tekmar 557 Thermostat Installation - Manual (Page 34)

© 2014 557_D - 09/14
34 of 52 A Watts Water Technologies Company
Radiant Floor Baseload ---------------------------------------------- ----------------------------------------------
When the terminal unit is selected to be a Hydronic Radiant Floor (HRF1 or HRF2)
and no floor temperature sensor is installed, the thermostat has option to provide
baseload heating. This allows the radiant floor to be heated even though the room air
temperature is satisfied. This is useful in areas where a radiant floor heating zone is
overlapped by an air heating system. The radiant floor heating is overwhelmed by the
quick heat up rate of the air heating system, resulting in a radiant floor heating zone
that rarely turns on. The radiant baseload option allows the radiant floor to counteract
the air heating system by heating the floor at a reduced output even when the room air
temperature is satisfied. This is also useful in areas that experience large solar gains
through windows. The radiant baseload is automatically shut off in the summer by the
warm weather shut down feature.
Warm Weather Shut Down -------------------------------------------- --------------------------------------------
When the outdoor air temperature exceeds the Warm Weather Shut Down (WWSD)
setting on the tekmarNet
® main control, the heating system is shut off.
A W1 HEAT WWSD setting is available to allow the heat pump to heat the building
while the radiant floor heat system is shut off during mild outdoor temperatures. This
is advantageous in the spring and fall when heating is required at night and cooling is
required during the day. As the outdoor temperature falls below the W1 HEAT WWSD
setting, the radiant floor becomes the primary heat source and the heat pump provides
supplemental heating.
Balance Point ------------------------------------------------------- -------------------------------------------------------
An air source heat pump’s Coefficient Of Performance (COP) decreases with colder
outdoor temperature. This affects the heating output capacity of the heat pump to
heat the building. When the COP is equal to 1, the heat pump no longer provides an
economic advantage over electric heating elements or other supplemental heating fuel.
The outdoor temperature at which this occurs is known as the balance point. When
the outdoor temperature falls below the balance point, the heat pump is shut off and
the backup supplemental heat source is operated to heat the building. The 557 has
the ability for the balance point setting change based upon a programmable schedule.
This is useful in cases where the electrical utility offers lower different energy pricing
throughout the day.