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Kitchen HVAC study by gegeshandong


									Elmwood Bldg 6186                       Overview of HVAC Study                              Page 1 of 6

Project: HVAC Study for Elmwood Bldg 6186
Bldg. 6186 is the Support Services Bldg. (Kitchen, Laundry, Warehouse)

By Blake Blakely, County of Santa Clara, Building Operations                            Dec. 12, 2008

This report serves as an overview of the study of the major HVAC equipment and adds other
miscellaneous related items that are not covered in the study.

This study was done because:
     There are serious comfort problems in the Kitchen and Laundry areas.
     The 7 large penthouse air handlers that serve the majority of the building are failing. They have
        many wetted parts which have short lives and high maintenance. See diagram below.
     Considering comfort, maintenance, and energy, I strongly suspected that the existing system
        design and system type is no longer optimal and should not be replaced with like kind. I wanted
        this study to prove and quantify what are the best system concepts.

                           EXISTING IDEC AHUs
                  (Indirect and Direct Evap. Clg. Air Handling Units)
          Elmwood Bldg 6186                        Overview of HVAC Study                                 Page 2 of 6

          THE STUDY
          The study, by Salas O’Brian Engineers, was to determine the best concepts for the HVAC systems, the
          initial construction cost, and the life cycle cost. The best concept was laid out and drawn to scale on full
          size drawings. The next steps would be detail design, then construction, when approved and budgeted.

          The study included comparison and life cycle costs for three options for the HVAC systems:
              1. Replacement with like-kind of what currently exists
              2. Replacement with conventional mechanical cooling.
              3. Replacement with a multipurpose cooling tower, ICH air handlers, and new chiller, as
                  diagrammed below.

                                                                  ?          ?

                                   RECOMMENDED - ICH

The diagram above shows a multi-purpose cooling tower that would:
              1. Circulate directly thru air handler coils to provide indirect evaporative cooling
              2. Provide water cooling of a new centrifugal chiller
              3. Have extra capacity to water cool much of the refrigeration equipment in the future or sooner.
Elmwood Bldg 6186                        Overview of HVAC Study                                  Page 3 of 6

This system keeps the numerous air handlers dry (for long life and low maintenance) and concentrates
the wetted equipment into a single cooling tower system which is much better designed to handle the
problems caused by the water.

I specifically directed the study to evaluate options #1 (like kind) and #3 (multi-purpose cooling tower),
and to also propose whatever concept they thought was best. They felt #3 was best, so they spent time
fine tuning that concept, and adding #2 (conventional HVAC) just for comparison purposes.

The study was also directed to evaluate all the air flows supplied, returned, exhausted, transferred, and
infiltrated to find problems with air balance.

The study report and drawings are now complete and available.

In the course of the study, I identified additional items that were outside the scope of the consultants
study. These are listed below.

Room 111 needs to have its wall modified to seal around the 3 huge dryers so it is moderately air tight.
This will cause make up air for dryer process air to be forced to come mainly from the existing roof
opening in room 111. This will keep the dryer process air separate from the occupied spaces which
improves comfort and saves energy. The subject wall is the one between room 111 and 109 (the south
wall of room 109).

To see if lint in the exhaust is causing any problems that may require redirecting the ducts, or adding
filter or screens.

There is much equipment that gives off large amounts of heat, such as laundry dryers, kitchen ovens,
griddles, kettles, automatic dishwashers, refrigerator heat rejection, etc. This heat rises up to the
ceiling. Nearly all spaces are “high bay” meaning that the ceiling, or structure above, is over 15’ high.
The existing supply air diffusers are the normal type, located very high up and blowing the air
horizontally. This creates problems.
      In cooling mode: high up, the cool supply air is mixing with the hot air that has risen up off
         equipment. This prevents cool air from getting down to the occupants before it is warmed and
         the cooling is wasted.
      In heating mode: the hot air is lighter so it is boyant and stays high and short circuits to the high
         returns back to the air handler. Again, the conditioned air does not reach the occupants.
One method of solving this is to remove the diffusers, extend the duct down until it is 12’ to 16’ above
the floor, and let it blow straight down. It must be done in areas that occupants do not stand at for long
periods. The air hits the floor and may spread horizontally across the floor. In cooling mode, this cool
air picks up heat from equipment and occupants and rises as it is heated. This stratification, of having
hot air up high and having conditioned air down low, can greatly improve the performance because the
hot air is removed from the room via the high return grills and ducts, and the conditioned air is more
Elmwood Bldg 6186                        Overview of HVAC Study                                 Page 4 of 6

directed to the occupants at floor level. This also increases the temperature difference that the HVAC
system can work on, which increases the cooling effect for a given air flow.
         This modification is a significant design effort as nearly every supply diffuser throughout the
building, and a few of the return grills, need to be carefully thought out and designed. Will it be run
straight down from the ceiling? Will it be routed to a nearby wall or column and then down? How will it
terminate and throw? What adjustability will it have? Will spot cooling be appropriate in certain areas?

Evaluate them in general with the goal of keeping heat separate from the lower working areas, letting
heat rise up to the grills where it is removed from the spaces. For example in the scullery and bakery,
move grills to be above the heat generating equipment and move supply air to be away from these heat
removal areas.

