M a i l Bag
Using Figure 6 we see that an oil valve will make a burner
get closer to its ability to run at True Zero Smoke also happens
during start-up and shut-down. By taking it further and mating that oil valve to a control that will accurately guarantee a
purge on start-up we allow the air currents (draft) to establish
themselves and prepare the combustion area, heat exchanger
and venting system to also be ready to accept our burner
operation at True Zero Smoke. Purges also lead to cleanliness
and keeping today's heat exchangers is not only as critical as
it has always been for efficiency, but also more difficult due to
the fuel make-up and quality issues.
Although most reading this will probably agree that a prepurge, no matter how short, does lead to overall better burner
operation I must admit that post-purges may not be necessary
everywhere. The key, as always, is draft. My experience is that
a small post-purge will always provide some benefit, but not
as necessary as a pre-purge. However, when you have venting problems or a restricted heat exchanger, the post-purge
becomes a MUST!
Venting problems are simply that and may include a
restricted heat exchanger. The advent of triple-pass boilers
is a great thing, but they do what they were designed to do,
slow flue gas down and retain the heat in the boiler. Couple
that with the reduced ability to make thermal draft with
lower stack temperatures and the post-purge now not only
can help with the cleanliness of the burner shut-down, but
also can help with heat exchanger cleanliness, the post-purge
does its job.
With today's burners achieving True Zero Smoke is easily
done during operation. Prolonging the life of ignition systems
and reducing NOX emissions is quickly achieved using an
interrupted control and by adding purges better start-up,
operation and shut downs leading to cleaner heat exchangers
is a matter of simply choosing a state-of-the-art top quality
control, setting the purges and done! Now if we could only do
something about the fuel. l F O N
See ya.
George Lanthier is the owner of Firedragon Academy, a teaching, publishing and consulting firm. He
is the author of over 40 books and manuals on gas and oil heating and HVAC subjects and can be
reached at 608 Moose Hill Road, Leicester, MA 01524. His phone is 508-421-3490, fax at 508-4213477 and his website can be found at www.FiredragonEnt.com
www.fueloilnews.com | FUEL OIL NEWS | April 2013
23
