Modulex EXT Series Piping Application Guide
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AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
TAG-0096
10/06/2021
Phone: 800-526-0288
1.
GENERAL INTRODUCTION
AERCO Modulex EXT gas fired boilers are modulating input boilers that require an adequate volume
and pressure of natural or propane gas for proper operation. The gas requirements specified herein
must be satisfied for efficient combustion. Designers and installers must adhere to the specifications
of AERCO and of the local authorities having jurisdiction. A thorough understanding and knowledge of
these guidelines is required for the successful design and installation of Modulex EXT boilers.
2.
GAS TRAIN COMPONENTS
The Modulex EXT is a cast aluminum body boiler consisting of mutually connected combustion chambers,
each having its own gas train (gas valve, pre-combustion chamber, and burner), blower, air pressure
switch, check valve, igniter, and flame detector. Each group of these components is referred to as a
module. The gas train components have been designed to operate at high combustion and seasonal
efficiencies by closely controlling both the volume and air/fuel mixture to the burner. Below are
descriptions of each of the gas train components for each module.
•
GAS VALVE
– An electronic, modulating gas valve with 100% tight shutoff. It controls the
amount of gas delivered to the burner.
•
PRE-COMBUSTION CHAMBER
– A plastic chamber mounted to the blower, where combustion
air and gas mix prior to entering the burner, providing controlled combustion. The outlet of the
chamber leads to a check valve, which prevents any backflow of combustion gases.
•
LOW NOx BURNER
– A metal fiber mesh covering a stainless steel burner head on which
combustion occurs. The burner operation is stable throughout the entire input range of the boiler.
NOTE:
The optimum gas pressure for the Modulex EXT boiler is 7.0” W.C. However, the
Modulex EXT boiler can be safely operated at pressures ranging from 3.5” W.C. to 10.5” W.C.
3.
GAS PRESSURE REQUIREMENTS
AERCO Modulex EXT boilers require a stable gas input pressure. The inlet supply to the unit must be
at least 3.5
“ W.C. when firing at maximum input. A minimum supply gas pressure switch prevents the
boiler from operating without sufficient pressure. Maximum allowable gas pressure is
10.5” W.C. Static
gas pressure (when the unit is not firing) may vary, however actual gas pressure should be measured
when the unit is in operation (firing). Measure the gas pressure with a manometer at the port provided
in the inlet manifold. In a multiple boiler installation, gas pressure should initially be set for a single
boiler in operation and then remaining boilers should be staged on at full fire to ensure that gas
pressures never fall below the minimum allowable pressure of 3.5” W.C.
An external gas pressure regulator is mandatory for the State of Massachusetts, regardless of supply
pressure; for all other jurisdictions, a lock-up style regulator is required when supply pressure is greater
than 10.5” W.C. (see Fig. 1). The regulator must be installed with at least 2 feet of pipe between the
regulator and the unit gas inlet. The regulator discharge range must able to maintain 3.5” W.C. Gas
regulators are self-contained with tapped diaphragm vent ports allowing the diaphragm to change its
position. These vents typically require piping to the outside.
Every Modulex boiler requires a manual shutoff valve. CSA requires that no other components can be
installed between the boiler and this shutoff valve except for pipe fittings such as a pipe union. If an
external regulator is used, an additional isolation/service valve must be installed upstream of the regulator
(see
Figure 1
). Gas piping should contain ground unions for removal of the gas piping to the unit for
maintenance or service as required. Gas piping should never obstruct removal of the unit side panels and
should not be supported from the unit itself. Gas piping should be supported properly from the floor or
overhead as the installation allows.
