Crestron electronic 3.5, 2.5, 1.5 service manual Sequence of operation

Page 50

Installation & Operation Manual

10 Operating information

Sequence of operation

Note: This unit is equipped with two (2) gas train systems. Gas Train 1 will fire first. If the demand cannot be met by the first gas train, the second gas train (Gas Train 2) will fire.

1.Upon a call for heat, the control turns on the appropriate pumps (system and boiler pumps for a space heating call, HW pump for a domestic hot water call).

2.The control confirms that the low water cutoff contacts are closed and energizes the louvers (optional) and damper (optional) relays.

3.The control confirms that the gas pressure switch, blocked drain switch, limits, louver proving switch (optional) and damper proving switch (optional) contacts close. The Pre-Purge cycle begins.

4.The control confirms both blowers come up to the desired speed, both blower proving switches close, and the air pressure switch is closed.

5.Once the Pre-Purge cycle is complete, the control lowers the blower speeds, initiates sparking of the ignition electrode, and opens Gas Valve 1.

6.After a short wait, the control stops sparking and checks for the presence of flame current through the flame sense electrode.

7.If the control does not detect flame current, the control will lockout indefinitely, until the RESET button on the touch screen LCD is pressed. Models FB 1500 - 2500 will have one retry.

If the control detects flame current, the control will hold the blower speed constant for a few seconds to allow the

8.flame to stabilize, then begin modulating the firing rate in order to maintain the controlling sensor to the desired set point temperature.

If the current call for heat is for space heating and a HW call for heat becomes active, the control will turn on the HW

9.pump relay output, then turn off the boiler pump. It will then modulate the blower speed in order to maintain the outlet temperature to the desired HW outlet set point temperature.

If the first combustion system in the boiler is unable to maintain the desired set point temperature, the second combustion system in the boiler will be started. Both blowers will modulate to a set speed, and the second gas valve

10.will be energized. The second combustion system will light from the first combustion system. The second flame will be monitored much like the first. Once both combustion systems are firing, the control will work in synchronization to maintain the desired set point temperature. If the heat load should decrease sufficiently, the second combustion system will be shut down.

11.Once both the space heating and HW calls for heat are satisfied, the control will turn off the gas valve(s) and begin the Post-Purge cycle. Any pumps that are running will begin their respective Pump Delay cycles.

12.At the end of the Post-Purge cycle, the louver relay contacts will de-energize.

13.The control verifies that the blowers stop running and the blower proving switches open.

14.At the end of the Pump Delay cycle(s), the pump(s) will be turned off.

50

Page 49 Page 51
Image 50
Page 49 Page 51
Contents Save this manual for future reference Contents When servicing boiler Please read before proceedingCrest How it works BlowersCrest How it works Models 1.5 2.0 2.5 3.0 Ratings Crest Ahri RatingBefore locating the boiler, check Installation must comply withDetermine boiler location Provide clearancesVent and air piping Provide air openings to roomFlooring and foundation Prevent combustion air contaminationAreas likely to have contaminants When using an existing vent system to install a new boilerProducts to avoid 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 Optional room air General ventingDirect venting Install vent and combustion air piping Air inlet pipe materialsApproved Stainless Steel Vent Manufacturers Make Model Air intake/vent connectionsRemoving from existing vent Common venting Determine location Vertical direct ventingVent/air termination vertical Prepare roof penetrationsMultiple vent/air terminations 4Alternate Vertical Terminations with Multiple BoilersSidewall direct venting Vent/air termination sidewallPrepare wall penetrations 2Clearance to Doors and WindowsRoom air 4Multiple Vent Terminations must also comply with FigureHydronic piping 20F 40F 60F Circulator sizingModel Near boiler piping components System Multiple Boilers Common Header Primary / Secondary Flow For all equipment and detailing required by local codes Hydronic piping Model Gas Inlet Size Connecting gas supply pipingGas connections Natural gas Propane GasGAS Piping Size Chart Check inlet gas supplyGas valve replacement Gas PressureLine voltage connections Field wiringInstallation must comply with Louver proving switch EnableOutdoor temperature sensor Low voltage connectionsWiring of the cascade Auxiliary switch 1Alarm contacts System supply sensorWiring FieldCondensate disposal Condensate drainCheck/control water chemistry Freeze protection when usedStart-up Fill and test water systemInspect condensate system Check for gas leaksCheck thermostat circuits Inspect/check condensate lines and fittingsIf boiler does not start correctly Final checks before starting the boilerStart the boiler Check system and boilerFor Your Safety Read Before Operating Set space heating operation Gas Natural Gas Propane ValveSet clock Verify HWG circulator mode Set HWG target temperatureConfiguration of the cascade Operating information GeneralProtection features Boiler temperature regulation Outdoor reset operation, if usedCascade Sequence of operation Crest control module Home Screen2Main Menu Screen Owner maintenance Maintenance Maintenance and annual startupService technician See the Crest User’s Information Manual for InstructionsMaintenance Check expansion tank Flue vent system and air pipingCheck water system Check boiler relief valveCheck control settings Check ignition ground wiringCheck all boiler wiring Check flame signalHandling ceramic fiber materials Cleaning boiler heat exchangerReview with owner Niosh stated First AidDiagrams Integrated Control2Wiring Diagram
Top Page Image Contents