Add vinyl hanging gates to control infiltration from roll-up doors that stay open for long periods. This is
a suggestion from the resident engineer, Glenn Butler, 408-957-5447. It is an excellent idea. One gate
would go in hall way 145 approximately at column H.5 and 1.7. A second one would go in hallway 152 at
approximately column L.7 and 1.5. A third may go near the rool-up door to the scullery room 189 at
approximately column M.1 and 1.4.
         These gates need to be selected carefully. Each would be a double swinging door with clear
vinyl hanging down, similar to the ones at the doors of the refrigerated rooms. Although they normally
spring return closed, they must be able to be pushed open all the way to stay opened. They must be
taller than ones to the refrigerated room. Evaluate if any should be motorized to open automatically
based on a sensor or switch. The space above the gate must be filled with wall to prevent air flow.

Do a thorough inspection, operational check, and air balance reports with full profiling of AH-1 thru AH-
10 and their controls. Replace, repair, or refurbish as needed. If kept, thoroughly clean the coils and
fan, in addition to service or replacement of bearings, pulleys, belts, filters, etc.

This is the room in which meals are prepared for special diets e.g. vegetarian etc. This room is
constantly too hot, even though the stove and oven are never used, and even though the exhaust hood
is turned on to increase air changes. There are refrigerators and freezers that dump their heat rejection
into the room. Some items to evaluate:
     1. Remove the stove/oven and possibly remove the exhaust hood or give it a much smaller fan.
     2. Separate the refrigeration heat rejection from the room by one of the following:
              a. By careful supply of cooling air down low, using stratification, place return grills above
                 the refrigeration units, let the heat rise undisturbed to the return grills. (see above
                 section “Change How Air Blows Into the Spaces”)
              b. Changing them to water cooled via the proposed new cooling tower system
              c. Create a plenum to have the heat rejection communicate to the ceiling space and not
                 the room
              d. Use a cabinet fan with condensing coil to duct discharge to the ceiling space.
Elmwood Bldg 6186                        Overview of HVAC Study                                  Page 5 of 6

           e. Move the heat rejection to the ceiling space.
           f. Leave it alone, and overpower it with extra cooling capacity
    3. Evaluate if the DEC units can supply adequate cooling. If not, determine the best way to serve
       the room with a chilled water unit (mechanical cooling).

This room overheats considerably and frequently as massive amounts of bread are baked in the ovens.
In the northwest corner of the room, remove the oven and fryers, and remove the hood, all of which are
no longer used. Place ceiling return or exhaust grills above this area since often the bread is placed
there to cool after it comes out of the oven. Consider keeping the exhaust fan and ducting it to new
exhaust grills in the ceiling on the west side.
Move supply air to be at the east side of the room (opposite the ovens and cooling racks). Supply the air
low in the room so it can migrate west towards the ovens to replace the rising hot air. Move most, or all
of the ceiling returns to the west side.

Like the Bakery, this room overheats considerably and frequently as large amounts of heat rise from the
automatic dishwasher and the hot dishes, pans, and trays that come out. Like the Bakery, move the
ceiling return grills to be over the area of the automatic dishwasher and hot dish storage area. Supply
conditioned air down low on the opposite side of the room.

This room gets warm even though it has a dedicated heating and cooling unit, AH-1. Evaluate condition
of AH-1 and it’s controls, and replace, repair, or refurbish as needed. If kept, thoroughly clean the coils
and fan. If replaced, upsize to serve both 105 and 106 and change the return to come from the rooms
served. Balance the air to 30% outside air and provide balance report with a full profile of AH-1.
        Room 105 has a door to room 106 which may have originally been for storage, but is now used
as an office. The door between 105 and 106 is kept open for operation purposes. Unfortunately 106 is
not fed off of AH-1, which would have been ideal for the present use as an office. It is fed by one of the
large DEC (Direct Evaporative Cooled) units, DEC-1. After installing new ICH (Indirect evap w/CHilled
water) units per the study, it will improve the air conditioning in room 106. If it is not adequate, at that
time we can consider removing 106 from the ICH unit and splitting the feed off AH-1 to feed both 105
and 106. And we can change the return to come from the rooms instead of the general building ceiling

ROOM 133 - THE WAREHOUSE OFFICE near the loading dock.
One of the occupants, Mr. Nar, said that for many years it has not cooled or heated adequately, even
though it has a dedicated heating and cooling unit, AH-5. Evaluate condition of AH-5 and it’s controls,
and replace, repair, or refurbish as needed. If kept, thoroughly clean the coils and fan. Balance the air
to 20% outside air and provide balance report with a full profile of AH-1. Evaluate changing the return
to come from the room served.

Elmwood Bldg 6186                       Overview of HVAC Study                               Page 6 of 6

This room contains approximately 9 large boilers. It is very very hot inside. Evaluate improvement to
the ventilation reliefs at the roof by adding more gravity vents, or powered exhausts.

EVALUATE LIGHTING for possible energy savings.

 Capital cost estimate by Salas Engineers based on 2007 prices      $1,307,000
          this includes sales tax, freight, and a 30% contingency

 Add 15% for inflation if project is done in 2010                   $   196,050
 Add 15% for engineering design and support                         $   196,050
 Add 15% for Capital Programs Dept. to manage                       $   196,050
 Add for "additional items" described in the overview report.       $   600,000

 TOTAL                                                              $2,495,150

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