Gas Piping - IBC VFC 15-150 Installation And Operating Instructions Manual

NOTE
Due to the precision of
modern modulating boilers
it is important to pay special
attention to gas pressure
regulation.
It is essential to check gas
supply pressure to each
boiler with a manometer or
other high-quality precision
measuring device. Pressure
should be monitored before
firing the boiler, when the
regulator is in a "lock-
up" condition and during
operation, throughout the
boiler's full modulation range.
Pay special attention to
retrofit situations where
existing regulators may have
an over-sized orifice and/or
worn seats, causing pressure
"creep" and high lock up
pressures.
A high quality regulator will
maintain constant pressure
above the boiler's minimum
specification at all firing
rates, and will not exceed the
boiler's maximum pressure
rating when locked-up with no
load.
1-26
VFC 15-150, VFC 45-225 MODULATING GAS BOILERS
1.7

GAS PIPING

The boiler requires an inlet gas pressure of at least 3.0" w.c. for natural gas or
propane. For either fuel, the inlet pressure shall be no greater than 14.0" w.c.
Confirm this pressure range is available with your local gas supplier.
The inlet gas connection of the boiler's gas valve is 1/2" NPT (female).
Adequate gas supply piping shall be provided with no smaller than 1/2" Iron Pipe
Size (IPS), in accordance with the following chart:
MODEL
VFC 15-150 (Natural Gas)
VFC 15-150 (Propane)
VFC 45-225 (Natural Gas)
VFC 45-225 (Propane)
Table 7: Maximum Pipe Length (ft)
Gas piping must have a sediment trap ahead of the boiler's gas valve (see Figure
30). A manual shutoff valve must be located outside the boiler, in accordance with
local codes/standards. All threaded joints in gas piping should be made with an
approved piping compound resistant to the action of natural gas/propane. Use
proper hangers to support gas supply piping as per applicable codes.
The boiler must be disconnected or otherwise isolated from the gas supply
during any pressure testing of the system at test pressures in excess of 1/2 psig.
Dissipate test pressure prior to reconnecting. The boiler and its gas piping shall
be leak tested before being placed into operation.
The gas valve is provided with pressure taps to measure gas pressure upstream
(supply pressure) and downstream (manifold pressure) of the gas valve (see
Figure 32). Note that manifold pressure varies slightly in accordance with firing
rates with the modulating series boilers, but will always be close to 0" w.c.
Figure 30: Typical gas piping
1/2" IPS 3/4" IPS
10 40
50 180
5 20
25 90
INSTALLATION AND OPERATION INSTRUCTIONS
1" IPS
130
620
60
290