tekmar 557 Thermostat Installation User Manual
Page 40
© 2014
557_D - 09/14
40 of 52
A Watts Water Technologies Company
The thermostat has up to five dehumidification modes.
Operation
Mode
Required
Relay(s)
Sensor
Required
Stand Alone Dehumidifier
Dehumidifier operates independently or the
HVAC system.
Available in all modes except off.
DHM1
ACC RELAY
= DHUM
or
Y2 RELAY
= DHUM
None
Coil Dehumidification
A duct temperature sensor is required. A DX or
chilled water coil is operated to maintain a dis-
charge air temperature of 45°F (7°C). The room
air temperature is allowed to fall up to 3°F (1.5°C)
below the cooling setpoint while coil dehumidifi-
cation is operating, at which point dehumidifica-
tion is shut off. The fan relay (G) is not turned
on, rather the ACC or Y2 relay provides a signal
to the air handler unit to operate the fan at low
speed.
Available only when cooling.
DHM2
ACC RELAY
= DHUM
or
Y2 RELAY =
DHUM
Duct
Sensor
083
HRV Dehumidification
(only available with single stage heat pumps
or air conditioners)
The HRV is operated based upon indoor dew
point and outdoor air temperature. The HRV op-
erates when the indoor dew point is 5.5°F (3.0°C)
above the outdoor temperature. The HRV is shut
off when the indoor dew point falls to 2°F (1.0°C)
above the outdoor temperature.
Available in all modes except off.
DHM3
Y2 RELAY =
HRV
Outdoor
Sensor
070
Stand Alone + HRV Dehumidification
(only available with single stage heat pumps
or air conditioners)
During cooling mode, a stand alone dehumidifier
is operated in the same manner as DHM1.
During heating mode, an HRV provides dehu-
midification in the same manner as DHM3.
Available in all modes except off.
DHM4
ACC RELAY
= DHUM
and
Y2 RELAY =
HRV
Outdoor
Sensor
070
Coil + HRV Dehumidification
(only available with single stage heat pumps
or air conditioners)
During cooling mode, a coil dehumidifier is oper-
ated in the same manner as DHM2.
During heating mode, an HRV provides dehu-
midification in the same manner as DHM3.
Available in all modes except off.
DHM5
ACC RELAY
= DHUM
and
Y2 RELAY =
HRV
Duct
Sensor
083
and
Outdoor
Sensor
070