Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Chilled and Condenser Water Piping
…185 unchanged lines
### Chilled water supply temperature shall be as scheduled; the design setpoint is the most common comfort-cooling value unless process or low-temperature service is shown.
−### A 44°F supply with a 56°F return (12°F delta-T) is the dominant comfort-cooling design point. Lower supply temperatures raise compressor lift and energy use; higher delta-T reduces flow and pump energy but demands disciplined coil and control selection. {note}
−
```datasheet
label: Chilled Water Supply Temperature (Design)
…6 unchanged lines
```
+### A 44°F supply with a 56°F return (12°F delta-T) is the dominant comfort-cooling design point. Lower supply temperatures raise compressor lift and energy use; higher delta-T reduces flow and pump energy but demands disciplined coil and control selection. {note}
+
+### The chilled water design delta-T shall be specified, balancing compressor lift against flow and pump energy for the coil and control selection.
+
```datasheet
label: Chilled Water Design Delta-T
…8 unchanged lines
### Condenser water supply temperature (tower to chiller) shall be as scheduled; the design value reflects the project climate and tower selection.
−### 85°F entering condenser water at design load is the 80% case across most US climates, with a 10°F rise to 95°F leaving the chiller. The lower limit matters as much as the design point: most chillers require a minimum entering condenser water temperature to maintain refrigerant pressure differential. {note}
−
```datasheet
label: Condenser Water Supply Temperature (Design)
…6 unchanged lines
```
+### 85°F entering condenser water at design load is the most common design point across most US climates, with a 10°F rise to 95°F leaving the chiller. The lower limit matters as much as the design point: most chillers require a minimum entering condenser water temperature to maintain refrigerant pressure differential. {note}
+
+### The condenser water design temperature rise shall be specified, consistent with the chiller's minimum entering condenser water temperature requirement.
+
```datasheet
label: Condenser Water Design Rise
…8 unchanged lines
### The minimum entering condenser water temperature required by the chiller shall be specified, and a head-pressure control method (tower bypass valve, tower fan staging, or both) shall be provided to maintain it.
−### The minimum entering condenser water temperature is a chiller-imposed limit, typically in the 55°F to 65°F range; allowing condenser water to fall below it in spring and fall will trip chiller safeties. {note}
−
```datasheet
label: Minimum Entering Condenser Water Temperature
…6 unchanged lines
```
+### The minimum entering condenser water temperature is a chiller-imposed limit, typically in the 55°F to 65°F range; allowing condenser water to fall below it in spring and fall will trip chiller safeties. {note}
+
## Design Pressure {toc}
### The system design pressure for pipe, valve, and specialty selection shall be the greater of the static fill pressure plus pump head or the project-specified design pressure, and shall not exceed the ASME B31.9 limit of 150 psig.
−### Closed CHW loops typically operate at 30 psig to 80 psig static plus pump head; open CW loops at 20 psig to 60 psig. A 125 psig design pressure is the common selection basis for commercial central plants. {note}
−
```datasheet
label: System Design Pressure
…6 unchanged lines
```
+### Closed CHW loops typically operate at 30 psig to 80 psig static plus pump head; open CW loops at 20 psig to 60 psig. A 125 psig design pressure is the common selection basis for commercial central plants. {note}
+
# Pipe Materials and Joining {toc}
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### Condenser water pipe material shall account for internal corrosion from dissolved oxygen, chlorides, and microbiological activity inherent to open cooling-tower circuits.
−### Specifying bare black steel for the open condenser circuit without addressing oxygen-driven corrosion produces early wall loss; inhibitor treatment alone is insufficient for high-cycle or high-makeup systems. {note}
−
−### The open circuit is the most common premature-failure mode in central plants. Match the material to the water chemistry and cycles of concentration rather than defaulting to the chilled-water material. {note}
−
```datasheet
label: Condenser Water Pipe Material
…7 unchanged lines
```
+### Specifying bare black steel for the open condenser circuit without addressing oxygen-driven corrosion produces early wall loss; inhibitor treatment alone is insufficient for high-cycle or high-makeup systems. {note}
+
+### The open circuit is the most common premature-failure mode in central plants. Match the material to the water chemistry and cycles of concentration rather than defaulting to the chilled-water material. {note}
+
### Where FRP is selected for the open condenser circuit, pipe shall be filament-wound to the applicable ASTM D2310/D2996 classification with manufacturer-rated pressure and temperature for the service.
…2 unchanged lines
### Joining methods shall be selected by pipe size: threaded for 2 in. and smaller, grooved mechanical couplings for 2 in. through 12 in., butt-welding for 4 in. and larger mains, and flanged at equipment and at valves 4 in. and larger.
