Belimo 22HH-500X : Condensation Switch, External Sensor with 6.5 ft Cable, SPDT 1A Relay, LED, Auto Reset, 24V, NEMA 4X, UL 2043, 5-Yr Warranty

What does the 22HH-500X detect, and what does it do when condensation is found?

It detects condensation forming on chilled HVAC surfaces — chilled beam undersides, chilled water piping, AHU cooling coils, evaporator surfaces. When humidity in the room is high enough that the cold surface drops below the dew point, condensation begins to form. The switch trips at the very onset of dew-point formation — BEFORE droplets fall and damage ceiling tiles, finishes, or equipment below. The SPDT relay changes state, which can be wired to: (1) close the chilled-water valve in series with the valve coil to interrupt cooling immediately, (2) trigger a BAS alarm input to log the event and alert operations, or (3) raise the chilled-water supply temperature via a BAS reset routine.

How is a condensation switch different from a leakage switch?

Both are dry-contact relay switches with similar housings, but they detect different things at different stages. A condensation switch (22HH) detects dew-point formation directly on a chilled surface — it trips when water is about to form on cold metal, BEFORE droplets fall. A leakage switch (22HL) detects pooled liquid that has already accumulated. 22HH prevents drips at the trigger; 22HL alerts after the leak. Both can be used together: 22HH on the chilled beam, 22HL on the floor or ceiling tray below.

Why use the external-sensor variant instead of the integrated-sensor 22HH-50?

Two main reasons: (1) Installation flexibility — the housing with the electronics, terminals, and conduit connection can be located in a convenient electrical-access location (junction box, control panel, chilled-beam access panel), while the small sensor probe goes on the chilled surface itself. This is much easier to service than reaching above a suspended ceiling to access the housing. (2) Sensor placement — the small probe can fit in tight or awkward locations (between fins of an evaporator coil, on the underside of a small-diameter chilled-water pipe, in a corner of a chilled-beam coil) where the full housing wouldn't fit. The trade-off is a slightly higher price ($375 vs $343) and one extra cable to route during installation.

Where should I install this sensor on a chilled beam?

Mount the sensor (the housing for 22HH-50, the probe for 22HH-500X) on the coldest surface of the chilled beam — typically the chilled-water supply pipe inlet, or the underside of the beam at its lowest point where any condensation would naturally collect first. The sensor needs to be in direct thermal contact with the cold metal so it tracks the chilled surface temperature, not the room air temperature. Avoid mounting on the chilled-water RETURN side (slightly warmer than supply) or on insulated portions of the beam. For ceiling-mounted chilled beams, the typical installation is in the access panel area above the suspended ceiling, with the sensor in direct contact with the supply pipe.

How is the relay output wired to interrupt cold water flow?

Wire the relay's Normally Closed (NC) and Common (C) contacts in series with the cooling valve coil's power supply. Under normal conditions the contacts are closed, so the BAS can drive the valve normally. When condensation is detected, the contacts open, breaking the valve coil supply and forcing the valve closed (spring-return to closed on most Belimo cooling valves). This is fail-safe — if the sensor loses power, the contacts also open and the valve closes.

What happens when the condensation dries?

The unit automatically resets: the sensing element dries (room dew point falls below the chilled surface temperature, or the surface warms up), the LED returns to green, and the relay returns to its normal state. The cooling valve is automatically re-enabled to follow the BAS demand signal. No manual reset button, no field re-arming — particularly valuable for chilled-beam installations above suspended ceilings where service access requires removing ceiling tiles. If the BAS needs to log the event, the controller should latch the alarm signal internally; the sensor itself doesn't preserve event history.

Can I use this in a ceiling plenum / above suspended ceiling?

Yes — the unit is UL 2043 plenum compliant per NEC 300.22(C) and IMC Section 602, allowing installation in air-handling ceiling plenums. This is important because chilled-beam condensation switches typically mount in the access area above the suspended ceiling, where the chilled-water piping and beam access panels are. UL 2043 confirms the housing material and electronics meet the smoke and flame requirements for plenum use without requiring a separate conduit enclosure.

Does it need 24V power?

Yes — 24 VAC or 24 VDC supported (AC 21.6-26.4V / DC 13.5-26.4V). Power consumption is 1.6 VA AC / 0.8 W DC — compatible with standard 24V control transformers shared with actuators and other sensors. Note that the relay output is a dry contact (passive) — the supply voltage to the load circuit (valve coil or BAS alarm input) must be provided externally.

What temperature range does the sensor work in?

Ambient temperature -4 to 122°F (-20 to 50°C); the chilled-surface (fluid) temperature it can be mounted on ranges from -4 to 140°F (-20 to 60°C). This covers all standard HVAC chilled-water applications. For surfaces colder than -4°F (such as refrigeration evaporators below typical HVAC chilled-water temperatures), the sensor falls outside its rated range and a different condensation detection technology should be specified.