Raypak 399B-2339B Cold Water Operation, Models 399B-899B Models 989B-2339B, Cold Water Starts

Models 399B–899B

Models 989B–2339B

Fig. 9: Torque Sequence

the hydrostatic test before connecting gas piping or electrical supply.

Leaks must be repaired at once to prevent damage to the heater. NEVER use petroleum-based stop-leak compounds.

To perform hydrostatic test:

1.Connect fill water supply. With bleed valve open, fill heater with water. When water flows from bleed valve, shut off water. Close bleed valve. Carefully fill the rest of the system, making sure to eliminate any entrapped air by using high-point vents. Close feed valve. Test at standard operating pressure for at least 24 hours.

2.Make sure constant gauge pressure has been maintained throughout test.

3.Check for leaks. Repair if found.

Cold Water Operation

CAUTION: Damaging internal condensation may occur if the heater inlet water temperature does not exceed 105ºF (41ºC) within 7 minutes of start-up.

A heater operated with an inlet temperature of less than 105ºF (41ºC) must have a manual bypass or an approved low-temperature operation system to pre- vent problems with condensation. A manual bypass, shown in Fig. 15, must be piped into the system at the time of installation. This piping is like a pri- mary/secondary boiler installation with a bypass acting as the secondary boiler piping. Raypak strongly rec- ommends that thermometer(s) be placed into the heater piping next to the in/out header to facilitate tem- perature adjustment. Inlet water temperatures below 105ºF (41ºC) can excessively cool the products of combustion, resulting in condensation on the heat exchanger and in the flue.

Failure to exceed 105ºF (41ºC) within 7 minutes may result in the premature failure of the hot surface ignit- er, remote flame sensor, burners and heat exchanger. It can cause operational problems, bad combustion, sooting, flue gas spillage and reduced service life of the vent system. The bypass allows part of the heater discharge water to be mixed with the cooler heater return water to increase the heater inlet temperature above 105ºF (41ºC). This precautionary measure should prevent the products of combustion from con- densing in most installations. Warranty claims will be denied when condensation occurs.

Cold water operation issues are applicable to both cold water start and cold water run applications. Cold water operation for 7 minutes or less on start-up is acceptable. Where cold water starts will last longer than 7 minutes or where cold water operation is con- tinuous, provisions must be made to mix higher temperature outlet water with the colder inlet water and thereby raise the inlet temperature to at least 105ºF (41ºC) within the 7-minute time limit.

Cold Water Starts

Frequent (more than once a week) cold water starts, wherein the inlet water temperature remains below 105ºF (41ºC) for more than 7 minutes, must have cold water start protection. Known protection methods con- sist of mixing heated outlet water with the inlet water with a bypass to raise the inlet to 105ºF (41ºC) or high- er. Once the system is heated up and has return water temperatures of 105ºF (41ºC) or higher, the mixing of outlet water with inlet water is no longer needed and the bypass can be shut off. If the bypass is not shut off

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