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POWERS
HU 186 Room And Duct
Hygrostats
Description
Product Numbers
Application
TM
Controls
The HU 186 Room and Duct Hygrostats are pneumatic instruments sensitive to slight
changes in relative humidity. They feature adjustable sensitivity and bimetal temperature
compensation to minimize temperature effects. The room hygrostat comes complete with
standard cover and wall plate. The duct hygrostat is shipped inside the duct mounting
box.
See Table 1.
The sensing element of the HU 186 hygrostat consists of a highly sensitive hygroscopic
membrane. Typical applications include comfort control of hospitals, schools, and office
buildings. More critical applications include the control of humidity in museums or
computer rooms.
Figure 3 shows a typical application of a room type hygrostat. The duct hygrostat would
be used when humidity sensing is to be done with a duct sensor. For most applications,
the best location for a duct sensor is in the return air duct.
Technical Instructions
Document No. 155-027P25
Figure 1. Room Hygrostat.
Figure 3. Application of Room Hygrostat.
HU 186-1
February 14, 2005
Figure 2. Duct Hygrostat.
Siemens Industry, Inc.
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Summary of Contents for Siemens POWERS HU 186
- Page 1 Figure 3 shows a typical application of a room type hygrostat. The duct hygrostat would be used when humidity sensing is to be done with a duct sensor. For most applications, the best location for a duct sensor is in the return air duct. Figure 3. Application of Room Hygrostat. Siemens Industry, Inc.
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Page 2: Specifications
Dimensions, Duct Type See Figure 10 Air Connections Barb fitting for 1/4-inch (6.4 mm) OD Poly Tubing Membrane Element Kit 186-062 Accessories Restrictor Plate Kit (Pkg. of 10) 180-893 Calibration Tool (Pkg. of 5) 192-632 Page 2 Siemens Industry, Inc. -
Page 3: Operation
The hygrostat is factory calibrated to pass a control pressure of 9 + 4 psig at approximately 40% rh. The factory sensitivity setting is centered to give approximately 2 psig per 1% rh. Item numbers shown in parentheses are called out in Figure 5. Siemens Industry, Inc. Page 3... - Page 4 See Figure 4. An overtravel spring on the sensitivity adjustment assembly prevents damage to the nozzle on a reverse acting hygrostat. NOTE: When the sensitivity is changed, the element must be recalibrated for set point. Page 4 Siemens Industry, Inc.
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Page 5: Installation
(5) through (7), (10) through (13), and (16) in Table 2 and Figure 8. As an initial check, make certain that there is 15 to 25 psig of clean, dry supply air. Use a pressure gauge and rubber tubing to measure control pressure at the test screw (15). Siemens Industry, Inc. Page 5... -
Page 6: Troubleshooting
Membrane Element Kit. See Table 2. 2. Disconnect the old element by removing screws (12) and (16). 3. Attach the new element. 4. Recalibrate using the procedure in the Calibration section. Page 6 Siemens Industry, Inc. - Page 7 2-56 Hex Nut Brass Adjustment Screw Bronze Spring See 24 Lock Washer Steel 180-893 Restrictor Plate Kit Incl. Items 5, 6, 7 See 24 Short Element Brass 186-062 Membrane Element Incl. Items Screw 10, 11,12, 13, 16 Siemens Industry, Inc. Page 7...
- Page 8 Information in this publication is based on current specifications. The company reserves the right to make changes in specifications and models as design improvements are introduced. POWERS is a registered trademark of Siemens Industry, Inc. Product or company names mentioned herein may be the trademarks of their respective owners.