The System Builder · MrCool DIY · Single & Multi-Zone
Tell us your rooms.
We build your system.
One room or the whole house — a mini split system only works when the parts match: generation, voltage, line sizes, capacity. This builder does all of that for you. Describe each room, and it sizes the air handlers, matches a condenser (single-zone for one room, multi-zone for up to six), picks compatible line sets, and prices the complete system. If it lets you add it to the cart, it works. Guaranteed compatible.
1Describe your rooms
Square footage, sun, ceilings — we compute each room's BTU load.
2Pick your matched system
Only condensers that fit your rooms' combined load are shown.
3Add it as one bundle
Complete kit in the cart — nothing missing, nothing incompatible.
Every multi-zone combination is checked against MrCool's official condenser/air-handler matchup chart — the same chart in the factory catalog.
Which rooms do you want to heat & cool?
Each room gets its own indoor unit with its own remote and temperature. We size each one from the square footage — no HVAC math needed on your end. Only need one room? Remove the extra — we'll match single-zone systems too.
350 sq ft × 25 BTU ≈ 8,750 BTU
Mounts high on the wall. Most popular, best price, easiest DIY install.
250 sq ft × 25 BTU ≈ 6,250 BTU
Mounts high on the wall. Most popular, best price, easiest DIY install.
Freight is calculated at checkout by weight. Prefer a human? Call (657) 582-0899 and we'll spec your system for free.
What's in a complete system
Four kinds of parts, all of which this builder selects and checks for you:
Why DIY multi-zone works
One quick-connect port per room
Each room's pre-charged line set threads onto its own valve on the condenser — no vacuum pump, no brazing, no refrigerant license. Unused ports simply stay capped, which is why a 4-zone condenser can run two or three rooms today and pick up the rest when you finish the basement.
1 · Outdoor Condenser
The engine of the system. A single-zone condenser is factory-matched to one indoor unit of the same capacity — with a 25 ft pre-charged line set already in the box. A multi-zone condenser powers 2–6 rooms from one unit; every head combination we offer comes straight from MrCool's published matchup chart, and if all heads run at once the condenser automatically caps output at its rating.
1–6 · Indoor Air Handlers
One per room, each with its own remote, thermostat, and Wi-Fi control. Wall mounts are the workhorse; ceiling cassettes disappear into the ceiling; concealed ducted units hide entirely. Sizes run 6k to 36k BTU and can be mixed freely across a multi-zone system.
Pre-Charged Line Sets
Copper refrigerant lines factory-charged and sealed with quick-connect fittings — the reason no HVAC contractor is required. Single-zone condensers ship with a 25 ft set in the box. Multi-zone runs are bought per room and carry a DIYPro communication cable so the condenser can talk to each head. Diameter must match the head per the spec sheet; the builder pairs them automatically.
Mounting & Finishing
A wall-mount bracket keeps the condenser above snow and runoff. Line-set covers give the exterior runs a clean, finished channel. Optional — but this is the stuff people forget to order and wait two weeks for.
System builder questions, answered
How do I know the system it builds will actually work together?+
The builder enforces MrCool’s own compatibility rules on every choice: air handlers must match the condenser’s generation and voltage (single-zone pairs must also match capacity exactly), each line set matches the air handler’s connection size from the spec sheet, and multi-zone runs include the required DIYPro communication cable. For multi-zone systems the head combination is checked against MrCool’s published condenser/air-handler matchup chart — the same chart in the official catalog. If a combination isn’t on it, the builder won’t let you select it.
Can I really install a MrCool DIY multi-zone system myself?+
Yes — the DIY series is the only ductless system designed for homeowner installation. Line sets come pre-charged with refrigerant and use quick-connect fittings, so there’s no vacuum pump and no refrigerant license needed. You’ll need to mount the units, run the line sets through a 3-inch hole, connect the fittings, and have a 230V circuit for the condenser (an electrician is recommended for the circuit).
How many rooms can one system handle?+
One to six. A single room gets a single-zone system — a factory-matched condenser and indoor unit pair. Two to six rooms run from one multi-zone condenser, and each room gets its own indoor unit with independent temperature control — heat one bedroom while cooling the living room. A condenser’s zone count is a maximum, not a requirement: MrCool’s matchup chart lets a 4-zone condenser run two or three rooms today with the spare ports capped, ready for rooms you finish later.
What size air handler does each room need?+
Roughly 25 BTU per square foot: a 12×12 bedroom needs about 6,000–9,000 BTU, a 350 sq ft living room about 9,000–12,000 BTU. Rooms with strong sun or 9ft+ ceilings need about 10% more, and kitchens need roughly 4,000 BTU extra for cooking heat. The builder does this math for you room by room.
What’s the difference between 4th Gen and 5th Gen?+
The DIY 4th Generation runs R-410A refrigerant and carries a Limited Lifetime Compressor warranty when registered — it’s the proven, best-value platform. The DIY 5th Generation is MrCool’s newest: it runs R-454B, a refrigerant with about 78% lower global-warming potential, and posts higher SEER2 efficiency ratings.
What is a line set, and what length should I pick?+
The line set is the pair of pre-charged copper lines that connects each room’s indoor unit to the outdoor condenser. Single-zone condensers ship with a 25 ft set in the box — most installs need nothing more. Multi-zone systems need one line set per room, bundled with the required DIYPro communication cable. Measure the actual path the lines will travel — down the wall, along the exterior, up to the condenser — and choose the next length up. Excess line can be coiled; too short cannot be stretched. Runs past 50 ft on 24k/36k zones can join two sets with MrCool’s coupler kit.
Does the whole system ship together?+
Yes. Your configured system is added to the cart as one bundle — condenser, every air handler, every line set, and accessories — so it ships as a complete, matched package.