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Aprilaire 1750A - Service Manual

Aprilaire 1750A
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Wire
Routing
Port
Wiring
Access
Filter
A
ccess
Humidity
C
ontrol Inlet
Drain
On/Off
Switch
Filter
A
ccess
Service
A
ccess PortOutlet
Installation, Safety & Maintenance Manual
Model 1750A/1770A
Central Dehumidifier
INSTALLER – PLEASE NOTE!
1. Installation must conform to all applicable codes.
2. For the 1750A, a dedicated 15 Amp circuit is recommended but not required for proper operation of the
dehumidifier. If a dedicated circuit is not available, use a lightly loaded circuit. Do not use an extension cord.
3. For the 1770A, a dedicated 20 Amp circuit is required for proper operation of the dehumidifier.
If a dedicated circuit is not available, do not install unit. Dehumidifier must be plugged in directly to an outlet.
Do not use an extension cord.
4. For protection of the compressor, unit must be transported and installed in an upright position.
If the unit was shipped or stored on its side, a 24 hour settling period is required before running the unit.
TABLE OF CONTENTS
Safety Instructions . . . . . . . . . . . . . . .2
Overview . . . . . . . . . . . . . . . . . . . . . . .2
Specifications . . . . . . . . . . . . . . . . . . .2
Location Notes . . . . . . . . . . . . . . . . . .2
Ducting . . . . . . . . . . . . . . . . . . . . . . . .3
Drain Line . . . . . . . . . . . . . . . . . . . . . .3
Hanging . . . . . . . . . . . . . . . . . . . . . . .3
Installations
Central . . . . . . . . . . . . . . . . . . . . . . . .4
Localized . . . . . . . . . . . . . . . . . . . . . . .6
Central/Zoned . . . . . . . . . . . . . . . . . . .8
Air Cycling . . . . . . . . . . . . . . . . . . . .10
Float Switch . . . . . . . . . . . . . . . . . .12
Dip Switch Definitions . . . . . . . . . . .12
System Checkout . . . . . . . . . . . . . . .13
Troubleshooting . . . . . . . . . . . . . . . .14
Sequences
of Operations . . . . . . . . . . .Back Cover

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Preview: Installation Instructions
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Preview: Troubleshooting Manual
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Questions and Answers

