1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

MECHANICAL SYSTEMS – MULTIFAMILY

Steam System Basics

1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

2 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

By attending this session, participants will gain an understanding of:

• The fundamental principles of steam heating.

• The basic properties of steam.

• How steam moves through a building.

Learning Objectives

3 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

This section lays the framework. Later sections go into more detail on the following topics:

• Near-boiler piping

• Distribution systems

• Operations & maintenance (O&M)

• Steam boiler safety

• Steam boiler controls

Steam Heating

4 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

• Steam heating was invented in the 1800s and improved in the 1900s.

• Originally ran with coal and not electricity.

• Very simple concepts. • Dangerous in the early

days. • Recommended reading:

Lost Art of Steam Heating by Dan Holohan.

History

Photo source: Library of Congress

5 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

This is condensation, NOT steam.

What is steam?

STEAM is INVISIBLE

• Odorless, colorless, tasteless. • Gaseous form of water. • Very high heat content.

Where is the steam?

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STEAM SYSTEM BASICS

• Distributes heat in the form of heated water.

• Uses same water over and over. • Boiling/condensing/boiling/condensing. • No electricity needed for distribution. • Relatively easy to get heat to far away

places – steam expands into the ends of the system.

How does steam heat work? #1

Graphic source: Steven Winter Associates

7 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

• During boiling, the water temperature stays the same.

• Boilers full of water will never get hotter than the boiling point.

• It takes 5.4 times as much energy to boil water as it does to bring it from freezing to boiling. That’s LATENT (hidden) heat.

How does steam heat work? #2

Steam has a very high heat content. If you can transport steam, you can transport heat.

8 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

• 1 lb water = 1 lb steam. • Steam is lighter than

air. • Steam does not readily

mix with air. • Steam takes up 1,700

times as much space as water!

Properties of Steam

Graphic source: Steven Winter Associates

Water 1,700 times larger than liquid water

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STEAM SYSTEM BASICS

Grover Shoe Factory, Brockton, MA March 20, 1905

The Power of Steam #1

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STEAM SYSTEM BASICS

The Power of Steam #2

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STEAM SYSTEM BASICS

• Pressure is the force that moves steam.

• A common solution to heating problems: crank up the pressure a bit.

• But higher pressure isn’t always the answer to steam heating problems.

– Safety controls can shut the boiler off too soon.

– Higher pressure won’t fix the root of a distribution problem.

High pressure goes to low pressure.

12 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

• Steam with nowhere to go causes explosions.

• As steam system fills, steam pushes out the air.

• When steam condenses, it shrinks.

• As heating cycle ends, system sucks air back in.

Expanding and Contracting

Photos source: Steven Winter Associates

Radiator air vent

Main vents

Air vents allow system to fill with steam.

13 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

1. System at rest. 2. Boiler turns on, begins to boil. 3. Steam rises into pipes, forces air out. 4. Steam forces air out of radiators. 5. System mostly filled. Steam

continually condensing into water. 6. Boiler shuts off. All steam condenses

into water. Air moves back in to fill the void. Condensate flows back to boiler.

7. System at rest.

The Steam Cycle

Graphic source: Steven Winter Associates

14 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – January 2011

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STEAM SYSTEM BASICS

• Steam systems work by boiling water into steam. • Steam contains a lot of energy in the form of latent heat.

When the steam condenses, it gives up that heat to heat the building.

• Steam is distributed through a building by pressure, but too much pressure is dangerous.

• In modern steam systems, air vents on radiators and pipes regulate pressure.

Summary