are designed for homeowner installation. The pre-charged Quick Connect® line set means there's no refrigerant handling, no vacuum pump, and no special tools or license required.
How long does installation take?
Most single-zone systems go in within a few hours: mount the indoor air handler, set the outdoor condenser, connect the pre-charged line set, and power it on.
Do I need an electrician?
The system needs a dedicated circuit. Most homeowners have a licensed electrician add the breaker and disconnect — everything else you can do yourself.
Sizing & compatibility
What BTU size do I need?
As a rule of thumb: up to 400 sq ft → 9–12K BTU, 400–600 sq ft → 12–18K, 600–1,000 sq ft → 18–24K. Use the room-size guide above and factor in insulation, ceiling height and sun exposure.
Will it heat in winter?
Yes — these are heat pumps, so they heat and cool. Many MRCOOL® systems keep heating in sub-freezing temperatures; check each model's spec sheet for its low-temperature heating range.
115V or 230V — which do I need?
9K–12K units are usually 115V (standard outlet circuit); 18K and larger are typically 230V. The voltage is shown in the product options and specifications.
Warranty & support
What warranty is included?
MRCOOL® systems carry manufacturer warranty coverage — typically 5–10 years on major components when you register your system after installation.
How do I get help choosing or installing?
Email support@coolheatdirect.com — our U.S. team replies within one business day with sizing, voltage and compatibility help.
Shipping & returns
How fast does it ship?
Most products ship in 3–5 business days with free curbside delivery in the continental U.S. The freight carrier calls to schedule your delivery.
Can I return it?
Returns are accepted within 30 days on new, unopened items in original packaging. A restocking fee may apply to HVAC equipment — we always confirm before issuing a return authorization.
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