  • M
    Mr. John HayesSep 10, 2025
    Why does Aprilaire 1750A HVAC fan operate continuously?
    • T
      tinagriffinSep 10, 2025
      Continuous operation of the HVAC fan after moving the control knob out of the TEST position can be due to: * The HVAC equipment making a call for heating or cooling, or the HVAC fan being set to a constant ON setting. * The Dehumidifier air cycling/ventilation being set to constant ON. If the Cycle Time is equal to or greater than the Cycle Period, HVAC fan operation will be continuous. Reduce the Cycle Time if constant fan is not desired.
  • N
    Natalie ChenAug 23, 2025
    Why Aprilaire Dehumidifier blower is running but compressor is not?
    • R
      Rachel VaughnAug 23, 2025
      If your Aprilaire Dehumidifier blower is running but the compressor isn't, here are a few things to investigate: * If you have a float switch installed, check the connections at the control board and empty the condensate pan. * If there's no float switch, make sure the jumper is correctly installed at the float switch terminals on the control board. * Also, coil frosting, reduced airflow, or inlet air conditions below 60°F can cause this issue. Check/clean the filter and duct work. Use the control knob to turn down the dryness setting.
  • W
    wheelerjosephAug 25, 2025
    What to do if Aprilaire Dehumidifier blower is running but little or no airflow?
    • M
      mark92Aug 25, 2025
      If the blower in your Aprilaire Dehumidifier is running but there's little to no airflow, it might be due to a high-pressure drop. Here’s what you can do: * Inspect the dehumidifier's air filter and either wash or replace it. * Check for any blockages in the ductwork and clear them. * Ensure the backflow damper isn't blocked or stuck; remove any obstructions if found.
  • C
    Christopher WilliamsAug 27, 2025
    How to fix Aprilaire 1750A Dehumidifier that is not draining properly?
    • V
      Vanessa VillarrealAug 27, 2025
      If your Aprilaire Dehumidifier isn't draining properly, it could be due to a blockage in the drain line or drain trap. Here’s how to address it: * Ensure the drain trap is correctly installed. * Check for blockages by slowly pouring one pint of water into the dehumidifier drip pan below the coil. * Make sure the drain line has a continuous downward slope.
  • C
    Caitlyn DunlapAug 28, 2025
    Why does Aprilaire 1750A make the HVAC fan turn on unexpectedly?
    • D
      Donna MathisAug 28, 2025
      If the HVAC fan in your system turns on unexpectedly, it's likely due to the Aprilaire Dehumidifier's sampling or air cycling process. The dehumidifier activates the HVAC fan during sampling and as needed to meet air cycling or ventilation requirements, based on the Cycle Period and Cycle Time settings.
  • A
    Adam BeckerAug 29, 2025
    Why HVAC fan operates continuously after test on Aprilaire 1750A?
    • A
      Austin VillaAug 29, 2025
      If the HVAC fan operates continuously after moving the control knob out of the TEST position on your Aprilaire Dehumidifier, it could be due to a couple of reasons: * The HVAC equipment might be actively calling for heating or cooling. * The HVAC fan might be set to run constantly. * Alternatively, the dehumidifier's air cycling/ventilation could be set to constant ON. If the Cycle Time equals or exceeds the Cycle Period, continuous HVAC fan operation will occur. Reduce the Cycle Time if you don't want the fan running constantly.
  • A
    Alyssa MaloneSep 18, 2025
    Why does Aprilaire 1750A Dehumidifier HVAC fan turns on unexpectedly?
    • J
      Jack RichardSep 18, 2025
      The dehumidifier will turn on the HVAC fan during sampling and as needed to meet air cycling or ventilation requirements as determined by the Cycle Period and Cycle Time. This is normal function.
  • B
    Barbara RushSep 12, 2025
    How to fix Aprilaire 1750A with blower running but little airflow?
    • J
      Jamie ThomasSep 12, 2025
      If the blower in your Aprilaire dehumidifier is running, but there's little to no airflow, it could be due to: * High pressure drop: If the pressure drop across the dehumidifier is higher than 0.8”w.c. (1750A) or 1.5”w.c. (1770A). To resolve this: * Check and clean or replace the dehumidifier's air filter. * Clear any blocked ductwork. * Make sure the backflow damper is installed in the outlet duct collar, not the inlet duct collar. * Check the backflow damper for obstructions and remove them.
  • D
    Dana HoodSep 8, 2025
    Why is Aprilaire 1750A Dehumidifier blower running but compressor is not?
    • E
      Emma WilliamsSep 8, 2025
      There are a couple of reasons why the blower might be running without the compressor: * **Float switch issue:** If a float switch is installed, check its connections at the control board and ensure the condensate pan is empty. If no float switch is present, verify the jumper is correctly installed at the float switch terminals on the control board. * **Coil frosting:** This can be due to reduced airflow (check and clean the filter, and clear any blocked ductwork) or if the inlet air temperature is below 60°F. Try turning down the dryness setting using the control knob.
  • H
    Hannah ReedSep 5, 2025
    How to troubleshoot Aprilaire Dehumidifier damper that does not open in test mode?
    • B
      Becky BondSep 5, 2025
      To troubleshoot why the damper on your Aprilaire Dehumidifier isn't opening in TEST Mode, check the following: * Verify the wiring between the dampers and the 24 VAC transformer, ensuring it's correct. * If wired for Convertible operation, confirm that the 24 VAC transformer has a minimum rating of 40 VA. * Inspect all wiring connections between the dampers and the control board to ensure they are secure.

Summary

Safety Instructions

Warning!

Critical safety warnings regarding installation and electrical shock hazards.

Caution

Precautionary note regarding the use of solvents and cleaners near circuit boards.

Overview

Specifications

Location Notes

Ducting

Drain Line

Hanging

Central Installation and Operation

Required Components

List of essential parts needed for central installation.

Optional Components

List of optional accessories for enhanced functionality.

Localized Installation and Operation

Required Components

Essential components for localized installation.

Optional Components

Optional parts for localized operation.

Central;Zoned (Convertible) Installation and Operation

Required Components

Necessary components for central/zoned installation.

Optional Components

Optional components for central/zoned operation.

Ventilation; Air Cycling Settings

Air Cycling

How to set up the HVAC fan for cycling to ensure air circulation.

Outside Air Ventilation

Guidelines for using the ventilation damper with outdoor air.

Step 1: Calculate the Ventilation Requirement

Step 2: Determine the Fresh Air Delivery Rate

Step 3: Determine Cycle Time

Float Switch

Dip Switch Definitions

System Checkout

Troubleshooting Guide

LED Codes

Interpretation of LED indicator lights for status and errors.

Symptom

Common symptoms encountered with the dehumidifier and their potential causes.

Dehumidifier Sequence of Operation

Damper Sequence of Operation

Ventilation or Air Cycling Sequence of Operation

Aprilaire 1750A Specifications

General IconGeneral
Model1750A
Dehumidification Capacity70 pints per day
Energy Star RatedYes
Voltage115V
Hertz60 Hz
Drainage TypeGravity or pump
Amps5.5
DrainageGravity or pump

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