8 components coveredField manual · Dehumidifier
AlorAir Sentinel crawl space / basement dehumidifiers (HD55S, HDi65S, HD90, HDi90): quick sheet
Covers: AlorAir Sentinel low-profile commercial-style dehumidifiers sold for crawl spaces and basements: HD35P / HD35PS (35 PPD AHAM), HD55 (53 PPD), HD55S and HD55P (55 PPD), HDi65S (55 PPD with pump), HD90 (gravity) and HDi90 (90 PPD, built-in pump, duct-able and Wi-Fi versions), plus the larger HDi100 / HDi120. The 'i' models carry a built-in condensate pump; 'S' and 'P' suffixes vary by year. Read the model on the rating label.
Squat metal-cased refrigerant dehumidifiers that installers set in an encapsulated crawl space or on a basement floor. Unlike big-box portables they run in cool spaces (the HD55 sheet and retailer listings give a minimum near 33.8 °F) and drain continuously by gravity hose or an internal pump. Most calls are humidity readings the owner does not believe, a clogged filter or coil, drain or pump trouble, and E-code sensor faults. The refrigerant circuit is sealed and EPA 608.
Safety first
- Unplug before removing panels or the filter; crawl spaces are often damp, so use a GFCI-protected outlet.
- Refrigerant circuit is sealed: no recharge or brazing (refer to an EPA 608-certified technician).
- Crawl space work: check for standing water, exposed wiring and pests before you go in.
How it works
A fan pulls crawl space air through a washable/replaceable filter (MERV-8 on the HD55 / HDi65 family) and across a cold evaporator coil; moisture condenses and drips into a pan, and the air is reheated by the condenser before it leaves. Capacity is quoted two ways: AHAM (80 °F / 60% RH) and saturation (much wetter, warmer air), so a '120 pint' HDi65S is a 55 pint unit at AHAM conditions.
The control reads an onboard humidity sensor (or an optional remote sensor) and cycles the compressor to hold the set point. Continuous mode ignores the set point. Wi-Fi models report the same reading to the app.
In cold air the coil frosts; these units are built to run a defrost routine and keep working down to the low 30s °F, but water removal still drops sharply in a cold, dry crawl space. Little water in winter is normal.
Water leaves by gravity hose on HD models or by the built-in pump on HDi models, which pushes water up and out through a long discharge line; the pump models can still be set up for gravity drain.
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Always confirm values against the tech sheet for the exact model.
OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Large stainless refrigerator set flush between kitchen cabinets by Alex Qian, Pexels License
