Pressurized Water System Installations; Water-To-Water Heat Transfer System - Central Boiler Pallet Burner Dual Fuel Owner's Manual

Pressurized Water System Installations

Water-to-Water Heat Transfer System

To keep the existing system pressurized, a plate
exchanger or tube & shell water-to-water heat exchanger
installed in the return line of the existing system may be
used (see Fig. 25). The water from the existing system
passes through the heat exchanger when the thermostat
calls for heat. The water from the outdoor furnace
circulates through the other side of the heat exchanger
continuously.
It may be necessary to lower the water temperature at
which the burner in the existing boiler starts to a setting
that prevents the burner in the existing boiler from
cycling on when the outdoor furnace is heating the
building. Another option is to install a thermostatically
controlled interlock switch that prevents the burner
in the existing boiler from operating when the water
temperature in the outdoor furnace is above 150˚F.
Water-to-water heat exchangers will produce transfer
temperatures approximately 20ºF less than the outdoor
furnace water temperature; therefore if the outdoor
furnace water temperature is 185°F, it will produce
approximately 165°F of water temperature transfer.
The temperature controller on the outdoor furnace
may be adjusted to allow the outdoor furnace to reach
water temperatures up to 195ºF. Each system will vary
in water temperature transfer depending upon the heat
load of the existing heating system.
Fig. 25
Section 1 - Furnace Installation
The addition of a wraparound pump with a water-to-
water heat exchanger may increase heat transfer by
allowing circulation continuously through the existing
boiler and heat exchanger. This will maintain the
maximum temperature in the heat exchanger for heat
transfer to the existing boiler. Note the water flows in
opposite directions through the heat exchanger.
With this type of installation, the exchange temperature
may be more than 165°F and may eliminate the need
for additional baseboard heaters, panel radiators or heat
exchangers.
When installing water-to-water heat exchangers, be
sure to flush any rust particles or sediments out of the
existing boiler and install a Y-strainer as illustrated in
Fig. 25. Also be sure to add Corrosion Inhibitor Plus™
(p/n 1650).
A Taco 007 pump can be used as a wraparound pump
when a plate exchanger is installed. A Taco 009 pump
should be used when a shell and tube heat exchanger
(i.e., p/n 148, 151 or 177) is installed.
NOTE: See the Hydronic Component Selection
Guide (p/n 2482) for more detailed information.
Plate Exchanger
23