[Equest-users] Cooling Load not met!

Maryanne Mason maryanne.mason at ausencosandwell.com
Mon Sep 20 10:11:38 PDT 2010


Hi Siddharth

 

When I had issues with unmet load hours recently, it turned out to be the
temperature control setpoints. I produced an hourly report with air
temperatures at various parts of the air handling system, and was able to
see that the control for the supply temperature was causing the problem.

 

I hope this helps.

 

MaryAnne 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Siddharth V
Sent: Friday, September 17, 2010 7:29 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Cooling Load not met!

 


Hi All, 

I have created a System, which has only one zone(25000 sqft) using DX coils
for cooling, Furnace for heating; and system type is CAV Packaged Single
Zone system.   

I have set the COOLING-CAPACITY = 1500.00 kBTU/hr. 

When I was going through the HOURLY reports, I found the following data. 

Below are the Peak Cooling Report Summary, followed by the HVAC Cooling load
for the peak day(Jun 21) and the current zone temperatures/ Thermostat
Temperatures for that same day. 


MY Queries are: 

If my HVAC system is designed to remove a heat load of 1500kBTU, and the
total Heat to be removed on Jun21 (8am) was 1004375+44188 = 1048563 BTU/hr
only, why wasnt the HVAC system unable to remove it? The first doubt was
about insufficient CFM (of the used constant volume system). But the same
CFM is able to handle higher loads at other times. 

Please see the SS-J Report during the particular hour the load was never
met. 

Please resolve my confusion regarding this sufficient cooling capacity vs
unmet load scenarios. 

I am attaching the inp, weather file for your reference (in case it helps). 



REPORTS: 
 

REPORT- SS-J Peak Heating and Cooling for   Sys1 (PSZ) (G.1)
WEATHER FILE- EPW New Delhi,Delhi, 
----------------------------------------------------------------------------
----------------------------------------------------- 



          - - - - - C O O L I N G - - - - -       - - - H E A T I N G - - -
D A Y   C O O L I N G   P E A K 

                        JUN 14                              JAN 19
JUN 21 


          HOURLY                                    HOURLY
HOURLY 
         COOLING    SENSIBLE    DRY-   WET-        HEATING    DRY-   WET-
COOLING    SENSIBLE    DRY-   WET- 
            LOAD        HEAT    BULB   BULB           LOAD    BULB   BULB
LOAD        HEAT    BULB   BULB 
HOUR      (KBTU)       RATIO    TEMP   TEMP         (KBTU)    TEMP   TEMP
(KBTU)       RATIO    TEMP   TEMP 