−### Welded mains give the most leak-resistant, lowest-maintenance distribution; grooved couplings speed field assembly and provide controlled flexibility; flanges allow equipment and valve removal. Most plants mix all four, assigned by size and location. {note}
−
```datasheet
label: Primary Joining Method (mains 4 in. and larger)
…6 unchanged lines
```
+### Welded mains give the most leak-resistant, lowest-maintenance distribution; grooved couplings speed field assembly and provide controlled flexibility; flanges allow equipment and valve removal. Most plants mix all four, assigned by size and location. {note}
+
### Grooved coupling gaskets shall be selected for the full service-temperature range of the circuit; standard EPDM gaskets shall be verified against the design temperature excursions in heat-recovery or geothermal applications.
−### A gasket rated only for nominal CHW/CW temperatures can fail in systems that see wider temperature swings, such as heat-recovery condenser water. {note}
−
```datasheet
label: Grooved Coupling Gasket Material
…6 unchanged lines
```
+### A gasket rated only for nominal CHW/CW temperatures can fail in systems that see wider temperature swings, such as heat-recovery condenser water. {note}
+
### Flanges shall conform to ASME B16.5 through NPS 24 and ASME B16.47 for NPS 26 and larger, with pressure class matched to the system design pressure.
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### The hydraulic architecture shall be coordinated with the pump and chiller selections, because it determines header sizing, bypass requirements, and pump arrangement.
−### Constant-primary, primary/secondary, primary/secondary/tertiary, and variable-primary each impose different piping. Primary/secondary requires a decoupling bypass bridge; variable-primary requires a minimum-flow bypass and well-placed differential-pressure control. The piping cannot be sized until the architecture is fixed. {note}
−
```datasheet
label: Hydraulic Distribution Architecture
…7 unchanged lines
```
+### Constant-primary, primary/secondary, primary/secondary/tertiary, and variable-primary each impose different piping. Primary/secondary requires a decoupling bypass bridge; variable-primary requires a minimum-flow bypass and well-placed differential-pressure control. The piping cannot be sized until the architecture is fixed. {note}
+
### Where a decoupled or variable-primary architecture is used, a bypass shall be provided and sized for the chiller minimum-flow requirement.
### Differential-pressure transmitters shall be located to control the distribution against the most remote critical load, and the number and location of sensing points shall be coordinated with the pump control sequence.
−### Locating the DP sensor at the plant header rather than at the end of the loop over-pressurizes the distribution and contributes to low-delta-T operation; end-of-loop sensing with setpoint reset is preferred for variable-flow systems. {note}
−
```datasheet
label: Differential-Pressure Sensor Location
…6 unchanged lines
```
+### Locating the DP sensor at the plant header rather than at the end of the loop over-pressurizes the distribution and contributes to low-delta-T operation; end-of-loop sensing with setpoint reset is preferred for variable-flow systems. {note}
+
## Low-Delta-T Avoidance {toc}
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### Sectional isolation is what allows a single chiller or pump to be serviced while the plant stays online. The valve type follows from size and pressure class. {note}
+### Butterfly valves on condenser and chilled water mains 6 in. and larger shall conform to AWWA C504; valves 78 in. and larger shall conform to AWWA C516.
+
```datasheet
label: Header Isolation Valve Type (6 in. and larger)
…7 unchanged lines
```
−### Butterfly valves on condenser and chilled water mains 6 in. and larger shall conform to AWWA C504; valves 78 in. and larger shall conform to AWWA C516.
−
### Lug-type butterfly valves shall be used where downstream piping must be removed with the valve holding system pressure (dead-end service).
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### Motor-actuated isolation valves 6 in. and larger on condenser and chilled water mains shall have a minimum 15 second to 30 second close time to limit water-hammer transients.
−### Rapidly closing a large butterfly valve on a main flowing at 6 fps generates pressure transients that can exceed design pressure; slow-close actuation is the control. {note}
−
−### Water hammer at large valve closures and pump trips is a real overpressure source on central-plant mains. Slow-close actuators, and water-hammer arresters to ASSE 1010 where transients remain, protect the piping and joints. {note}
−
```datasheet
label: Motor-Actuated Valve Minimum Close Time (6 in. and larger)
…6 unchanged lines
```
+### Rapidly closing a large butterfly valve on a main flowing at 6 fps generates pressure transients that can exceed design pressure; slow-close actuation is the control. {note}
+
+### Water hammer at large valve closures and pump trips is a real overpressure source on central-plant mains. Slow-close actuators, and water-hammer arresters to ASSE 1010 where transients remain, protect the piping and joints. {note}
+
## Balancing and Check Valves {toc}
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### The flow-metering method shall be selected for accuracy, installed straight-pipe availability, and maintenance access.
