Heater replacement

December 30, 2019
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To support critical current and future business needs by increasing air-conditioning capacity and efficiency, and upgrading electrical service; to obtain an Energy Star rating.

Hvac design/build & retrofit solutions

To help this client meet its demanding commercial HVAC energy saving objectives, Mesa provided a high-performance HVAC design/build solution on a fast-track schedule. In addition to having maintained the client’s existing plant for many years, Mesa was chosen for this project because, as a HVAC design/build firm, the company offered more and better options than the single-source solutions proposed by two HVAC manufacturers.

More efficient cooling system, less space

Mesa’s HVAC retrofit solution involved replacing the hotel’s 350-ton industrial chiller plant with a more efficient 600-ton modular unit and performing a major electrical upgrade. In addition to accommodating the mechanical construction project’s fast-track delivery, the modular approach helped maintain the hotel’s historic character, minimized the central chiller plant’s footprint and allowed room for future needs.

The central plant was pre-built by the manufacturer, shipped in two sections and assembled on-site. The plant consisted of two centrifugal water-cooled chillers with factory-mounted variable-flow drives, and 2 two-cell stainless steel cooling towers with induced-draft, counterflow design, capable of cooling 2,000 gallons of water per minute. The plant also included chilled and condenser water pumps with variable speed drives, a cooling tower filtration and chemical feed system, a chilled water system expansion tank and air separator, two electric fan coil units for central plant air conditioning and a ventilation fan with gravity back-draft damper. A central plant industrial refrigerant monitoring system, a magnetic flow meter for monitoring the flow of main chilled water distribution and six automated isolation control valves completed the package.

Project delivery with no loose ends

In managing the project, Mesa┬ámade sure it took care of all the details. The company trenched new chilled water lines to an existing tunnel that led to the old chillers. It then installed new chilled water piping to — and within — the plant, as well as supply and return piping for the cooling towers. In addition, the company put in piping for chilled water, fan coil units and water treatment devices, and performed the various piping activities required to connect the chiller plant, the new cooling tower system and other equipment. The firm also installed a water source heat exchanger, which is part of the condenser loop. After completing the underground chilled and condenser water lines for the water source condensers, the company installed grade beams, structural pads and structural steel, so the towers could be set. The modular central chiller plant was then craned into place.

Cost-saving DDC system: BACnet

In addition, Mesa upgraded the plant’s existing direct digital control (DDC) system to the BACnet protocol, enabling it to better handle the new commercial cooling equipment. This protocol significantly reduced installation costs of labor, conduit and wire. Rather than pulling wire from all components back to the main controller, the company simply pulled the wire to the closest controller, from which BACnet can relay information throughout the system.

Hospitality facility background

The Mission Inn Hotel & Spa is a National Historic Landmark described by Will Rogers as “the most unique hotel in America.” Begun in 1876 as a boarding house, it now occupies an entire city block. Its multiple wings reflect architectural styles and furnishings ranging from the New World to the Far East. There are 239 guest rooms, including 28 suites, as well as 20,000 square feet of meeting and banquet space, a full-service spa and four restaurants.