CHILLED WATER AND CONDENSER WATER PIPING
In general, HVAC systems shall utilize parallel piping systems with a two-pipe main distribution system arranged in a reverse return configuration. If applied, series loop piping for terminal or branch circuits shall be equipped with automatic flow control valves at terminal units (all types of heat transfer units).
Each terminal unit or coil shall be provided with isolation valves on both the supply and return and a flow indicating balance valve on the return line. Isolation valves shall be provided on all major branches, such as at each floor level, building wing or mechanical room.
For new chilled water HVAC distribution, a pumping and piping arrangement is generally appropriate, with constant volume primary pumping and variable volume secondary pumping. The primary and secondary circuits shall be separate, with neither having an effect on the pumping head of the other. The primary circuit serves the source equipment (chillers), while the secondary circuit serves the load. Refer also to Pumping Systems in this chapter for additional requirements.
This procedure is to define the method used to ensure that the Chilled Water Pipework System comprising all pipes, tubes, valves, fittings, reducers, expanders, nipples, vents, bleed off, expansion and contraction devices, hangers, brackets, anchors, supports, sleeves, plates and all accessories and components connected thereto as an integrated pipework system, installation final connections and workmanship, is correct and acceptable and conforms to the contract documents and General Specifications.
Isolation of Piping at Equipment.
Isolation valves, shutoff valves, by-pass circuits, flanges and unions shall be provided as necessary for piping at equipment to facilitate equipment repair and replacement. Equipment requiring isolation includes boilers, chillers, pumps, coils, terminal units and heat exchangers. Valves shall also be provided for zones off vertical risers.
Provide channel supports for multiple pipes and heavy duty steel trapezes to support multiple pipes. Hanger and support schedule shall have manufacturer’s number, type and location. Comply with MSS SP69 for pipe hanger selections. Spring hangers and supports shall be provided in all the mechanical rooms.
Flexible Pipe Connectors.
Flexible pipe connectors shall be fabricated from annular close pitched corrugated and braided stainless steel. All pumps, chillers, and cooling towers shall have flexible connectors.
Piping System and Equipment Identification.
All pipes, valves and equipment in mechanical rooms, shafts, ceilings and other spaces accessible to maintenance personnel must be identified with color-coded bands and permanent tags indicating the system type and direction of flow for piping systems or type and number for equipment. The identification system shall also tag all valves and other operable fittings. Gas piping and sprinkler lines must be identified as prescribed by related authorities.
CHILLED WATER AND CONDENSER WATER PIPING
The expansion tank should be connected on the inlet side of the circulating pump.
It is a good idea to install a service valve at the expansion tank to facilitate future maintenance. However, the valve handle should be removed to prevent the tank from being isolated from the main loop.
The tank will function properly in any position, but it must not stress the connection to the supporting pipe. Thus, the tank should usually be mounted vertically. Do not install the expansion tank (and its service valve) in such a way that its weight is a big lever that stresses the pipe connection or pipe.
VFD – VARIABLE FREQUENCY DRIVE
Frequency drives are also known as VFDs, variable frequency drives, VSDs, variable speed drives, and sometimes just “drives”. Frequency drives are used primarily to eliminate the sudden current inrush that can cause lights to flicker when a compressor turns on. Frequency drives can also be used to convert single-phase power to 3-phase.
The chiller must have a 3-phase compressor, but the VFD can use either 1- or 3-phase input power. The control panel should match the ship’s power, whether 1 or 3 phase. Power wiring typically goes from the control panel to the VFD, and from the VFD to the compressor. The VFD functions as the contactor/starter. The control box typically provides a dry contact for the VFD to control when the VFD turns on/off.
Pump Installation Procedure Before starting the pump installation process mechanical or AC engineer to study the pump manufacturer’s written installation and alignment instructions. A layout drawing should be approved and pumps should be installed in locations indicated making sure that there is sufficient access space for periodic maintenance, removal of motors impellers, couplings and accessories. Set base-mounted pumps on concrete equipment bases as indicated on drawings. Suitable lifting equipment should be used to lift and place the pumps on its location. Disconnect couplings to the half before setting. Do not reconnect couplings until alignment operations have been completed. Install suction and discharge pipe sizes equal to or greater than the diameter of water pump connections. Install valves of types and at locations indicated that are same size as the piping connecting chilled water pump, bypasses, test headers and other piping systems. Install pressure gages on chilled water pump suction and discharge in such way to be easily readable and completely isolated from vibration.
Support pumps and piping separately so that weight of piping system does not rest on pumps or its support. Install piping accessories, hangers and supports, anchors, valves meters and gages, and equipment support as indicated for complete installation. Electrical Wiring: Install electrical devices furnished by equipment manufacturers but not specified as factory mounted. Furnish copy of manufacturers wiring diagram for submittal to the Consultant. Verify that electrical wiring is installed according to manufacturer’s recommendations and installation requirements. Work to be inspected and approved by consultant and do not proceed with equipment start up until wiring installation is acceptable.
Chilled Water Pump Alignment Align pump and driver shafts after complete unit has been leveled on foundation and after grout has set and foundation bolts have been tightened. After alignment is correct, tighten foundation bolts evenly but not too firmly. Fill base plate completely with non-shrink, non-metallic grout, with metal blocks and shims or wedges in place. After grout has hardened, fully tighten foundation bolts. Check alignment and take corrective measures required to ensure perfect alignment. Make piping connections and check alignment again, and take corrective measures if required. Connect flow-measuring and other hydraulic system components according to manufacturer’s written installation instructions