Installation Steam Coil Piping, Coil Damage

Trane CAH-SVX01A-EN manual Installation Steam Coil Piping, Coil Damage

Installation

Steam Coil Piping

M-Series air handlers fitted with steam coils have labeled holes for piping penetrations. Figure 28 and Figure 29 illustrate typical steam coil piping configurations. See Table 2 for the codes of system components in these figures.

Table 2. Code of system components for piping figures

Code System component

FT	Float and thermostatic steam trap
GV	Gate valve
OV	Automatic two-position (ON-OFF)
	control valve
VB	Vacuum breaker
ST	Strainer
AV	Automatic or manual air vent
MV	Modulating control valve

The coil condensate return line must be piped full size of the condensate trap connection, except for a short nipple screwed directly into the coil header’s condensate return tapping. Do not bush or reduce the coil return tapping size.

•Install a 1/2-inch NPT, 15 degree swing check valve vacuum breaker with cracking pressure of 0.25 inches Hg (3.5 inches water) or lower at the top of the coil. This vacuum breaker should be installed as close to the coil as possible.

•For coil types A, AA, N, NS, and NN, install the vacuum breaker in the unused condensate return tapping at the top of the coil.

•Types T and ST coils require that the vacuum breaker be located as near as possible to the supply connection.

•Vent the vacuum breaker line to atmosphere or connect it into the return main at the discharge side of the steam trap

Note: Vacuum breaker relief is mandatory when the coil is controlled by a modulating steam supply or automatic two position (ON-OFF) steam supply valve. Vacuum breaker relief is also recommended when face-and- bypass control is used.

CAUTION

Coil Damage!

In all steam coil installations, the condensate return connections must be at the low point of the coil. Failure to properly install the condensate return connection may result in coil damage from water hammer, unequal thermal stress, freeze-up and/or corrosion.

Note: The 1/2-inch NPT, 15 degree swing check valve vacuum breaker is recommended because other vacuum breakers, such as spring- loaded ball-check breakers, have cracking pressures as high as 1.25 inches Hg (17 inches of water). Vacuum breakers with fitting sizes smaller than 1/2 inch NPT are too small to relieve vacuum quick enough to ensure complete condensate drainage. Other types of swing check valve vacuum breakers are acceptable if the fittings size is not smaller than 1/2-inch NPT and the cracking pressure is not larger than 0.25 inches HG (3.5 inches of water).