Why does the lag alarm on my vacuum system come on even though Im confident the system is not too small?
First, there may be numerous reasons why this is so (artificial leak in the system, motor starter not engaging, etc) but a common cause is the improper setting of the vacuum switches. Via shipping or the normal shake of a system, the switch settings may deviate from their factory settings. If the low switch setting (switch closes) of switch #2 is set at or above the low point of switch #1, the lag vacuum pump will start, sounding off the lag alarm. (the same will be true for triplex system…if the low point of switch #3 is set at or above the low point of switch #2) Consult the manufacturers switch settings and make sure the high and low set points of all switches are correct. The second most common reason for an inadvertent lag alarm is a blown control relay. If the relay that opens and closes the vacuum switch contacts for the lead pump is blown, the 1st pump will not start…necessitating the starting of the 2nd pump and the lag alarm will sound. (triplex and quadraplex systems can
