U.S. Boiler Company MPO - IQ, Service Instructions Manual

Page: 15 / 92

15
Figure 5: Return Injector Piping and Relief Valve
Assembly Details
II. PACKAGED BOILER ASSEMBLY - TRIM & CONTROLS (cont'd)
Figure 4D: Burner Swing Door Insulation
1. Install return injector piping and relief valve, refer to
Figure 5.
Step a.
Locate the return pipe fittings and injector. Apply
sealant to the 2” NPT injector threads. Insert injector
into 2” NPT upper rear tapping on rear section. Thread
2” NPT x 1-1/2” Reducing Elbow onto 2” NPT injector.
Apply thread sealant to the 1-1/2” NPT nipple. Thread
1-1/2” NPT nipple into 1-1/2” NPT end of reducing
elbow. Thread 1-1/2” NPT x 1-1/2” NPT x 3/4” NPT
Tee onto 1-1/2” NPT nipple. Tighten pipe fittings until
relief valve orientation is correct for your installation
and joints are watertight.
Note: Based on system return piping and access to service
boiler, see Figures 1, 13A and 13B, predetermine if
injector piping orientation is to be positioned for
vertical, horizontal left or horizontal right side return
piping as shown in Figure 5.
Step b. Install relief valve using 3/4" NPT tapping on tee.
Relief valve must be installed in vertical position. If
orientation of return injector piping is for:
• 1-1/2" NPT vertical return piping - Install
3/4" NPT x 90° street ell (not furnished)
into 3/4” NPT tapping on tee. Install relief
valve vertically into street ell. See Figure 5.