   1       0.000       0.000    93.F   74.F          0.000    49.F   48.F
0.000       0.000    89.F   79.F 
   2       0.000       0.000    95.F   74.F          0.000    48.F   47.F
0.000       0.000    89.F   78.F 
   3       0.000       0.000    96.F   73.F          0.000    47.F   47.F
0.000       0.000    87.F   78.F 
   4       0.000       0.000    95.F   74.F          0.000    47.F   47.F
0.000       0.000    86.F   78.F 
   5       0.000       0.000    89.F   76.F          0.000    47.F   47.F
0.000       0.000    85.F   79.F 
   6       0.000       0.000    89.F   77.F          0.000    48.F   47.F
0.000       0.000    84.F   80.F 
   7    1100.896       0.763    89.F   77.F          0.000    48.F   48.F
1065.103       0.708    85.F   80.F 
   8     988.670 *     0.732    90.F   78.F          0.000    49.F   48.F
1004.375 *     0.685    86.F   80.F 
   9     996.547       0.747    92.F   78.F          0.000    51.F   50.F
988.282       0.686    90.F   81.F 
  10     982.636 *     0.731    94.F   79.F          0.000    52.F   51.F
1006.017       0.678    92.F   81.F 
  11     987.969       0.734    97.F   79.F          0.000    54.F   52.F
988.014       0.678    95.F   82.F 
  12     998.494       0.711    99.F   81.F          0.000    55.F   54.F
989.553       0.669    97.F   83.F 
  13    1004.154       0.694   100.F   82.F          0.000    57.F   54.F
990.271       0.662    98.F   84.F 
  14     979.070       0.691   100.F   83.F          0.000    59.F   55.F
955.878       0.668    99.F   83.F 
  15     934.561       0.711   100.F   81.F          0.000    59.F   55.F
942.959       0.676   101.F   83.F 
  16     863.300       0.735   100.F   78.F          0.000    59.F   55.F
899.941       0.683   101.F   82.F 
  17     737.102       0.770    99.F   75.F          0.000    58.F   55.F
814.377       0.687   102.F   82.F 
  18       0.000       0.000    97.F   75.F         -6.497    56.F   53.F
0.000       0.000   101.F   81.F 
  19       0.000       0.000    96.F   74.F          0.000    53.F   52.F
0.000       0.000   100.F   81.F 
  20       0.000       0.000    94.F   76.F          0.000    51.F   50.F
0.000       0.000    98.F   81.F 
  21       0.000       0.000    93.F   77.F          0.000    49.F   49.F
0.000       0.000    98.F   82.F 
  22       0.000       0.000    91.F   78.F          0.000    48.F   48.F
0.000       0.000    96.F   81.F 
  23       0.000       0.000    90.F   78.F          0.000    48.F   48.F
0.000       0.000    95.F   81.F 
  24       0.000       0.000    89.F   78.F          0.000    49.F   48.F
0.000       0.000    93.F   81.F 
        --------                                  --------
--------- 
SUM
10644.770 
MAX     1100.896                                    -6.497 


              SYSTEM-TYPE         PSZ                      SQFT/TON
544.9 
              COOLING PEAK          22.02 (BTU/HR- SQFT)   HEATING PEAK
-0.13 (BTU/HR- SQFT) 
              SUPPLY AIR PEAK FLOW   0.53 (CFM/SQFT)       MIN-OA/PERSON
35.00 (CFM ) 
              OA FRAC AT CLG PEAK   0.164                  OA FRAC AT HTG
PEAK   0.164 

              * ASTERISKS INDICATE HOURS LOADS NOT MET 
----------------------------------------------------------------------------
----------------------------------------------------------------------- 

          BUILDING      Zn (G.1) 
          -HVAC                 
          COOLING       LOAD NOT 
          LOAD          MET     
          BTU/HR        BTU/HR   
                                
          ----( 1)      ----(16) 
 621 7      1065103.            0. 
 621 8      1004375.        44188. 
 621 9       988282.            0. 
 62110      1006017.            0. 
 62111       988014.            0. 
 62112       989553.            0. 
 62113       990271.            0. 
 62114       955878.            0. 
 62115       942959.            0. 
 62116       899941.            0. 
 62117       814377.            0. 

 DAILY SUMMARY (JUN 21) 


----------------------------------------------------------------------------
--------------------------------------------------------------------- 
       Zn (G.1) Zn (G.1) 
                        
       ZONE     THERMOST 
       TEMP     SETPOINT 
       F        F       
                        
       ----( 6) ----( 7) 
 621 7     76.9     76.0 
 621 8     79.4     76.0 
 621 9     76.9     76.0 
 62110     77.0     76.0 
 62111     76.9     76.0 
 62112     76.9     76.0 
 62113     76.9     76.0 
 62114     76.8     76.0 
 62115     76.8     76.0 
 62116     76.7     76.0 
 62117     76.6     76.0 


 DAILY SUMMARY (JUN 21) 





Regards,
Siddharth Venkataraman
Tata Consultancy Services
Mailto: siddharth.v at tcs.com
Website:  <http://www.tcs.com/> http://www.tcs.com
____________________________________________
Experience certainty.        IT Services
                       Business Solutions
                       Outsourcing
____________________________________________

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