tekmar 553 Thermostat Installation - Manual (Page 35)

© 2014 553_D - 09/14
35 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 an 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 W HEAT WWSD setting is available to allow a forced air heating system 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 W 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 553 has the
ability for the balance point setting change based upon a programmable schedule. This
is useful in cases where the electrical utility offers different energy pricing throughout
the day.
Freeze Protection ---------------------------------------------------- ----------------------------------------------------
The thermostat operates the heat whenever the room or floor temperature falls below
40°F (4.5°C) even when the mode is set to off.
Two-Stage Heating -------------------------------------------------- --------------------------------------------------
The 553 generally operates a radiant floor or baseboard as the first stage of heat and
a forced air heating system as the second stage. When an outdoor temperature sensor
is available, the 553 can change the order of the heat stages using the Radiant Floor
Warm Weather Shut Down or the Balance Point to operate the system as comfortably
and efficiently as possible. For additional control of the second stage operation, the
553 includes a time delay and a temperature differential setting. Both setting conditions
must be met before the second stage heat is allowed to turn on.