Lennox International Inc CBX40UHV02, XP2101 Staged operation, Variable Capacity Furnace Operation

Page 35

Variable Capacity Control of Gas Heat Mode (G71MPP and SLP98V)

The thermostat includes a feature that provides variable capacity control of the gas heat mode. The purpose of variable capacity control is to keep the room temperature at, or near, the desired setpoint with minimum system cycling. The thermostat bases its

using the following inputs:

SRoom temperature,

SHistory of cycle times (how long does it typically take to bring the room temperature to the desired setpoint),

STarget setpoint, and

SDifferential temperature settings between 1st − 4th stage.

The thermostat uses this information to vary the heating capacity to efficient- ly satisfy the heating demand. The full range of the furnace heating capacity (low end is a percent of the 1st stage capacity; high range is 100% of full capacity) is used. When in variable capacity gas heat mode, the furnace op- eration includes longer run times at lower heat stages.

Table 2 details the variable capacity furnace operation.

Staged operation

Some furnaces can be configured to provide up to four stages of gas heat operation. When staged heating is chosen, the icomfort thermostat allows you to choose between 1, 2, 3 and 4 stages of heat.

Single−stage heat: 1st stage provides 100% of full capacity.

Two−stage heat: 1st stage provides 70% of full capacity; 2nd stage provides 100% of full capacity.

Three−stage heat: 1st stage provides 60% of full capacity; 2nd stage provides 80% of full capacity; 3rd stage provides 100% of full capacity. Four−stage heat: 1st stage provides 35 or 40% of full capacity; 2nd stage provides 60% of full capacity; 3rd stage provides 80% of full ca- pacity; 4th stage provides 100% of full capacity.

SLP98 variable capacity furnaces BTU’s firing rates can be incremented by as little as 1% (35% to 100% range available) as the thermostat may dictate.

The thermostat monitors room temperature, previous heat cycle times, and target setpoint to determine the starting firing rate, and any required firing rate increases or decreases during the thermostat demand.

During a heat demand, the icomfort thermostat monitors the differential be- tween setpoint and room temp. As this differential increases and reaches field adjustable levels (stages), the thermostat will increase firing rate ac- cordingly to maintain room temperature and ultimately satisfy the heat de- mand. On the next heat cycle, the icomfort stat will calculate a new starting firing rate (in 1% increments) with the goal of maintaining room temperature at, or near, thermostat setpoint with a minimum of system cycling. The prin- ciples of operation are described in figure 36 and table 2.

Table 2. Variable Capacity Furnace Operation

T’stat Demands

Operation

 

 

None

Furnace is off

 

 

 

First level heat de-

1.

Furnace BTU rate is calculated by the icomfort integrating al-

mand.

 

gorithm.

 

2.

Furnace firing rate will continue at current heating rate until

 

 

first stage demand is satisfied or an additional thermostat de-

 

 

mand is received.

 

 

 

Second level heat

1.

Thermostat will immediately increase variable capacity fur-

demand added

 

nace firing rate to the calculated BTU percentage represent-

 

 

ing the second stage thermostat demand.

 

2.

Furnace firing rate will increase by 5% every 5 minutes (up to

 

 

100% if second stage thermostat is not satisfied.) If thermo-

 

 

stat second stage demand is satisfied the current firing rate

 

 

will continue until all thermostat demands are satisfied.

 

 

 

Third level heat de-

1.

Thermostat will immediately increase variable capacity fur-

mand added.

 

nace firing rate to the calculated BTU percentage represent-

 

 

ing the third stage thermostat demand.

 

2.

Thermostat will increase the firing rate by 5% every 5 minutes

 

 

(up to 100% if third stage thermostat is not satisfied.) If ther-

 

 

mostat third stage demand is satisfied the current firing rate

 

 

will continue until all thermostat demands are satisfied.

 

 

Fourth level heat de-

Icomfort thermostat will immediately set variable capacity

mand added.

furnace firing rate to 100% until all thermostat demands are

 

satisfied.

