How does a vacuum switch work? (Passage and benefits)
Content
Like most homeowners, you probably don't know how a vacuum circuit breaker works. Here is a brief overview of what it does and how it does it.
The vacuum interrupter works like a normal check valve. Air from outside can enter the system through the air intake. But the vacuum interrupter shuts off tightly when water or steam tries to escape.
I'll go into more detail below.
How do you use a vacuum switch?
The following example shows how to properly use a vacuum breaker in a steam system and why you need one.
Think about how it is transmitted:
We have steam from the boiler at 10 psi or a little more. Then comes the control valve, which goes through the pipe to the top of the heat exchanger.
We have a condensation line that leads to a steam trap. The water passes through a check valve into our atmospheric condensate return system.
So, if the control valve is fully open, there is a small pressure difference between the valve and the heat exchanger. But we will see that there is still enough pressure drop here to push the condensate through the primary trap, and everything works fine.
As the product inside the heat exchanger starts to heat up, our control valve will modulate down so you can see the pressure start to drop.
In addition, there will be less pressure on the condensate lines. If the condensate pressure has to be higher to push the condensate through the trap, or if there is more modulation in the control valve, which can cause backflow to the heat exchanger, or worse, create a vacuum, problems will arise.
This can cause line temperature control problems, water hammer, chances of freezing or corrosion of our system over time, so this problem needs to be addressed with a vacuum interrupter.
Suppose we put a vacuum interrupter in front of the heat exchanger and open this valve. In this case, you will hear air from outside entering the vacuum breaker and you will be able to watch the gauge go from vacuum pressure to zero, which means there is no pressure in the system.
We can always stay below zero, even if we have positive pressure, or drop to zero. Now, if we place our trap 14-18 inches below our heat exchanger, we can always provide positive pressure. If the vacuum interrupter is installed correctly, we will have good drainage.
What does a vacuum switch do?
So, to sum up the pros, here are the top 4 reasons why you should have a vacuum interrupter in your system:
- This helps ensure that all condensate is drained in both on-off and modulating mode.
- This will protect you from water hammer.
- This makes the temperature more stable and less likely to change.
- This will help prevent food spoilage.
How does a vacuum switch work?
Typically, a vacuum interrupter has a plastic disc that is pushed out by the pressure of the water supply and closes small vents. If the supply pressure drops, the disc springs back, opening the air inlets and preventing the water from flowing back.
The ventilated chamber opens when the air pressure exceeds the water pressure. This interrupts the low pressure suction and prevents the water from flowing back. Before water reaches the sprinkler valves, a vacuum switch is installed near the water source.
You should place it above the highest point in the system, usually above the sprinkler head, which is the highest or highest slope in the yard.
Why do you need a vacuum switch?
Contamination of the water supply can have many different consequences, so its prevention is important. Most local building codes state that all plumbing systems need a backflow prevention device.
Because most homes have only one water supply for drinking water and other uses, including irrigation, there is always the potential for contamination through cross connections.
A return can occur if the water pressure in the main water supply of the house drops sharply. For example, if the city water supply fails for any reason, this can result in low pressure in the house's main plumbing.
With negative pressure, water can flow through the pipes in the opposite direction. This is called siphoning. Although this does not happen very often, it can cause water from the sprinkler lines to enter the main water supply. From there, it can enter your home's plumbing.
What are the types of vacuum circuit breakers and how do they work?
There are many different types of vacuum interrupters. Atmospheric and pressure vacuum interrupters are the most common.
Atmospheric Vacuum Breakers
The Atmospheric Vacuum Breaker (AVB) is a backflow prevention device that uses a vent and check valve to prevent non-potable liquids from being sucked back into the potable water supply. This is called back siphoning, caused by negative pressure in the supply pipes.
Pressure Vacuum Breakers
The Pressure Vacuum Breaker (PVB) is an integral part of irrigation systems. It prevents water from flowing back from your irrigation system to your home's fresh water source, which is your drinking water.
The pressure vacuum breaker consists of a check device or check valve and an air intake that releases air to the atmosphere (outdoors). Typically, a check valve is designed to let water through but close the air inlet.
F.A.Q.
Why is a vacuum switch important?
The vacuum breaker is important because it keeps the water from flowing back. Reverse flow can make your irrigation and plumbing system less efficient, allowing water and runoff to flow backward instead of forward. This can introduce harmful bacteria into your pipes and fittings. Therefore, the vacuum interrupter is an important part of pollution prevention.
How does a vacuum switch prevent reverse flow?
The vacuum interrupter stops the reverse flow by forcing air into the system, which creates a pressure difference. Most likely, the water will move towards the injected air. If the water were flowing in the opposite direction, there would be no difference in pressure, so the air forced into the pipes would be pushed past the water molecules.
What are the code requirements for vacuum circuit breakers?
A vacuum switch is essential in any place where water is used for more than just drinking. State and federal laws state that vacuum breakers must be installed in outdoor faucets, commercial dishwashers, squeegee faucets, and hose mixers for spraying dishes.
Take a look at some of our articles below.
- How to test a purge valve without a vacuum pump
- What size switch is needed for a dishwasher
- How to Stop Water Hammer in a Sprinkler System
