How far can the outdoor unit be from the indoor head?

The published maximum line-set length is 65 ft. Measure the planned routing before ordering.

Mitsubishi Electric / M-Series HM

Mitsubishi M-Series HM 18k R-410A 208/230V Mini-Split

Certified capacity: 17,200 BTU/h[3]
SEER2: 19 SEER2[3]
Heating floor: -4 F[4]
Voltage: 208/230V[1]
Install path: Professional install

The M-Series HM 18k is an obsolete (Production Stopped) R-410A value unit at 1.5 tons: SEER2 19, EER2 10.5, HSPF2 9.5, with 18,000 BTU of heat at 47F. It was a budget large-room unit; the current equivalent is the R-454B HX 18k.

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Error Codes

Mitsubishi Electric M-Series HM 18,000 BTU R-410A 208/230V (MSZ-HM18NA / MUZ-HM18NA)

Image: Mitsubishi Electric

Data completeness: 95%

Last sourced: Jul 23, 2026

SplitAtlas score

7.8 / 10

Methodology

Cooling efficiencyBottom quartile

(19.0 SEER2) among 18k systems

Heating efficiencyBelow average

(9.5 HSPF2) among 18k systems

Cold-weather performanceBottom quartile

(17F certified capacity: 63.9% of the 47F rating; -4 F heating floor) among 18k systems

NoiseAbove average

(30 dBA indoor min / 51 dBA outdoor) among 18k systems

WarrantyTop quartile

(10 yr parts / 10 yr compressor) across the catalogue

Feature setBottom quartile

(1 verified feature) across the catalogue

Documentation & partsTop quartile

(9 manuals; spec sheet; parts channel) across the catalogue

Not evaluated

Installation accessibility — not applicable (professional install)N/A
professional install - DIY-accessibility not applicable
Price-to-value — not evaluatedN/A
This is a professionally installed, quote-only system, so we can't score its price. Get an installed quote to compare real cost.
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Key ratings

Rated cooling

17,200BTU/h[3]

Rated heating

18,000BTU/h[3]

Buyer review snapshot

Best for / skip if

Skip if

You are shopping for a current-generation recommendation; catalog lifecycle is LEGACY.

Install difficulty

Professional install

Electrical: 208/230V; MCA 10 A; breaker/fuse 15 A.
Line set: connection type not sourced; max 65 ft.

Alternatives

Blueridge XS6 Max Efficiency 18,000 BTU R-454B 208/230V (BXS6A18WM0 / BXS6A18UC0)
9.2 score / 18k / SEER2 25.6 / -22 F heating floor / 230V
Exact destination at Alpine Home Air: $2,359.00, checked Jul 24, 2026
Senville ELITE 18,000 BTU R-454B 208/230V (SENE-18EL-IHH / SENE-18EL-OH)
9.0 score / 18k / SEER2 25.6 / -22 F heating floor / 187-253V
Exact destination at Senville: $1,899.99, checked Jul 24, 2026
ACiQ Standard 18,000 BTU R-454B 208/230V (ACIQ-18WS-HP230C / ACIQ-18ZS-HP230C)
9.0 score / 18k / SEER2 24 / -13 F heating floor / 230V
Exact destination at HVACDirect: $1,299.99, checked Jul 26, 2026

Availability and price context

This system needs a professional install, so its real price is an installed quote that depends on your home. We don't link to a listing for this exact model; get installation quotes to price it.

Source date

Model data sourced: Jul 23, 2026
Page reviewed: Jul 23, 2026
Source-backed records: 5
Newest source retrieved: Jul 23, 2026

Warranty tiers

Base: 5 yr parts / 7 yr compressor - licensed HVAC contractor installation
Registered: 10 yr parts / 10 yr compressor - owner-occupied residence registered within 90 days of installation
Program: 12 yr parts / 12 yr compressor - owner-occupied residence installed and registered by a Diamond Contractor within 90 days

The score uses Registered. Additional published terms are shown for reference and not counted in the score.

Review methodology

Model context

Mitsubishi dealer channel: Mitsubishi Electric equipment is sold through its dealer network; installed price depends on the local contractor.

