What the Quest 876 Exhaust Duct Kit Does
This factory accessory adapts the discharge face of a large Quest dehumidifier to a ducted run. Quest lists it as part number 4039868 for three units. It fits the Quest 876 (4037600), the earlier Quest 746 480V (4037610) and the Quest 706 50 Hz (4041800). The matching intake kit, part 4038642, ducts the return side of the same units. With both kits fitted, the dehumidifier can sit outside the room it serves and still treat the air inside. The 876 moves 1,850 CFM at zero static and removes 876 pints a day at 80 °F and 60% RH. Its ducted energy factor is 6.2 pints/kWh at 73 °F and 60% RH, which meets California Title 24 for ducted installs. Those figures make the exhaust kit worth fitting in rooms where ceiling space is already full of lights and fans. Pair it with the intake kit when the unit has to draw its air from the same room it serves.
Running a Dehumidifier Exhaust Duct the Right Way
A dehumidifier exhaust duct only performs if the run stays short and open. Quest's ducting guidance for the 876 sets a 25 ft limit for the total run. Leave at least 4 ft of straight duct off the unit before the first turn. Keep external static pressure under 0.5 in WG, since more resistance cuts airflow and capacity. Choose grilles and diffusers that do not choke the outlet. Give each dehumidifier its own duct line rather than tying it into a fan or HVAC system. Branch the discharge when the room has corners or benches where air goes stagnant. Seal joints with foil tape and support the duct so it does not sag between hangers. Mount the humidity control in a central spot in the room, not beside the unit. Fitted this way, the dehumidifier treats the whole room while staying out of the canopy space.
Key Features
- Part 4039868: Factory exhaust kit from Quest.
- Three compatible units: Quest 876, 746 480V (4037610) and 706 50 Hz.
- Pairs with intake kit: Part 4038642 ducts the return side.
- Remote placement: Run the unit from a mechanical space.
- Ducted energy factor: 6.2 pints/kWh on the Quest 876 when ducted.
Technical Specifications
| Specification | Value |
|---|---|
| Brand | Quest |
| Part number | 4039868 |
| Type | Exhaust (discharge) duct kit |
| Compatible models | Quest 876 (4037600), Quest 746 480V (4037610), Quest 706 50 Hz (4041800) |
| Matching intake kit | 4038642 |
| Max total duct run | 25 ft |
| Max external static | 0.5 in WG |