Rinnai Q series, Troubleshooting Manual

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008082013GW
Check the installation for the presence of air.
If there is a secondary pump installed and it
is not hydraulically separated, it could cause
a loss of pressure difference.
Check to ensure the pump is functioning and/or water
pressure sensor is working properly.
Ensure water pressure sensor is not clogged or defective.
Inspect water filter for debris.
Check pump for proper operation and flow rates.
Check for proper wiring of pump.
Check for use of balancing valves.
AIR: if boiler, inner boiler piping, or Low Loss
Header has a large air bubble in it the
pressure sensor will not see the pressure
spike that the pump generates when it starts.
The pressure spike is what tells the MCBA that
the pump has started.
The air bubble will absorb that spike. Bleed all
air from the system.
If an additional expansion tank is placed in the
system alongside an E-boiler that tank can
absorb the pump pressure spike as well. You
may need to isolate that tank to see if this
corrects the issue with BL 85.
An expansion that is not charged properly can
cause the pump’s pressure spike not to be
seen by the sensor causing a BL85.
Expansion tank pressure should be air charged
to match whatever water fill pressure that is
chosen for the closed loop. (Always above
14.5 psi)
Expansion tanks must be air charged only
when there is no water pressure on the wet
side of the diaphragm or the tank is removed
from the system. Once charged to the correct
air pressure it may be placed into the system
and the water fill pressure now may be set to
match the new tank pressure.