LP-428 Rev. 6.6.16
4
Table of Contents
Part 1 - General Safety Information 5
A. Improper Combustion 6
B. Gas 6
C. When Servicing the Water Heating System 6
D. Boiler Water 6
E. Freeze Protection 6
F. High Elevation Installations 6
Part 2 - Before You Start 6
A. What’s in the Box 6
B. How the Boiler Operates 6
C. Optional Equipment 7
Part 3 - Prepare the Boiler 7
A. Locating the Boiler 8
B. Flooring 9
C. Leveling 9
D. Clearances for Service Access 9
E. Residential Garage and Closet Installations 9
F. Exhaust Vent and Intake Pipe 10
1. Direct Vent of Exhaust and Intake 11
2. Indoor Combustion Air in Conned or Unconned Space
11
G. Prevent Combustion Air Contamination 11
H. Removing a Boiler from a Common Vent System 11
I. Water Chemistry Requirements* 12
Part 4 - Piping 13
A. General Plumbing Information 13
B. Relief Valve 14
C. Backow Preventer 14
D. Expansion Tank 14
E. Circulators 14
F. Hydronic Piping with Circulators, Zone Valves, and
Multiple Boilers 15
G. Circulator Sizing 15
H. Check / Control Water Chemistry 17
I. Plumbing 17
J. Fill and Purge Heating System 17
K. Freeze Protection Fluids 18
L. Zoning with Zone Valves 18
M. Zoning with Circulators 18
The CSD-1 ASME Code, Section CW-400 requires that hot
water heating and supply boilers have a) a UL 353 temperature
control device, b) at least one (1) temperature-actuated control
to shut o the fuel supply when system water reaches a preset
operating temperature, c) a high temperature limit control that
prevents the water temperature from exceeding the maximum
allowable temperature by causing a safety shutdown and
lockout, and d) its own sensing element and operating switch.
The temperature control system integrated into the 926
control provided with this heating appliance complies with
the requirements of CSD-1 Section CW-400 as a temperature
operation control. The control monitors the temperature
dierence between the inlet and the outlet sensor, which is
aected by boiler water ow. If this temperature dierence
exceeds 55°F (typically because of low water ow or very low
heat load), the control will reduce the maximum fan speed.
If the temperature dierence exceeds 60°F, the control will
eectively sense there is little or no water ow or heat load and
shut the boiler down. The controller will restart automatically
once the temperature dierence has dropped below 55°F and
the minimum o time (anti-cycle time) has expired. In addition,
if the control senses that the outlet water temperature has
reached 210°F, the boiler is put into a hard lockout and requires
manual reset to restart.
IMPORTANT
In accordance with Section 325 (f) (3) of the Energy Policy
and Conservation Act, HTP, Inc. has provided this boiler with
multiple features designed to save energy by reducing the
boiler water temperature as heating load decreases.
These features include:
• A modulating combustion system that adjusts ring
rate based on heat demand.
• Adjustment of boiler set point based on inferred heat
load as determined by an outdoor sensor. The outdoor
sensor is supplied by HTP, Inc. with this boiler.
• This boiler does not include a standing pilot.
• This boiler is designed and shipped to assure the
highest eciency operation possible. Such high
eciency is achieved by limiting heating circuit water
temperature to 140°F when there is no anticipated
heat load, based upon the outdoor sensor and the
Outdoor Reset Curve (sensor response curve) in the
boiler software.
• This feature may be over-ridden as described below in
specic installations:
• The boiler control is equipped with an outdoor sensor
override for use with building management systems
or in cascaded systems (for systems with total input of
300,000 BTU/hr or greater).
See statement below for an important notice on the use of
the override.
IMPORTANT
In accordance with Section 325 (f) (3) of the Energy Policy and
Conservation Act, this boiler is equipped with a feature that
saves energy by reducing the boiler water temperature as
the heating load decreases. This feature is equipped with an
override which is provided primarily to permit the use of an
The hydronic supply and return connections of these
products are for installation in closed loop systems ONLY!
Use of this product in any manner other than described in this
manual may result in premature product failure, substantial
property damage, severe personal injury, or death. Damage
or failure of this product (or the system in which it is installed)
due to unauthorized use IS NOT COVERED BY WARRANTY.
external energy management system that serves the same
function. THIS OVERRIDE MUST NOT BE USED UNLESS AT
LEAST ONE OF THE FOLLOWING CONDITIONS IS TRUE:
• An external energy management system is installed
that reduces the boiler water temperature as the
heating load decreases.
• This boiler is not used for space heating.
• This boiler is part of a modular or multiple boiler
system having a total input of 300,000 BTU/hr or
greater.
• This boiler is equipped with a tankless coil.
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