HVAC 232 Unit 82-HYDRONIC HEATING SYSTEMS

A building requires a pump with a head pressure of 15 feet and a flow rate of 12 gallons per minute. Which of the following pumps should be used, based on the supplied performance data?

Total head pressure range: 16 to 2 feet; flow rate: 0 to 14 gallons per minute

A modern hydronic heating system typically:

Heats by circulating hot water through a closed system of piping.

A piping system that has the main supply pipe from the boiler enter the first baseboard unit, all baseboard sections connected in series, and the outlet from the last baseboard section connected to the circulator pump, which connects to the boiler, is called a:

Series loop, single circuit hot water piping system.

Balancing valves are required:

To allow adjustable flow.

Compared to air heating systems, hydronic heating systems:

Are normally more expensive to install.

How do mixing valves save energy?

By delivering only enough heat to the loop to meet the load.

In a one-pipe venturi system:

Only part of the water flows through each convector in the loop.

In a series loop system:

All the water flows through each convector in the loop.

In a two-pipe system:

Each convector is supplied with the same temperature hot water.

In the zoned system, how many motorized vales does each circuit contain?

1

Mixing valves control the final temperature of radiant loops:

By mixing the hot boiler water with cooler return water.

Most hydronic heating systems are:

Closed piping systems.

Pumps for hydronic heating systems are usually:

Centrifugal pumps.

Sensors for the mixing valve control are located:

Outside the building, on the supply line, and on the boiler.

The different types of terminal units used for hot water heating systems include:

Baseboard heaters, convectors, fan coil units, and radiators.

The mixing valve controls the temperature of water supplied to the:

Radiant loop.

Typically, the zone control valve not only opens to allow water to flow to the zone, but also turns on:

Circulator pump

Water circulating pumps are rated by:

Flow and head pressure.

What component is used to compensate for different pressure drops and load requirements?

Balancing valves

What do modern hydronic systems use to circulate the hot water?

Pumps

What happens when the electrical contacts close in the motorized valve?

The circulator pump starts.

What is a hydronic terminal unit?

The coils and devices that heat the building.

What is the lowest water temperature required for effective radiant floor heating?

90°F to 105°F

What is the primary way a convector heats a room?

Through natural convection along the outer walls

What is the purpose of a reverse return piping system?

To keep the length of piping the same for each convector unit

What is the purpose of the expansion tank?

To allow for water volume changes due to temperature change

What is the purpose of the venturi on a one-pipe venturi system?

The venturi creates a negative pressure at the main connection, drawing the necessary flow through the branch.

What materials are most commonly used for hydronic piping?

Copper and cross-linked polyethylene

Which of the following statements about zoned systems is correct?

Water flow in zoned systems is controlled by a motorized valve.

Which piping arrangement allows every unit to receive the same temperature water?

Two-pipe system, direct return

Which system heats a room more evenly, leading to fewer cold spots?

Radiant floor heating system.

Why do closed hydronic systems include pressure-relief valves, expansion tanks, and temperature and pressure-limiting devices?

Because water expands and contracts as its temperature changes.

You will never see a pump with a profile of:

High pressure and high flow

Zone control is accomplished in hydronic systems using thermostats that activate:

A zone control valve for each zone.