In exhaust heating plants the condensation is returned to the boilers by means of some form of return pump. A combined pump and receiver of the form illustrated in Fig. 59 is generally used. This consists of a cast or wrought iron tank mounted on a base in connection with a boiler feed pump. Inside of the tank is a ball float connected by means of levers with a valve in the steam pipe which is connected with the pump. When the water line in the tank rises above a certain level, the float is raised and opens the steam valve which starts the pump. When the water is lowered to its normal level the valve closes and the pump stops. By this arrangement a constant water line is maintained in the receiver and the pump runs only as needed to care for the condensation as it returns from the heating system. If dry returns are used they may be brought together and connected with the top of the receiver. If it is desired to seal the horizontal runs, as is usually the case, the receiver may be raised to a height sufficient to give the required elevation and the returns connected near the bottom below the water line.

A "balance pipe," so called should connect the heating main with the top of the tank for equalizing the pressure, otherwise the steam above the water would condense and the vacuum thus formed would draw all the water into the tank leaving the returns practically empty and thus destroying the condition sought. Sometimes an independent regulator or pump governor is used in place of a receiver. One type is shown in Fig. 60. The return main is connected at the upper opening and the pump suction with the lower. A float inside the chamber operates the steam valve shown at the top and the pump works automatically as in the case just described.

Automatic Return Pumps 1000139

Fig. 58.

Automatic Return Pumps 1000140

Fig. 59.

If it is desired to raise the water line the regulator may be elevated to the desired height and connections made as shown in Fig. 61.