Revision 11 reflects the following changes:
Obsolete models 181, 261, 331 and 401 removed from text, figures and table throughout. Text added to "General Specifications" on
page 4. Dimension table moved to page 5. Figures 1 and 2 revised on page 5. "Venting" text revised on page 7. Figure 4 revised on
page 8. "Start Up Procedures" point 1 text revised on page 12. Figure in "Illustrated Parts List" revised on page 14.
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