AERCO SWDW68 U-Tube Double-Wall Heaters w/ECS - Manual (Page 71)

HE-
111 − CORRECTIVE MAINTENANCE
Rev B Mar 2013
8-17
3. IN THE FOLLOWING ORDER, close the stop valves in the:
a. Hot Water Output line
b. Recirculation line
c. Cold Water Input line
When the heat exchange has been shut down according to steps 1 and 2, drain the heat exchanger as
follows:
4. CAREFULLY open the relief valve in the heat exchanger upper head assembly to relieve pressure in
the heat exchanger shell. If fluid continues to flow from the relief valve, one of the cold water stop
valves is either leaking or is not shut tightly. Stop the flow from the relief valve and proceed.
5. Holding the relief valve open (to prevent creating a vacuum in the shell), open the plugged drain at
the bottom of the Heater Shell and drain the heat exchanger completely.
6. Disconnect the power leads from the recirculation pump.
7. Remove the bolts on the recirculation pump flanges and slide the pump out from between the flanges.
8. When installing the replacement recirculation pump, ensure that the seals are in place and not
pinched.
9. Reinstall the flange bolts and reconnect the power leads to the pump.
10. Refill the heat exchanger and put it back into operation in accordance with section 5.3, steps 1
through 14.
8.3 ELECTRONIC CONTROL SYSTEM
The corrective maintenance procedures for the ECS consist of replacing the Control Box components and
subassemblies that were identified as being faulty following the procedures listed in Chapter 7
Troubleshooting. The ECS replaceable items include the:
• Control Box Assembly (8.3.1)
• Temperature Controller (8.3.2)
• Over-temperature Switch (8.3.3)
• DC Power Supply (8.3.4)
• DC Voltage Regulator (8.3.5)
WARNING
BE SURE TO TURN OFF THE CONTROL BOX POWER SWITCH (see Figure 8-7) AND
DISCONNECT AC POWER BEFORE PERFORMING ANY CORRECTIVE
MAINTENANCE PROCEDURES LISTED IN THIS SECTION. FAILURE TO OBSERVE
THIS WARNING CAN RESULT IN SERIOUS PERSONAL INJURY.
8.3.1 Replacing the Control Box Assembly
If necessary, replace the complete Control Box assembly as follows:
1. Referring to Figure 8-8, loosen the captive screws on the Control Box door and the recessed panel.