Must the backwater valve be closed when heating and emptying?

I don't think it is necessary to close the return valve when the radiator deflates. My understanding is that there will be air in the backwater and it needs to be discharged. Of course, some people say that they should close the backwater valve to exhaust. Next, I will talk about my understanding of them.

Open the wall-hung boiler, operate the heating system and exhaust air directly.

This method is the one I use the most. I will first raise the system pressure to about 2.2pa, and then run the heating function of the wall-hung boiler. In about 10 minutes, I will start to exhaust.

1. Touch and sense the surface temperature of all radiators by hand.

2. Find the radiator with uneven heat and cold, and unscrew the exhaust valve at the upper side with a screwdriver. Usually, the position of the exhaust valve must be on the other side of the radiator switch and at a high place. At this time, there will be a sound of air coming out of the exhaust valve.

3. For a long radiator, the exhaust valve side of the radiator can be raised appropriately to make the exhaust valve at the height of the system. At this time, you will obviously feel the air flow.

4. For some radiators with higher height, such as 1.8 m and 1 m, you can beat the radiator with your hands or shake it properly when exhausting, and you will feel that the air will come out of the exhaust port one by one.

5. In the surface-mounted radiator, a certain group is not hot, and its water supply end temperature is relatively cold, indicating that the hot water in the previous section has not come yet, and it is likely that there is gas in the pipeline, just like the radiator, and all the cold water in the radiator should be discharged until it is all hot water.

After each group of radiators repeatedly exhausts until the heat is uniform, it means that the exhaust is successful. When exhausting, pay attention to the system pressure to make up the pressure.

Run the heating system, close the return valves respectively, and then exhaust.

In this operation, in the self-heating system, each group of exhaust backwater valves can be closed, and the main backwater valve cannot be closed before the exhaust of the wall-hung boiler is operated. Otherwise, the system will be directly ultra-high temperature protected or will not work because there is no backwater entering.

1, run the wall-hung boiler, increase the pressure to 2.2pa, and start to touch the radiator at a high place or find that the radiator is unevenly heated.

2. Open the exhaust valve and close the reflux valve of the radiator. At this time, the exhaust valve is equivalent to the return valve, and any air will be discharged directly from here.

3, after the completion of the exhaust, open the backwater valve here, into the next group of radiator operation.

I think this method is not suitable for self-heating system, but it is very suitable for central heating; Because our self-heating is a small closed system, the air inside can be understood as fixed, and the pressure of the whole system will be lost quickly after the radiator is exhausted, so we will add tap water and there will be air in the water; So I want to circulate the heating water and exhaust the air in the system repeatedly.

Why is the indoor backwater valve closed under the central heating system? I think it's because under this system, if the indoor system is not disconnected from the outdoor, it will form a big cycle and it will be more difficult to exhaust. We only need to discharge the indoor air in stages, and the outdoor air can be discharged automatically or manually.

In practical work, my exhaust method

At work, we often meet 4-8 groups of radiators as a system. In this way, I directly intervene in the exhaust of the system, and then pay attention to replenishing water to maintain the pressure of the system, so that repeated exhaust can be completed in 30 minutes.

When there are more than eight groups of two-layer or three-layer radiator systems, I will disconnect the exhaust of each layer (that is, close the return valve). Of course, at this time, I will exhaust air downward from the top floor. In the same way, I must replenish water while exhausting to maintain the system pressure and repeat the exhaust operation.

In addition, I often use this method-no matter how many layers the radiator is, first find out which radiator has problems, then turn off all the radiators in front of it, then only exhaust, and finally open all the radiator valves.