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Added to comparison 
GOODMAN · Series 19 · Series 21 · GLZS4B · GLZS4MThe GOODMAN space at AirGreenSold and installed by AirGreen. Montreal, Laval, Longueuil, the South Shore and the North Shore.
All of GOODMANGOODMAN//Multi-zone//2 zones
Goodman 2-zone heat pump: eight head pairs, three outdoor units
For two rooms, the GOODMAN Series 21 has three multi-zone outdoor units, and GOODMAN publishes the head pairs each one accepts: three on the 18,000, six on the 27,000, eight on the 36,000. Pick your two heads: the tool shows which outdoor unit they go on.
The question this page answersTwo rooms: which pair of heads on which Goodman outdoor unit, 18,000, 27,000 or 36,000?
17,000 BTU/hrated cooling of the "18,000"Source 1, p. 7
11,800 BTU/hrated heating of the 18,000 at -8.3 °CSource 2, p. 7
28,800 BTU/hpublished maximum of the 36,000 at -15 °CSource 1, p. 7
131 fttotal line length allowed on the 18,000Source 1, p. 7
Goodman dual-zone systems, one per outdoor unit
One product page per outdoor unit, one variant per pair of heads. Each page leads to a quote request.
Tool//The pair
Your two heads on the three outdoor units
Pick the size of each head. For the 18,000, the 27,000 and the 36,000, the tool shows whether GOODMAN publishes the pair, compares the head total with the outdoor unit's rated cooling, and shows the heating GOODMAN publishes for that unit at -8.3 and -15 °C.
The pair, MST…E21 outdoor unitsSources 1 and 2, p. 7
First head (BTU/h)
Second head (BTU/h)
9,000 + 12,000: heads totalling 21,000 BTU/h
Wall heads MSH093E21AXAA + MSH123E21AXAA
18,000Published pair
MST183E21MCAA
Your heads: 4,000 BTU/h more than the unit's rated cooling (17,000 BTU/h, AirGreen calculation)
- Rated heating at -8.3 °C
- 11,800 BTU/h
- Maximum heating at -15 °C
- 14,200 BTU/h
27,000Published pair
MST273E21MCAA
Your heads: 6,000 BTU/h less than the unit's rated cooling (27,000 BTU/h, AirGreen calculation)
- Rated heating at -8.3 °C
- 16,800 BTU/h
- Maximum heating at -15 °C
- 20,900 BTU/h
36,000Published pair
MST363E21MCAA
Your heads: 15,000 BTU/h less than the unit's rated cooling (36,000 BTU/h, AirGreen calculation)
- Rated heating at -8.3 °C
- 25,400 BTU/h
- Maximum heating at -15 °C
- 28,800 BTU/h
Total of your headsOutdoor unit's rated coolingFull bar: 48,000 BTU/h
Pair published on all three outdoor units. It is sold as a variant on all three product pages; the heating needs of both rooms decide between the 18,000, the 27,000 and the 36,000.
All three bars use the same scale, from 0 to 48,000 BTU/h: black is the total of your heads, the turquoise mark is each outdoor unit's rated cooling. The GOODMAN brochures we read give no maximum ratio between the two. The heating shown is what GOODMAN publishes for the outdoor unit; no value is published pair by pair. The rated value at -8.3 °C and the maximum at -15 °C are two different measures: the maximum can exceed the rating without the unit heating better in deeper cold.
GOODMAN//Before you choose
Two single-zone wall units or one dual zone?
Without multi-zone, each room needs its own single-zone wall unit. Here we compare with two Goodman 21 12,000 units, the smallest single-zone Series 21 unit, the same series as the dual zone's heads.
| Published value or sum | 2 × Goodman 21, 12,000 | Dual zone 18,000 |
|---|---|---|
| Outdoor units | 2 | 1 |
| Rated cooling | 2 × 12,000 = 24,000 BTU/h | 17,000 BTU/h |
| Rated heating at 8.3 °C (47 °F) | 2 × 12,000 = 24,000 BTU/h | 18,000 BTU/h |
| Published maximum at -15 °C | 2 × 8,000 = 16,000 BTU/h | 14,200 BTU/h |
| SEER | 21.5 | 21.3 |
| Minimum circuit ampacity / maximum fuse | 12 / 15 A, two circuits | 18 / 25 A, one circuit |
| Outdoor unit sound | 55 dB(A) each | 62.4 dB(A) |
| Outdoor unit, W × D × H | 31.50 × 13.11 × 21.81 in | 33.27 × 14.29 × 27.64 in |
| Maximum line length | 82 ft per unit | 82 ft per head, 131 ft in total |
With two single-zone units, GOODMAN publishes more capacity in total; the dual zone fits on one outdoor unit and one circuit. Where the documents disagree, we picked one value and say which. Sound of the single-zone 12,000: 40 dB(A) in the 03-21 brochure, 55 in the 06-21 revision, 57.5 in the 2018 document; we keep the 06-21 revision. Line length on the 18,000: 131 ft in total and 82 ft per head in the 03-21 and 06-21 brochures, 98 and 25 ft in the 2018 French-language document; we keep the two 2021 brochures, more recent and in agreement.
