Relative Calibration Functional Test

Instructions:  For each system included on the checklist, verify the items indicated using Yes for acceptable, No for unacceptable, or NA for Not Applicable.  For unacceptable items, identify what is required to correct the problem in the comments area provided. Use numbers to refer to comments.  Identify the responsible contractor, if know, for any items requiring further action.

Equipment Required:

1.  Field thermometer of some sort.

2.  Lab grade thermometer (Optional, but highly desirable)

3.  Minute by minute trending of points to be tested (Optional)

4.  Shortridge meter with temperature probe (Optional but if available can be used as the field thermometer)

Acceptance Criteria:  This test places the system in a steady state operating mode and then adjusts the return air temperature sensor, the mixed air temperature sensor, the warm-up coil discharge temperature sensor and the air handling unit discharge temperature sensor so that they read the same value when subjected to the same operating condition.  Acceptance criteria are as follows:

1.  With the system in a steady state condition, all sensors read the same value relative to a baseline, with-in their accuracy tolerance prior to adjustment.

2.  With the system in a steady state condition, all sensors read the same value after adjustment.

The test will be performed at two different temperature levels in an effort to provide consistent readings from these sensors under all normally encountered operating conditions.

Date(s) of Test:           _______________________________________________________________________

Time(s) of Test:           _______________________________________________________________________

Test Technician           _______________________________________________________________________

 

 

Item Number

Requirement

Initial and Date when Complete

Prerequisites

1

Verify that all applicable prestart and start-up verification checks from the equipment manufacturer have been completed and that the system is fully functional.

 

2

Verify that the sensors that are to be tested are certified and installed per the accuracy requirements of the specifications.

 

3

Visually inspect the sensors that are to be tested to verify that they are installed in a manner that will allow them to measure the parameter intended and are free from influences due to mounting arrangement or configuration.

 

4

Verify that the loads served by the system can tolerate the 15 to 60 minute period of operation with out active discharge temperature control that is required to perform this test.

 

5

Target a day for the test when it is anticipated that the outdoor conditions will be in the mid 50°F range and suitable for operating on 100% outdoor air with out the need to heat or cool.  This will allow calibration at two operating points.  If the test cannot be scheduled for such a day prior to substantial completion, then proceed with the test in the full recirculation mode only.

 

Preparation

1

Coordinate with the Owner and end-users served by the system for an appropriate test time. Note limits on deviations from set point that can be tolerated in the areas served during the test window and monitor these parameters during the test period.  Terminate the test if they are about to be exceeded.

 

 

 

 

     Area                                                                             Criteria

 

     General office area (monitor return temperature)             75+/- 3°F   

      Verified

     Computer room                                                              72+/- 3°F

      Verified

     Return air CO2 level                                                       less than 750 ppm

      Verified

2

Obtain copies of the specifications for accuracy for the sensors to be tested.  Note the accuracy spec in the space provided below in step 10 of the procedure.

 

3

Obtain copies of the factory calibration certificates for the sensors to be tested

 

4

Place the following AHU01 points into trending or install data loggers.

          

     Return air temperature AHU01RAT

      In trend

     Mixed air temperature AHU01MAT

      In trend

     Preheat coil discharge temperature AHU01PhT

      In trend

     Supply fan discharge air temperature AHU01LAT

      In trend

The following system points will also be trended to document that the temperature in the area they serve did not exceed the limits requested by the Owner.

 

     Computer room temperature 01VAV15SpT

      In trend

     Return air CO2 level AHU01RtCO2

      In trend

Procedure

1

With the system operating, document the supply and return fan heat by measuring the entering and leaving air temperature at each fan with the same thermometer and then subtracting the two readings[1].

Supply fan heat

     Fan inlet temperature                                                                                   °F

     Fan outlet temperature                                                                                 °F

     Fan heat (outlet temperature - inlet temperature                                            °F

Return fan heat

     Fan inlet temperature                                                                                   °F

     Fan outlet temperature                                                                                 °F

     Fan heat (outlet temperature - inlet temperature)                                           °F

 

2

Document the current software calibration and scaling factors for the sensors to be tested in the space below.

Point                                                                                 Slope         Intercept

     Return air temperature AHU01RAT                                                              

     Mixed air temperature AHU01MAT                                                              

     Preheat coil discharge temperature AHU01PhT                                              

     Supply fan discharge air temperature AHU01LAT                                          

 

3        

Modify the software calibration and scaling factors to return them to the standard upon which the input is based.  For example, if the sensor is a 4-20 ma sensor with a range of 0-100°F, then set the system up so that 4ma indicates 0°F and 20ma indicates 100°F[2].  Document these settings in the space provided.

Point                                                                                 Slope         Intercept

     Return air temperature AHU01RAT                                                              

     Mixed air temperature AHU01MAT                                                              

     Preheat coil discharge temperature AHU01PhT                                              

     Supply fan discharge air temperature AHU01LAT                                          

 

4

Disable alarms that could be triggered by the deviations from normal that will be seen during the test or coordinate with the operators to acknowledge them.  Note all alarms that are disabled in the space provided for future reference when returning the system to normal operation.

