PVI Industries U-TUBE SINGLE-WALL PV500-34 - Manual (Page 7)

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PV500-34 05/03 7 Section 34
STEAM WITH SINGLE-WALL / DOUBLE-WALL (con't)
b. Cause: Steam valve(s) not fully opening
Solution: Check steam pressure before and after steam valve. The pressure drop should not
be more than half of the inlet pressure. Check valve for blockage. Check linkage for adjustment.
Check modulating signal (if applicable). Check the supplied voltage to the valve coil.
c. Cause: Piping flow restricted.
Solution: Calculate the flow velocity and expected friction loss. If excessive, larger inlet and
outlet piping are necessary.
d. Cause: Main valve malfunction.
Solution: Refer to the valve manual for instructions on main valve repair.
e. Cause: Main valve undersized.
Solution: Check steam pressure before and after steam valve. Check valve capacity against
the load. If insufficient, increase trim or valve size.
Problem:
4. Outlet water temperature not constant.
a. Cause: Insufficient recovery
Solution: If the thermostat or controller is always open, then the outlet temperature will vary
with load. See above for causes of insufficient recovery.
b. Cause: Malfunctioning thermostat
Solution: Measure the tank temperature near the thermostat and compare to setpoint. The
thermostat should turn on and off within 5°F of setpoint.
Problem:
5. Unusual noises coming from heater.
a. Cause: Flashing condensate
Solution: Pinging, rattling or banging noises are usually the result of condensate flashing to
steam. Condensate not draining properly. Check that there is not excessive condensate lift.
Check the sizing of the trap. Check that the condensate receiver is not pressurized. Check that
there is no blockage in the condensate line from the trap to the receiver. Unclog any strainers in
the system.
Problem:
6. Heat exchanger visibly leaking.
a. Cause: Plumbing connection loose
Solution: Check and tighten plumbing connection.
b. Cause: Double-wall heat exchanger tube leak
Solution: If one of the tube walls is breached, a double-wall heat exchanger will leak at the
joint between the tubesheets. Isolate the heater and replace the heat exchanger.
Since PVI cannot control the use of the water heater, water conditions, or maintenance, the
warranty on the water heater does not cover poor performance, structural failure,
or leaking due to an excessive accumulation of scale.