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GeneralAire · Updated October 20, 2026
GeneralAire is General Filters, a family company founded in 1937 in Detroit. At AirGreen: 10 humidifiers (bypass, fan-powered or steam) and 2 Wi-Fi dehumidifiers. Before any model, one question: does your heating air reach 120 °F?
One question · your heating
Furnace air: 120 °F or more
10 of 10 humidifiers suit.
Verdicts from GeneralAire’s manuals. See the quotes
01 · Three ways to humidify
All three mount on the ducts of a forced-air system. What changes: where the heat that evaporates the water comes from.
Water runs over a pad. A 6 or 7 in bypass duct sends warm air through it. Water that does not evaporate goes to the drain, which carries the minerals away.
Same idea, with a built-in fan that pulls warm furnace air through the pad (GeneralAire FAQ).
Current runs through the water between electrodes inside a cylinder, and the steam is blown into the duct. GeneralAire: “Operates independently of the furnace” (GF5500).
In summer, the opposite: GeneralAire also makes two Wi-Fi dehumidifiers. See section 06.
02 · Heat pump or furnace
A heat pump blows cooler air than a furnace. GeneralAire rates its evaporative humidifiers at 120 °F plenum air. Here is what it writes, word for word.
| Model | GeneralAire writes | In plain words | Source |
|---|---|---|---|
| GF1042DMM, GF1042DMD | The unit is not recommended for heat pumps. | Not recommended Not recommended with a heat pump. | GF-1042DMM manual, 10-2023 |
| GF1099LHD | The unit is not recommended for heat pumps or plenum temperatures < 120° F. | Not recommended Not recommended with a heat pump or below 120 °F plenum air. | 1099LHS manual, 02-2022 |
| GF1137L | The unit is not recommended for heat pumps or plenum temperatures < 120° F. | Not recommended Not recommended with a heat pump or below 120 °F plenum air. | GF-1137L manual, 05-2021 |
| GF4200DMM | Designed for Lower Plenum Temperatures | Cooler air Built for cooler plenums; its output is still rated at 120 °F. | GF4200DMM page, generalaire.ca |
| GF3200DMM | — | Not stated GeneralAire says nothing about heat pumps. | GF-3200DMM/4200DMM manual |
| GF5500 | Operates independently of the furnace | Suitable Steam does not depend on furnace heat. | GF5500 page, generalaire.ca |
| GFDS15PBU, GFDS25PBU, GFDS25LCBU | Self contained immersed electrode design | Suitable Electrode steam; needs at least 1,000 CFM in the duct and an air pressure switch. | DS15P/DS25/DS25LC spec sheet and manual 25-32 |
Plenum air temperature is measured on site, with the system running.
AirGreen × GENERALAIRE
GeneralAire designs three technologies and publishes its outputs, its limits and its warranty. AirGreen looks at your heating, your plenum air, the duct and the drain, then installs. Each does what it does best.
The result: the right GeneralAire for your heating, chosen with you and installed by AirGreen.
03 · The lineup
Figures from GeneralAire’s spec sheets and manuals. The bar shows the published output, out of 35 gal/day.
12 gal/day at 120 °F
17 gal/day at 120 °F
17 gal/day at 120 °F
17 gal/day at 120 °F
19 gal/day at 120 °F
18 gal/day at 120 °F
Up to 28.5 gal/day (230 V, 14.5 A); 20.9 as shipped
15.8 gal/day (5.5 lb/h)
25 to 35 gal/day (9 to 12 lb/h), factory-set at 70%
25 to 35 gal/day, for 125 to 400 µS/cm water
75 pints/24 h at 80 °F and 60% RH
100 pints/24 h at 80 °F and 60% RH
GF1042DMM and GF1042DMD: the same unit, only the control differs (MHX3 manual or GF-X3 digital). Areas are “up to” figures from GeneralAire, which publishes no figure by construction type. Elsewhere on the site: GeneralAire humidifiers · all our humidifiers.
04 · How many gallons
The method printed in GeneralAire’s steam manuals (GF5500 and DS series): area × ceiling height × factor × 1.05 per fireplace × 2.88. The factor assumes 0.5 air changes per hour.
Ceiling height
Indoor temperature
Target humidity
Fireplaces
20.0 gal/day
3,500 sq ft × 9 ft × 0.0002 × 1.052 × 2.88
Models whose published output meets this need:
Starting values: the example in GeneralAire’s manual (3,500 sq ft, 9 ft, 70 °F and 40%, 2 fireplaces = 20 gal/day). It is a ballpark: the quotation decides.
05 · The right setting
The table printed in GeneralAire’s manuals (1042, 1099, 1137, 5500, DS series). Slide the outdoor temperature.
| Outside | Suggested setting |
|---|---|
| −29 °C (−20 °F) | 15% |
| −23 °C (−10 °F) | 20% |
| −18 °C (0 °F) | 25% |
| −12 °C (+10 °F) | 30% |
| −7 °C (+20 °F) | 35% |
| −1 °C (+30 °F) | 40% |
25 %
Closest row in GeneralAire’s table: −18 °C (0 °F).
