Piping components, Water chemistry, Delta T

Installation & Service Manual

6System piping (continued)

The following chart (Table 6A) details the relationship of water temperature and time with regard to scald injury and may be used as a guide in determining the safest water temperature for your applications.

Table 6A Approximate Time / Temperature Scald Chart

APPROXIMATE TIME / TEMPERATURE

RELATIONSHIPS IN SCALDS

120°F	More than 5 minutes

125°F	1 1/2 to 2 minutes

130°F	About 30 seconds

135°F	About 10 seconds

140°F	Less than 5 seconds

145°F	Less than 3 seconds

150°F	About 1 1/2 seconds

155°F	About 1 second

Piping components

Check valves:

Field supplied. Check valves are recommended for installation as shown in FIG.’s 6-2 thru 6-4.

Water heater isolation valves:

Field supplied. Full port ball valves are required. Failure to use full port ball valves could result in a restricted flow rate through the water heater.

Anti-scald mixing valve:

Field supplied. An anti-scald mixing valve is recommended when storing domestic hot water above 115°F.

Unions:

Field supplied. Recommended for unit serviceability.

Temperature and pressure relief valve:

Factory supplied on water heaters. The temperature and pressure relief valve is sized to ASME specifications.

Water chemistry

	NOTICE	The Shield water heater is designed for
	NOTICE	heating potable water with a hardness of 5
		heating potable water with a hardness of 5
		to 25 grains per gallon and a total
		dissolved solids not exceeding 350 ppm.

The water must be treated if it is not between 5 to 25 grains per gallon or above 350 ppm of total dissolved solids. Hardness exceeding 25 grains or 350 ppm can cause non-warrantable premature failure of the heat exchanger. Water with a hardness of less than 5 grains per gallon will usually have a pH which can be aggressive and corrosive causing non- warrantable damage to the pump and associated piping.

CAUTION

No valves shall be placed between the relief valve, heat exchanger, or tank. The relief valve shall be piped to a suitable drain as close as possible to the heater with no reducing couplings or other restrictions. The piping must be sloping away from the heater at all times.

The heater is equipped with 3/4" CPVC (SDR11) pipe and elbow connections. If local codes prohibit the use of CPVC, the CPVC pipe, elbow, and 3/4" NPT adapter can be replaced with a copper equivalent.

Corrosion due to water chemistry generally shows up first in the hot water system because heated water increases the rate of corrosive chemical reactions.

Delta T

If the temperature rise or difference between the HEX IN and HEX OUT is greater than 30°, scaling of the heat exchanger has already begun. A de-liming solution should be used that is acceptable for use with potable water to remove the scale. The local water utility should be consulted for appropriate water treatments.

See the *piping illustrations included in this section, FIG.’s 6-2 thru 6-4 for suggested guidelines in piping the Shield water heater.

	NOTICE	*Please note that these illustrations are
	NOTICE	meant to show system piping concept only,
		meant to show system piping concept only,
		the installer is responsible for all
		equipment and detailing required by local
		codes.

SNA400-125, SNR150-100, SNA285-125, SNR200-100, SNA500-125 specifications

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