A. The partial vacuum in the front end; when excessive it indicates
dampers closed, fire clinkered or insufficient opening for the admission
of air under the fire.
47. Q. If upon opening the fire-box door you discover there what is
commonly called a red fire, what might be the cause?
A. The grates may have become clogged with ashes or clinkers so that
sufficient air could not pass through them to the fire.
48. Q. Is it not a waste of fuel to open the fire-box door to prevent
pops from opening? How can this be prevented more economically?
A. Yes. This can usually be prevented by putting the heater into the
tank, or putting on the injector, or by more careful firing.