Install Instructions

28
16 - OPERATING THE BOILER - SYSTEM START-UP
16.6 Activating Thermal Pre-Purge (optional)
Activation of this feature is not recommended for boilers
with tankless coils.
• Limit has thermal pre-purge feature to maximize
efciency. When activated, control will purge higher
boiler temperatures down to 135°F at start of any
thermostat call and supply latent energy in boiler to
heating zone calling.
• During purge cycle, display will indicate PUR.
• If heat is not sufcient to satisfy thermostat, control will
energize burner.
• Feature works with single and multi-zone heating
systems utilizing circulators or zone valves. No change
in wiring is needed.
To Activate Thermal Pre-Purge
1. Push and hold TEST/SETTINGS button for 20 seconds.
2. Display will read PURR On.
3. To deactivate feature, push and hold button a second
time for 20 seconds.
4. Display will read PURR OFF.
16.7 Control Action On System Start-Up
At initial start-up, with economy feature active, control
establishes 145°F target temperature. To test high limit
shut-off function, economy dial must be turned to off.
Once tested, restore economy setting.
If heating demand is high, target will increase over time to
satisfy heat load.
To reduce potential for condensing, control will allow boiler
to heat to 125°F prior to energizing the circulator.
16.8 How Thermal Targeting Works
Thermal targeting technology analyzes thermostat activity
and continually evaluates how much heat the house
requires.
When it is very cold outside, heat demand is high and limit
control will raise boilers target temperature to provide heat.
When outside temperature is mild, heat demand is low.
Limit control will lower boiler’s target temperature saving
fuel.
Figure 26 - LED Legend
1
TEMP ACTIVE Indicates Limit Control is powered
and temperature function is active.
2
TEMP HI TEMP Illuminates when boiler water
temperature reaches high limit setting. Remains lit until
water temperature falls 10°F. Limit control prevents burner
operation while this LED is on. See Differential explanation
page 27.
3
LWCO ACTIVE I ndicates low water cut-off (LWCO)
function of limit control is active. Boiler is factory equipped
with Hydrolevel electro-well, enabling control’s low water
cut-off function. LED will be on at all times when control is
powered.
Important: If control well is replaced with a well other than
Electro-Well, LED will not illuminate indicating control is not
providing low water cut-off functionality.
WARNING
Burn and scald hazard. Do not add water until boiler
has fully cooled. Failure to follow these instructions
could result in death or serious injury.
!
4
LWCO LOW WATER Illuminates if boiler is in low
water condition. Limit control will prevent burner operation
during this condition.
Important: System must be checked by a qualied service
agency prior to resuming operation.
5
ECONOMY ACTIVE Indicates thermal targeting
function is active and limit control will reduce boiler
temperature to conserve fuel. Economy feature is activated
using the Economy dial. See “How Thermal Targeting
Works” this page.
PN 473900000