MRCOOL DIY 5th Gen 4-Zone Ceiling Cassette Systems
One outdoor unit runs 2 to 6 rooms, and each room gets its own temperature. Every system here is a complete kit: outdoor unit, an indoor unit per room and an R-454B pre-charged line set for each one.
- No vacuum pump or HVAC tech
- Heats down to −13°F
- Free shipping on kept orders, 48 states
51ready-made systems
How many rooms are you cooling and heating?
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How to pick a multi-zone system
Three steps, and you only need a tape measure.
Count your rooms
Each room with its own temperature needs its own indoor unit. Pick that number above.
Size each room
Multiply length by width for each room and match it to an indoor unit size in the table below.
Office 10×12 = 120 sq ft → 6K
Bedroom 14×16 = 224 sq ft → 9KCheck the outdoor unit
Add up the room units. The outdoor unit should be close to that total, and every system on this page is already matched.
6K + 9K + 12K = 27K → 27K outdoor unit
2Size each room
| Room size | Indoor unit |
|---|---|
| Under 150 sq ft | 6K BTU |
| 150–350 sq ft | 9K BTU |
| 351–500 sq ft | 12K BTU |
| 501–750 sq ft | 18K BTU |
| 751–1,000 sq ft | 24K BTU |
| 1,001–1,500 sq ft | 36K BTU |
3Pick the outdoor unit
| Outdoor unit | Rooms | Whole area |
|---|---|---|
| 18K BTU | 2–3 | Up to 750 sq ft |
| 27K BTU | 2–4 | Up to 1,125 sq ft |
| 36K BTU | 2–5 | Up to 1,500 sq ft |
| 48K BTU | 2–6 | Up to 2,000 sq ft |
| 55K BTU | 2–6 | Up to 2,300 sq ft |
Multi-zone questions
Can the room units add up to more than the outdoor unit?
Yes, in combinations MRCOOL approves. For example, MRCOOL lists four 12K rooms (48K) on the 36K outdoor unit. When every room runs at full power at once, they share the outdoor unit’s capacity. The build-your-own page only offers combinations from MRCOOL’s matchup list.
Which line set length do I get?
The price shown includes 16 ft line sets. On the system page you pick 16, 25, 35 or 50 ft for each room, and the price updates.
Wall mount or ceiling cassette?
Wall units are the easiest install and cost less. Cassettes sit flush in the ceiling and blow four ways, which suits open rooms or walls with no space. You need attic or ceiling access for a cassette.
Do I need an electrician?
The refrigerant side is DIY. Every multi-zone outdoor unit runs on 230V, so if you’re not comfortable adding that circuit, have an electrician do just that part.
Can I add a room later?
Only if the outdoor unit has a free port and BTU to spare. If you might add rooms, pick the bigger outdoor unit now.
About these systems
One outdoor unit powers four indoor ceiling cassettes. Ideal for three-bedroom homes where every room runs at its own temperature. DIY installation with full warranty. Operates from -13°F to 122°F outdoor temperatures.