When purchasing water supply equipment, one of the most common questions customers encounter is: Should they purchase non-negative pressure water supply equipment, or purchase variable frequency constant pressure water supply equipment? The following will introduce to you the difference between variable frequency constant pressure water supply equipment and non-negative pressure water supply equipment.
First of all, you must understand that non-negative pressure water supply equipment and variable frequency constant pressure water supply equipment have the same properties and functions. They both play the role of constant pressure. Microscopically speaking, non-negative pressure water supply equipment also belongs to variable frequency constant pressure water supply. Equipment, variable frequency constant pressure water supply equipment is also a non-negative pressure water supply equipment from a macro perspective.
What is no negative pressure means that the tap water pipe network is not allowed to generate negative pressure. For example, when the tap water pressure of an ordinary water pump is lower than the specified pressure value, the ordinary water pump will continue to pump water, which will produce negative pressure on the tap water pipes.
Why are the properties and functions of non-negative pressure water supply equipment and variable frequency constant pressure water supply equipment macroscopically and microscopically the same? Because non-negative pressure water supply equipment is directly connected to the tap water pipe, and non-negative pressure equipment has a steady flow tank. This steady flow tank has a vacuum suppressor, a pressure detection device, and a water shortage protection device. When the tap water supply fails or is lower than the rated pressure, the equipment will automatically stop the water supply to protect the pipe network, and the two non-negative pressure water supply equipment work It is controlled by a frequency conversion control cabinet to control the number and frequency of working pumps, so as to achieve the effect of constant pressure water supply, so water supply without negative pressure is also constant pressure.
Why is the variable frequency constant pressure water supply equipment also a non-negative pressure water supply equipment? Because the water source of the variable frequency constant pressure water supply equipment is the water tank pool. The tap water first enters the water tank or pool, and then is pressurized twice through the variable frequency constant pressure water supply equipment. Even if the tap water When the water is cut off or the pressure is too low, when there is no water in the water tank or pool, the water level information is detected by the detection device and sent to the frequency converter, which is controlled by the frequency conversion control cabinet. This will not produce negative pressure on the tap water pipe network, so the frequency conversion constant pressure is also non-negative pressure.
So it can be said that non-negative pressure water supply equipment must be variable frequency constant pressure water supply equipment; however, if variable frequency water supply equipment has no measures to prevent negative pressure or does not directly absorb water from the municipal pipe network, it is not non-negative pressure equipment.
1. The difference between the two types of equipment is mainly in the operating principle:
The biggest difference in appearance between variable frequency constant pressure water supply and non-negative pressure water supply is that variable frequency constant pressure water supply requires a large water tank, while non-negative pressure water supply equipment only has a small steady flow tank.
- Frequency conversion constant pressure water supply requires water tank storage. The water supply unit pumps water from the water tank to provide water to users.
- There is no negative pressure water supply equipment and no water tank is required. The water supply system comes with a steady flow tank that can store a small amount of water.
When selecting equipment, the pressure calculation of non-negative pressure equipment must subtract the water pressure of tap water, so the selection head of the water pump is lower. During operation, low area water supply, non-negative pressure equipment can use the pressure of the tap water pipe network to supply water without starting the water pump.
However, no matter what the situation is, the constant voltage frequency conversion equipment needs to start the water pump to supply water. When water is cut off, non-negative pressure equipment will stop water supply. Because there is a water tank to store water, variable frequency constant pressure water supply can effectively provide water for 2 days according to specifications.
2. The usage and operating costs are different
The cost of variable frequency constant pressure water supply equipment is lower than that of non-negative pressure water supply equipment, but the subsequent maintenance costs of variable frequency constant pressure equipment, such as cleaning water tanks, are high.
From a usage perspective, there are several differences:
- Health aspects. Frequency conversion water supply equipment first needs to inject municipal water into the water tank for storage and then pump it out through the water pump, which causes secondary pollution; while non-negative pressure water supply equipment is directly connected to the municipal pipe network, completely isolated from the external environment, and there is no secondary pollution.
- Energy saving. Frequency conversion water supply completely wastes the pressure of the municipal pipe network. The non-negative pressure water supply is directly connected to the municipal pipeline, and the original pressure of the municipal pipe network is used to pressurize the water supply.
- Covered area. Frequency conversion water supply equipment requires water tanks to be configured according to the number of users, occupying a large area, while non-negative pressure water supply equipment is highly integrated and saves land.
3. Differences in pipe network stability
Both types of equipment have their own advantages and disadvantages in terms of stability of use. In two cases, the first case is when the municipal pipe network shuts down water. Users using variable frequency water supply equipment can continue to use the water in the water tank without negative pressure. Users of water supply equipment will have no water available. The second situation is a power outage. If there is a power outage, users using variable frequency water supply equipment will have no water available, while users using non-negative pressure water supply equipment can rely on the original pressure of the municipal pipe network. The water supply for low-floor users is not affected. Influenced.
Conclusion
When the pressure of the municipal water supply network is stable and the water volume is sufficient: non-negative pressure variable frequency water supply can give full play to its advantages, and its energy-saving effect is better than ordinary variable frequency constant pressure water supply; the cost of equipment is also lower than ordinary variable frequency constant pressure water supply.
When the municipal water supply pressure is unstable and the water volume is insufficient: non-negative pressure variable frequency water supply equipment needs to add a water tank as a backup water source, and the equipment cost is already higher than ordinary variable frequency constant pressure water supply equipment; the energy saving effect will not be obvious.