OLMO Sierra 42,000 BTU 4-Zone 9k+12k+12k+12k Wall Mount, 230V, R454B - Ductless Mini Split Air Conditioner Heat Pump | No Kit
OLMO5-Yr Warranty
Product specifications
| Brand | |
|---|---|
| Voltage | |
| SEER | |
| WiFi | |
| Zone | |
| Type | |
| Freon | |
| Compressor |
Please note that all delivery dates and estimated transit times are approximate and are not guaranteed. Delivery times may vary due to carrier delays, weather, holidays, peak shipping periods, or other circumstances beyond our control. How delivery dates are calculated
Pickup currently unavailable at Medley Warehouse
Questions about this system?
Answers in seconds — tap a question below
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Covers about 1800–2400 sq ft total, split across its indoor units — each head handles its own room, so you put the right capacity where you need it. Rule of thumb: ~20 BTU per sq ft, and 12,000 BTU = 1 ton (this system is 42,000 BTU (3.5-ton)). Want help splitting the zones? Our team can map it out.
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12,000 BTU = 1 ton — "tons" is just the older way of stating capacity. So 24,000 BTU = 2 tons, 36,000 = 3 tons, and so on. This system is 42,000 BTU (3.5-ton). BTU tells you the capacity; SEER2 tells you the efficiency.
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It uses R454B — the newest low-GWP eco refrigerant, so it's future-proof and efficient. The outdoor unit ships pre-charged for a standard line set, so most installs need no extra refrigerant; your licensed, EPA-608-certified installer verifies the charge and tops it off if your line set is longer.
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Rated SEER2 21.0 — a strong efficiency number, and the higher it is the lower your energy bills. Its inverter compressor ramps up and down instead of cycling on/off, so it holds the temperature steadily, runs quietly, and uses less power than a standard AC or window unit.
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Needs a dedicated 230V circuit, like a large household appliance, so it can deliver full capacity to larger rooms and multi-zone setups. Your licensed HVAC installer or electrician sets up the correct breaker and disconnect to meet local electrical code.
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Yes — a big upgrade. It's far more efficient (inverter, SEER2 21.0) and much quieter, since the compressor sits outside instead of in your window or on the floor. It mounts permanently, doesn't block a window, and heats as well as cools year-round. Higher upfront cost, but lower bills and a longer lifespan.
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Yes to all three. It's an inverter heat pump — cools in summer, heats in winter (even in the cold), far more efficiently than electric heaters. A Dry mode also pulls out humidity, so rooms feel cooler and less muggy.
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Yes. Each indoor unit has its own remote/thermostat — set different temperatures or turn one off, so you only condition the rooms you use and save energy on the ones you're not. One outdoor unit powers them all, keeping install and running costs lower than separate systems per room.
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Yes — WiFi is included, so you can set schedules, change the temperature, and even turn it on before you get home, all from the mobile app (and pair it with voice assistants). A standard remote is included too.
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Ships as a complete set: OS-RMS42-230VO, OS-RM09SW-230VI, OS-RM12SW-230VI, OS-RM12SW-230VI, OS-RM12SW-230VI. Everything arrives together — check the photos and specs for the full kit.
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It should be installed by a licensed, EPA-608-certified HVAC professional — we don't recommend DIY installation. Handling refrigerant requires EPA Section 608 certification under U.S. law, and professional installation keeps the system safe, code-compliant, and your manufacturer warranty valid.
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Yes — you get full inverter heat-pump technology and the same core features as premium brands without paying for the name, which is how we keep prices low. Shipping is free on U.S. orders over $300, and our team can help with sizing and support.
Why buy this mini split from MiniSplitsForLess
- Free Shipping over $300Ships free to the lower 48 states — flat rate, no surprises at checkout.
- USA-Based Expert SupportReal U.S. HVAC pros help with BTU sizing, refrigerant and install questions.
- Genuine Units & Full WarrantyBrand-new, authorized-dealer equipment backed by the full manufacturer warranty.
- Fast Nationwide ShippingIn stock and ready to ship from U.S. warehouses across all 48 states.
What Stands Out
Complete 4-Zone System
Heat or cool 4 rooms independently from one 42000 BTU outdoor unit (9K+12K+12K+12K) — every zone sets its own temperature, delivered by wall mount indoor units.
Inverter Efficiency — SEER2 21
A variable-speed inverter compressor ramps to match the load instead of cycling on/off, holding SEER2 21 on 230V — steady comfort with noticeably lower energy bills.
