14
110839-01 - 8/20
AP-U
Installation & Service Manual
Figure 3-5: Schematic Tankless Heater Piping
Table 3-6: Tankless Heater Ratings
dishwashers and automatic washers is
possible by piping the hot water from the
heater prior to entering the mixing valve. The
mixing valve should be “trapped” by installing
it below the cold water inlet to heater to prevent
lime formation in the valve. Refer to Figure 3-5.
3. FLUSHING OF HEATER — All water contains
some sediment which settles on the inside of
the coil. Consequently, the heater should be
periodically backwashed. This is accomplished
by installing hose bibs as illustrated and
allowing water at city pressure to run into hose
bib A, through the heater, and out hose bib B
until the discharge is clear. The tees in which
the hose bibs are located should be the same
size as heater connections to minimize
pressure drop.
4. HARD WATER — A water analysis is
necessary to determine the hardness of your
potable water. This is applicable to some city
water and particularly to well water. An
appropriate water softener should be installed
based on the analysis and dealer’s
recommendation. This is not only beneficial to
the tankless heater but to piping and fixtures
plus the many other benefits derived from soft
water.
Boiler Model
Tankless Heater Model
S-5A
GPM
PSID
AP-110U-T
3½
15
AP-154U-T
3¾
25
3
Water Piping and Trim
(continued)
THE FOLLOWING GUIDELINES SHOULD BE
FOLLOWED WHEN PIPING THE TANKLESS HEATER:
1. FLOW REGULATION — If flow through the
heater is greater than its rating, the supply of
adequate hot water may not be able to keep
up with the demand. For this reason a flow
regulator matching the heater rating should be
installed in the cold water line to the heater.
The flow regulator should preferably be located
below the inlet to the heater and a minimum of
3’ away from the inlet so that the regulator is
not subjected to excess temperatures that may
occur during “off” periods when it is possible
for heat to be conducted back through the
supply line. The flow regulator also limits the
flow of supply water regardless of inlet
pressure variations in the range of 20 to 125
psi.
2. TEMPERING OF HOT WATER — Installation of
an automatic mixing valve will lengthen the
delivery of the available hot water by mixing
some cold water with the hot. This prevents the
possibility of scalding hot water at the fixtures.
In addition, savings of hot water will be
achieved since the user will not waste as much
hot water while seeking a water temperature.
Higher temperature hot water required by
Summary of Contents for AP-U AP-110U-N
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