Siemens POWERS HU 186 Manuel du propriétaire

POWERS

Controls

Technical Instructions

Document No. 155-027P25

HU 186-1

February 14, 2005

HU 186 Room And Duct

Hygrostats

Figure 1. Room Hygrostat.

Figure 2. Duct Hygrostat.

Siemens Industry, Inc.

Description 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.

Product Numbers See Table 1.

Application 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.

Figure 3. Application of Room Hygrostat.

Technical Instructions HU 186 Room and Duct Hygrostats

Document Number 155-027P25

February 14, 2005

Page 2 Siemens Industry, Inc.

Table 1. Product Numbers.

Product Numbers Model Maximum

Dry Bulb Temp.

Control

Range (rh)

Direct Action

Reverse Action

186-0013 186-0019 Room 135°F 20 to 90%

186-0087 186-0088 Duct

- 186-0090 140°F 55 to 95%

- 186-0091 25 to 65%

Specifications

Operating

Physical

Direct or Reverse Acting Range See Table 1

Maximum Operating Temperature See Table 1

Sensitivity (adjustable) 1/4 to 4 psi per 1% rh

(1.7 to 28 kPa per 1% rh)

Normal Supply Pressure 15 to 25 psig (103 to 172 kPa)

Maximum Supply Pressure 30 psig (207 kPa)

Air Consumption 20 scim (5.5 ml/s)

Effect of 10° F Temperature Change Shift of 1% rh

Effect of 5 psi Supply Pressure Change

(mid-sensitivity) Shift of 1% rh

Air Capacity (time rating per 155-202P25

(TB-113) 0.7 min/vol unit

Dimensions, Room Type See Figure 9

Standard Room Cover Finish Desert Beige

Dimensions, Duct Type See Figure 10

Air Connections Barb fitting for 1/4-inch

(6.4 mm) OD Poly Tubing

Accessories Membrane Element Kit 186-062

Restrictor Plate Kit (Pkg. of 10) 180-893

Calibration Tool (Pkg. of 5) 192-632

HU 186 Room and Duct Hygrostats Technical Instructions

Document Number 155-027P25

February 14, 2005

Siemens Industry, Inc. Page 3

Operation

Reverse Acting

The action consists of a combination of force-balance and flappernozzle characteristics with

internal feedback.

A decrease in humidity causes the membrane sensing element to shrink. The contracting

element, which is attached to the element lever, exerts greater force on the nozzle lever

through the sensitivity adjustment assembly. The nozzle lever closes off the nozzle, building

up pressure above the relay diaphragm. Movement of the diaphragm closes the exhaust

valve and opens the supply valve ball. Supply pressure passes into the control pressure

chamber below the diaphragm. The control pressure increases until its upward force on the

diaphragm is balanced by the pressure in the chamber above the diaphragm plus the bias

spring. The valve spring then closes the supply valve and a new balance point is reached

until a humidity change upsets it. Because of the bias spring, the minimum control pressure

is about 1/2 psig.

Direct Acting Here the basic sensing and lever movement is the same as described above. See Figure 4.

However, the nozzle is in a different location; it's on the opposite side of the nozzle lever.

Thus a decrease in humidity results in the flapper pulling away from the nozzle and

decreasing the control pressure.

The element and nozzle levers pivot on flexure pivots to minimize hysteresis. A bimetal link

on the element lever compensates for ambient temperature changes.

Figure 4. Hygrostat Operation.

Calibration 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.

Technical Instructions HU 186 Room and Duct Hygrostats

Document Number 155-027P25

February 14, 2005

Page 4 Siemens Industry, Inc.

Calibration,

continued

Room Type

1. Remove the cover using the calibration tool.

2. Loosen the test screw (2) 1/2 turn. Slide the rubber tubing of a pressure gauge over

the test port to measure the control pressure.

3. Measure the relative humidity near the hygrostat. See the Use of Psychrometric

Chart section.

4. If the room humidity is higher than desired, use the calibration tool to turn the

adjustment screw (1) counterclockwise to lower the humidity. A 1/4 turn of the

adjustment screw will change the set point about 10% rh

5. Cam post (4) is a coarse adjustment and should only be used if the desired set point

cannot be obtained by the adjustment in Step 4. It is primarily a factory adjustment to

obtain a parallel relationship between the nozzle lever (7) and the element lever (6).

Duct Type

1. Connect pressure gauge to control connection on duct box.

2. Measure relative humidity in duct.

3. Remove cap plug on duct cover and insert calibration tool to make adjustments given

in Step 4 above. See Figure 6.

4. Replace cap plug.

Figure 5. Hygrostat Assembly.

Figure 6. Hygrostat Calibration.

Sensitivity

Adjustment Item numbers shown in parentheses are called out in Figure 5.

1. Carefully loosen sensitivity adjustment (8) using a 3/16-inch wrench.

2. Slide the sensitivity adjustment (8) to desired position on the element lever (6).

Sensitivity will be 4 psi per 1% rh at the end nearest the element, down to 1/4 psi per 1%

rh at the end attached to the flexure pivot. 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.

HU 186 Room and Duct Hygrostats Technical Instructions

Document Number 155-027P25

February 14, 2005

Siemens Industry, Inc. Page 5

Use of

Psychrometric

Chart

A sling psychrometer is probably the most readily available humidity measuring device.

Plotting the wet and dry bulb temperature readings from it on a psychrometric chart

determines the relative humidity.

