Insufficient Tap Water Pressure

- Aug 25, 2019 -

When the tap water pressure is insufficient, the booster pump should be used for boosting. The heating system should generally use a circulating pump to overcome the resistance and improve the cycle power of the system. In practical applications, it is often necessary to use several pumps in series or in parallel. The purpose of the pumps in series is to increase the lift, and the purpose of the parallel use is to increase the flow.

First, the choice of pump

1Select the pump according to the purpose

If you want to increase or stabilize the water pressure of the household, you can choose a small booster pump; if you want to overcome the system resistance and increase the system's circulating power, you should choose a circulating pump.

2Select pump according to pressure and flow

The pressure mentioned here means that the pressure provided by the pump is greater than the total pressure loss of the system. If there is a requirement for the indenter in the construction drawing, the pump must meet this requirement. In addition to considering the pressure, we must also consider the impact of water flow. The greater the water flow, the smaller the useful pressure provided by the pump. Conversely, the greater the pressure, the greater the pressure when the water flow is zero.

In addition to considering the pump diameter and the pipe diameter, the selection of the booster pump should also consider whether the selected power and head can be truly boosted and regulated, and the convenience of use should be considered.

Determine the static head of the water flow when determining the operating voltage, current, head and flow, the size of the bore, and the maximum lift of the pump. If the user asks to pump water to a certain height and maintain a certain amount of water flow, the head required to select the pump must be higher than the specified pumping height. The determination can be made by referring to the head flow graph.

Select the volume and shape requirements (threaded interface, inlet and outlet direction, diameter, etc.).

Determine the working environment (temperature, medium).

Determine functional requirements (time control, motion control, pressure control, flow control, speed control, etc.).

The so-called convenient use means that the water pump has a control function; when the hot water valve is opened, the water pump runs; and when the hot water valve is closed, the water pump stops running, so that the water pump is still running after the valve is closed, thereby damaging the water pump . What kind of booster pump can I choose to solve this problem? That is the automatic booster pump.

The working principle of the automatic booster pump is: the built-in water flow sensor allows the pump power to be turned on by detecting the flow when there is water flowing, and the water wheel rotor decelerates or stops when the water flow becomes smaller or equal to zero, the water pump The power is cut off. Another solution is the external water pressure switch of the booster pump. When the valve is opened, the pressure difference increases, the water pressure switch operates, the power is turned on, and the water pump starts. When the valve is closed, the pressure difference is reduced, and the water pressure is reduced. The switch returns to the position, the power is turned off, and the pump stops. This method of installing the water pressure switch externally is troublesome.

2. Determination of the installation position of the circulating water pump in the open or closed expansion tank system

Install a circulating water pump in a system with an open or closed expansion tank, so that the pump is in the best position to maximize the use of the expansion tank.

1 expansion tank system concept

The expansion water tank in the heating water heating circuit of the heating water heater is connected to the atmosphere, which is called “open expansion water tank system”; the expansion water tank in the heating water circulation path of the heating water heater is isolated from the atmosphere and is called “closed expansion water tank system”.

2 The role of the expansion tank in the water system

The expansion tank is one of the main equipment for the mechanical ring hot water heating system. Its role is mainly the pressure of the constant system, the amount of water in the containment and compensation system, and the role of exhaust. Usually, the expansion tank is connected to the return water main pipe near the suction port of the circulating water pump.

The expansion tank is used in the closed water circulation system to balance the water capacity and pressure, avoiding frequent opening of the safety valve and frequent replenishment of the automatic water supply valve. The expansion tank functions to accommodate the expansion water, and can also function as a water supply tank. The expansion tank is filled with nitrogen gas, and a larger solvent can be obtained to accommodate the amount of expansion water. The high and low pressure expansion tanks can be connected to the voltage stabilization system by using their own pressure. Replenish water.

The expansion water tank is used in the open water circulation system. The installation position has a great influence on the system pressure. The position of the connection point between the expansion water tank and the heating system pipeline is different, which determines the position of the constant pressure point of the system is also different. The pressure at this point is constant regardless of whether the system is working or stopped. The position of the constant pressure point is different, which affects the pressure distribution of the water supply pipe and the user of the heating system. Therefore, the determination of the constant pressure point position plays a decisive role in the mechanical circulating hot water heating system. The installation height of the open expansion tank must exceed the maximum user's water filling height and be connected to the return pipe of the circulating pump suction port.

The hydrostatic pressure of the system is related to the installation height of the expansion tank. As long as the pressure at each point of the system pipeline exceeds the atmospheric pressure, no negative pressure will occur, and the hot water will not be vaporized or the air will be sucked in. In order to prevent vaporization, cavitation noise and bearing damage, the pump suction port must maintain a certain pressure (generally about 30KPa ~ 40KPa). Since the expansion tank is connected to the vicinity of the suction port of the circulating water pump, the minimum installation pressure of the expansion tank can meet the minimum pressure required for the pump suction port when delivering different temperature liquids.

Third, the installation of the booster pump

If the installation site belongs to a higher level of high-rise buildings and the water pressure is low, consider installing a booster pump in the tap water pipeline. When selecting the pump and installing it, consider that the pump interface is consistent with the tap water interface.

1 pump installation position

The booster pump is usually installed behind the water meter at home, that is, the water meter is installed to install the water pump, or it can be installed in front of the water inlet of the gas water heater. When installing in the hot water outlet, choose a hot water pump and the temperature is above 85 °C.

2 pump installation

Remove the short pipe connecting the cold water valve and the water heater inlet, install the booster pump at the right position on the lower right side of the water heater (two self-tapping screws are fixed on the wall), and connect the water pump to the water heater with a metal hose or aluminum plastic pipe. In the chill pipe line; the external water pressure switch is generally connected to the inlet section of the booster pump, and the direction of the arrow should be pointed out according to the instructions. The automatic booster pump does not require an external water pressure switch.

3 pump installation precautions

Before installing the diesel engine water pump, read the installation and operation manual carefully and install it according to the requirements of the manual.

Check the power supply data on the pump nameplate to verify that the pump is suitable for the power supply to be used and that the outlet is reliably grounded.

The connection in the junction box of the pump can only be made when the power supply is switched off.

It is advisable to install the hot water pump on the pipe where the liquid flows upward.

Source: Wall-mounted boiler monthly

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