Symaro dual-output sensing for ventilation and air-conditioning ducts
The Siemens QFM1660 is an active Symaro duct sensor designed to measure relative humidity and temperature in ventilation and air-conditioning systems. A capacitive element monitors duct humidity, while a temperature sensing element measures air temperature. The electronics convert both measurements into separate continuous DC 0...10 V signals for compatible HVAC controllers. The sensor supports AC 24 V or DC 19...30 V supply and is intended for direct duct mounting. Procurement should verify the complete model QFM1660, Siemens stock number S55720-S198, controller input ranges, supply voltage, installation position and production-date-related accuracy before replacement or new installation.
| Item | Status | Basis |
|---|---|---|
| Product Condition | Original new | Stockoems commercial term |
| Availability | In stock | Stockoems commercial term, subject to order verification |
| Official Life Cycle | PM300: Active Product | Siemens product status |
| Warranty | With 1 year warranty | Stockoems commercial term |
Condition, availability and warranty are Stockoems commercial information and are not Siemens manufacturer commitments.
| Parameter | QFM1660 verified value |
|---|---|
| Manufacturer / family | Siemens / Symaro |
| Product number / stock number | QFM1660 / S55720-S198 |
| Product type | Duct humidity and temperature sensor |
| Operating voltage | AC 24 V ±20% or DC 19...30 V (SELV) |
| Power consumption | ≤1 VA |
| Humidity range of use | 10...90% r.h., non-condensing |
| Humidity output U1 | DC 0...10 V corresponding to 0...100% r.h. |
| Temperature range | 0...50 °C |
| Temperature output U2 | DC 0...10 V corresponding to 0...50 °C |
| Measuring accuracy | Humidity ±5% r.h. within range; temperature ±0.5 K at 23 °C for production from July 18, 2023 |
| Housing protection | IP42 in built-in state |
| Protection class / material | Class III / ABS housing, tube and filter tube |
| Weight with package | 160 g |
| Check | Requirement |
|---|---|
| Controller inputs | Two matching DC 0...10 V analog inputs for U1 humidity and U2 temperature |
| Supply | Verify AC 24 V ±20% or DC 19...30 V supply and common signal ground arrangement |
| Installation | Mount in the center of the duct wall; with steam humidifiers, maintain 3 to 10 m separation |
| Revision check | Match QFM1660, S55720-S198, production date and label data to project documents |
PM300: Active Product. This is the current Siemens product-status wording identified for QFM1660. Procurement review should use the complete model and stock number.
It measures relative humidity and temperature in an air duct.
Terminal U1 supplies DC 0...10 V for relative humidity, and U2 supplies DC 0...10 V for 0...50 °C temperature.
The documented supply is AC 24 V ±20% or DC 19...30 V (SELV).
The stock number associated with QFM1660 is S55720-S198.
No. Siemens identifies QFM1660 as PM300: Active Product.
Verify the complete label, supply, both controller input ranges, wiring, duct position and environmental limits.
Send us the complete part number, required quantity, destination country and product label photos. Our team will check availability, condition, compatibility requirements and shipping options.
Our service process combines identity checks, technical review, visual evidence, careful logistics and documented after-sales communication without promising unverified quantities or lead times.
| Stage | Service action | Buyer evidence |
|---|---|---|
| 1. Identity | Model and suffix verification | QFM1660 and S55720-S198 label match |
| 2. Condition | Condition confirmation; product and label photo confirmation | Clear full-unit, label, terminal and probe images |
| 3. Technical fit | Technical compatibility review | Supply, output ranges, wiring and duct application checked |
| 4. Packing | Protective packaging | Housing, probe and filter protected against transit damage |
| 5. Logistics | Worldwide shipping, shipment tracking and customs documentation | Destination and documentation requirements reviewed |
| 6. After sales | Written warranty terms, return authorization process and after-sales response | Commercial terms recorded before order placement |
A qualified supplier should identify the exact manufacturer and complete part number, provide current product and label photos, describe condition in writing, explain warranty and return terms, review technical compatibility, issue consistent company and payment documents, use protective packaging and provide traceable shipping records.
Risk signals include refusal to provide label evidence, incomplete suffix handling, unexplained specification changes, unverifiable stock claims, pressure for payment without written terms, inconsistent company details, vague return procedures, missing shipment tracking, or promises of universal compatibility.
Check QFM1660 and S55720-S198, the two DC 0...10 V outputs, controller scaling, AC/DC supply, duct mounting position and the project temperature range.
For model verification, photo evidence, compatibility review, packing details, shipping options or after-sales communication, contact our team.
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