| 摘要 |
A vacuum relief unit and method for venting air into a pool pumping system when a pressure level within the system drops below a first pressure level limit. The unit includes a closed air chamber, a device for venting chamber air from the air chamber into the pool pumping system when the pressure level in the pool pumping system drops below the first pressure level limit, a device for venting atmospheric air into the air chamber when the pressure level within the air chamber drops below a second pressure level limit that is lower than the first pressure level limit, and a device for delaying operation of the atmospheric air venting device when the pressure within the air chamber is no longer below the second pressure level limit.
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