Statement_of_Work.pdf

Project: Renovation of the HVAC System, 525 S. Wilson Ave. Rm 102

Goal

Design and install a reliable, redundant, and maintainable HVAC solution that provides 24/7 cooling for seismic network equipment in the 525 South Wilson Ave (525SW) server room.

Background

The USGS and Caltech jointly operate the Southern California Seismic Network (SCSN), a collection of seismographs and computers that detects and reports on earthquakes in southern

California. The SCSN operates redundant server rooms for this mission, one being Room 102 of the 525 S. Wilson Ave building. SCSN requires reliable air conditioning to protect seismic network servers from overheating.

The 525 S. Wilson Ave building is a former residence now adapted for professional office use.

Caltech owns 525SW and the USGS leases it. The replacement system must respect the character and main physical characteristics of the building. Modifications to the building itself will require Caltech approval in advance.

The server room equipment occupies six full height racks. The floor has been reinforced to support the racks.

The computer equipment produces a relatively stable heat load of about 10,700 BTU based on measured electricity usage (details in attachment). Room lights are normally out, and the room is not used for any other occasional work that would add to the heat load. The room is divided by plexiglass sheets into a hot-aisle, cold-aisle configuration. Cold air is supplied through floor registers and returns through the equipment. Currently cool air is supplied at 69 F. The room measures 16'x11'x8 1/2' (LxWxH). It has one north-facing window about 30" square.

The Room 102 A/C system currently has two "downshot" air handlers both installed in the room itself. The primary unit is rated at 5 tons (product: FEM4X6000BL08E, model FEM4X6000BL, manufacture year: 2020). The compressor is outside, about 40' away. The second air handler is a

Trane TEM3A0C48S41SAA, with two side by side units, rated at 7.5 tons, also with the compressor outside about 30 feet away. Notes indicate it was installed in 2014. Ducting is in the crawl space under the floor. Separate ducts and floor registers connect to each air handler. In the room there are also two decommissioned wall-mounted split air handler units, each having outside compressors. This equipment is to be removed and disposed of.

The air conditioning for the 525SW server room has required a significantly more maintenance and attention by Caltech facilities staff than similar systems elsewhere on campus. Current systems have a history premature compressor failure. The room experiences occasional extreme heat conditions, recently including March and April 2024. Icing has contributed to or caused recent over-temperature conditions. Based on measured heat load at least one of the A/C units could be oversized. An informal evaluation also questioned whether the existing duct sizing under the floor is sufficient for proper air flow. Considered together, Caltech engineering staff recommended that the USGS replace the current piece-wise components with a right-sized A/C and ducting solution system designed to work as a unit. Variable refrigerant flow systems and alternate duct routing may have application. Sizing of the unit is considered critical. Having flexibility to control the cooling capacity may help save energy while maintaining indoor room temperatures. To improve the likelihood of success, proposals are solicited from qualified

HVAC engineering firms. The review of offers will give weight to clarity of analysis, and adequacy and responsiveness of the proposed replacement system and not consider cost alone.

Statement of Work

Task 1. Conduct an engineering evaluation of the 525SW server room air flow, thermal characteristics and operating characteristics sufficient to propose an integrated A/C solution.

Assume the current locations of computer racks and main computer cabling systems. Assume also that the current power supplies for air handlers can be adapted in a new design.

Task 2. Propose a new or modified A/C system that incorporates proper sized A/C units and ductwork. The replacement system must provide system redundancy and the proposed design will be evaluated for likely system life, reliability and maintainability. The replacement A/C system shall provide in-room connections for remote monitoring of key A/C system parameters.

Task 3. Install ducting and equipment as required to implement the replacement system. Plan and document acceptance tests including demonstration of automatic fail-over/redundancy.

Provide system documentation and familiarization to Caltech HVAC team who will be doing periodic maintenance. Provide warranty information.

Task 4. Remove and dispose of any existing A/C equipment that is not retained in the new system.

Project constraints:

Respondents are strongly encouraged to participate in a job walk with Caltech HVAC and USGS representatives at the physical site on Tuesday June 4th at 10AM local time. Respondents may remain during the day to make measurements for proposal development.

Computer racks cannot be moved during modifications and new system installation.

Computers remain on-line during work.

Major changes to the building itself will not be considered and building changes must be approved by Caltech Facilities.

Appendix 1: Summary of Measured Heat Load

The electrical contribution to heat load was estimated by measuring amperage through the service panel for several weeks (Figure A1). A preliminary heating load estimate was developed an engineer on the Caltech facilities team. His description should be considered preliminary, for information only, and subject to conditions stated. Information below is copied from his email:

Assumptions:

35 amps of steady state load (measured)

208 Volt, 3 phase power

0.85 power factor

• The resulting heat dissipation will be about 10,717 Watts

• Add another 1,500 watts for envelope loads

• Add 250 watts for lights

• Add 500 watts for misc. loads

The approximate total load will be around: 12,970 watts or 44,260 BTUH or 3.68 tons.

A 5-ton unit should be adequate to handle the base cooling load without short-cycling.

Keep in mind a nominally rated 5-ton unit will likely provide closer to 4 tons of sensible cooling, depending on ambient temperature and the relative humidity.

This response is consistent with my response from the last analysis. One of the issues we are noticing is the air delivery bottlenecks under the floor.

Additional Notes:

Only the actual electrical load to computer racks was measured. Since the time of the measurements, electrical load has not materially changed.

Lights are normally on only a few hours/week or less. No one regularly works in the room.

There are no other regular electrical operations or machinery in the room.

The one outside wall in the room faces north and gets no direct sun. Other walls and the ceiling are shared with office spaces maintained by a separate house HVAC system.

Figure A1: Plot of measured current draw to computer equipment. Measurements on four lines were recorded every 15 minutes for roughly 48 days. The actual time series of measurements is available. Lines 1, 2, and 3 are in Amps rms; line 4 is in milliamps rms.

Appendix 2. Annotated floor plan and project photos. (Continued on next page)

Floor registers 6”x14” 4 for 5 Ton unit 6 for 7.5 Ton unit

6 Racks, 23 ½ ”x42”

54” wide doorway

”hot” aisle

“cold” aisle

7.5T air handler

5 T air handler

Trane 7.5 T Compressor

5 T compressor

Plan View, 525 SW, Room 102

Pl ex ig la ss d iv id er

Window

Room: 10’7” x 15’8” Drawing to approximate scale. Contractor to confirm all necessary measurements on site.

Outside

Not to scale

Compressors for 7.5 T Trane

(L) and 5 T. unit on west side of 525SW.

Compressors for earlier generation A/C; out of service and to be removed.

Pads can be used in current project. Window with A/C opens to Rm 102.

West and north faces of 525

SW.

Hot aisle showing cable-trays above rack (3 total).

Window and small A/C unit partially shown on far wall.

Current 5-Ton and 7.5-Ton air handlers. Air flows down, under the floor and up the cold aisle registers. Floor tiles are ~12”x12”

Access through plexiglass, looking toward cold aisle, from the doorway on the S. side of room. Note cable-tray above rack (1 of 3 total).

Legacy AC on wall above electrical panel to be removed (1 of 2).

208 V supply to racks overhead. Not for AC.

Right: Cold aisle and registers. Second legacy wall unit is on the far wall behind the back cable tray.

Below: rack detail.