The maker's photo for this series, not this exact size; the outdoor unit grows with capacity
MRCOOL · Multi-Zone DIY
DIYM336HPW06C28
~$4,600approximate retailer price at last check, equipment only
Discontinued. MRCOOL replaced it with the MRCOOL DIY 5th Gen Multi-Zone 36,000 BTU (3-zone). Leftover stock still turns up; the specs below are for this model.
Best forZoning three bedrooms or a whole ranch-house level without ductwork or a pro install budget.
This is the 'zone the whole upstairs' package: a 36k condenser driving three 12k heads, most commonly master, kids' room, and office. At roughly $4,600 it undercuts pro-installed three-zone systems by $6,000-8,000, which is why it shows up constantly in ranch-house retrofit threads. The install is genuinely a weekend for two people, but the complexity is in planning: three wall penetrations, three condensate drains, and three precharged linesets converging on one pad. Owner grumbles mirror the 2-zone — no mixed heating/cooling across zones, and with three small heads the condenser's minimum output can overshoot a single lightly loaded room, so bedrooms can drift a degree or two past setpoint overnight. MRCOOL publishes 21.5 SEER for the multi condenser but no verified HSPF2 for this configuration. If a zone board dies, all three rooms are down until parts arrive — the flip side of the single-condenser convenience. Leftover stock is still the cheapest legitimate path to a zoned, ducted-free house you install yourself.
No current listing on NEEP's cold-climate heat pump list. NEEP drops models that are no longer made, so a retired unit can be missing even if it was once listed. MRCOOL rates it to keep running down to -13°F; without a listing there's no certified 5°F capacity figure to check that claim against.
Covers the MRCOOL DIY (4th and 5th Gen) line as a whole, summarised from 75 owner discussion threads, with the replies on the 12 most-discussed.
Owners who have lived with MRCOOL DIY systems mostly talk about them as the cheap, do-it-yourself way to get a heat pump into a garage, shed, outbuilding or a few rooms. Several owners describe the install as easy: one dual-zone 18k owner put the cost at about a third of a comparable installed Mitsubishi, another says it saved them $9,200 in labor, and an owner who has installed about five in a garage and individual rooms says they have been working well so far and is considering another. A common attitude is that if the unit dies in seven years they will buy another and still be ahead. A 5th Gen 18k owner running it alongside an oil boiler ran the numbers through a fuel-cost calculator and concluded the heat pump is cheaper than oil at their prices. Most of the specific multi-zone ownership stories come from 4th Gen systems (27k and 36k outdoor units with 9k to 24k heads).
The problems owners bring back are leaks and multi-zone quirks. One 27k multi-zone owner had a good first six months, then heads freezing over, eventually weekly, which turned out to be a refrigerant leak; another had a leaking low-pressure switch that led to a compressor warranty swap and left them unsure how to reconnect the sealed line set without letting air in. On a two-zone system, an idle head and its attic line set sweated and dripped into the house while the other zone ran, and heads piped through an attic need a condensate pump that one owner could not find listed for the small 9k wall unit. In the cold, a 24k garage owner who calls the install poorly done says it does not come close to its published efficiency, a reply says it works only a little below zero, and another points out the ductless DIY line is not a hyper-heat unit. The newer DIY Easy Pro on R-454B needs a 7.3 ft minimum room height, and MRCOOL told one buyer not to go below it in a 7 ft basement.
By the evidence, it suits handy owners conditioning a garage, shop, outbuilding or a few rooms who value the precharged quick-connect line sets over a long service life. Owners who have installed both kinds say a standard flare-and-vacuum mini-split is only a little more work and more flexible, and a couple would skip the quick-connect next time. Expect that local techs may not want to touch it.
Plan a real two-person weekend, not an afternoon. Each of the three 12k heads gets the same no-vacuum quick-connect process, but you're making three wall penetrations, running three condensate drains, and routing three linesets back to a single condenser location — the routing puzzle is usually the hardest part. Sketch every lineset run before you drill the first hole.
No. All three heads share one compressor, so every zone follows the condenser's mode — all heating or all cooling. Each room does get its own independent temperature setpoint, remote, and schedule through the SmartHVAC app, which covers the common case of bedrooms wanting different temperatures at night.
All three rooms lose conditioning at once — that's the structural tradeoff of any multi-zone versus separate single-zone systems. Given that board failures are the most-reported repair across the DIY series, it's worth registering the 7-year/5-year warranty immediately and keeping a backup heat option for bedrooms in winter.
Not perfectly. The 36k condenser's minimum modulation is more than one lightly loaded 12k head needs, so a single closed-door bedroom calling for a small load tends to overshoot, and owners report some nighttime temperature drift. Running multiple zones together keeps the system in its comfortable modulation range.
A lot — at roughly $4,600 for the kit, it typically undercuts pro-installed three-zone quotes by $6,000-8,000, which is why it shows up constantly in ranch-house and whole-upstairs retrofit threads. Everything runs off one 208/230V circuit and one outdoor unit, which also simplifies the pad, disconnect, and yard layout.
MRCOOL · Multi-Zone DIY
~$5,063
Zoning three rooms you'll install yourself, in a house cold enough that certified 5°F output matters more than the lowest kit price.
Series photoMRCOOL · Multi-Zone DIY
~$3,971
Two rooms now, with a third or fourth possible later, where yard space or panel capacity allows only one condenser and one circuit.
Series photoDiscontinuedMRCOOL · Multi-Zone DIY
~$3,500
Two-room setups — master plus living area — where yard space or panel capacity only allows one condenser and one circuit.