                                                                                                                         

                                                                                                                         

                                                                                                                         

                                                                                                                         

                                                                                                                         

 

5

Place the system into steady state operation in the full recirculation mode via the following steps.

 

Close the manual isolation valves on the steam and condensate lines for the preheat coil.

 

      Complete

Place the preheat coil in full bypass.

      Complete

Close the manual isolation valves on the steam and condensate lines for the humidifier, including the jacket heater.          

 

      Complete

Close the manual isolation valves on the chilled water supply and return connections.

 

      Complete

Shut down the exhaust systems associated with AHU01.

 

           Toilet exhaust fan EF-1.

      Complete

           Janitor’s closet exhaust fan EF-2.

      Complete

Place the system in full recirculation (verify by visually checking the dampers).

 

           Minimum outdoor air damper fully closed.

      Verified

           Maximum outdoor air damper fully closed.

      Verified

           Return air damper fully open.

      Verified

           Relief damper fully closed.

      Verified

6

While waiting for the system to stabilize, document any temperature change that is occurring through the mixing box due to damper leakage.

     Return air temperature ahead of the return damper.                                       °F

     Average mixed air temperature at the discharge of the

           mixed air plenum[3].                                                                                 °F

     Change (difference between the two readings).                                             °F

 

7        

Document the standard that will be used for comparison of all temperatures during the test.  The allowable choices are listed below in the order of desirability.  Use the most desirable option available at the time of the test. (Check off which will be used).

     Lab grade mercury thermometer                                                                      

     Field thermometer                                                                                      

     Discharge temperature sensor                                                                     

      Location where the standard will be inserted into the system to take the baseline reading.                                                                                                     

 

8        

Allow the system to stabilize in the full recirculation mode for 10-15 minutes.

 

9

If the discharge sensor has been selected as the standard, evaluate its reading relative to other indicators like the apparent operating conditions and information from the other sensors taking fan heat into consideration.  If the indication from the discharge sensor is significantly out of line from what would be anticipated based on the other available information, then it’s accuracy may be out of spec and the test should be discontinued until the sensor’s accuracy can be checked or a different standard becomes available.  Indicate pass or fail in the check-off column.

 

 

 

 

 

      Pass/Fail

10

At this point, all of the sensors should be reading nearly identical values since they are all being subjected to the same condition.  The only difference between what the sensors indicate should be due to their accuracy tolerance and/or due to the effect of fan heat and damper leakage in the mixing plenum. Document the readings from the sensors and the deviation from the selected standard[4].  Compare the deviation from the selected standard to the accuracy specification to determine if the sensor passes this portion of the test or not (deviation from the standard outside the accuracy window fail).  Include compensation for other offsets like fan heat and damper leakage in the mixing plenum where appropriate using the information gathered in steps 1 and 6[5].

Notes:                                                                                                                

                                                                                                                          

                                                                                                                          

 

                                                                       Baseline reading from the standard                                                                                                          °F

 

                                   Point       Reading        Deviation                  Accuracy                                      Other         Allowable

                                                                       Tolerance                 Offsets                                          Deviation

 

Return air temperature

     AHU01RAT                                                                                                 

 

      Pass/Fail

Mixed air temperature

     AHU01MAT                                                                                                

 

      Pass/Fail

Preheat discharge air

     temperature

     AHU01PhT                                                                                                  

 

 

      Pass/Fail

Supply fan discharge

     temperature

     AHU01LAT                                                                                                 

 

 

      Pass/Fail

11

Resolve all problems with sensors that fail the test in step 10 prior to proceeding.  

 Notes:                                                                                                              

                                                                                                                         

                                                                                                                         

 

12

Skip this step if all of the sensors passed step 10.  Otherwise, retest and document the results below after completing step 11.

 

                                                                       Baseline reading from the standard                                                                                                          °F

 

                                   Point       Reading        Deviation                  Accuracy                                      Other         Allowable

                                                                       Tolerance                 Offsets                                          Deviation

 

Return air temperature

     AHU01RAT                                                                                                 

 

      Pass/Fail

Mixed air temperature

     AHU01MAT                                                                                                

 

      Pass/Fail

Preheat discharge air

     temperature

     AHU01PhT                                                                                                  

 

 

      Pass/Fail

Supply fan discharge

     temperature

     AHU01LAT                                                                                                 

 

 

      Pass/Fail

13

Modify the software calibration factors as required to cause all of the sensors to read the same value as the baseline sensor.  Remember to compensate for the effects of fan heat and damper leakage in the mixing plenum.  Document the results below.

Point                                                                Slope         Intercept    Final

                                                                                                           Value

Return air temperature AHU01RAT                                                                     

Mixed air temperature AHU01MAT                                                                     

Preheat coil discharge temperature AHU01PhT                                                                                                                           

Supply fan discharge temperature AHU01LAT                                                     

 

14

If time and outdoor conditions permit, perform the following additional steps to ensure the relative accuracy of the sensors over a range of operating conditions.  Otherwise, proceed to the Follow-up/Return to Normal section of the procedure.

