By design, these systems are divided into two groups: flowing, and with bypasses. Each of them can be vertical or horizontal (see Figure 20).
In the flowing one-piped systems, the water heated in the boiler rises up along the main vertical pipe into the horizontal supply pipeline, from which it goes to the vertical pipelines. From the vertical pipelines, the water goes not to the individual devices but first it goes into the devices of the upper floor. The water which has been somewhat cooled from the devices on the upper floor goes through the same vertical pipeline to the devices on the lower floors. Thus the water sequentially goes through all the devices which are located on the same vertical pipeline. Having gone through all the devices on the vertical pipelines, the cooled water is collected in the return horizontal pipeline from which the pump forces it into the boiler. In the flowing one-piped systems, in rooms with equal heat loss, the devices of the lower floors must have larger surfaces for heating than the devices on the upper floors.
The expansion tank, as in the two-piped heating systems, is installed on the return pipeline before the pump. The air from the system is removed through the air collector. The warmth output of the heating devices in the flowing scheme (without bypasses) can be regulated only by closing Mayevsky valves.
In one-piped vertical heating systems with shifted bypasses, the hot water from the boiler going through the main vertical pipeline and supply horizontal pipeline goes into the vertical pipelines. In the places where the heating devices are connected to the vertical pipeline, the flow of water is divided: some water continues along the vertical pipeline through bypasses, and some water goes into the heating devices.
The water which has been cooled in the heating device of the upper floor leaves it and mixes with hotter water which went through the bypass. The mixed water goes on the vertical line to the heating device of the lower floor where the flow of water is divided again — i.e. some water goes into the device and some goes through another bypass. Such motion of water repeats on each floor as the warmth carrier moves through the system.
In this scheme of heating, in each lower situated device on the path of the warmth carrier, the water goes with lower temperature. Thus the last heating devices must be more powerful (larger in size and number of sections).
The warmth output of the heating devices in such systems is regulated by turning a three-way valve. Due to these fittings, some of the warmth carrier goes to the radiator and some goes through a bypass and doesn’t get cooler. In fact, the bypass can be turned off — all the water goes through the device; or the device is turned off — all the water goes through the bypass. In the intermediary position of the valve, some water will go through the device and some through the bypass.
One-piped heating systems, compared with two-piped systems have the following advantages: less length of the system; and simpler pipe connections, which simplify the preparation and installation of the system.
Depending on the direction of the motion of the warmth carrier in the horizontal pipelines, the heating system can be «dead end» or «continuing flow» of motion of water. We looked at these schemes in the section on gravity systems. In pumped systems, it is the same. The difference is that on the main vertical pipelines (return or supply) circulating pumps are installed, and air removal must be done through automatic, semi-automatic or manual devices.
The boiler in pumped systems can be located in any place of the heating contour: in the basement, on the floor, or in the attic, but the most traditional place is in a «technical room» which is located in the basement in most cases.
