Dielectric unions at reheat coils are prone to leaking due to expansion and contraction and subsequent damage to the union seat. Specify dielectric fittings that are not subject to leaking.
Drain and dirt leg valves shall be full port, line-size for pipe up to 2″ and a minimum of 2″ for larger pipe.
For coils, provide isolation valves on individual branch piping whenever combination strainer and isolation valves are provided at the equipment.
Upon request by UNC, the designer shall provide schematic piping drawings for each system and identify major components and provide enough information to determine design flow, redundant equipment, diversity factors, etc. This will be typically provided for all complex projects.
Upon request, the designer shall furnish detailed calculations for the highest pressure losses in the piping systems at design flows. Diversity factors and other assumptions shall be clearly identified.
Piping larger than 2″ diameter, shown in mechanical rooms, shall be shown double lined to reflect the insulated diameter of the pipe.
All take-offs shall be off of the side or top of the horizontal mains and shall not be off the bottom.
Provide a dial pressure gauge at the highest point in the system.
For heating hot water systems, the pressure relief pipe shall be piped and drain at a visible location such as to the side of the floor drain.
Provide a make-up flow switch (e.g., McDonnell & Miller FS5-3/4 or equal) connected to a BAS alarm.
Heating hot water coils shall be sized for 160 °F supply temperature and 140 °F return temperature. (Exception: Condensing boiler systems shall have a return temperature below the boiler condensing temperature and may require more frequent pasteurization cycles.)
For systems prone to freezing specify a minimum of 30% inhibited propylene glycol solution. (glycol solutions below 25% accelerate microbe growth)
Provide a glycol make-up tank system (include make-up water meter and alarm contacts for BAS monitoring) for all glycol loops.
All closed loops must have owner furnished contractor installed pot feeders with integral filters, Neptune model FTF-5150DB. This is necessary to standardize filters for campus and ensure the treatment tablets fit into the feeder opening.
The pot feeder with integral filter must be installed across the pump or supply and return lines (one line on suction side of pump, other line on discharge side) to ensure adequate flow. Supply flow needs to travel in a straight line into the pot feeder intake pipe.
Except for sensing tubing, the minimum pipe size is ¾”.
Each loop must be piped to a sanitary sewer drain to permit flushing.
Air and dirt separators shall be the high efficiency, coalescing type. Spirotherm – Dirt and B&G – CRS are approved. Separator media shall be removable. Separators shall be a minimum size of the pipe served.
Specify a quarterly pasteurization sequence to heat all piping branches to a minimum of 170 °F for 60 minutes. Typically, this is performed at night and airflow is reduced to avoid overheating spaces.
- Approved pump brands are B&G, Taco, and Armstrong.
- Mechanical schedules for circulation pumps shall indicate minimum pumping efficiencies.
- Specify that all pump mechanical seals shall have ceramic stationary seats.
- Specify a (single) pressure gauge with isolation valves on base mounted pumps to provide suction pressure, discharge pressure, and differential pressure.
- Provide a minimum clearance of 24″ on sides and ends of base mounted pumps and motors to allow access for service and repair.
- Specify isolation valves allowing removal of pumps for repair.
- Specify the installation of bleed valves and gauge ports at accessible locations.
- All pumps shall be serviceable without removing the volute from piping connections.
Alignment for Flexible Coupled Pumps
- A technician certified by the selected pump manufacturer shall field align flexible coupled pumps after the base has been grouted and flushing and cleaning procedures are completed.
- Align pump and motor in the vertical angular, horizontal angular, vertical parallel and horizontal parallel. Alignment shall be within the recommended value by pump manufacturer (not coupler manufacturer) but not over 0.002″ parallel and 0.005″ angular per radius-inch.
- The contractor record and submit all results of alignment procedure and the pump manufacturer’s alignment specifications to the design engineer. The specifications should also require this approved submittal information is included in the O&M Manual.
For loops equipped with pumps over 10 hp, slip stream filters with depth cartridge filters shall be provided (these are important to project pump seals).
This section covers steam piping downstream of the building pressure reducing valve. Specify a piping inspection prior to insulation and invite UNC Engineering Services.
Specify a minimum schedule 80 piping for steam and condensate piping 2 inches and smaller. Specify steam piping (and associated devices) within the building envelope compliant with ASME Standard B31.1 Power Piping.
- Steam traps and steam control valves shall be insulated with easily removable and reusable insulation jackets.
- For coils supplied with modulated steam, locate steam traps a minimum of 12 inches below the coil condensate outlet.
- Trap assemblies shall be equipped with a dirt pocket, two isolation valves, a strainer, two unions, and test valve.
- Test valves shall be installed on a Tee immediately downstream of the trap. Specify ½” ball valves with locking handles and hand-tight caps. Direct towards the floor.
- Provide steam condensate site glasses when the operation of trap testing ports is not advisable such as when installed above ceilings.
- The designer must specify the minimum and maximum trap size or design capacity for each application. Excessively oversized and undersized traps must be avoided.
Steam condensate from equipment served by modulating steam control valves shall drain by gravity and shall not be lifted.
Contaminated steam condensate shall go to sanitary sewer. Uncontaminated steam condensate shall return to the steam plant.
Isolation valves, strainers, blow down valves and other components exposed to full steam pressure shall be steel.
Strainers in horizontal steam piping shall be installed pointing to the 3:30 position (slightly down from horizontal). Strainers in condensate piping shall be pointed down (6:00 position).
Vacuum breakers: Vacuum breakers are required on the steam inlet side of coils and heat exchangers. Vacuum breakers are also required on the outlet side of modulated coils and converters. Install vacuum breakers on a 15″ cooling nipple. Pre-approved models: Hoffman model 62, Barnes and Jones VB 3875. Construction: brass body, stainless steel spring and valve, silicon o-ring. WP 125 psig, WT 350 °F. Typically set pressure: 2″ vacuum.
A vented flash tank shall be provided to cool condensate receivers
Provide drip legs before control valves to protect control valve seats. Slope steam supply piping between the drip and the control valve back towards the drip.
Provide steel blow down valves on all drip legs. Install on the side of the dirt leg, 2″ up from the bottom. Provide piping to direct the blow-down to an impervious surface (usually downward) and in such a way that building materials will not be damaged during blow-down.
If there is any chance of process water mixing with campus water, for example if an emergency bypass is installed around a heat exchanger, then the process loop needs to be treated with non-nitrate chemicals such as phosphates. Provide a placard which reads, “Do not treat with nitrate based chemicals. Treatment chemicals must be compatible with the campus chilled water loop”.