1. According to your description, it is normal that there are a lot of unstable gases in the early stage of temperature rise. This will not happen during normal operation and heating. (Because the heating is not particularly stable during the warm-up test, the temperature of water in the system is high and low, and it is easy to produce a lot of gas. The exhaust volume of automatic exhaust valve is limited, and it will definitely be concentrated at other relatively high points, so the situation you mentioned will appear. )
If this happens in normal heating, then I can tell you for sure that the automatic exhaust valve on the main road is broken.
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