Nortec On Digital Duct Humidistat User Manual

1 - Duct High Limit Installation

When installed as a high limit, the humidistat prevents over humidification as
well as wetting of the supply duct. Do not use fan relay when configuring as a
high limit.

Location:

1 Install directly on the supply duct in an area where the air is well mixed with

uniform flow.

2 Install downstream of the steam distributor at a distance 1.5 times the

absorption distance (typically 10-12 feet or 3-3.7 m). Must be in a location to
sense high humidity in addition to sensing when representative air is over
humidified or approaching saturation.

Installation:

1 Use the provided humidistat template and small level to mark outline of

humidistat body and location of probe hole. Ensure template is level before
marking.

2 Open the housing by removing the screw securing the face of the housing.
3 Drill a 5/8” (16 mm) hole in the duct at the marked location for probe

insertion.

4 Insert the probe into the air stream and place humidistat against duct wall.
5 Secure the duct humidistat to the duct using 4 sheet-metal screws (#6 x 3/4”

Phillips).

6 Wire as per wiring diagram 2548733 in this document.
7 Close the cover and secure using the screw removed in step 2.

Configuration:

1 Using keypad, set humidity to specified level (85% maximum) as a safety to

prevent saturation.

On/Off Digital Duct Humidistat Installation Instructions

76 (3.0)

47 (1.9)

91 (3.6)

68 (2.7)

Humidify Relay

24 Vac

Com

Fan (Furnace)Relay
NTC Sensor

Figure 2: Dimensions

Figure 3: Terminal Strip

Figure 1: Duct Humidistat Installation Locations

2 - Humidity Control Installation

When configured as a humidity controller, the humidistat provides
accurate control of the RH in a return duct and will activate/deactivate
a furnace or circulation fan.

Location:

1 Install on the return air duct, close to the air inlet but upstream from

a return fan if one is present.

Installation:

1 Use the provided humidistat template and small level to mark outline

of humidistat body and location of probe hole. Ensure template is
level before marking.

2 Open the housing by removing the screw securing the face of the

housing.

3 Drill a 5/8” (16 mm) hole in the duct at the marked location for

probe insertion.

4 Insert the probe into the air stream and place humidistat against

duct wall.

5 Secure the duct humidistat to the duct using 4 sheet-metal screws

(#6 x 3/4” Phillips).

6 Wire as per wiring diagram 2548733 in this document. Figure 3

outlines the terminal layout.

7 Close the cover and secure using the screw removed in step 2.

Configuration:

1 Using keypad, set specified humidity level. For general health and

comfort, a humidity setting of 50% is recommended.

2 See Table 3 for outdoor temperature setback configuration, if

optional outdoor temperature sensor is supplied (P/N 2520263 or

2553858).

This document covers the operation and installation instructions for the following digital humidistat:
Part #: 2548732
Description: On/Off Duct Humidistat

The humidistat can be configured for either humidity control or as a high limit safety device:

2549737-D | 22 July 2014 Introduction | 1

45.5%

35.0%

1
2

3

4

6

7

5

Legend:

1 Display of current humidity value.
2 Display of setpoint
3 Snowflake displayed if outdoor temperature setback active.
4 Adjusts setpoint and calibration (up)
5 Power ON/OFF
6 Toggles between RH setpoint and temperature (if temperature sensor

present)

7 Adjusts setpoint and calibration (down)

Parameter

Description

Range

Default

UP 00

Enable change of operation modes

ON, OFF

ON (Enabled)

UP 01

Enable change of setpoints

ON, OFF

ON (Enabled)

UP 02

State after power failure:
0 = Switched OFF, 1 = Switched ON, 2 = state before power failure

0, 1, 2

2

UP 03

Celsius or Fahrenheit, Select ON for Fahrenheit, OFF for Celsius

ON, OFF

OFF (Celsius)

UP 04

Select contents of small digits in standard mode:
00 = OFF
01 = Setpoint
02 = Humidity Sensor
03 = External Temperature Sensor

0…3

01 Standard:

show setpoint

Parameter

Description

Range

Default

CP 00

Minimum setpoint limit in humidification mode

0…100%

10%

CP 01

Maximum setpoint limit in humidification mode

0…100%

90%

CP 02

Start delay for fan
(Time the fan runs before control output starts)

0…255 s

10 s

CP 03

Stop delay for fan
(Time the fan keeps running after control output stops)

0…255 s

90 s

Parameter

Description

Range

Default

CP 04

Enable temperature setback
OFF = Temperature setback is disabled
ON = Temperature setback is enabled

ON, OFF

OFF

CP 05

Setpoint limit at full setback

0…100%

20%

CP 06

Lower temperature limit:
Outside temperature with maximum setback
The setpoint will be equal to the minimum setpoint limit

-40…60°C

-40…160°F

-30°C (-22°F)
CP 07

Upper temperature limit:
Outside temperature at begin of setback.

-40…60°C

40…160°F

0°C (32°F)

CP 08

Number of seconds taken into account to calculate the averaging input signal.
Low value = fast response
High value = slow response

0…100

30

Duct Humidistat LCD Display

Sensor Calibration

The humidity sensor is factory calibrated, however, it can be field recalibrated. The calibration routine can be accessed by pressing the option key for > 3
seconds. Option key = the right key on the wall mount and middle key on the right side of the duct mount. Once the display changes select CAL H, press OPTION
key again - the offset value is now shown.
Press up down keys to change. Press option key again to save changed value and return to previous level.

Login Procedure

Most applications can use default values.
User Parameters (Password 0009)

1 Press UP and DOWN button simultaneously for three seconds. The display shows the software version in the large digits and the product code in the small

digits.

2 Pressing the OPTION button will indicate CODE on the small digits and 0000 on the large digits.
3 The code for accessing the control parameters is 0009
4 Select this using UP or DOWN buttons.
5 Press OPTION button after selecting the correct code.
6 Once logged in, the parameter is displayed immediately.
7 Select the parameters with the UP/DOWN buttons. Change a parameter by pressing the OPTION button. Three triangles will show up on the lower right and

indicate that the parameter may be modified now. Use UP or DOWN buttons to adjust the value.

8 After you are done, press OPTION or POWER in order to return to the parameter selection level.

Table 1: User Parameters

Control Parameters (Password 0241)
NOTE: Only experts should change these settings! See user parameters for login procedure.

Table 2: Output Configuration

Table 3: Temperature Setback Configuration - *For humidity control only.

2 | Introduction