GOODMAN//The three outdoor units
18,000, 27,000, 36,000: what GOODMAN publishes for each outdoor unit
Values with wall heads, from the 03-21 brochure and its 06-21 revision. In its 2018 French-language document, GOODMAN writes that they apply to the maximum number of 9,000 wall heads recommended on each outdoor unit (source 3, p. 11).
GOODMAN data, sources 1 to 3
| Published value | 18,000 | 27,000 | 36,000 |
|---|---|---|---|
| Outdoor unit | MST183E21MCAA | MST273E21MCAA | MST363E21MCAA |
| Number of heads | 2 | 2 or 3 | 2 to 4 |
| Published pairs (AirGreen count) | 3 | 6 | 8 |
| Rated cooling | 17,000 BTU/h | 27,000 BTU/h | 36,000 BTU/h |
| SEER | 21.3 | 22.0 | 22.5 |
| Rated heating at 8.3 °C (47 °F) | 18,000 BTU/h | 28,000 BTU/h | 36,000 BTU/h |
| COP at 8.3 °C (47 °F) | 3.7 | 3.7 | 3.1 |
| Rated heating at -8.3 °C (17 °F) | 11,800 BTU/h | 16,800 BTU/h | 25,400 BTU/h |
| Published maximum at -15 °C (5 °F) | 14,200 BTU/h | 20,900 BTU/h | 28,800 BTU/h |
| HSPF region IV / region V | 10.0 / 8.6 | 9.8 / 8.0 | 10.3 / 9.0 |
| Minimum circuit ampacity / maximum fuse | 18 / 25 A | 25 / 35 A | 30 / 45 A |
| Outdoor unit sound | 62.4 dB(A) | 63.4 dB(A) | 62.3 dB(A) |
| Outdoor unit, W × D × H | 33.27 × 14.29 × 27.64 in | 37.24 × 16.14 × 31.89 in | 37.24 × 16.14 × 31.89 in |
Two rows, two measures: the rated heating at -8.3 °C and the published maximum at -15 °C. A higher value at -15 °C does not mean more heat in deeper cold.
Compare//Same outdoor unit
The 27,000 as a 2-zone or a 3-zone system
The same MST273E21MCAA is sold twice, as a dual zone and as a tri-zone. What changes is how it is shared. GOODMAN values from sources 1 and 2, p. 7; the head totals are sums.
2 zonestwo heads on the 27,000
3 zonesthree heads on the 27,000
| On the MST273E21MCAA | 2 zones | 3 zones |
|---|---|---|
| Published combinations | 6 | 5 |
| Smallest head total | 18,000 BTU/h, 9 + 9 | 27,000 BTU/h, 9 + 9 + 9 |
| Largest head total | 36,000 BTU/h, 18 + 18 | 36,000 BTU/h, 9 + 9 + 18 or 12 + 12 + 12 |
| 18,000 heads | in 3 pairs out of 6 | in 1 trio out of 5 |
| Ports in use | 2 of 3 | 3 of 3 |
| Outdoor unit's rated heating at -8.3 °C | 16,800 BTU/h, one published value | the same |
No heating value is published for two heads. See the 3-zone page.
Did you know//GOODMAN documents, AirGreen calculations
Three dual-zone figures from GOODMAN's documents
01
Same box as the 18,000 wall unit
The dual zone's MST183E21 outdoor unit has the same footprint as the outdoor unit of the Series 21 MSH183E21 wall system: 33.27 × 14.29 × 27.64 in. It holds 70.5 oz of R-410A, against 68.8 oz for the wall system.
Source 1, p. 6 and 702
On the 18,000, the total limit already bites with two heads
GOODMAN publishes 82 ft per line and 131 ft in total: two 82-ft lines would make 164 ft. If one runs 82 ft, the other stops at 49 ft (AirGreen calculation).
