The high points of closed-loop systems containing solar fluids must be vented, but
with manual (coin) vents. (Figure 5-15) The vent should be a simple needle valve,
with absolutely no plastic seals, seats, wafers, or other non-metal components.
During installation and maintenance procedures, service personnel can open the
valve to check for air or to let it out. Otherwise, the vent stays closed.
A Manual Air Vent
The high points of draindown and drainback collector loops, and the high point of
storage water loops should use a high-pressure automatic air vent. Confirm that the
vent is capable of handling at least 125 PSI, although 150 PSI is better. Check the
pressure relief valve setting to ensure protection for the vent.
The cap on automatic air vents must not be fully tightened. It is there only to
prevent the entry of dust which would clog the mechanism. The vent must be
The air vent should be constructed of metal. Plastic air vents are not recommended
because catastrophic failure is common.
5.2.3 Dry Rotor Pumps (Lubricated by Oil or Grease).
Before making any repairs on these pumps, follow the procedures in Section 4.3.4
to use an ammeter to determine the most likely problem.
5.2 REPAIR PROCEDURES