−### Inline magnetic meters are accurate and unobstructed but require flanged insertion and straight-run length; ultrasonic clamp-on meters avoid penetration but depend on pipe condition; orifice plates are simple but lossy. The choice is constrained by available straight pipe upstream and downstream. {note}
−
```datasheet
label: Chiller Flow Measurement Method
…6 unchanged lines
```
+### Inline magnetic meters are accurate and unobstructed but require flanged insertion and straight-run length; ultrasonic clamp-on meters avoid penetration but depend on pipe condition; orifice plates are simple but lossy. The choice is constrained by available straight pipe upstream and downstream. {note}
+
### Flow meters shall be installed with the manufacturer's required upstream and downstream straight-pipe runs; insufficient straight run shall be corrected before acceptance.
…41 unchanged lines
### Chilled water insulation shall have a continuous vapor retarder.
−### The vapor seal shall be maintained unbroken at fittings, valves, flanges, hangers, and supports.
−
−### A single break in the vapor barrier admits moisture that migrates through the insulation and condenses on the cold pipe, causing corrosion under insulation and mold; continuity is the entire point. {note}
−
```datasheet
label: Vapor Retarder / Jacket
…6 unchanged lines
```
+### The vapor seal shall be maintained unbroken at fittings, valves, flanges, hangers, and supports.
+
+### A single break in the vapor barrier admits moisture that migrates through the insulation and condenses on the cold pipe, causing corrosion under insulation and mold; continuity is the entire point. {note}
+
### Insulated chilled water piping shall have a thermal-protection shield and a load-bearing insert at each hanger to carry pipe loads without crushing the insulation or breaking the vapor seal.
…4 unchanged lines
### Expansion compensation shall be sized for the full installation-to-operating temperature differential of each service, including the contraction of chilled water piping installed warm and operated cold.
−### Chilled water at 44°F installed at a 70°F ambient contracts measurably; designing only for heating-side expansion ignores it. Expansion loops, offsets, or joints, with anchors sized for the resulting forces, must accommodate the movement of both circuits. {note}
−
```datasheet
label: Expansion Compensation Method
…6 unchanged lines
```
+### Chilled water at 44°F installed at a 70°F ambient contracts measurably; designing only for heating-side expansion ignores it. Expansion loops, offsets, or joints, with anchors sized for the resulting forces, must accommodate the movement of both circuits. {note}
+
### Anchors shall be designed to resist the thrust and expansion forces developed by the selected compensation method.
…18 unchanged lines
## Buried and tunnel chilled water distribution shall use a pre-insulated piping system or a field-insulated system with protective casing appropriate to the soil and groundwater conditions.
−## Campus loop extensions and tunnel runs are where most long-term insulation and corrosion failures originate. The carrier-pipe, insulation, and jacket are selected as a system, and the field joints determine whether the system survives. {note}
−
```datasheet
label: Buried Piping System
…6 unchanged lines
```
+## Campus loop extensions and tunnel runs are where most long-term insulation and corrosion failures originate. The carrier-pipe, insulation, and jacket are selected as a system, and the field joints determine whether the system survives. {note}
+
## Buried steel piping in corrosive soils shall be provided with cathodic protection appropriate to the soil resistivity.
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### The system shall be flushed at a minimum velocity of 3 fps through each pipe segment until strainer baskets retain no particles larger than 1/32 in.
−### Temporary fine-mesh startup strainers shall be installed at each chiller evaporator and condenser connection during flushing, then cleaned and either removed or replaced with the permanent screen before chiller startup.
−
−### Construction debris, weld slag, and mill scale released during flushing will foul the chiller tube sheet within the first operating season if temporary strainers are omitted; they are mandatory, not optional. {note}
−
```datasheet
label: Minimum Flushing Velocity
…6 unchanged lines
```
+### Temporary fine-mesh startup strainers shall be installed at each chiller evaporator and condenser connection during flushing, then cleaned and either removed or replaced with the permanent screen before chiller startup.
+
+### Construction debris, weld slag, and mill scale released during flushing will foul the chiller tube sheet within the first operating season if temporary strainers are omitted; they are mandatory, not optional. {note}
+
### Initial corrosion inhibitor shall be dosed in accordance with the water-treatment program before the chillers are placed in service.
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## The Contractor shall furnish the spare parts and special tools below for Owner stock.
−## Spare gaskets, strainer screens, and the special tools for grooved and flanged joints keep the plant serviceable without procurement delay during the first operating season. {note}
−
```datasheet
label: Spare Parts and Special Tools
…9 unchanged lines
- Spare strainer screens / baskets (each size)
```
+
+## Spare gaskets, strainer screens, and the special tools for grooved and flanged joints keep the plant serviceable without procurement delay during the first operating season. {note}