INSTALLATION AND OPERATION INSTRUCTIONS
2-8
SL 20-115 MODULATING GAS BOILER
Contacts are provided for connection of an outdoor sensor (a
tekmar 070
or
similar sensor is shipped with each boiler) to be placed in an appropriate outdoor
position. The temperature management algorithm flexes the boiler supply
temperature according to characterized heating curves that are automatically
called up through the load declaration process. Curves are provided for each
of the radiation terminal types offered - e.g. high or low mass radiant floor, air
handler, finned tube baseboards etc.
in an “open loop” reset system, a room or zone thermostat is used to send a call
for heat over a 24VaC lead; this opens the respective zone valve, and signals the
boiler to fire using onward leads to the boiler’s dry contacts (use one of the pairs
marked “therm 1, 2 or 3” on the orange connector terminal located on the right
edge of the controller). gang such leads in parallel from multiple zone valves for
single connection to the boiler. note that typical room thermostats simply provide
a call for heat, they do not control the circulating water temperature from the
boiler in an open loop reset system. adjustment of a room thermostat from 23°C
to 30°C will make no further difference to the delivered temperature if the floor
slab has stabilized at the boiler temperature served up by the reset curve.
Where outdoor reset is applied without the indoor sensor feedback option, some
manual adjustment may be required to achieve the desired comfort level. Fine
adjustment can be made at the keypad using the
Indoor Setpoint Temperature
variable, located as line 1 in the user screen. to increase heat (e.g. from 72°F to
73°) - move the indoor value upward (warmer) from the level otherwise chosen.
this shifts the position of the reset curve, will amend the boiler water temperature
by a similar amount. do not adjust the
Design Indoor Temp.
value - a movement
upward in concert with line 1 adjustment will have the effect of neutralizing the
intended effect.
An optional indoor temperature feedback routine can be activated (with field
installation of an indoor sensor, connected to the contacts located on the
controller) to automate adjustment of the outdoor reset routine.
the key inputs on initial set up are (1)
Design Outdoor Temperature
– the coldest
expected weather typically experienced at the installation site; (2) the
Design
Supply Temperature
– the desired boiler operating level to occur at that coldest
day; and (3) the
Design Indoor Temp.
- this is the value that anchors the reset
curve. the
Indoor Set Point Temp.
variable is the primary means for the user to
“bias” the outdoor reset routine to add or reduce heat.
Figure 37: Outdoor reset curves