Installation guide

Page 28 • DRI-STEEM GTS Humidifier Installation, Operation, and Maintenance Manual
Example
For this example, refer to the tables on the previous page.
To determine gas piping size, begin by calculating the cubic
feet/hour (ft
3
/hr) or m
3
/hr using the following formula:
Btuh (kW) input
Calorific value of gas
Calorific values are:
• Natural gas: 1025 Btu/ft
3
(10.6 kW-hr/m
3
)
• Propane: 2500 Btu/ft
3
(25.9 kW-hr/m
3
)
For example, if you have a GTS-400 operating on natural gas,
calculate the ft
3
/hr or m
3
/hr as follows:
400,000 Btuh
= 390 ft
3
/hr
1025 Btu/ft
3
117.2 kW
= 11.1 m
3
/hr
10.6 kW-hr/m
3
If you need to run your gas piping 60 feet (18 m), see Table 27-2 on
the previous page and look horizontally across the 60 ft (18 m) row
until you locate the next highest value above your calculated ft
3
/hr
or m
3
/hr. In this example, you are looking for the next highest value
above 390 ft
3
/hr (11.05 m
3
/hr), which is 400 ft
3
/hr (11.3 m
3
/hr) and
indicates the use of a 1¼" (DN32) pipe for this application.
Using the same example, if the specific gravity of your natural
gas was 0.55 (instead of the 0.60 standard), see Table 27-2 for an
adjustment factor. In this case, the factor would be 1.04, which you
multiply by the 390 ft
3
/hr (11.05 m
3
/hr) value. This gives you a new
value of 406 ft
3
/hr (11.49 m
3
/hr). Referring again to the gas pipe
capacities table (Table 27-2), you see that for the same 60 ft (18 m)
length, you now need to use 1½" (DN40) pipe due to the change in
the specific gravity of the gas.
Gas leak testing
• When leak-testing the gas supply piping
system, disconnect the humidifier and
its gas shutoff valve during any pressure
in excess of 24" wc (6 kPa). Isolate the
humidifier from the gas supply piping
system by closing its field-installed
manual shutoff valve during any pressure
not equal to 24" wc (6 kPa).
• With all burners running, check gas
supply pressure at the inlet pressure tap
of the combination gas control valve.
For North American models, the
recommended supply pressure is
7" wc (1.75 kPa) for natural gas or
11" wc (1.83 kPa) for LP gas. Perform
gas piping purging as described in ANSI
Z223.1 (latest edition) or in Canada, CAN/
CGA-B149 codes. The minimum supply
pressure is 6" wc (1 kPa) for natural gas
or LP gas.
For European models, the required supply
pressure is 20 or 25 mbar for natural gas
and 30, 37, or 50 mbar for propane gas.
More gas piping instructions on the next page ▶
Installation
Piping:
Gas piping