 

 

 

Page 35

icomfort Wi-Fit 7−Day Programmable Communicating Thermostat

Page 34 Page 36
Image 35
Page 34 Page 36
Contents CONTROLS INSTALLER’S SYSTEM SETUP GUIDEicomfortt−Enabled Units 2P0912**P506920-01Page Setting up typical icomfortt systemsTable of Contents Figure 1. icomfort by Lennoxt system SupportsOutdoor Temperature Sensor option Installation and Setup Figure 4. Entering Change settingsFigure 3. Settings change tools Dealer NumberTable 1. System setting defaults and range Circulate fan ON time settingFigure 6. Set current time and date Set time and date09 39 am Figure 5. View/edit time and dateFigure 7. Using the HUMIDITY CONTROL TIPS Add or Remove Non−communicating equipmentSystem Add Non−Communicating Outdoor unitFigure 8. Add non−communicating device red settingsHumidifier 5a 5bFigure 9. Add or remove non−communicating device SystemDehumidifier Figure 10. Add or remove non−communicating deviceSystem DehumidifierFigure 11. Adjust communicating device screens Adjust a setting screen communicating devicesG71MPP or SLP98 Furnace Note Figure 12. Accessing device to modifyFigure 13. Modify device settings Figure 14. Adjust a non−communicating device setting Figure 15. Adjust a non−communicating device setting Figure 16. Adjust dehumidification when not using Humiditrol or an auxiliary dehumidifier DEHUMIDIFICATION modes Humidification and Dehumidification ModesHUMIDIFICATION modes Figure 19. Typical tests results screens Use the Tests / Diagnostics featuresFigure 17. Start testing screen Figure 18. Select tests to run screenFigure 21. Equipment parameters screen Equipment, Alerts, DiagnosticsSet up Equipment parameters Figure 20. Testing finished screenFigure 22. Edit equipment details Run DiagnosticsView and clear Installer Alerts Figure 23. Select device and run diagnosticsFigure 26. Cleared alerts screen Figure 25. Cleared alert confirmationView cleared alerts Figure 24. Selecting and viewing alertsHERE Figure 27. Wi−Fi setupSecure Connection Recommended STARTFigure 28. Change Networks Registering the icomfort Wi-FitthermostatRegistration for online access Figure 30. icomfort Wi-FitRegistration screen Wi-FitTher Welcome homeHow Do I Upload a Skin? Figure 31. PC Welcome Screenyes no Access installer program from Home screenFigure 34. Re−configuration process Reconfigure a system2nd Stage Differential where applicable2 Rules for SSR Smooth Setback Recovery SSRHigh Balance Point Heat Pump, Dual Fuel and Balance PointsHeat Pump Balance Points Low Balance PointShut down HP Gas Heat Control Mode Figure 36. Variable Capacity Operation Flow ChartTable 2. Variable Capacity Furnace Operation Staged operationLoad−tracking Variable Capacity FAQs SLP98V only Installer entry Table 3. Adjustable Parameters Table InstallerLock in 2nd stage HP by Outdoor Temp Table 3. Adjustable Parameters Table InstallerAIR HANDLER Table 3. Adjustable Parameters Table InstallerFURNACE Gas Heat Airflow SettingsTable 3. Adjustable Parameters Table Installer Table 3. Adjustable Parameters Table Installer Cooling Airflow SettingsHeat Pump Airflow Settings Table 3. Adjustable Parameters Table Installer Other ParametersTable 4. Adjustable Parameters Table User Filter 1 Timer Table 5. Alert Codes and Troubleshooting Alert Table 5. Alert Codes and TroubleshootingAlert Table 5. Alert Codes and TroubleshootingAlert Table 5. Alert Codes and TroubleshootingAlert Table 5. Alert Codes and TroubleshootingAlert Table 5. Alert Codes and TroubleshootingAlert Table 5. Alert Codes and TroubleshootingAlert Table 5. Alert Codes and TroubleshootingAlert Table 5. Alert Codes and TroubleshootingTable 5. Alert Codes and Troubleshooting Homeowner Service Alert Codes8Corrective Action / Comments Table 6. Troubleshooting TipsIssue / Problem Possible CauseHigh Balance Point and Low Bal Table 6. Troubleshooting TipsDetermine the actual Software ver Table 6. Troubleshooting TipsDuring the cooling mode the dis Table 6. Troubleshooting Tipsicomfortt Communicating System Wiring Wiring Diagramsicomfort by Lennoxt AIR HANDLER AHC Wiring Diagramsfor use with any icomfort by Lennoxt system Optional Accessories WiringLVCS Ventilation Control System Optional Accessories Wiringfor use with any icomfort by Lennoxt system attached to the PUSHBUTTON TIPS Setting up typical systemsTIPS TIPS Setting up typical systemsT PUMP DUAL FUELTIPS TIPS Setting up typical systemsTIPS TIPS Setting up typical systemsT PUMP UNITSTIPS Replacement Kit Catalog No Table 7. Replacement ControlsREVISION HISTORY icomfortt−Enabled Unit
Top Page Image Contents