The GF5500 comes with the GFX4 humidistat, which has an outdoor sensor and an outdoor-temperature compensation mode (GFX4 brochure).
06 · Dehumidifiers
Two Wi-Fi touchscreen dehumidifiers, standalone or ducted (GeneralAire spec sheet 06-2021, manual 300-8105).
The GF-DH75 covers up to 3,800 sq ft according to GeneralAire; the GF-DH100 does too, with more headroom.
| GF-DH75 | GF-DH100 | |
|---|---|---|
| Capacity | 75 pints/24 h | 100 pints/24 h |
| Test condition | 80 °F, 60% RH | 80 °F, 60% RH |
| Area | Up to 3,800 sq ft | Up to 5,200 sq ft |
| Airflow | 180 CFM, 8 in collars | 220 CFM, 10 in collars |
| Efficiency | 2.0 L/kWh | 1.86 L/kWh |
| Power | 120 V, 6.2 A | 120 V, 8.8 A |
| Filter | MERV 11, 10 × 12 × 1 in, every 6 months | MERV 11, 12 × 12 × 1 in, every 6 months |
| Drain | ¾ in gravity drain, trap included; optional pump | ¾ in gravity drain, trap included; optional pump |
| Operating air | 50 to 90 °F | 50 to 90 °F |
| Weight | 58 lb | 65 lb |
When ducted, GeneralAire calls for an interlock with the system fan. See also: GeneralAire dehumidifiers · all our dehumidifiers.
07 · Warranty
GeneralAire’s Canadian warranty chart (updated November 14, 2025), its Warranty Coverage page and manuals.
5 years on the solenoid valve only
For the whole brand
08 · Rebates
Checked on October 20, 2026, on each program’s own site.
Guide v1.10 of September 15, 2026 covers no humidifier or dehumidifier.
No standard for humidifiers. Dehumidifiers (V6.0 spec): GF-DH75 and GF-DH100 are not on the certified list.
Covers air exchangers and drain-water heat recovery, not these units.
Nothing for these units; the federal Greener Homes program is closed.
09 · GeneralAire
Today: General Filters, Inc., a third-generation family company based in Novi, Michigan. In Canada: Canadian General Filters Ltd., 400 Midwest Road, Toronto, selling through wholesalers. The “GF-” codes are the Canadian model codes.
10 · FAQ
GeneralAire advises against the GF1042, GF1099LHD and GF1137L with a heat pump. It presents the GF4200DMM as built for cooler plenums, and its steam humidifiers do not depend on furnace heat.
Bypass evaporates water from a pad using the system’s warm air (24 V). Steam boils the water between electrodes using electricity, on a dedicated 120 or 230 V circuit, and needs a new cylinder at least once a year.
It is the same humidifier. The DMM comes with the MHX3 manual humidistat, the DMD with the GF-X3 digital humidistat.
Use the calculation in section 04: it is the method from GeneralAire’s steam manuals. The manual’s example, a 3,500 sq ft home with 9 ft ceilings and 2 fireplaces, gives 20 gal/day.
According to GeneralAire’s table: 15% at −29 °C (−20 °F) outside, 25% at −18 °C (0 °F), 35% at −7 °C (+20 °F) and 40% at −1 °C (+30 °F). Section 05 gives the row that matches your temperature.
Yes. On bypass and fan units, water that does not evaporate goes to the drain. On steam units, the cylinder drains with water tempered below 140 °F. The dehumidifiers have a ¾ in gravity outlet, with an optional pump.
A new pad each season on bypass and fan units, a new cylinder at least once a year on steam units, and a MERV 11 filter every 6 months on the dehumidifiers.
No. GeneralAire covers parts only, and the warranty is void if the unit is not installed by a licensed contractor.
For steam units, the 5-year warranty depends on registration. Dehumidifiers must be registered within 30 days of installation. Without registration, GeneralAire accepts a proof of purchase or installation.
No, not as of October 20, 2026: no LogisVert, ENERGY STAR, Rénoclimat or Énergir program for these units (section 08).
Cold tap water, with no softener. The GF5500 accepts 125 to 1,250 µS/cm, the GFDS15PBU and GFDS25PBU 400 to 1,250, and the GFDS25LCBU is made for very soft water, 125 to 400 µS/cm.
Yes, on 115 V it tops out at 13.9 gal/day. It ships set to 230 V and 11 A, or 20.9 gal/day; set to 14.5 A, it gives 28.5 gal/day. It needs a dedicated 20 A circuit.
Price on quotation. The quotation is free.
No answer contains that word. Call us at 514-316-2973.
AirGreen · Montréal, Laval, Longueuil, South Shore and North Shore
Heating type, air temperature, room on the duct, electrical circuit, drain: it all shows on site. The in-home estimate is free.
Sources checked on October 20, 2026. Figures are GeneralAire’s; the quotation confirms the model and the installation.
Price on quotation. The quotation is free.
AirGreen × GENERALAIRE
The product count updates by itself.
The GeneralAire shop
Bypass, fan-powered, steam and dehumidifiers: open each model’s product page. Price and availability on quotation.
