Instructions

Troubleshooting
Under normal operating conditions the Caleffi 521 series thermostatic mixing valve will provide
a very high level of performance. However, in some circumstances, where our maintenance
plan is not followed, the following problems may arise.
Symptom
Hot water at the cold taps
Fluctuating mixed water
temperature
Erratic flow of water from
the valve
No flow of water from the
valve
Cause
a) Operation of check valve
is hindered;
check valve is not
sealing correctly.
b) Check valves not fitted.
a) Erratic supply
temperatures at the
inlets of the valve.
b) Starvation of the water
supplies at the inlets
of the valve.
c) Incorrect commissioning
of the valve.
a) Insufficient water
supplies.
b) Fluctuations in supply
pressures/temperatures.
c) Adverse effect created
by other draw off points
on the system.
a) In-line filters blocked.
b) Insufficient supply
pressures.
c) Debris obstructing valve
operation.
Corrective action
· Replace faulty check
valves
· Restore inlet conditions
within the limits of the
valve.
· Stabilise inlet supply
conditions.
· Clean filters.
· Restore inlet supplies.
· Clean debris or scale
from valve.
1/2 inch 3/4 inch 1 inch
Item Description
Item Qty NPT Sweat NPT Sweat NPT Sweat
per Valve
521400A, AC 521409A, AC 521500A,AC 521509A,AC 521600A,AC 521609A,AC
521519A,AC 521619A,AC
Union Washer 3 R50055
Union Nut 1" 3 R61008
Male Tailpieces 3 R31981 NA10002 31901A NA10003 59817A* 59834A*
(2 only-'519') (2 only-'619')
Inlet Male Tailpiece
with Check Valve- 2 59893A 59904A 59840A 59905A 59894A 59906A
"AC" Models only
Outlet Tailpiece-
1 R31981 NA10002 31901A NA10003 59817A* 59834A*
"AC" Models only
Outlet Adapter with
1 ---- ---- ---- NA10056 ---- NA10058
temperature gage
*Tailpiece fitting with integral union nut. 1" NPT and Sweat models require only 2 separate 1" union nuts (R61008)