GENERAL AIRSTAGE Downflow Conversion Kit for AMUH Air Handler
The genuine GENERAL AIRSTAGE kit for installing an AMUH multi-position air handler in downflow, with air discharged downward.
AirGreen codeAG-AC-00301
514 316-2973 · sales@airgreen.ca
Quick facts
With the GENERAL AIRSTAGE downflow configuration kit (UTD-DFMSB1 or UTD-DFMMB1), an AMUH multi-position air handler can be mounted so that it pushes air downward, into a plenum set below the unit. It carries the GENERAL label, but it is the kit that is also sold under the Fujitsu AIRSTAGE brand. On January 1, 2026, Fujitsu General Limited traded its name for GENERAL Inc.; the kit itself still comes out of the same factories. Since the manufacturer’s R-32 air handlers come in two cabinet sizes, the kit also comes in two sizes.
An air handler installed above its duct system
A common case in the area: the air handler occupies a main-floor closet, while its ducts run lower down, in the basement or the slab. To reach them, the air has to travel down, which is known as the downflow configuration. Same logic for a replacement: if the old unit already blew downward, the kit lets you keep its plenum and the original duct system.
One size per cabinet size
- UTD-DFMSB1: AMUH12KUAS, AMUH18KUAS and AMUH24KUAS air handlers, which share the small cabinet
- UTD-DFMMB1: AMUH30KUAS, AMUH36KUAS and AMUH48KUAS air handlers, which share the medium cabinet
What the conversion requires you to plan
It is best to settle the air handler’s position before installation: the plenum connection, the route the condensate drain will follow and how easily the filter can be reached all flow from that choice. For orientation and drainage, the air handler’s installation manual has the final say. If a GENERAL AIRSTAGE electric heater kit or filter base is added to the project, we account for it in the same visit.
The right mounting, done by our refrigeration technicians
Throughout Montreal, Laval, Longueuil, the North Shore and the South Shore, our refrigeration technicians install AMUH air handlers, GENERAL or Fujitsu AIRSTAGE, in the position that suits the home. RBQ licence: 5645-9605-01. To find out whether the kit is in stock or for a quote, call 514 316-2973 or send an email to sales@airgreen.ca with the air handler model and the number of kits.
When the air handler has to push air down
An air handler set above its ductwork, on a main floor or in a closet, blows downward: this kit makes that configuration possible.
- Air handler in a closet above a basement duct system
- Replacing an existing downflow unit
- Homes where the supply plenum sits below the air handler
- New slab-on-grade builds with floor ducts
2 sizes, one page
Each size has its own AirGreen code. Tap a row to select it.
| Modèle | Cabinet | Air handlers listed by the manufacturer | Part no. | AirGreen code |
|---|---|---|---|---|
| UTD-DFMSB1 – AMUH12, 18 et 24 | Small | AMUH12KUAS, AMUH18KUAS, AMUH24KUAS | UTD-DFMSB1 | AG-AC-00301 |
| UTD-DFMMB1 – AMUH30, 36 et 48 | Medium | AMUH30KUAS, AMUH36KUAS, AMUH48KUAS | UTD-DFMMB1 | AG-AC-00302 |
UTD-DFMSB1: AMUH12, 18 and 24KUAS. UTD-DFMMB1: AMUH30, 36 and 48KUAS.
Specifications
From the manufacturer’s documentation. A value the manufacturer does not publish is not listed.
What to know before installing
- Pick the size by cabinet: AMUH12, 18 and 24 (small) or AMUH30, 36 and 48 (medium).
- The mounting position is decided before installation: it affects the plenum, drain and filter access.
- Follow the air handler installation manual for orientation and condensate drainage.
- The conversion is a job for a qualified refrigeration technician.
You may also need
GENERAL AIRSTAGE Electric Heat Kit for AMUH12-24 Air Handler
GENERAL AIRSTAGE Electric Heater Kit for AMUH30-48 Air Handler
GENERAL AIRSTAGE Filter Base for AMUH Air Handler
GENERAL AIRSTAGE Remote Temperature Sensor – UTY-XSZXZ1
Fujitsu Leak Detection System Accessory – UTYSGZU
GENERAL AIRSTAGE Leak Detection System Accessory – UTYSGZU
Hitachi 5-Wire Adapter for 24 V Thermostat – C3STAT01
Hitachi C1STAT01 5-Wire Thermostat Adapter (airHome)Original partsSee all
Frequently asked questions
Which kit for my air handler?
The manufacturer lists UTD-DFMSB1 for the AMUH12KUAS, AMUH18KUAS and AMUH24KUAS, and UTD-DFMMB1 for the AMUH30KUAS, AMUH36KUAS and AMUH48KUAS. Send us the air handler model number to confirm.
Is it needed for horizontal or upflow installs?
The manufacturer names it a downflow configuration kit. For other positions, follow the air handler installation manual; we confirm what your project needs.
Can it be added to an installed air handler?
Yes, if the unit is being moved or reoriented. The plenum, drain and filter access then need to be reworked.
Can you install it?
Yes. We do the conversion when we install the air handler, everywhere in Greater Montréal.
An AMUH air handler mounted the right way
Tell us the size and the quantity: we confirm availability and send you a quote. Or let our technicians install it for you.
Specifications from the manufacturer’s documentation, checked on October 7, 2026.