Selection Guide

Coil Piping Packages

Engineering reference for coil piping packages (CPPs / runout kits) at terminal units � VAV reheat coils, fan coils, AHU coils, induction units, and chilled beams. Covers valve type and authority, actuator signal, isolation method, balancing strategy, and pressure class.

What a Coil Piping Package Contains

A complete CPP at a hydronic terminal unit typically includes:

Component	Purpose
Isolation Valves (2)	Allow coil to be removed without draining the system; ball valve standard, butterfly above 2-1/2"
Strainer	Protects control valve from debris; typically Y-type with blowdown valve
Control Valve	Modulates flow to coil; 2-way (variable flow) or 3-way (constant flow, legacy)
Actuator	Drives the control valve; floating, 2-position, or modulating (0�10V / 4�20mA)
Balancing Valve	Sets design flow on constant-flow systems; not required with PICVs
Union or Flange	Allows coil disconnection without cutting pipe
P/T Test Ports	Field verification of flow and temperature at supply and return
Air Vent / Drain	Manual or automatic; required at coil high point

2-Way vs. 3-Way vs. PICV

Factor	2-Way Modulating	3-Way (Mixing or Diverting)	PICV
System Flow	Variable	Constant	Variable
Pump Energy Savings	Yes (with VFD pumps)	None	Yes
ASHRAE 90.1 Compliance	Required above 10 HP pump systems	Allowed only in specific exceptions	Required / preferred
Valve Authority Design Effort	High � must match Cv to coil ?P at design	None � bypass legs balance the loop	Built-in � integral pressure regulator handles authority
Balancing Required	Manual balance required	Manual balance required	None � flow setpoint dialed in
First Cost	Lower	Lower	Higher
Commissioning Time	Significant	Significant	Minimal
Best Application	Smaller systems where commissioning is well-controlled	Legacy retrofits, snow melt, specific equipment requirements	Modern variable-flow systems, large building distribution, fast commissioning

Sizing Control Valves for Authority

For traditional 2-way modulating valves, valve authority (�) should be 0.5 or higher for stable modulating control:

� = ?P_valve � (?P_valve + ?P_coil + ?P_balance + ?P_strainer)

This means the fully-open valve pressure drop should be at least equal to the rest of the coil-circuit pressure drop. In practice:

Target valve ?P at design flow: 1.5�5 ft (3�12 ft for systems with high distribution head)
Avoid oversized valves � a Cv larger than needed produces low authority and unstable control
For VAV reheat coils, valve ?P at design typically ranges 2�5 ft
PICVs eliminate the authority sizing exercise because the integral differential pressure regulator maintains the same ?P across the control element regardless of system pressure changes

Actuator Selection

Signal Type	Use Case	Notes
Floating (3-Wire) On/Off/Stop	Simple modulation from a thermostat	Lower cost; slower response; no positive position feedback unless specified
2-Position (On/Off)	Snow melt, simple zone control	Spring-return preferred for fail-safe close
0�10 VDC Modulating	BMS-controlled VAV reheat, fan coils	Most common in commercial spec
4�20 mA Modulating	Industrial / longer cable runs / noisy environments	More immune to electrical noise
Spring-Return (Fail-Safe)	Critical applications � fail open or fail closed	Required where loss of power could damage coil (e.g., chilled water coils that could freeze)

Verify torque requirements against the valve manufacturer's published close-off pressure. Undersized actuators are a leading cause of leaking control valves in service.

Selection Checklist

Flow & Pressure

Coil design GPM and ?T documented
Coil pressure drop at design flow confirmed from manufacturer data
System differential pressure at the coil documented: min and max, accounting for variable-flow pressure swings
Control valve type selected: 2-way modulating, 2-way 2-position, 3-way, or PICV
Valve Cv sized for required ?P � confirm authority � = 0.5 if not using PICV
Maximum close-off pressure verified against actuator torque rating

Components

Isolation valve type by line size: ball for =2", butterfly for =2-1/2"
Strainer included with blowdown valve and stainless steel screen (20 mesh standard for hot water; finer for chilled water with low-temp glycol)
Balancing valve specified if not using PICV
P/T test ports included on supply and return
Air vent and drain provided
Unions or flanges on both sides of the control valve to permit removal

Actuator

Actuator signal type matches BMS specification (0�10V most common)
Spring-return vs. non-spring-return decision documented
Actuator pre-wired to valve from manufacturer specified where possible
Actuator location accessible after coil installation
24V transformer load checked: actuator VA + cable losses within transformer rating

Pressure & Materials

Pressure class matches system: 150# or 300# typical for commercial
Bronze or stainless trim for chilled water with high oxygen exposure
Body material: forged brass (small sizes), bronze, or ductile iron (larger sizes)
O-rings and seats compatible with system fluid and temperature
Lead-free brass specified for any potable water contact

Installation

Connection type matches piping: sweat, threaded, press, grooved, or flanged
Coil kit assembled and pressure tested at the factory (preferred) or pre-cut and bagged for field assembly
Shipping configuration documented: full assembly, pre-cut with fittings, or components only
Insulation requirements specified � chilled water requires vapor-tight insulation
Heat trace requirements identified for outdoor or unconditioned spaces

Commissioning

Method statement for setting design flow defined: PICV setpoint, balancing valve handle position, or DP measurement
Test report deliverable required (yes/no) documented
BMS integration verified: signal commands match valve position at multiple set points
Coil capacity verified at design flow and design supply temperature

Counting Coil Kits from a VAV Schedule

For takeoff purposes, the count of coil kits equals the count of hydronic-served terminal units. The VAV or fan coil schedule typically includes:

Tag (e.g., VAV-1-01)
Coil type: HW reheat, CHW cooling, or both
Design GPM
Design EWT/LWT (entering and leaving water temperature)
Coil pressure drop at design flow
Connection size

Group coil kits by line size and valve type for the most efficient quote. For mixed-size projects, separate the takeoff into bins � for example: 1/2" HW reheat, 3/4" HW reheat, 1" CHW coils.

Common Selection Mistakes

Oversizing control valves to match line size instead of sizing to Cv � destroys valve authority and causes hunting
Specifying PICVs without confirming actuator-to-valve compatibility from the same manufacturer
Mixing 2-way valves on terminals with constant-flow primary pumps � starves the boiler or chiller of minimum flow
Forgetting the air vent at the coil high point � air binds the coil and reduces capacity with no visible indication
Undersizing actuator torque relative to close-off pressure � leads to leaking valves and failed commissioning
Using 3-way valves on systems that require ASHRAE 90.1 variable-flow compliance without reviewing applicable exceptions