Strengths

18,000 BTU rated heat at 47F at a value tier.

Weaknesses

Production Stopped/obsolete and R-410A - phase-out refrigerant.
SEER2 19 / HSPF2 9.5 - basic efficiency; no published 5F rating.
The current HX 18k (R-454B) is the recommended replacement.

Climate suitability

Minimum heating ambient: -4 F[4]
Certified heating at 5F: not published
Rated heating at 17F: 11,500 BTU/h[3]
Rated heating at 47F: 18,000 BTU/h[3]

Specifications

Show

Manufacturer: Mitsubishi Electric
Brand: Mitsubishi Electric
Product line: M-Series HM
Model number: MSZ-HM18NA-U1 indoor / MUZ-HM18NA-U1 outdoor
Indoor unit model: MSZ-HM18NA-U1
Outdoor unit model: MUZ-HM18NA-U1
Number of zones: 1
Max indoor units: not published
Rated cooling capacity: 17,200 BTU/h[3]
Rated heating capacity: 18,000 BTU/h[3]
Voltage: 208/230V[1]
MCA: 10 A[2]
Maximum fuse or breaker size: 15 A[2]
Breaker needed: not published
SEER2: 19 SEER2[3]
EER2: 10.5 EER2[3]
HSPF2 (Region 4): 9.5 HSPF2[3]
HSPF2 (Region 5): not published
COP: not published
COP at 47F: 3.32 COP[2]
COP at 5F: not published
Minimum outdoor heating temperature: -4 F[4]
Minimum outdoor cooling temperature: 14 F[4]
Maximum outdoor temperature: 115 F[4]
Indoor noise range: cooling 47-42-37-30; heating 47-42-37-30[2]
Outdoor noise rating: 51 dBA[2]
Indoor weight: not published
Outdoor weight: 81 lb[2]
Refrigerant: R-410A[3]
Refrigerant charge: not published
Manufacturer coverage: not published
Line-set size: 1/4 in liquid / 1/2 in suction
Included line-set length: Mitsubishi submittals publish line-size and maximum/precharged piping data; the installer supplies the line set.
Maximum line-set length: 65 ft[2]
Max line set per indoor: not published
Maximum elevation difference: 40 ft[2]
Max height between indoor units: not published
Wi-Fi support: supported[2]
Energy Star status: Not ENERGY STAR certified[3]
AHRI certification number: 202680603[3]
Warranty: Base: 5 yr parts / 7 yr compressor (licensed HVAC contractor installation); Registered: 10 yr parts / 10 yr compressor (owner-occupied residence registered within 90 days of installation); Program: 12 yr parts / 12 yr compressor (owner-occupied residence installed and registered by a Diamond Contractor within 90 days). Score uses Registered. Additional published terms are shown for reference and not counted in the score.. Standard residential M-Series warranty is 5 years parts and 7 years compressor from installation by a licensed HVAC contractor. Enhanced residential terms are 10 years parts and compressor for an owner-occupied residence registered within 90 days of installation, and 12 years parts and compressor when installed in an owner-occupied residence by a Diamond Contractor and registered by that Diamond Contractor within 90 days.
Install path: Professional install
Retail price: Installed quote only
Available retailers: not published
Manual links: AHRI certificate 202680603, AHRI public detail 202680603, ENERGY STAR exact row for AHRI 202680603, M-Series HM Mitsubishi Comfort product page, M-Series HM Mitsubishi Comfort product page, MitsubishiPro product record MUZ-HM18NA-U1, MSZ-HM18NA & MUZ-HM18NA Mitsubishi Electric submittal, METUS Residential M-Series, P-Series and SMART MULTI Limited Warranty Statement
Specification sheet: MSZ-HM18NA & MUZ-HM18NA Mitsubishi Electric submittal
Last sourced date: Jul 23, 2026

Parts and filters

Fits Mitsubishi Electric M-Series HM 18,000 BTU R-410A 208/230V (MSZ-HM18NA / MUZ-HM18NA). Part numbers and fit notes identify compatibility only; no manufacturer endorsement is implied.

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