Right-Sized Coverage
Engineered to heat & cool up to 1800–2400 sq ft across 4 zones — matched capacity so you never over- or under-size the space.
Sierra Wall Mount
OLMO's Multi-Zone Sierra Series is a versatile HVAC solution that provides efficient heating and cooling for multiple rooms, featuring advanced inverter technology for precise temperature control and significant energy savings. Using eco-friendly R410A refrigerant, the system delivers reliable performance with minimal environmental impact. Ideal for both residential and commercial applications, the Sierra Series combines quiet operation, flexible installation, and user-friendly controls, making it a perfect choice for maintaining year-round comfort across multiple zones with one efficient system.
Warranty and Tech Support Info
By selecting OLMO products for your home or business, you’ll receive expert technical support from heating and cooling specialist, including access to product manuals, troubleshooting guides and warranty information.
The manufacturer provides a Limited Warranty of 5 years for the compressor and 2 years for parts.
Warranty terms
Main Features
OLMO's Multi-Zone Sierra Series delivers efficient multi-room comfort with advanced inverter technology for precise temperature control. Its eco-friendly R454B refrigerant reduces environmental impact, while quiet operation ensures minimal disruption. With flexible installation options, sleek design, and reliable heating and cooling, it’s the perfect solution for modern multi-zone climate control needs.
All Accessories Included
With your purchase, you receive a comprehensive MiniSplit system. MiniSplits4Less ensures you have everything needed for a seamless installation. Your package includes an Indoor Unit, Outdoor Unit, Remote Control, Manuals, optional LineSet, and a Smartkit (WIFI). We've meticulously thought of every detail to provide you with all the essentials for your installation.
Technical Specifications
Outdoor Unit Specs
| Model | OS-RMS42-230VO |
|---|---|
| Net/Gross Weight | 172/194 lb |
| Power Supply | 208-230V, 1Ph, 60Hz |
| Maximum Fuse Size | 60 A |
| Min. Circuit Ampacity | 36 A |
System Specs
| Cooling Capacity | 42,000 BTU |
|---|---|
| SEER2 | 21 |
| Zones | 4 |
| Voltage | 230V |
| Refrigerant Type | R454B |
| Compressor | Inverter |
| WiFi | Included |
Series Comparison Table
Technical specifications for every model in the series — this product is one of them.
| Indoor Models | OS-ARM09SW-230VI | OS-ARM12SW-230VI | OS-ARM18SW-230VI | OS-ARM24SW-230VI |
|---|---|---|---|---|
| Power Supply (V-Ph-Hz) | 208/230V-1Ph-60 | 208/230V-1Ph-60 | 208/230V-1Ph-60 | 208/230V-1Ph-60 |
| Cooling Capacity (Btu/h) | 9000 | 12000 | 18000 | 23400 |
| Heating Rated Capacity (Btu/h) | 9500 | 13000 | 19000 | 26000 |
| Output Power (W) | 25 | 25 | 35 | 35 |
| Rated Current (A) | 0.11 | 0.11 | 0.17 | 0.17 |
| Indoor Air Flow (CFM) | 341 | 365 | 647 | 706 |
| Indoor Noise Level (Hi/Mi/Lo) (dB(A)) | 39/35/30 | 39/35/30 | 45/41/37 | 47/45/42 |
| Net Dimensions (WxHxD) (in) | 32.02x10.75x8.13 | 37.38x10.75x8.13 | 48x12.63x9.25 | 48x12.63x9.25 |
| Packing (WxHxD) (in) | 39.38x13.19x6.38 | 39.38x13.19x6.38 | 51.75x15.44x12.50 | 51.75x15.44x12.50 |
| Net/Gross Weight (lbs) | 19.84 / 24.25 | 19.84 / 24.25 | 31.97 / 37.48 | 31.97 / 37.48 |
| Refrigerant Piping (Liquid Side / Gas Side) (in) | 1/4" / 3/8" | 1/4" / 3/8" | 1/4" / 1/2" | 3/8" / 5/8" |
| Outdoor Models | OS-RMS18-230VO | OS-RMS24-230VO | OS-RMS36-230VO | OS-RMS42-230VO |
|---|---|---|---|---|
| Power Supply (V-Ph-Hz) | 208/230V-1Ph-60 | 208/230V-1Ph-60 | 208/230V-1Ph-60 | 208/230V-1Ph-60 |
| Cooling Capacity (Btu/h) | 18000 | 27000 | 36000 | 42000 |
| EER2 | 13.33 | 12.85 | 12.85 | 12.0 |
| SEER2 | 22.0 | 23.0 | 22.0 | 22.0 |
| Heating Rated Capacity (Btu/h) | 18000 | 27000 | 36000 | 36000 |
