Thermolec · Acu-Steam steam humidifiersThe Thermolec space at AirGreenAcu-Steam steam humidifiers from Thermolec, a Montréal manufacturer, sold and installed by AirGreen in Montréal, Laval, Longueuil, the South Shore and the North Shore.

Mon–Thu 8 a.m.–6 p.m., Fri 8 a.m.–4 p.m.

Thermolec · Steam humidifiers · Updated October 14, 2026

Thermolec Acu-Steam: real steam, no cylinder to replace

Thermolec humidifiers: installation in Montréal, Laval, Longueuil, the South Shore and the North Shore

A Montréal manufacturer founded in 1973, Thermolec makes its steam with heating elements in a stainless tank: nothing to throw away, the tank comes out and gets cleaned. Three sizes, from 4.8 to 12.8 lb/h, sent into your furnace ducts.

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Furnace supply duct
≥ 35 in. of straight duct downstream
Steam hose
Stainless tank and heating elements
Cold water only (≤ 30 °C)
Drain: purge at about 60 °C
≥ 12 in. below the duct

Steam: 9.6 lb/h (4.4 kg/h)
About: 27.6 US gal/day
Electrical: 3 kW · 240 V · 12.5 A
Recommended airflow: 1,200 CFM
Diffusers supplied: 1
At AirGreen: ACU-10PN

Thermolec Acu-Steam manual (Jan 2022, V1.3); two diffusers on the Acu-15 per the brochure.

3: sizes: Acu-5, Acu-10, Acu-15
0: disposable cylinder to buy
10 years: on the element, Thermolec warranty
1973: founded in Montréal

AirGreen × ThermolecSold and installed by AirGreenMade in Montréal since 1973Heating elements, stainless tankNo cylinder to rebuy10-year element warranty, by ThermolecMontréal · Laval · Longueuil · South Shore · North Shore

01 · Which size?

Your furnace sets the starting size.

Thermolec sizes the Acu-Steam by the airflow in the duct: 600, 1,200 or 1,500 CFM recommended. Pick your furnace’s airflow: we show the models it allows. The final choice between them is made on site, based on the house.

Furnace airflow

The airflow is on the furnace’s nameplate or spec sheet.

Your starting point

Acu-5 · Acu-10

Your airflow reaches what Thermolec recommends for the Acu-5 and Acu-10.

Largest model allowedAcu-10
The final choiceon site, based on the house

See the ACU-10PN page

At AirGreenACU-5Acu-5 · 4.8 lb/h · 600 CFM · 1 diffuserSee the product At AirGreenACU-10PNAcu-10 · 9.6 lb/h · 1,200 CFM · 1 diffuserSee the product At AirGreenACU-15PNAcu-15 · 12.8 lb/h · 1,500 CFM · 2 diffusersSee the product

The three Acu-Steam units, per Thermolec’s manual
Model	Steam	US gal/day	Electrical	Recommended airflow	Diffusers	At AirGreen
Acu-5	4.8 lb/h (2.2 kg/h)	13.8	1.5 kW · 120 V · 12.5 A	600 CFM	1	ACU-5
Acu-10	9.6 lb/h (4.4 kg/h)	27.6	3 kW · 240 V · 12.5 A	1,200 CFM	1	ACU-10PN
Acu-15	12.8 lb/h (5.9 kg/h)	36.8	4 kW · 240 V · 16.6 A	1,500 CFM	2	ACU-15PN

Capacities, electrical and recommended airflows: Thermolec Acu-Steam manual, Jan 2022, V1.3. Gallons a day: lb/h × 24 ÷ 8.34 (calculation). Diffusers: Acu-Steam brochure. Thermolec publishes no floor area for the Acu-5, Acu-10 and Acu-15: the final size is confirmed on site.

02 · The cycle

Five steps, from cold water to steam.

Heating elements, not electrodes: in the Acu-Steam, elements boil the water in a stainless tank. Follow the cycle step by step, as Thermolec’s manual describes it.

