11 Operating information

Outdoor reset operation, if used

Target temperature with outdoor reset

This feature improves the system’s efficiency as the outdoor temperature warms up.

See the Knight Boiler Service Manual to change the settings.

Reset curve

The reset curve looks at outdoor air temperature and adjusts the set point.

Cascade

When multiple boilers are installed, they can be wired together in a cascade sequence. A maximum of eight boilers can be controlled from a single control. In this application one boiler would be designated as the Leader control and all others would be designated as Member controls. If installing the boilers in an existing system, the new boilers should be programmed as the Leader and/or the higher number addresses. The Leader control can be programmed to use Lead/Lag or Efficiency Optimization control methods.

Once the Leader boiler receives a call for heat from a room thermostat, BMS, or Modbus, the control will determine what the set point will be. If outdoor air reset is desired, connect the outdoor air sensor to the terminals on the Low Voltage Connection Board on the Leader boiler. The set point will be calculated based on the programmed reset curve parameters. See the Knight Boiler Service Manual to program the reset curve. If outdoor air reset is not desired, do not connect the outdoor air sensor. A fixed temperature set point can be programmed into the control. See page 59 of this manual to program the set point.

If the water temperature at the system supply sensor is less than the set point + the turn-off offset - the off-on differential, then the control will initiate a call for heat on the Cascade (see the Knight Boiler Service Manual for an explanation of the offset and differential). The Leader will energize the lead boiler on the Cascade. For a new startup this will be the Leader boiler.

Installation & Operation Manual

Sequence of the cascade

To equalize the run time of all boilers on the Cascade, the firing sequence will automatically be changed at set intervals.

The sequence will be changed once every 24 hours. The switching on/off sequence will be as follows:

DAY

SWITCHING ON SEQUENCE

 

 

Day 1

L-M1-M2-M3-M4-M5-M6-M7

Day 1 + 1 hour

M1-M2-M3-M4-M5-M6-M7-L

Day 1 + 2 hours

M2-M3-M4-M5-M6-M7-L-M1

 

 

If a boiler is used to heat an indirect DHW tank, or locks out, it will automatically be given the lowest priority for the rest of that 24 hour period.

DHW, Night Setback, and Ramp Delay operation with cascade

For Normal Mode DHW operation any boiler(s) in the Cascade can be selected to provide heat for a DHW call. Select a boiler to be designated as the DHW boiler. Connect the DHW thermostat or sensor to the terminals on the Low Voltage Connection Board marked for the corresponding device. When the boiler receives a DHW call, the Leader control will take that boiler out of the Cascade sequence. If another boiler is available, the Leader will start it up to take its place.

The DHW boiler will adjust its set point to the programmed DHW set point and will adjust its firing rate to maintain this. Once the DHW call has been satisfied, the Leader control will place that boiler back into the Cascade sequence.

Switching of the boiler between DHW operation and SH operation when there is a call for both does not occur in Cascade Mode.

When DHW is programmed for Zone Mode, connect the DHW thermostat or tank sensor to the Leader boiler. When a DHW call is received, the Leader will modulate the entire Cascade to bring the system supply temperature up to the DHW boiler set point.

Night Setback operation of the boilers within the Cascade is available. Programming of the Night Setback will be done through the Leader boiler. Refer to the Knight Boiler Service Manual for information regarding Night Setback.

Ramp Delay operation of the boilers as described in the Knight Boiler Service Manual is available when the boilers are part of a Cascade system.

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Lochinvar 81 - 286 operation manual Outdoor reset operation, if used, Cascade

81 - 286 specifications

Lochinvar 81 - 286 is a state-of-the-art boiler recognized for its efficiency and reliability in both residential and commercial applications. This high-performance heating solution is designed to meet the diverse needs of users while adhering to modern environmental standards.

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The Lochinvar 81 - 286 incorporates a robust stainless steel heat exchanger that guarantees durability and longevity. This corrosion-resistant material not only prolongs the unit's life but also ensures consistent performance over time. Additionally, the heat exchanger’s design facilitates optimal heat transfer, further enhancing the boiler's efficiency.

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