MRCOOL DIY 4th Gen 36K 3-Zone (12K x3) vs MRCOOL DIY 5th Gen Multi-Zone 36,000 BTU (3-zone)
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Quick take: The MRCOOL DIY 5th Gen Multi-Zone 36,000 BTU (3-zone) replaced the MRCOOL DIY 4th Gen 36K 3-Zone (12K x3), which is discontinued; the MRCOOL DIY 5th Gen Multi-Zone 36,000 BTU (3-zone) is the more efficient unit (23 SEER2).
| Spec | MRCOOL DIY 4th Gen 36K 3-Zone (12K x3) | MRCOOL DIY 5th Gen Multi-Zone 36,000 BTU (3-zone) |
|---|---|---|
| Price | $4,600 | $5,063 |
| Rating | — | — |
| Type | Multi-Zone DIY | Multi-Zone DIY |
| Capacity | 36k BTU | 36k BTU |
| Coverage | ~1,500 sq ft | ~1,250 sq ft |
| SEER2 (cooling) | 21.5 | 23 |
| HSPF2 (heating) | — | 9.9 |
| Low-Ambient Heating | to -13°F | — |
| Max heat at 5°F (NEEP) | not listed | 25,200 BTU |
| Heat kept at 5°F | — | 70% of rated |
| Refrigerant | R-410A | R-454B |
| Zones | 3 zones | 3 zones |
| Voltage | 230V | 230V |
| WiFi Control | Built-in | Built-in |
| Install | Three 12k wall heads off one 36k multi condenser, each with its own precharged quick-connect lineset — the same no-vacuum process three times over. One 208/230V circuit feeds everything. Routing three linesets to one condenser location is the real puzzle; sketch the runs before you buy lengths. | Same no-vacuum idea as the 4th Gen: every head gets its own lineset precharged with R-454B and quick-connect fittings, so there is no vacuum pump or gauge set. The condenser is a 5-port unit (it takes up to five heads), so a 3-zone bundle leaves two ports spare for a later room. It wants a 35A breaker on a 208/230V circuit. Linesets come in 16, 25, 35 and 50 ft; pick each length from the routed path, because a precharged set can't be trimmed. |
| Warranty | 7-year compressor / 5-year parts with online registration | 7-year compressor / 5-year parts, registered within 60 days of installation |
Pros & cons
MRCOOL DIY 4th Gen 36K 3-Zone (12K x3)
- ✓Three independently controlled 12k zones from a single 36k condenser and one 230V circuit
- ✓Heating rated to -13°F covers cold-climate bedroom duty
- ✓Per-zone scheduling via the SmartHVAC app and per-room remotes
- ✓Single outdoor unit dramatically simplifies pad, disconnect, and yard layout
- ✗One shared compressor: a condenser or board failure knocks out all three rooms at once
- ✗Can't heat one zone while cooling another — all zones follow the condenser's mode
- ✗Minimum modulation overshoots single lightly loaded rooms; expect nighttime temperature drift
- ✗No published HSPF2 and no verifiable retail star rating for this exact bundle
- ✗Three penetrations, three drains, and three lineset runs make this a real two-person weekend, not an afternoon
MRCOOL DIY 5th Gen Multi-Zone 36,000 BTU (3-zone)
- ✓Certified 23 SEER2 and 9.9 HSPF2, where the 4th Gen kit had no published HSPF2 at all
- ✓NEEP-listed at 25,200 BTU/h max heat at 5°F with Energy Star cold-climate designation, which helps with rebate paperwork
- ✓Precharged quick-connect linesets in four lengths up to 50 ft, still no vacuum pump
- ✓A 5-port condenser can take a fourth and fifth head later without replacing the outdoor unit
- ✓SmartHVAC app control per zone, with Alexa and Google support
- ✗One compressor for every room: a condenser or board fault leaves all three zones without heat or cooling
- ✗All zones share one mode, so you can't heat one room while cooling another
- ✗No published minimum heating temperature for this condenser, so you can't plan winter heating around a floor yet
- ✗The 12k x3 layout the 4th Gen was known for isn't listed for the 5th Gen; the priced bundle is 9k + 9k + 12k
- ✗About $460 more than the 4th Gen kit it replaces