1 · Call

The humidistat calls for humidity. The electric valve fills the tank with cold water.

Sequence of operation: Thermolec Acu-Steam manual, Jan 2022, V1.3.

Electric valve (step 1)
Pressure switch (step 2)
Heating elements (step 3)
Hose and diffuser (step 4)
Drain: flush (step 5)
Removable stainless tank, water-level sensors

Removable stainless tank
It comes off with a quick-release clamp for cleaning, with no electrical or plumbing connection to undo.
Nothing to rebuy
No replacement cylinder or liner: the self-cleaning elements stay in place.
No steam without airflow
A pressure probe in the duct stops the unit if air isn’t moving, then it restarts on its own.
Automatic flush
The tank flushes after a number of cycles set to the water hardness, and after 7 days without demand.
Display and safeties
Status display, silent relays, high-limit cut-outs, removable pan with an overflow sensor.
Acu-15: two diffusers
The largest model ships with two diffusers, hoses and clamps.

Thermolec Acu-Steam components: stainless diffuser, steam hose, water hammer absorber, solenoid valve — Components from Thermolec’s brochure.

03 · Humidity

The colder it is outside, the lower the setting.

Humid air condenses on cold windows. So Thermolec gives a humidity setting that drops with the outdoor temperature. Move the slider.

Outdoor temperature

‑15 °C

30%

Setting recommended by Thermolec

‑30 °C‑5 °C +

Optional humidistat: wall (RH) or duct (DH), not interchangeable, with an optional S-15 outdoor sensor.

Source: Thermolec Acu-Steam manual, Jan 2022, V1.3, fig. 4a (recommended setting by outdoor temperature).

AirGreen × Thermolec

Thermolec’s steam, a local install.

Thermolec designs and builds the Acu-Steam in Montréal. AirGreen looks with you at the furnace, the panel, the water and the drain, then gives you a quote for the installed unit. Each does what it does best.

What Thermolec brings

Made in MontréalA company founded in 1973, making steam humidifiers since 2007, part of SPX Technologies since January 2026.
Three sizesFrom 4.8 to 12.8 lb/h, matched to the furnace airflow (Acu-Steam manual).
No cylinderHeating elements in a stainless tank that comes out and gets cleaned.
2, 5 and 10 yearsDefects, tank and element, on Thermolec’s terms; labour is not covered (English manual).

What AirGreen brings

Sold and installed by AirGreenIn Montréal, Laval, Longueuil, the South Shore and the North Shore.
Free estimateWe look at the furnace, the airflow, the panel, the water and the drain before pricing.
The manual’s requirementsDedicated circuit, cold water, drain, 35 in. of straight duct: it is all on this page, section 04.
RBQ 5645-9605-01Subclasses 15.8, 15.10 and 16.

The result: the Acu-Steam size that fits your furnace, chosen with you.

Find my size Book my free estimate

04 · On site

What the installation needs in your home.

All of it comes from Thermolec’s installation manual. It’s what our estimator looks at before giving you a quote. Tick what you already have.

≥ 35 in. of straight duct after the diffuser, no elbow
Unit ≥ 12 in. below the bottom of the duct
Hose sloping all the way (4 ft supplied)
Drain: 18 in. free vertical
24 in. clear in front; room above 0 °C, never the attic

0 of 6Tick what is already in place at home. We look at the rest during the estimate.