| HSPF2 | 10.0 | 10.0 | 10.0 | 9.5 |
| COP2 (W/W) | 3.82 | 3.60 | 3.91 | 3.60 |
| Max Fuse (A) | 30 | 40 | 50 | 60 |
| Outdoor Air Flow (Hi) (CFM) | 1850 | 3357 | 3357 | 3357 |
| Outdoor Side Noise Level (dB(A)) | 55 | 62 | 64 | 64 |
| Dimensions (WxHxD) (in) | 33.88x26.38x12.25 | 38.38x32.88x14.12 | 38.38x32.88x14.12 | 38.38x32.88x14.12 |
| Outdoor Unit Packing (WxHxD) (in) | 39x28.75x17.75 | 43.75x37.75x18.12 | 43.75x37.75x18.12 | 43.75x37.75x18.12 |
| Net/Gross Weight (lbs) | 101.4/112.4 | 160.6/183.2 | 169.8/191.8 | 172/194 |
| Refrigerant Type/Quantity (oz) | R454B/51.15 | R454B/76.2 | R454B/105.8 | R454B/105.8 |
| Refrigerant Piping (Liquid Side / Gas Side) (in) | 1/4" / 3/8" | 1/4" / 3/8" | 1/4" / 3/8" | 1/4" / 3/8" |
| Max Refrigerant Pipe Length Each/Total (ft) | 82/164 | 82/230 | 82/230 | 82/262 |
| Ambient Outdoor (Cooling) (°F) | 5~125 | 5~125 | 5~125 | 5~125 |
| Ambient Outdoor (Heating) (°F) | -13~75 | -13~75 | -13~75 | 4~75 |
What’s Included
| Outdoor condenser | OS-RMS42-230VO |
|---|---|
| Indoor unit | OS-RM09SW-230VI |
| Indoor unit | OS-RM12SW-230VI |
| Indoor unit | OS-RM12SW-230VI |
| Indoor unit | OS-RM12SW-230VI |
Installation kit is not included in the selected option — pick 16ft, 25ft or 50ft above to add one.
Shipping & Returns
- Free shipping on every order over $300.
- Delivery estimate for your ZIP is shown in the buy box above.
- Returns accepted per our policy — unopened units in original packaging.
Warranty
5-year manufacturer warranty
- Limited manufacturer warranty on the compressor and sealed system components.
- Your order number is the proof of purchase — keep it for any claim.
Multiple Control Methods
Olmo’s Multi-Zone Sierra Series can be managed with a user-friendly remote control and the. This options offer precise temperature adjustments and optimal climate control for ultimate convenience.
Frequently Asked Questions
How many rooms can the Olmo 4 Zone 42,000 BTU mini split cool?
The Olmo 4 Zone mini split system, with a total capacity of 42,000 BTU, is designed to effectively cool multiple rooms, typically accommodating up to four individual zones. Each zone can be tailored to a specific room or area, allowing for efficient temperature control.
Can I mix different BTU sizes with the Olmo mini split system?
Yes, the Olmo mini split system allows for mixing different BTU sizes across its four zones, as long as the total capacity does not exceed the 42,000 BTU limit. This flexibility enables you to customize heating and cooling to match specific room sizes and usage.
Do all zones run simultaneously in the Olmo mini split system?
In the Olmo 4 Zone mini split system, you have the option to run zones simultaneously or independently. This allows for personalized comfort, as you can operate only the zones that are in use, optimizing energy efficiency.
What is the efficiency of the Olmo mini split compared to multiple single-zone units?
With a SEER rating of 21.0, the Olmo 4 Zone mini split system offers superior efficiency compared to using multiple single-zone units. This high efficiency not only reduces energy costs but also simplifies installation and maintenance across your home.
What warranty does the Olmo 4 Zone mini split offer?
The Olmo 4 Zone mini split system comes with a comprehensive 5-year parts and compressor warranty, providing peace of mind for your investment. This warranty covers major components, ensuring reliable performance for years to come.
Does the Olmo mini split come pre-charged with refrigerant?
Yes, the Olmo mini split system is pre-charged with R454B refrigerant for up to 25 ft of line set, making installation more straightforward. Just ensure that you follow the installation guidelines to maintain the system's efficiency and performance.
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