PB Heat WV Series - Manual (Page 5)

3
C. CHIMNEY / VENT AND DRAFT CONTROL
1. Draft Requirement – Minimum draft required in the
vent system is -.03" to -.06" W.C. depending on
boiler model, see Table 7.1 (Section 7). This draft is
necessary to provide the necessary draft over fire of
-.01" to -.02" W.C. See discussion in paragraph 5
below regarding draft.
2. A barometric draft control is recommended for
regulation of overfire draft. Follow manufacturer's
instructions to locate and adjust the control.
3. Inspect the existing chimney or vent system. Make
sure it is in good condition. Inspect chimney liner
and repair or replace if necessary.
4. The vent system and installation must be in
accordance with the current edition of the American
National Standard ANSI/NFPA 211, "Chimneys,
Fireplaces, Vents, and Solid Fuel Burning
Appliances," or applicable provisions of the local
building codes. Typical minimum chimney size is
8" x 8", 15 feet high, unless otherwise allowed by
code. If the vent system is not sized properly, the
burner may not operate properly. This can cause
poor combustion, sooting and odors to occur.
5. Background Information Regarding Draft:
Modern boilers operate with higher efficiencies than
older boilers. Smaller flueways, as well as bars, pins
and fins are designed into modern boilers to transfer
as much heat as possible from the hot gases to the
water or steam and prevent heat loss up the
chimney. However, these design features result in
higher pressure, or draft loss, in the boiler.
This draft loss must be taken into account when
installing an oil boiler into a new or old chimney.
New chimneys are less likely to have poor draft.
However, they must have sufficient draft to support
combustion. A -.06" draft is desirable and preferred.
Older chimneys may require a replacement liner to
have them perform well enough to support
combustion.
For Example:
The above readings are "cold" readings (before the
boiler and chimney are heated up).
Note also that the higher the firing rate on a unit
which has multiple firing rates, the higher the draft
required. For example, increasing the firing rate 1/4
gallon may increase the draft loss in a unit by
approximately +.01".
D. INSTALLATION SURVEY
For new and existing installations, a Water Installation
Survey or a Steam Installation Survey is available from
P.B. Heat, LLC. The surveys will provide information on
how the boiler works with your specific system and will
provide an overview of boiler system operation in
general.
You can also use this survey to locate system problems
which will have to be corrected. To obtain copies of
these Surveys, contact your PB Heat representative or
download it from PeerlessBoilers.com.
E. PLANNING THE LAYOUT
Prepare sketches and notes of the layout of the
installation. Include boiler location, venting system,
existing piping and wiring. Show existing equipment that
may interfere with installation of new equipment.
PREINSTALLATION
Old
Installation
New
Installation
Comments
Chimney
Draft
-.04" -.04"
No change, but older
chimneys (especially unlined
ones) have leaks which
reduce draft.
Boiler
Design
Pressure
Drop
+.01" +.04"
Required for mandated
efficiency increases.
Draft
Over Fire
-.03" 0.00"
The old installation would
have had a higher
temperature in the chimney
[as high as 800 degrees vs.
400 degrees F], which would
increase the draft.
An oil-fired unit shall be connected
to a flue having sufficient draft at all
times, to assure safe proper
operation of the unit.
CAUTION