Hydronic System Components: Pumps, Valves, Storage & NPSH

Storage Inertia

Storage Inertia: Bulk cold/hot water storage to supply the facility during plant stops. Mounted on the supply. Sometimes, to protect the heat exchanger, it is placed on the return. It serves to prevent a high frequency of starts and abrupt changes in temperature.

Kv (Valve Flow Coefficient)

Kv: Valve flow coefficient. Kv relates flow through a valve to the pressure drop: when the valve is fully open, the Kv value is the flow (in m3/h) that produces a 1 bar pressure drop. Kv allows you to select valves for the required flow and pressure conditions.

Expansion Vessel (Vaso Expansion)

Vaso Expansion: Allows the system to accommodate volume changes. Its second function is to protect the pump from running without pressure and to help avoid water hammer. Ideal to install on the suction side.

• Open: Located at the highest point, usually on the external side and return. Prone to calcification problems.
• Closed: Located in the return. Two chambers separated by a membrane.

Pump Characteristic Curve

Pump characteristic curve: A graphic representation that relates flow to head (height gauge). The curve varies according to the pump model and operating conditions.

NPSH (Net Positive Suction Head)

NPSH: The difference between the pressure at the pump inlet and the vapor pressure of the liquid being pumped. It is the margin necessary to avoid cavitation. NPSH is a function of pump flow and helps determine the risk of cavitation and related pump losses.

Wet-Rotor Pumps

Wet rotor pumps: The impeller is directly coupled to the rotor, separated by a membrane. They are cooled with water from the pump itself. Used for domestic hot water (DHW) and heating. Typically installed in a horizontal position. The junction box is always on top. Do not start until the system is filled with liquid.

Cavitation

Cavitation: Vapor bubbles caused by fluid pressure variations that eventually erode and damage material.

Water Hammer and Causes

Water Hammer: Effects produced in the installation by a sudden stop of the fluid. It can break pipes.

Appears on:

• Opening and closing a valve
• Start / stop pump
• Sudden decrease in flow (fault, power failure, supply interruption)

Valves and Types

Valves:

Ball Valve

Ball: Often used for small pipes. Primarily used for sealing. Not for flow regulation.

Butterfly Valve

Mariposa (butterfly): Serves as a seal and can be used for coarse hydraulic control. Common from 2" and larger.

Gate Valve

Gate: Used for sealing. Helps prevent water hammer when used appropriately.

Seat Valve

Seat: Used to regulate the circuit.

Safety Valve

Safety: Protects the installation from overpressure. The installer determines the pressure at which the valve will pass water.

Check (Standing) Valve

Standing: They prevent backflow and help keep the pump primed.

One-Way Valve

Valve: Allows the passage of fluid in one direction.