Installation Instructions

Series and Parallel (Low Pressure) System
DETERMINE TOTAL CAPACITY NEEDED FOR APPLIANCES.
Data can be obtained from the manufacturers nameplate located on the gas appliance. BTU equivalents
for CFH can be obtained from the local utility. In most cases, one Cubic Foot per Hour (1 CFH) is
e
stimated to be 1,000 BTUH heating value (natural gas) and Propane has a heating value around 2,500
BTUH, making the capacity tables easy to utilize with appliance BTU input loads.
DETERMINE THE TYPE OF PIPING LAYOUT WHICH BEST FITS THE INSTALLATION
S
ERIES SYSTEMS
A series layout is the most common arrangement
utilized for rigid pipe systems for low pressure.
These usually consist of a main run (header) with
tees branching off to each appliance. In a traditional
series system, the service pressure down stream of
the meter is typically less than 1/2 PSI.
The minimum pressure supplied to any given appli-
ance is an important consideration. To operate prop-
erly, most Natural Gas appliances require a mini-
mum of 4”WC pressure and most Propane
(Liquefied Petroleum) appliances require a mini-
mum of 10”WC pressure. Allowable pressure drop
along any particular run may be dictated by local
code restrictions.
PARALLEL SYSTEMS
In a parallel system, appliances are serviced by
individual runs that stem off from a central distribu-
tion manifold. A main run from the meter supplies
the manifold. The manifold station is located close to
the greatest load, typically the boiler or furnace. A
parallel layout is most likely to be used in 1/4 to 1/2
psi systems.
DUAL PRESSURE SYSTEM
A dual pressure system incorporates two operating
pressures downstream from the meter. The first
pressure
, set b
y the service regulator at the meter,
is usually 2 psi, but can be higher or lower depend-
ing on code restrictions and gas company policy.
This part of the system is sized separately and ends
at the pounds-to-inches regulator inlet. The allow-
ab
le pressure loss f
or this par
t of the system must
be added to the eff
ect of the regulator to deter
mine
the available pressure at the regulator outlet. See
chart page 35, Regulator Capacity Table.
The second pressure, at the outlet of the pounds-to-
inches regulator is under 1/2 PSI, usually 8”WC for
natural gas and 11”WC f
or propane
.
Gener
ally
, a
parallel system requires a higher total footage of
smaller diameter tubing and f
ewer fittings compared
to a series la
y
out.
8
MULTI-UNIT APARTMENT BUILDING