Crestron electronic 1.5, 3.5, 2.5 service manual Cascade

Page 49

Installation & Operation Manual

10 Operating information (continued)

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.

Once the Leader boiler receives a call for heat from the Enable input, the 0 - 10 VDC input, 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 Crest 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, or provided through the ModBus interface.

If the water temperature at the controlling sensor is less than the set point + the turn-off offset - the off-on differential, the control will initiate a call for heat on the Cascade (see the Crest 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.

The two (2) types of Cascade control are listed below:

Efficiency optimization

Efficiency optimization is chosen when the application is such that overall heating efficiency is most important. The Cascade will fire the boilers in a way that is the most efficient. This allows more boilers to fire at one time, at a lower rate, thus more efficient. This Cascade is also required when cascading boilers in a common vent application.

Lead/Lag

The Lead/Lag method is chosen when the application requires firing as few boilers at a time as possible. This method will not bring on another boiler until the current number of boilers cannot meet the demand. This Cascade is NOT allowed in a common vent application.

The parameters for both types of Cascade are adjustable. Reference the Crest Service Manual for a more detailed description of these adjustments.

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.

For the first 24 hours after initializing the Cascade, the sequence will be changed every hour. After that the sequence will be changed once every 24 hours.

HW operation with cascade

For HW operation any boiler(s) in the Cascade can be selected to provide heat for a HW call. Select a boiler to be designated as the HW boiler. Connect the HW thermostat or sensor to the terminals on the Low Voltage Connection Board marked for the HW Thermostat or sensor. When the boiler receives a HW 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 HW boiler will adjust its set point to the programmed HW set point and will adjust its firing rate to maintain this. Once the HW call has been satisfied, the Leader control will place that boiler back into the Cascade sequence.

Night Setback and Ramp Delay operations with cascade

Night Setback and Ramp Delay operation of the boilers within the Cascade are available. Programming will be done through the Leader boiler. Refer to the Crest Service Manual for information regarding Night Setback and Ramp Delay.

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Contents Save this manual for future reference Contents Please read before proceeding When servicing boilerBlowers Crest How it worksCrest How it works Models 1.5 2.0 2.5 3.0 Crest Ahri Rating RatingsDetermine boiler location Installation must comply withBefore locating the boiler, check Provide clearancesFlooring and foundation Provide air openings to roomVent and air piping Prevent combustion air contaminationProducts to avoid When using an existing vent system to install a new boilerAreas likely to have contaminants When removing a boiler from existing common vent system Remove boiler from wood pallet 7Combustion Air from Outside Single Opening Minimum Recommended Combustion AIR Supply to Equipment Room Direct venting General ventingOptional room air Air inlet pipe materials Install vent and combustion air pipingAir intake/vent connections Approved Stainless Steel Vent Manufacturers Make ModelRemoving from existing vent Common venting Vent/air termination vertical Vertical direct ventingDetermine location Prepare roof penetrations4Alternate Vertical Terminations with Multiple Boilers Multiple vent/air terminationsVent/air termination sidewall Sidewall direct venting2Clearance to Doors and Windows Prepare wall penetrations4Multiple Vent Terminations must also comply with Figure Room airHydronic piping Model Circulator sizing20F 40F 60F Near boiler piping components System Multiple Boilers Common Header Primary / Secondary Flow For all equipment and detailing required by local codes Hydronic piping Gas connections Connecting gas supply pipingModel Gas Inlet Size Propane Gas Natural gasCheck inlet gas supply GAS Piping Size ChartGas Pressure Gas valve replacementInstallation must comply with Field wiringLine voltage connections Outdoor temperature sensor EnableLouver proving switch Low voltage connectionsAlarm contacts Auxiliary switch 1Wiring of the cascade System supply sensorField WiringCondensate drain Condensate disposalStart-up Freeze protection when usedCheck/control water chemistry Fill and test water systemCheck thermostat circuits Check for gas leaksInspect condensate system Inspect/check condensate lines and fittingsStart the boiler Final checks before starting the boilerIf boiler does not start correctly Check system and boilerFor Your Safety Read Before Operating Gas Natural Gas Propane Valve Set space heating operationConfiguration of the cascade Verify HWG circulator mode Set HWG target temperatureSet clock General Operating informationProtection features Outdoor reset operation, if used Boiler temperature regulationCascade Sequence of operation Home Screen Crest control module2Main Menu Screen Service technician Maintenance Maintenance and annual startupOwner maintenance See the Crest User’s Information Manual for InstructionsMaintenance Check water system Flue vent system and air pipingCheck expansion tank Check boiler relief valveCheck all boiler wiring Check ignition ground wiringCheck control settings Check flame signalReview with owner Cleaning boiler heat exchangerHandling ceramic fiber materials Niosh stated First AidIntegrated Control Diagrams2Wiring Diagram
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