Aprilaire 8120 owner manual Principle of Operation, II. Operating Instructions

I. PRINCIPLE OF OPERATION

With your purchase of the Aprilaire® Ventilation Controller, you have invested in an intelligent way of providing fresh air to your home. Working in conjunction with an Aprilaire® Damper, the Ventilation Controller makes decisions regarding when – and how long – to ventilate. It does this through continuous monitoring of indoor relative humidity, outdoor temperature, and user-adjusted timer settings.

•The jumper on the 5 pin header determines the cycle time interval. The interval can be 1, 2, 3 or 4 hours. (The default setting is 1 hour.)

•Move the jumper to the desired setting. The jumper can be removed by pulling it straight out from the header pins.

•Snap the cover back on the controller and slide the knob onto the shaft.

2.SETTING THE VENTILATION TIME

Indoor relative humidity is monitored to help prevent high humidity conditions inside your home. The Aprilaire® Ventilation Controller will not open the damper to the outside air if there is a chance of raising the humidity inside the house to high levels. The Aprilaire® Ventilation Controller is designed to prevent indoor relative humidity levels from increasing beyond 60% due to ventilation.

If the outdoor air temperature is below 0°F or above 100°F, the motorized normally-closed damper to the outside will not be opened. This feature can be disabled at installation if the installer chooses not to use outdoor air temperature as a parameter.

II. OPERATING INSTRUCTIONS

Your Ventilation Controller is installed in the return duct of your furnace or heat pump. There are two settings that are adjustable: the cycle time and the ventilation time within cycle.

•The knob on the exterior of the controller

is used to set the ventilation time within the interval you set in Step 1.

•The knob settings range from “OFF” which is all the way counter-clockwise, to “TEST”† which is all the way clockwise. While labeled in 15 minute increments, the controller may be adjusted within the 15 minute interval to the nearest minute.

†Test mode is used to check the device at installation. In Test mode the Ventilation Controller activates the HVAC fan and opens the damper for one minute or until the knob is taken off the “Test” setting, whichever occurs first. After the minute has passed, the Ventilation Controller will not work until the knob is taken off “Test.”

FIGURE 2 – Ventilation Time
		60
PER CYCLE	45	TEST
	30
MINUTES	15	OFF
		0
	VENTILATION CONTROLLER
		90-702

Here’s how this works: if you set the cycle time to 1 hour and the ventilation time knob to 20 minutes, you will get 20 minutes of ventilation every hour. It is important to understand that the ventilation requirement – 20 minutes per hour in this example – may be satisfied by a heating, cooling, or fan call initiated by your thermostat, or from a fan call initiated by the Ventilation Controller itself. The following steps explain how to adjust these settings.

1. SETTING THE CYCLE TIME INTERVAL

III.OUTDOOR TEMPERATURE & INDOOR HUMIDITY CONTROL LIMITS

In a standard installation, your Aprilaire Ventilation Controller will use measurements of Outdoor Temperature and Indoor Humidity, along with the user-adjustable timer settings, to determine when to ventilate. Outdoor Temperature is measured with a sensor placed at the inlet of the fresh air intake duct. Indoor Humidity is measured in the return duct with a sensor built into the Controller. In conjunction with the timer settings, the Controller then operates

• Remove the knob by

pulling it straight out

FIGURE 1 – Cycle Time

according to the temperature and humidity control limits shown in Figure 3 below.

from the controller.

Remove the cover by

grabbing along the

top and bottom

edges of the cover

and pulling straight

out from the base.

Refer to Figure 1 to

locate the cycle time

header & jumper.

CYCLE TIME
1 HR 3 HR
	CYCLE TIME		WIRING AND￿
	1 HR 3 HR		JUMPER￿
		CONFIGURATION
	2 HR 4 HR
2 HR 4 HR	GS TO STAT	C	R D	D T	T
	GH TO HVAC	TO HVAC	DAMPER	SENSOR	￿TEMP
	W TO HVAC
					10005991
		24VAC A/ A			OUTDOOR￿
					TEMPERATURE￿
					SENSOR
					90-698

FIGURE 3 – Model 8120 Operating Limits

(°F)	100			SECTION A
TEMPERATURE
		SECTION B
OUTDOOR	20
	0	SECTION A
		SECTION C
		INDOOR RELATIVE HUMIDITY (%)	55
		SECTION A: Controller will not ventilate due to temperature extremes
		SECTION B: Controller will ventilate according to timer settings
		SECTION C: Controller will ventilate only when heating is on according to the timer settings

50

90-713