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POWER
VT®WATER
HEATER
GAS BURNER START-UP (con't)
While firing, check the gas pressure at the inlet of
the gas train. The minimum supply pressure
requirement on the Power VT water heatet is 4.5"
W. C. supply flow pressure unless otherwise
specified on the data plate. It shou/o be a
minimum of that shown above with the water
heater running at high fire. This is recoi'ded as
inlet flow pressure. It is important ihcoming
pressure does not fall below this minimum or
nuisance control lockouts could occur.
This section is for two-stage firing only: After
adjusting the high fire manifold gas pressL:re, it is
now important to check the operation of
t~e
first
stage (low fire). There is a toggle switch on the
control cabinet labeled "Auto/Low Fire",Switch
from the auto position to low fire and the main
valve will de-energize shutting off the high fire gas
supply and the air damper will close reducing the
airflow to a minimum. Once the water heat~r is at
low fire the manifold gas pressure can be adjusted
as described in the previous paragraph but using
the pilot gas regulator instead of the main gas
regulator. Proceed to paragraph
10
to tAst and
document combustion results for low fire and high
fire,
10.
Check flue gases with an electronic flue a;,alyzer
to make final settings of gas pressure regulator.
a) The readings need to be taken from a :101e in
the vent several inches downstream of the fan
outlet connection.
b) Insert 0-6" W.C. manometer into
ttl:!
test
opening in the vent. Pressure in stack should
not exceed 2" W.C.
c) When water in tank is above 120°F, insert
analyzer or O
2
testing in test opening; take O
2
reading in percentage.
d) Increase manifold gas pressure at the main
gas pressure regulator taking O
2
rearJ!:lg at
each
adjustment of
gas
regulator
until
optimum O
2
%
(5-7%) is reached. If, O
2
%
decreases, reduce the gas pressure i' : :> last
reading
where
the
greatest
reading
is
achieved.
e) CO should not exceed 200 ppm. A reading
greater than 200 ppm indicates lack of air.
Reduce manifold gas pressure slightly and
take readings until CO is within proper range.
Optimum reading is no CO.
f)
If manifold pressure was changed during
startup, take a final CO and O
2
reading.
g) Record CO
2
and NO
x
if applicable. See
paragraph 11 if NO
x
measurement is required,
h) Insert vent temperature gauge in test opening
and read gross vent temperature; maximum
gross stack is to be 250°F. If an excessively
high gross vent temperature is recorded;
consult the factory.
11.
When the Power VT water heater is equipped
for Low NO
x
operation, it may be necessary to
measure the NO
x
levels
in
the flue
prodUcts
for
compliance verification. The NO
x
concentrations
are measured in ppm (parts per million). When
documenting the measurements on the startup
report, be sure to note whether or not the
readings are corrected to a baseline O
2
level. If
during the course of startup the NO
x
levels do
not meet your locally mandated requirements, it
may be necessary to change the FGR (flue gas
re-circulation) orifice, This orifice is contained in
the FGR union shown on page 11, Figure 19-6.
This union may contain two or more orifices.
This allows the removal of one or more of the
orifices in order to increase the flow of FGR and
thereby reduce NO
x
in the flue products. If the
FGR orifice is changed for any reason, the
startup procedure in paragraph 10 should be
repeated.
12.
Check each operating and limit control to be
sure they function properly by lowering and
raising the temperature setting on each of the
controls, causing burner to cycle on and off.
NOTE: During the initial firing of the burner,
smoke that is not related to the burner will be
emitted from the heater. This is normal during
"burn in" and could possibly continue for
several hours.
PV500·19 04-2005
13
Section 19
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