HIGH TEMPERATURE WATER DISTRIBUTION
APPLICATIONS AND SYSTEMS
1 SCOPE Direct buried conduit systems shall be installed, maintained, and
repaired in accordance with the Manufacturer's Approved Brochure and NAVFAC
Guide Specifications NFGS-15705, Underground Heat Distribution Systems
(Prefabricated or Pre-Engineered Types). Systems shall have a Letter of
Acceptability issued by Federal Agency Committee on Underground Heat
D i s t r i b u t i o n Systems. T h e Letter of Acceptability is signed by
r e p r e s e n t a t i v e s of federal agencies participating in the committee and stating
that the supplier's system is approved for use for the site ground-water .
c o n d i t i o n s , operating temperature, a n d soil classification(s) indicated.
Shallow concrete trench systems shall be installed in accordance with
NFGS-15751, Heat Distribution System Outside of Buildings (Concrete Shallow
Trench Type). Hot water can be distributed more efficiently and cost
e f f e c t i v e l y than steam. For this reason hot water should be utilized over
steam wherever feasible. E n g i n e e r i n g Field Divisions shall assist and
activities shall assure that operation and maintenance of hot water
distribution systems are performed. The Power Principles Video Training
Program shall provide further assistance to all concerned.
2 HTW HEAT TRANSMISSION. High temperature water (HTW) is an alternate medium
to steam for conveying heat to customers located some distance from the
g e n e r a t i n g plant. HTW can be efficiently generated and distributed, easily
controlled, and accurately measured. I t is distributed in a closed system
from the generating plant to customers within a radius of 6 miles; although,
with booster pumps-this distance can be extended. The system experiences
l i t t l e energy loss except for line heat losses of 3F to 8F per mile of
3 HTW DISTRIBUTION SYSTEMS.
An HTW distribution system consists of the following
(a) Piping to transport high temperature supply water from a central HTW
generating plant to consumers;
( b ) Piping to return the high temperature water to the generating plant;
( c ) Equipment, instrumentation, a n d related facilities to safely and
efficiently accomplish these tasks.
3.2 Types of HTW Distribution Systems.
(a) Low Temperature Water System (LTW). A hot water heating system operating
with a pressure of approximately 30 psig and a maximum temperature of 250F.
(b) Medium Temperature Water System (MTW). A hot water heating system
operating at temperatures of 350F or less, with pressures not exceeding
150 psig. The usual supply temperature is approximately 250 to 325F.