The 01HT-5M is a Belimo passive surface contact temperature sensor with a NTC 10K Type III (Precon) sensing element and a spring-loaded brass contact pin for fast response and accurate readings on pipe surfaces. It strap-mounts directly to the pipe — no thermowell, no penetration, no shutdown required to install. The included fixing strap fits pipes up to 110 mm (4.33") outside diameter; longer-pipe straps are available as accessories. The signal returns directly to the controller as a resistance — no 24V supply or signal conditioning required.
Chilled-water and hot-water supply/return temperature sensing on copper, steel, and PVC pipe — boilers, chillers, heat pumps, fan coils, and zone hydronic loops. Ideal for retrofits and existing systems where draining the loop or installing a thermowell is impractical. Spring-loaded contact pin and thermal paste deliver response time competitive with insertion sensors.
Key Features
Constant-pressure brass contact pin maintains thermal coupling to the pipe surface even on slightly out-of-round or rough piping. With thermal paste, the typical 63% time constant is just 16 seconds on a water pipe.
Mounts in minutes with the included fixing strap (fits pipes up to 4.33" OD). No pipe penetration, no shutdown, no draining the loop. For larger pipes, the A-22P-A42 strap fits up to 9.8" OD.
Factory-trimmed NTC 10K Type III element delivers stable long-term accuracy with no field calibration required.
Passive resistance returns directly to the controller — no 24V supply, no signal conditioning, no scaling required.
Pluggable terminal block accepts up to 2.5 mm² conductors. The block lifts out for bench-side wiring, then snaps back in — faster than fixed terminals at field installs.
Industry-leading factory warranty backed by Belimo's worldwide service network.
Technical Specifications
| Specification | Detail |
|---|---|
| Sensor Style | Pipe surface contact temperature sensor with spring-loaded brass contact pin |
| Measured Value | Temperature (pipe surface) |
| Sensing Element | NTC 10K Type III (Precon) |
| Measuring Range | -30...195°F [-35...90°C] |
| Application | Water — pipe surface contact |
| Pipe Compatibility | Up to 4.33" [110 mm] OD with included strap; up to 9.8" [250 mm] OD with A-22P-A42 accessory strap |
| Mounting | Strap-on (no penetration, no thermowell required) |
| Cable Entry | 1/2" NPT conduit adapter included — cable gland with strain relief, ø6...8 mm |
| Electrical Connection | Pluggable spring-loaded terminal block, max 2.5 mm² |
| Housing | UV-resistant polycarbonate, orange — UL94 5VA |
| Enclosure Rating | NEMA 1 / IP54 (UL Enclosure Type 1), UL 2043 plenum compliant |
| Protection Class | IEC/EN III, Protective Extra-Low Voltage (PELV) |
| UL Approval | cULus per UL60730-1A/-2-9, CAN/CSA E60730-1/-2-9 |
| UL 2043 Compliance | Suitable for use in air plenums per NEC 300.22(C) and IMC Section 602 |
| Time Constant τ (63%) | 16 s on water pipe with thermal paste |
| Power Required | None — passive resistance element |
| Weight | 0.33 lb [0.15 kg] |
| Manufacturer | Belimo |
| Manufacturer Part Number | 01HT-5M |
| Warranty | 5-year factory warranty |
What's In the Box
- 01HT-5.. surface contact sensor in orange UV-resistant housing
- Fixing strap for pipes up to 110 mm (4.33") outside diameter
- 1/2" NPT conduit adapter
Pluggable terminal block is part of the housing. For optimal accuracy, Belimo recommends thermal paste between the contact pin and pipe — see the A-22P-A40, A-22P-A42 (strap kits with paste pre-applied), or A-22P-A44 (paste-only syringe) in Compatible Accessories below.
Compatible Accessories
Documentation
Frequently Asked Questions
Does this need 24V power?
No. The 01HT-5M is a passive resistance temperature sensor — the controller reads its element directly through the analog input. No 24V supply or signal conditioner needed.
What sensing element is in the 01HT-5M?
The 01HT-5M uses a NTC 10K Type III (Precon). The letter after '01HT-5' identifies the element: A=Pt 100, B=Pt 1000, E=Ni 1000 (JCI), L=NTC 10K Type II, M=NTC 10K Type III (Precon), Q=NTC 20K. Match this to your controller's input curve.
What pipe size does the included strap fit?
The included fixing strap fits pipes 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 accessory strap (linked above).
Do I need thermal paste for accurate readings?
Belimo specifies thermal paste between the contact pin and pipe for the rated 16-second time constant. Without paste, the response slows and absolute accuracy drops by a few tenths of a degree. The A-22P-A40 and A-22P-A42 strap kits ship with paste pre-applied; A-22P-A44 is a paste-only syringe for use with the included strap or for re-application.
Is this a substitute for an immersion sensor in a thermowell?
For most BAS applications — supply/return loops, condenser water, secondary loops — yes. The 16-second time constant rivals many insertion sensors. For high-accuracy primary loops or process control where ±0.1°F matters, a thermowell-mounted insertion sensor (01CT or 01DT) is still preferred. The advantage of the 01HT is no shutdown and no penetration.
What temperature range does it handle?
-30...195°F [-35...90°C]. The brass contact pin and orange polycarbonate housing handle hot-water loops up to about 195°F. For higher pipe temperatures, use a thermowell-mounted insertion sensor.
Does it work with my BAS?
Any BAS controller with a temperature input configured for the NTC 10K Type III curve will read this sensor directly. See the linked Resistance Characteristics PDF for the full curve table at standard temperature points.
How is this different from the 01CT cable sensor with a thermowell?
Both can sense pipe temperature, but the install is different: 01HT is strap-on (no penetration, no shutdown, no thermowell purchase) — fastest for retrofits and existing systems. 01CT in a thermowell penetrates the pipe wall — better isolation from ambient and slightly tighter accuracy, but requires a tap, a thermowell, and a system shutdown to install.
- Sensor Type:
- Strap On (Housing)
- Output Signal:
- Temperature Only
- Temperature Element:
- 10K Type III
- Humidity Element:
- None
- CO2 Element:
- None
- VOC Element:
- None
- Display:
- No Display
- Setpoint:
- No Setpoint
- Override:
- No Override
- Lead Length:
- Terminal Block
- Supported Protocols:
- None
- Enclosure:
- NEMA 1 Enclosure