Electrical
Dedicated circuit: Acu-5 on 120 V (12.5 A); Acu-10 on 240 V (12.5 A); Acu-15 on 240 V (16.6 A). Wire and protection per the Electrical Code.
Water
Cold water only, 1/4 in. tube, 90 psi max and 30 °C (86 °F) max. Non-demineralized water; a softener is suggested above 180 mg/L.
Drain
Rigid drain of at least 1 in. inside diameter, with an air gap; 18 in. of free vertical drop below the unit. Purged water comes out at about 60 °C (140 °F). No drain: a condensate pump of at least 65 GPH at 1 ft.
Duct
Diffuser in the supply duct (1 1/8 in. hole, lower third of a horizontal duct), with at least 35 in. of straight duct downstream. Unit at least 12 in. below the bottom of the duct.
Steam hose
4 ft hose supplied, cut as short as possible (2 ft minimum), sloping all the way; otherwise an S-trap at least 4 in. high.
Location
24 in. clear in front of the unit; never in the attic or a room at 0 °C (32 °F) or colder. Optional wall (RH) or duct (DH) humidistat.

Source: Thermolec Acu-Steam manual, Jan 2022, V1.3 (sections 11 to 18).

05 · Upkeep and warranty

Two cleanings a season, a warranty with dates.

Enter the installation date: we work out the next due dates from Thermolec’s manual and FAQ.

Installation date

Upkeep

Clean the tankat least twice per heating seasoneach season
Replace the STM076 water filterevery year (6 to 12 month life)—
Maintenance checkat least once a year—
Silicone drain tube and water-level sensorsreplace at least every 2 years, with the O-ring—
Summer shutdownfull service, power off, water shut off, tank driedeach summer

Thermolec warranty

Defects
2 years
until —
Tank
5 years
until —
Element
10 years
until —

The 2 years run here from installation, as the English manual says; the French manual counts them from factory shipment.

Defective parts replaced at no charge, shipping included.
Labour not covered (English manual).
Installed by a certified technician, per the written instructions.
Void with misuse or repairs without Thermolec’s written consent.

Sources: Thermolec manual, section 10 (warranty) and sections 8 and 9 (upkeep, summer shutdown); thermolec.com FAQ, read October 14, 2026.

06 · Videos

Thermolec shows it on video.

Two official Thermolec videos: the Acu-Steam cycle and homeowner upkeep. The video loads only when you click.

Watch on YouTube

Thermolec videos on YouTube, linked from the AcuSteam page on thermolec.com (read October 14, 2026).

07 · 2026 rebates

No program pays for a humidifier in 2026.

Checked on October 14, 2026 on each program’s own site. If a rule changes, the official source is what counts.

LogisVert

Hydro-Québec, guide v1.10 of September 15, 2026

No · No humidifier among the eligible measures.

Rénoclimat

Québec.ca, page updated October 13, 2026

No · No humidifier among the mechanical systems.

ENERGY STAR

energystar.gov, product category list

No · No category for humidifiers.

Énergir

energir.com, residential rebates

No · No rebate for a humidifier.

08 · Thermolec

A local manufacturer, on our job sites.

1973Founded in Montréal
2007A full line of steam humidifiers
Jan. 2026Part of SPX Technologies; the Thermolec brand stays

Thermolec designs and builds electric duct heaters, electric boilers, modulating controls and steam humidifiers in Montréal.

2 published Thermolec projects on our projects blog:

February 4, 2026Acu-5 humidifier in Ville-MarieAn Acu-5 on the ducts, in a compact mechanical room.October 7, 2026Thermolec electric backup in CarignanA Thermolec duct heater as backup for a GREE UNIX R32 central heat pump.

Thermolec Acu-Steam humidifier with the Thermolec and AirGreen logos

Thermolec humidifiersThe installation page for the three Acu-Steam units.All our humidifiersSteam, bypass and fan units, all brands.Our projectsAll our published installations.

09 · FAQ

The questions we get.

Search the FAQ

What is a Thermolec steam humidifier?

A unit mounted near the furnace that boils water with heating elements and sends the steam into the supply duct. The furnace air spreads it through the whole house.

Which size do I need?

Thermolec recommends 600 CFM of airflow for the Acu-5, 1,200 for the Acu-10 and 1,500 for the Acu-15. The tool in section 01 shows the models your furnace allows; the final choice is made on site, based on the house.

Do I need to buy a cylinder?