 

15

Place the system in the 100% outdoor air mode to subject the sensors to a different operating condition (verify by visually checking the dampers).

 

           Minimum outdoor air damper fully open.

      Verified

           Maximum outdoor air damper fully open.

      Verified

           Return air damper fully closed.

      Verified

           Relief damper fully closed.

      Verified

Restart the exhaust systems associated with AHU01.

 

           Toilet exhaust fan EF-1.

      Complete

           Janitor’s closet exhaust fan EF-2.

      Complete

16

Allow the system to stabilize in the 100% outdoor air mode for 10-15 minutes.

 

17

Verify that the sensors are still reading the same or nearly the same values. (Note that the return air sensor cannot be tested in this mode.) If there are differences “tweak” the software calibration factors to eliminate them and/or provide a good compromise between the values indicated at this condition and the values indicated in the full recirculation condition.  Remember to compensate for the effects of fan heat and damper leakage in the mixing plenum.  It may be necessary to toggle back and forth between the recirculation mode and the 100% outdoor air mode to fine tune the settings.  Document the final results below if they differ from the results on the full recirculation cycle.

Point                                            Slope         Intercept     Final          Final

                                                                                         Value         Value

                                                                                         100% OA                                                       Recirc.

Return air temperature

    AHU01RAT                                                                   N/A                          

Mixed air temperature

    AHU01MAT                                                                                                  

Preheat coil discharge temperature

     AHU01PhT                                                                                                    

Supply fan discharge temperature

     AHU01LAT                                                                                                   

 

Follow-up/Return to Normal

1

Return the system to normal operation via the following steps.

 

Open the manual isolation valves on the steam and condensate lines for the preheat coil.

 

      Complete

Return the preheat coil face and bypass dampers to automatic control.

      Complete

Open the manual isolation valves on the steam and condensate lines for the humidifier, including the jacket heater.          

 

      Complete

Open the manual isolation valves on the chilled water supply and return connections.

 

      Complete

Return the economizer and minimum outdoor air control cycles to automatic (verify by visually checking the dampers).

 

           Minimum outdoor air damper released to automatic control.

      Verified

           Maximum outdoor air damper released to automatic control.

      Verified

           Return air damper fully released to automatic control.

      Verified

           Relief damper fully released to automatic control.

      Verified

Return the exhaust systems associated with AHU01 to automatic control.

 

           Toilet exhaust fan EF-1.

      Complete

           Janitor’s closet exhaust fan EF-2.

      Complete

2

Re-enable all alarms that were disabled previously.  Use the items noted under step 4 of the procedure as a guide.

 

3                   

Print trend reports from the trends that were running during the test and save the trend files to a floppy to document the test process and results.

 

4

Remove all trends that the Owner does not which to retain.  Remove data loggers if they were installed in place of trending or to supplement trending.

 

5

Back-up the controller database to ensure that the new calibration factors are saved to the system hard disk. 

 

6

Recommend that the Owner back up the system hard disk at the completion of the current commissioning process to ensure that the modifications and adjustments made can be recovered if the system hard disk fails.

 

Comments:

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[1]   This information will be used later in the test if a fan is located between two sensors under test.  Thermometer accuracy for this measurement is not critical as long as the same thermometer is used for both readings since the readings are subtracted from each other, thus canceling any error.

[2]   You may discover that the system has already been set up to do this.  However, it is not uncommon to adjust the software scaling and calibration factors to “tweak” a sensor to compensate for its certified accuracy limitations so that it reads closer to the true temperature.  In fact, this is exactly what we will do later in the procedure to calibrate the sensors relative to each other.  At this stage of the test, it is important that the system be set up to the sensor standards to allow a baseline to be established and evaluate if everything is reading with-in its certified accuracy specification.

[3]   Take multiple readings  - one at the center of each filter in the filter bank - and average them.  Using the Shortridge meter in the automatic mode makes this very easy.

[4]   At this point, if all of the sensors were identical and there was no such thing as calibration error, then all of the readings would be identical to each other and have the same deviation from the standard (probably none).  But, this will very seldom be the case in the field due to manufacturing tolerances and other effects that combine to show up as the calibration tolerance for the sensors.

[5]   Compensation for fan heat should be included for each fan that is between the baseline sensor and the sensor under consideration.  For example if the fan heat were measured to be 1°F, and the discharge sensor is in the fan discharge and the baseline is a lab grade thermometer, also located in the fan discharge, then the only allowable deviation from the baseline for the discharge sensor will be its accuracy tolerance.  But, the deviation from baseline allowable for the sensor in the preheat coil discharge would include the fan heat in addition to its accuracy tolerance.  Similar considerations apply to the effects of damper leakage and the temperature change it creates across the mixed air plenum.