AERCO Innovation (G-10-1350 to G-11-0563) - Manual (Page 145)

07/21/11 AERCO International, Inc.
· 100 Oritani Dr. · Blauvelt, NY 10913 · Ph: 800-526-0288
Page 145 of 200
GF-5030
Gas Supply Design Guide
TAG-0044_0A
Gas Piping
All gas piping and components must comply with NFPA local codes, and utility requirements minimum. Only gas
approved fittings, valves, or pipe should be utilized.
Standard industry practice for gas piping is Schedule 40 iron pipe and fittings. All high and low gas pressure piping
systems must comply with local utility and building codes.
Assembled piping should be clean of all debris, pipe chips, or foreign material to prevent any from entering the
Innovation Low NOx series heater gas train. Piping should be tested as prescribed in NFPA 54. Equipment should be
isolated before testing any piping system over the allowable pressure. DO NOT EXCEED 14.0” W.C.on the inlet side
of the Innovation water heater at any time.
Gas Supply Main Sizing
Gas pipe sizing, for either a single or multiple heater installation, shall be sized for a maximum pressure drop of 0.3”
W.C., from the source to the final heater. The maximum gas flow rate required is the sum of the maximum inputs of
each unit divided by the heat of combustion of the fuel supplied at the location, (approximately 1,030 BTU per cubic
foot). The fuel supplier or utility should be consulted to confirm that sufficient volume and normal pressure is provided
to the building at the discharge side of the gas meter or supply pipe. For existing installations with gas equipment, gas
pressure should be measured with a manometer to be certain sufficient pressure is available. Before sizing gas piping,
a survey of all connected gas devices should be made. Gas piping supplying more than one gas device must be able
to handle the total connected input within the allowable gas pressure drop. The allowable minimum and maximum gas
pressure for each device should be considered. Whenever the minimum and maximum gas pressures vary between
devices, gas pressure regulators at each unit should be installed to allow regulation at any individual unit. Gas pressure
must never exceed the maximum allowable rating of any connected device.
The total length of gas piping as well as fitting pressure drop must be considered when sizing the gas piping. Total
equivalent length should be calculated from the meter or source location to the last heater connected on the header.
Gas piping tables 1, 2 and 3 containing data extracted from NFPA 54 should be used as a minimum guideline. (See
Tables on the following pages). Gas pipe size should be selected on the total equivalent length from the appropriate
pressure table. The gas volume for cfh flow will be the input divided by the calorific value of the fuel to be supplied.
Gas Header Sizing
Main supply gas pipe sizing should be developed for the total plant. Heater gas manifold piping should be sized based
on the volume requirements and lengths between heaters and the fuel main. Multiple heater manifold sizing (Diagram
2) indicates the proper sizing for units placed on the factory standard 52” centers with 2” takeoffs for each unit. Header
sizes can be either full size or stepped in size as units are connected. A typical gas piping header diagram for a 3-
Module Innovation Heater Plant is illustrated in Diagram 3.
INNOVATION SERIES GAS HEADER SIZING
No. of Heaters 1 2 3 4 5 6 7 8
Sch 40 Iron Pipe* 1.5” 2.5
”
3” 3.
”
4
” 4” 5
”
5
”
Diagram 2. Multiple Heater Manifold Chart
*Based on Table 1 on the following page, 1,000
cfh/unit, actual header sizes will vary with length of
pipe run and fittings employed.
If supply gas pressure exceeds 14.0” W.C., a single
header gas manifold lock-up type regulator, -or-
individual lock-up regulators can be used to bring the
gas pressure down to 14.0” W.C. Header should be
located above or behind heater. Gas piping should not
be installed directly over top or front of any part of
heater. Sufficient clearances for maintenance are
required.
Pg. 5 of 10
GAS SUPPLY
MANUAL
SHUTOFF
VALVE
DRIP
LEG
DRIP
LEG
MANUAL
SHUTOFF
VALVE
Diagram 3
Typical Multiple Heater Manifold Construction