27
Finned copper tube gas boilers & water heaters – Boiler manual
FTXLF-IOM-HN-1-110308 Copyright 2008 Mestek, Inc.
Verify low fire operation
Connect a manometer or Magnehelic gauge with the pressure
1.
side to the manifold pressure port and the other to the manifold
reference port. See Figure 18, page 26 for locations.
Set Honeywell R7800 control to RUN position. The boiler will
2.
operate at low fire because the low fire switch is in the low fire
position.
Measure the flue gas CO
3.
2
with the boiler running at low fire. Set
low fire CO
2
to 8.0% – 8.5% by adjustment on the Dungs valve
using a 3mm Allen wrench.
Turn the wrench in small increments (10 degrees at a time).
a.
Allow time after each adjustment for the boiler to reach steady
b.
state.
After setting the CO
4.
2
, measure the pressure signal,
Ps
.
Press the
a.
Ps (signal)
button and read the pressure. The pres-
sure at low fire should be as shown in Figure 13.
If the pressure is outside this range, follow instructions in the
b.
XLF Control IOM to calibrate the firing rate. Increase rate
if the pressure signal is low, or decrease rate if the signal is
high.
Return to step 1 to adjust low fire CO
c.
2
after changing low
fire firing rate.
If using a U-tube manometer turned sideways for low
pressure readings, you MUST turn the manometer
upright before attempting to measure pressures at
other than low fire. Pressure signal will reach up to 9
inches when the boiler is at high fire, and can cause
fluid to be pulled out of the manometer into the boiler.
Should this occur, immediately shut down the boiler
and contact the factory for procedure. Preferably, use
a Magnehelic gauge instead of a U-tube manometer to
measure the pressure to avoid this potential hazard.
Pressure signal (Ps)
table 13
Firing
rate
%
XLF-3000
XLF-4000
input
mBH
signal
inches w.c.
input
mBH
signal
inches w.c.
100%
3000
-5.5
4000
-8.7
50%
1500
-1.4
2000
-2.1
33%
990
-0.6
1320
-0.9
25%
750
-0.35
1000
-0.6
20%
600
-0.25
800
-0.4
To determine signal in mm w.c., multiply signal in inches by 25.4.
To ensure proper boiler operation, boilers that use
room air must not be fired at less than 33 % input.
Observe the burner flame after setting low fire. Make sure the
5.
flame is stable, but not too tight on the burner (causing infrared
operation).
Do not LeAVe tHe BUrner in An inFrAreD stAte
.
A few random speckles of red are acceptable, but large
concentrations of spots or large areas of red are not.
If large amounts of red concentrations are observed,
verify combustion readings.
Leave the manometer connected to the test manifold.
It will be needed for high fire operation testing.
Verify high fire operation
Jumper the AA terminals on the HeatNet board and allow the
1.
boiler to rise to maximum (100%) input.
Allow the boiler to reach steady state combustion at high fire.
2.
Verify high fire blower speed as follows:
3.
With the manometer (or gauge) connected to the test mani-
a.
fold, press the
Ps (signal)
button and read the pressure.
The pressure at low fire should be as shown in
b.
Figure 13.
If the pressure is NOT correct, follow step 4.
c.
If the high fire signal pressure is not correct:
4.
Remove the jumper on A-A. The boiler will return to low
a.
fire.
Follow the instructions in the XLF Control IOM to calibrate
b.
the high fire firing rate. (Slide the HeatNet control calibrate
switch to
CAL
. Follow the Control IOM procedure to navi-
gate to the HeatNet control calibration screen.)
The maximum firing rate value in the HeatNet control
is factory set at 90%. At this setting, at sea level, and
with typical vent length, the
boiler will be at rate
.
DO NOT increase the HeatNet control's maximum
rate setting above 90% unless needed for high altitude
installations.
If
c.
Ps
is too high, reduce the HeatNet control's maximum
firing rate setting by 2%. Then slide the calibration switch to
NORMAL
and exit the HeatNet control's calibration screens.
Replace the jumper on A-A and allow the boiler to return
to high fire. Return to step 2 to repeat the process. If neces-
sary, repeat this sequence, reducing the firing rate by 2% each
time.
If
d.
Ps
is too low, increase the firing rate setting by 2%. Then
slide the calibration switch to
NORMAL
and exit the Heat-
Net control's calibration screens. Replace the jumper on A-A
and allow the boiler to return to high fire. Return to step 2 to
repeat the process. If necessary, repeat this sequence, increas-
ing the firing rate by 2% each time.
Check the pressure signal again. If the signal is now correct,
e.
reconnect the jumper on AA and proceed to step 5.
If the pressure signal is still not correct, verify that the air trim
f.
adjustment (see Figure 19, page 26) is in the half-open (fac-
tory setting) position. If it is at factory setting, you will need
to contact technical support at the factory to troubleshoot
the pressure signal issue.