Source 1, p. 703
No 18 + 24, no 24 + 24
A 24,000 head forms only two pairs, 9 + 24 and 12 + 24, both on the 36,000. The same unit does take 18 + 18.
Source 1, p. 7AirGreen × GOODMAN//Who brings what
What each one brings to your two rooms
What GOODMAN brings
- Three Series 21 multi-zone outdoor units, from 18,000 to 36,000 BTU/h, on R-410A
- A table of allowed head pairs, outdoor unit by outdoor unit
- Published heating values at 8.3, -8.3 and -15 °C for each outdoor unit
- Wall heads from 9,000 to 24,000 BTU/h, the largest kept for the largest outdoor units
What AirGreen brings
- The on-site estimate: both rooms, the size of each head, the wall for the outdoor unit
- Installation by our refrigeration technicians, under AirGreen's RBQ licence 5645-9605-01
- Running both refrigerant lines within the lengths GOODMAN publishes for the chosen outdoor unit
- One quote for the outdoor unit, both heads and the installation
Questions//2 zones
Questions about the Goodman dual zone
Which outdoor unit for two rooms?
The one whose GOODMAN combination table lists your pair. 9 + 9, 9 + 12 and 12 + 12 fit all three; an 18,000 head needs the 27,000 or the 36,000; a 24,000 head, the 36,000. When the pair is published on more than one outdoor unit, the on-site assessment of each room's heating needs decides.
Does the "18,000" cool 18,000 BTU/h?
Not with wall heads: in the 06-21 revision of its brochure, GOODMAN rates it at 17,000 BTU/h of cooling, and 18,000 with all-ducted heads. For heating at 8.3 °C, it is rated at 18,000 BTU/h.
Can the two heads add up to more than the outdoor unit?
Yes, GOODMAN's combination table allows it: on the 18,000, the 12 + 12 pair adds up to 24,000 BTU/h against 17,000 of rated cooling. The outdoor unit supplies heat and cooling to both heads, and GOODMAN publishes its capacities for that unit.
Can a ducted head be part of the pair?
The 2-zone table in GOODMAN's 2021 brochure covers "Wall mount and ducted" heads. The variants we sell are wall heads; a pair with a ducted unit is quoted separately. With two ducted heads, the 06-21 revision gives the 18,000 a SEER of 18.5 instead of 21.3.
Does the Goodman dual zone qualify for Hydro-Québec's LogisVert financial assistance?
No, not today. Since November 26, 2025, Hydro-Québec only accepts ENERGY STAR certified heat pumps. The ENERGY STAR list read on November 5, 2026 holds no MST…E21 system. GOODMAN's 2018 and 2021 documents announced the 18,000 and the 27,000 as ENERGY STAR compliant with the right head combination; none of those combinations is on the list we read.
Read next//The GOODMAN space
Related pages
Two rooms in your home: we start with the rooms, not the equipment
Each head is chosen for its room; the outdoor unit comes next, among the ones GOODMAN lists for that pair.
Sold and installed by AirGreen.Montreal, Laval, Longueuil, the South Shore and the North Shore.
Free on-site estimate
An AirGreen technician assesses the heating and cooling needs, where the units will go and the refrigerant line route on site before proposing a model.
RBQ licence 5645-9605-01
Subclasses 15.8, 15.10 and 16. Gas and oil work is done by a partner holding the required licence.
The equipment is GOODMAN-branded. AirGreen sells it, installs it and services it across Greater Montreal.
Sources
- GOODMAN, "Heat Pump and Air Conditioner Ductless Units", 19 Series and 21 Series, code CB-DL-1921S-HP 03-21, p. 6 and 7. GOODMAN document kept in AirGreen's files.
- GOODMAN, same brochure, revision CB-DL-1921S-HP 06-21, p. 6 and 7.
- GOODMAN, "Thermopompe et climatiseur simple et multizones" (French-language document), code CB-GDuctless2018-FR 10.18, p. 9 to 11.
- ENERGY STAR, certified heat pumps (dataset w7cv-9xjt), Canadian market, read November 5, 2026. energystar.gov
- Hydro-Québec, "LogisVert Efficient Homes Program – ENERGY STAR® Heat Pump", partner notice of September 25, 2025 (required from November 26, 2025). hydroquebec.com
Read and dated by AirGreen. Capacities and limits are the ones GOODMAN publishes; a real installation can give other values.