Robertshaw 9801i, 9815i, 9851i, 9865i, 9820i User Manual

1

CONTROL TIPS

A ROBERTSHAW®INFORMATIONAL GUIDE

HOW HUMIDIFICATION/DEHUMIDIFICATION FEATURES OPERATE

THIS ISSUE

Congratulations, you are the proud owner of a Robertshaw®9801i, 9815i, 9820i, 9851i, 9865i, or 9870i
series thermostat. This Control Tips guide will provide you with the necessary information to set up
your thermostat for maximum humidity and dehumidification operation.

MODES

Manual with Heating

When the thermostat has a call for heat, the W terminal is energized (24VAC). If the relative humidity
(RH) drops 2% below RH setpoint, the H terminal is energized. When the temperature setpoint is
reached, both terminals are de-energized and the fan will shut off after the purge cycle or remain on
if the thermostat was set to Fan On.

Manual Independent

When the thermostat has a call (in heat mode) for humidity, and no call for heat, the H (24VAC) and G
terminals are energized.

When a call for heat is made, the H and G terminals will remain on while the W terminal is energized.
The fan remains on at the speed chosen for the furnace control for G only.

The second stage W2 energizes after a user-selected time (5 to 40 minutes) when the room
temperature is 0.5°F above the setpoint, or a 2°F differential has been met.

Auto with Heating or Auto Independent

These features can be selected from the Humidity Menu, but only when an outdoor sensor (9025i) is
connected. Humidity set point adjustment is an automatic adjustment made by the thermostat. The
indoor Relative Humidity (RH) is adjusted based on the outdoor temperature compared to the indoor
temperature. After the humidity set point has been automatically determined, there is a manual
adjustment that can be selected (±1% RH to ±15% RH) at 1% increments.

NOTE: When connecting the outdoor sensor, use a shielded, twisted pair of 18 guage 2-wire.

The wire length should not exceed 300 feet.

2

USING THE INDEPENDENT HUMIDITY SETTING

Use the Independent Humidity setting with the outdoor sensor for dew-point adjustment so moisture
will not condense or freeze on windows.

The bypass humidifier can be used, and is recommended, with the Independent Humidity setting.
This will allow additional moisture to be added and distributed throughout the house without a call for
heat. The added humidity would increase the comfort levels of the dwelling.

The mist humidifier generates more water directly than the other two types of humidifiers. The
Independent Humidity setting SHOULD NOT be used.

If a power (fan-style) humidifier is used, (one equipped with a separate transformer) it will be
necessary to use an isolation relay.

Application Example:

A bypass humidifier is installed with a down-flow furnace. The house temperature (setpoint is 73°F) is
75°F (The graph above shows that the automatic setpoint for RH is 30%, when the outdoor temperature
is 10°F). The thermostat is user selected to the Auto humidity setting.

The humidifier and fan activate adding moisture to the dwelling as needed to reach 32%RH. The
humidifier and fan will reactivate when the humidity drops below 28%RH. The setpoint is ±2%RH.

Condensation – If humidity levels cause condensation on windows, then this control needs to be adjusted.
This adjustment must be made over a 12-hour period to allow the humidity levels to stabilize.
For instance, by selecting –5% RH on the adjustment, the humidity will maintain 25% ± 2%RH with an
outdoor temperature of 10°F. If -5% is not enough to avoid condensation, then lower the Auto Humidity
Setting to -10%RH. The controlling RH will be 20%+ -2RH with an outdoor temperature of 10°F.

Recommended Settings

Auto Humidity Setting (AHS) +/- Dew Point Adjustment

50

45

40

35

30

25

20

Auto Humidity Setting

-40 -30 -20 -10 0 10 20 30 40 50 60 70

15

10

Outside Temperature °F

AHS + 15%
AHS + 10%
AHS + 5%
Auto Humidity Setting
AHS - 5%
AHS - 10%
AHS - 15%