Trane High Rise Fan Coil Reference Guide

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High Rise Fan Coil

Riser Selection How-To

June 2010 UNT-PRC015-EN

Introduction

The purpose of this manual is to aid in the selection and pricing of water pipe risers for high rise
fan coils. Because of the volatility in copper cost, the proper selection of riser diameter is critical
to designing a cost effective job. If the riser diameter is too small, the water velocity through the
riser pipe may cause excessive water pressure drop due to friction loss and/or erosion of the pipe.
If the riser diameter is too large, the cost of the fan coil unit and riser system may become
unnecessarily high making the equipment bid uncompetitive. Therefore riser sizes are chosen to
minimize initial cost while avoiding the undesirable effects of high water velocities.

Noise, erosion, and installation and operating costs all limit the maximum and minimum velocities
in the riser system.

Trademarks

Trane and the Trane logo are trademarks of Trane in the United States and other countries. All
trademarks referenced in this document are the trademarks of their respective owners.

© 2010 Trane All rights reserved UNT-PRC015-EN

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

General Information on Riser Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Know the Riser Design—Design Return versus Reverse Return . . . . . . . . . . . . . 6

Riser Selection and Sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Riser Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Expansion Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Determining Riser Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

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General Information on Riser Systems

The riser is a vertical pipe system, usually copper, that carries the chilled water and hot water supply
and return and coil condensate to and from a fan coil air handler. Other materials can be used, but
copper pipe is desirable due to its light weight, ease of installation, widespread availability,
durability and reasonable cost. Riser systems are installed in multi-story buildings where high rise
fan coil units are installed floor-by-floor on top of each other. The risers interconnect floor-by-floor
as the fan coil units are installed on top of each other. This allows the riser to ascend vertically to
each of the individual units.

Figure 1.

Installation of the fan coil units is quick with no lateral runs of copper piping off the main riser lines.

Copper tubing is commonly used for the risers. Job specifications will dictate the type of piping
used. There are three types of copper risers available, type K, L, and M, the difference being the
thickness of the wall of the copper pipe. For most applications, type L or type M copper is adequate.
Type K copper risers are used in high pressure applications, are very high priced and usually not
necessary for most high rise fan coil applications. Type K copper risers should not be bid unless
specified. Tab l e 1 provides dimensional data of type M, L, and K copper risers.

Table 1. Dimensional data of type M, L, and K copper risers (in.)

Type M Type L Type K

Riser Size

1/2 0.625 0.569 0.028 0.625 0.545 0.04 0.625 0.527 0.049

3/4 0.875 0.811 0.032 0.875 0.785 0.045 0.875 0.745 0.065

1 1.125 1.055 0.035 1.125 1.025 0.05 1.125 0.995 0.065

1-1/4 1.375 1.291 0.042 1.375 1.265 0.055 1.375 1.245 0.065

1-1/2 1.625 1.527 0.049 1.625 1.505 0.06 1.625 1.481 0.072

2 2.125 2.009 0.058 2.125 1.985 0.07 2.125 1.959 0.083

2-1/2 2.625 2.495 0.065 2.625 2.465 0.08 2.625 2.435 0.095

3 3.125 2.981 0.072 3.125 2.945 0.09 3.125 2.907 0.109

4 4.125 3.935 0.095 4.125 3.905 0.11 4.125 3.857 0.134

4 UNT-PRC015-EN

OD ID

Wall

Thickness OD ID

Wall

Thickness OD ID

Wall

Thickness

General Information on Riser Systems

Hot water, cold water, and condensate risers are factory insulated to avoid condensation and/or
heat loss. Factory insulation is recommended to minimize installation costs and assure quality
control on the insulation application.

Two-pipe and four-pipe riser systems are available. Two-pipe risers provide pipes for hot or chilled
water supply and return only, but not both hot and chilled water simultaneously. Four-pipe risers
provide pipes for hot plus chilled water supply and return simultaneously. Riser systems may be
selected without a condensate riser—not required for a heating-only system. Very tall buildings
may have more than one riser system with each system independent of the other.

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