As an example, assume a dry bulb temperature of 70°F, and a wet bulb temperature of

53°F, measured with a sling psychrometer. Using the psychrometric chart illustrated in

Figure 7, follow the 70° dry bulb temperature line vertically until it intersects the 53°F wet

bulb temperature line. This determines the relative humidity point. In this case, the 30%

relative humidity line goes through the point; therefore, the relative humidity is 30%.

Figure 7. Psychrometric Chart.

Installation

Room Type

See Technical Bulletin 155-210P25 (TB-145) for instructions covering terminal

roughing-in through the wall plate stage. HU 186 plugs into the terminal connector

through two holes in the wall plate. When facing the wall, the supply connection will be on

the left for a horizontal installation and on the bottom for a vertical installation. Two

captive mounting screws fasten the hygrostat body assembly to the wall plate. The cover

is held in place by two button head cover screws which are tightened with the calibration

tool. Wall Plate Kit No. 180-443 is included with the room hygrostat.

Duct Type Cut an opening in the air duct. See Figure 10 for dimensions. Fasten the duct box flange

to the duct using four No. 8 sheet metal screws.

Maintenance Item numbers in parentheses are called out in Figure 8 and Table 2. Clean the

membrane element (13) with a soft, dry brush when dirt or dust accumulates. The

hygrostat should not be totally disassembled in the field. The only parts which should be

replaced are items (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).

Technical Instructions HU 186 Room and Duct Hygrostats

Document Number 155-027P25

February 14, 2005

Page 6 Siemens Industry, Inc.

Troubleshooting

Control Pressure

Remains at 1/2 psig

Troubleshooting contains the most common problems and solutions.

1. Remove the cover and connect a pressure gauge.

2. Gently press the nozzle lever against nozzle. The control pressure should increase. If

not, the restrictor hole in the restrictor plate (6) is clogged.

3. Replace the restrictor plate using the replacement parts in the Restrictor Plate Kit.

See Table 2.

4. Remove the old gaskets (5 and 7) and restrictor plate (6). Reassemble with the new

kit parts, putting them in the same relative positions as the original parts. Make sure

that the gasket connecting the two holes is between the restrictor plate and the

cover.

Control Pressure

Remains at Maximum

(15—25 psig)

1. Gently push the nozzle lever (2) away from nozzle (17).

2. If the control pressure does not drop to approximately 1/2 psig, check for a clogged

nozzle.

3. Carefully clean the tip of the nozzle. Also clean the nozzle lever where it contacts the

nozzle, as dirt will accumulate and clog the nozzle opening.

Excessive Air Leakage

from Nozzle-Control

Pressure Does Not

Drop

1. If excessive air leakage occurs and the control pressure does not drop to 1/2 psig

when the nozzle lever is pulled away from the nozzle, then there is dirt on one of the

relay ball valves. See Figure 4 in the Operation section.

2. The dirt particle on either the supply or the exhaust balls can usually be removed by

moving the lever so that it alternately opens and closes the nozzle. This fluttering

action will usually dislodge dirt from the ball valves.

3. Disassembly of the body (19) and base (20) to access the relay is not recommended.

Replacement of

Membrane Element 1. If the membrane element (13) is damaged and becomes cracked or torn, replace it

with parts in the 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.

HU 186 Room and Duct Hygrostats Technical Instructions

Document Number 155-027P25

February 14, 2005

Siemens Industry, Inc. Page 7

Hygrostat

Components

Figure 8. Hygrostat Construction.

Table 2. Parts List for Hygrostat (Item Numbers See Figure 8).

Item

Part

No.

Part Name

Qty.

Material

Item

Part

No.

Part Name

Qty.

Material

I - Adjusting Screw 1 Brass 13 See 24 Membrane Element

Assembly 1 -

2 - Nozzle Lever 1 Stainless

Steel 14 - Cam Post 1 Brass with

Teflon®

3 - Sensitivity Adj.

Assem. (RA)

Sensitivity Screw

(DA)

1 - 15 833-009 Test Screw 1 Bronze

4 - Restrictor Cover 1 Brass 16 See 24 Long Element Screw - Brass

5 See 23 Upper Gasket 1 Neoprene 17 186-162 Nozzle Assembly

Nozzle Assem. Mod 5

to 7

1 Brass

Brass

6 See 23 Restrictor Plate 1 Brass 18 - Cover Screw 2 Stainless

Steel

7 See 23 Lower Gasket 1 Neoprene 19 - Body Assembly - -

8 - Restrictor Cover

Screws 2 Brass 20 - Base - -

9 - Element Lever

Assembly 1 - 21 - Lockwasher No. 8 1 Steel

10 See 24 2-56 Hex Nut I Brass 22 - Adjustment Screw

Spring 1 Bronze

11 See 24 Lock Washer I Steel 23 180-893 Restrictor Plate Kit - Incl. Items

5, 6, 7

12 See 24 Short Element

Screw 1 Brass 24 186-062 Membrane Element

Kit - Incl. Items

10, 11,12,

13, 16

Technical Instructions HU 186 Room and Duct Hygrostats

Document Number 155-027P25

February 14, 2005

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

Siemens Industry, Inc.

Building Technologies Division

1000 Deerfield Parkway

Buffalo Grove, IL 60089

+ 1 847-215-1000

Your feedback is important to us. If you have

comments about this document, please send

them to technical.editor@sbt.siemens.com

Document No. 155-027P25

Printed in the U.S.A.

Page 8

Dimensions

Figure 9. Room Hygrostat Dimensions.

Figure 10. Duct Hygrostat Dimensions.

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