Mueller Fre-Heater D Series User Manual

Mueller Model D Fre-Heater Installation and Operation Manual Eective March 1, 1993
Part No. 8800430 Revised November 6, 2019
2.4 INSTALLING WATER PIPING (CONTINUED)
Some plumbing codes require the installation of dielectric unions in the water lines connected to any water heating
devices. This code would include Fre-Heaters. The purpose of a dielectric union is to interrupt the flow of transient
or induced voltage in the water piping that would increase the corrosive activity of the water. Mueller strongly
recommends the use of dielectric unions in all Fre-Heater installations.
In many multiple-unit D-120 installations, it is advantageous to install a circulating pump and form a loop
plumbing circuit through the Fre-Heaters. Doing so will usually increase the system’s heat recovery efficiency by
keeping the total system’s water volume at a uniform temperature and picking up the most available heat from any
condensing units that may be running. See Figure 7 for typical plumbing. Consult a plumbing supply house for a hot
water circulating pump suitable for the particular installation. All pumps used in a Fre-Heater water circulation
system must be suitable for potable water use. The Mueller hot water circulating pump, Part No. 8801091, is
suitable for many installations. Multiple Fre-Heater installations may be piped in parallel if care is taken to assure
equal flow through all of the Fre-Heaters. Parallel plumbing is usually reserved for installations having a common
refrigeration compressor on all of the Fre-Heaters. Refer to Figure 8 for a typical parallel plumbing diagram.
Under certain circumstances, it may be necessary to operate a high temperature or booster heater loop at
temperatures above those attainable or desirable in the Fre-Heater. At those times, a piping scheme such as shown
in Figure 9 should be used. This allows the Fre-Heater to operate at its optimum heat reclaim while the system
temperature is at a higher level.
FIGURE 7: TYPICAL MULTIPLE-UNIT SERIES PLUMBING FOR FRE-HEATERS
(COMMERCIAL APPLICATIONS)
8
Drain
N.C.
Cold
Water
Inlet
Drain
Drain
Circulating Pump
Hot
Water
Outl
et
Pressure
Temperature
Relief Valve
N.O.
Gate
Valve
N.O.
Mueller
Fre-Heater
Check Valve
Mueller
Fre-Heater
Mueller
Fre-Heater
Hot Water Outlet
Check Valve

Mueller Fre-Heater D Series Specifications

General

Brand	Mueller
Model	Fre-Heater D Series
Category	Water Heater
Language	English