Rear Refractory Replacement - Watts AERCO Benchmark BMK750 Operation And Service Manual

Benchmark with Edge [I]: Operation-Maintenance Manual
SECTION 8 – MAINTENANCE

Rear Refractory Replacement

8.10.1
Rear Refractory Replacement Instructions
1. Turn off gas and electrical power to the unit. In addition, turn off any other units sharing the
exhaust flue.
2. Disconnect the flue from the exhaust manifold of the boiler being serviced and remove flue
sections up to the top of the unit enclosure.
3. Remove the small O
Eductor assembly is clipped to the bottom edge of this opening. Lift the Air Eductor assembly
up off the left-rear panel, then secure it in place with a length of cord or wire. DO NOT
REMOVE THE LEFT-REAR PANEL without first securing the Air Eductor assembly in place.
NOTE:
At the top, the left and right-rear panels are attached to the left and right top rails by nuts. At
the bottom, each rear panel is attached to the base with one nut each. Access the nuts for
removal through the side panel, as shown in Figure 8-8.
4. Remove the left-rear panel, which is held in place by 2 spring latches and 7/16" bolts, inside
the panel on the top rail and bottom lip. See Figure 8-8, below.
5. With the panels removed, the rear plate of the combustion chamber can be accessed, as
shown in Figure 8-9, below.
CAUTION!
The surfaces of the heat exchanger may be hot. Allow the unit to cool sufficiently before
proceeding to the next step.
6. Remove the O
2
7. Disconnect the wires from the thermal switch on the rear plate.
8. Remove all of the nuts from the rear plate, EXCEPT for the one at the top of the plate.
9. Loosen (but DO NOT REMOVE) the top nut and slide a thin metal object (such as a hacksaw
blade) between the rear plate and the fiber material of the rear refractory to separate the
material from the plate.
CAUTION!
The rear plate weighs approximately 40 pounds. It is therefore recommended that 2 people
remove the plate.
10. Remove the top nut from the plate and remove it from the unit.
11. Optionally, you can thread 2 small nipples into the rear plate to act as handles, which will
ease removal and reinstallation.
OMM-0145_A99 • GF-218 •
Sensor Cover from the rear sheet metal enclosure panel. The Air
2
sensor and the 1/4" stainless steel tube from the rear plate.
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9/18/2019 Page 136 of 157