No. The steam comes from elements in a stainless tank that comes out and gets cleaned. There is no replacement cylinder or liner.

What electrical circuit is needed?

A dedicated circuit: 120 V and 12.5 A for the Acu-5, 240 V and 12.5 A for the Acu-10, 240 V and 16.6 A for the Acu-15.

Hot or cold water?

Cold only. Thermolec says hot water harms the unit’s operation; the supply must stay at or below 30 °C (86 °F).

Does it need a drain?

Yes: a rigid drain of at least 1 in., or a condensate pump of at least 65 GPH at 1 ft. Purged water comes out at about 60 °C (140 °F).

Where does it go?

In a heated room, never in the attic or below 0 °C (32 °F), at least 12 in. below the bottom of the duct, with 24 in. clear in front. The diffuser needs at least 35 in. of straight duct downstream.

Is the humidistat included?

No, it’s optional: wall (RH) or duct (DH), with an optional S-15 outdoor sensor.

What humidity should I aim for?

Thermolec recommends a setting that drops with the cold: 40% at -5 °C and up, 35% at -10 °C, 30% at -15 °C, 25% at -20 °C, 20% at -25 °C and 15% at -30 °C, to avoid condensation on windows.

What upkeep does it need?

Clean the tank at least twice a season, replace the STM076 water filter every year, a yearly check, and replace the drain tube and water-level sensors at least every 2 years.

What about summer?

Thermolec calls for a summer shutdown: full service, power off, water supply closed and the inside of the tank dried.

What is the warranty?

Thermolec: 2 years against defects, 5 years on the tank, 10 years on the element. Parts are replaced at no charge, shipping included; labour is not covered per the English manual.

Is there a rebate?

No. LogisVert, Rénoclimat, ENERGY STAR and Énergir don’t cover humidifiers (checked October 14, 2026).

Is Thermolec local?

Yes. Thermolec was founded in Montréal in 1973 and designs and builds its products there. It has belonged to SPX Technologies since January 2026.

How much does it cost?

Price on quotation. The on-site estimate is free: we look at the furnace, the electrical panel, the water and the drain before pricing.

10 · AirGreen

A well-installed Acu-Steam starts with a visit.

We come to see the furnace, the airflow, the panel, the water and the drain. Then, a quote for the installed unit.

Book my free estimate 514 316-2973

RBQ 5645-9605-01 · subclasses 15.8, 15.10 and 16Showroom: 1370 Joliot-Curie St., Unit 712, BouchervilleMon–Thu 8 a.m.–6 p.m. · Fri 8 a.m.–4 p.m.

Sources checked October 14, 2026

Thermolec, Acu-Steam manual (English, Jan 2022, V1.3; French, Jan 2023, V1.3): capacities, airflows, sequence of operation, fig. 4a, installation, upkeep, warranty.
Thermolec, AcuSteam Steam Humidifier page (official videos), Acu-Steam brochure, FAQ and About page, read October 14, 2026.
Thermolec, AcuSteam cleaning flowchart, V1.2 of October 15, 2024.
SPX Technologies, press release of January 20, 2026 (Thermolec acquisition).
Hydro-Québec, LogisVert residential participant guide, v1.10 of September 15, 2026.
Government of Québec, Rénoclimat, page updated October 13, 2026.
ENERGY STAR, product category list, and Énergir, residential rebates, read October 14, 2026.

Price on quotation · free estimate. The three Acu-Steam units are right below.

The Thermolec shop

The three Acu-Steam units, right below.

ACU-5, ACU-10PN and ACU-15PN: filter, then open the product page. Price on quotation.

Thermolec Acu-Steam: real steam, no cylinder to replace

Your furnace sets the starting size.

Five steps, from cold water to steam.

Removable stainless tank

Nothing to rebuy

No steam without airflow

Automatic flush

Display and safeties

Acu-15: two diffusers

The colder it is outside, the lower the setting.