Belimo 22HT-54 : Active Pipe Surface Contact Temperature Transmitter, 4–20 mA (loop-powered), 24 VAC/VDC, 8 Selectable Ranges, NEMA 4X / IP65, Strap Fits Pipes to 4.33" OD, 5-Year Warranty

What output signal does the 22HT-54 provide?

4–20 mA (loop-powered), with max. 500 Ω loop resistance. Two-wire 4-20mA current loop — preferred for long cable runs because the current loop is immune to voltage-drop errors that affect 0-10V signals over distance.

How do the 8 selectable measuring ranges work?

An onboard jumper selects one of 8 measuring ranges, S0 through S7, each spanning a different temperature window. The factory default is S0 (-30 to 130°F), the widest range — useful when you don't yet know what range you need. Once you know your actual monitoring window, switching to a narrower range (e.g. S2 = 40-140°F for domestic hot water) gives you higher analog resolution because the same 0-10V or 4-20mA output span maps to a smaller temperature range. See the Selectable Measuring Ranges table on this page for all 8 options.

Does this need 24V power?

Yes. The 22HT-54 is an ACTIVE transmitter — it requires 24 VAC or 24 VDC power (21.6-26.4 VAC or 13.5-26.4 VDC). Power consumption is 0.8 VA AC / 0.4 W DC. This is the key difference from the passive 01-series equivalent: the 01-series sends raw resistance to the controller, while the 22-series outputs a scaled voltage or current after onboard signal conditioning. The advantage is compatibility with controllers that don't have Pt 1000 input curves; the cost is the need to provide 24V power to each sensor.

What pipe size does the included strap fit?

Up to 4.33" (110 mm) outside diameter — covers most copper and steel pipe through 4" nominal. For larger pipes up to 9.8" OD, use the A-22P-A42 strap accessory.

Do I need thermal paste?

Belimo specifies thermal paste between the brass contact pin and the pipe for the rated 17-second time constant. Without paste, response slows and absolute accuracy drops a few tenths of a degree. The A-22P-A40 / A-22P-A42 strap kits ship with paste pre-applied; A-22P-A44 is a paste-only syringe for use with the included strap.

How is this different from the passive 01HT?

The 01HT family is a passive resistance temperature sensor — it sends raw Pt 1000 (or NTC, Ni 1000) resistance to your controller, which must have a matching input curve. The 22HT family is an active 24V transmitter — it applies onboard signal conditioning and outputs a scaled 0-10V or 4-20mA signal. Choose passive when your BAS has Pt 1000/NTC inputs and you want fewer parts and no power supply concerns. Choose active (this product) when your BAS only accepts voltage/current analog inputs, when you need long cable runs (4-20mA versions are immune to voltage drop), or when you want the jumper-selectable range narrowing for higher resolution.

Does it work with my BAS?

Any BAS controller with a 4–20 mA analog input will read this transmitter directly. Set the controller input scale to match the selected measuring range (e.g., for S0 default, scale your input as -30°F = 0V/4mA, 130°F = 10V/20mA). No special curve or driver needed — it's a standard linear analog signal.