Mini-Therm II Hydronic Boiler
Page 17
10.
Low water cutoffs should be inspected and
flushed periodically.
Note: The Warranty does not cover damage
caused by lack of required maintenance, lack of
water flow, or improper operating practices.
Fouling on the external surfaces of the heat
exchanger is caused by incomplete combustion, and is
a sign of venting and/or combustion air problems. The
heat exchanger can be inspected by using a flashlight
and placing a mirror under the burners. An alternate
method is to remove the venting and top panel to
inspect the exchanger from above. The vent system
should be inspected at the same time. If cleaning is
required:
a.
Shut off all power to the boiler.
b.
Remove the draft hood, venting top, flue
collector, and heat exchanger baffles.
c.
Remove the burners by lifting them off the
orifices and pulling them out of the boiler.
d.
Use a hand-operated spray bottle filled with
water, and a wire brush to clean soot and loose
scale from the underside of the heat exchanger.
DO NOT USE COMPRESSED AIR, HIGH
PRESSURE WATER OR A GARDEN HOSE.
e.
Clean any fallen debris from the bottom of the unit.
f.
Check to make sure the burner ports and pilot
assembly are free of debris before returning the
burners to their original position.
g.
Reassemble the boiler in reverse order, making
sure to replace the heat exchanger baffles.
2D. Electrical Troubleshooting
1.
Remove the control box cover on the front of the
boiler.
2.
Verify that 115V is reaching the boiler by testing
across the black wire on the pump relay and the
white wire on the transformer.
3.
Verify 24V transformer output by placing the
meter leads on the yellow and red wires. If 24V
is not evident, replace the transformer. Perform
the following series of tests with one meter lead
attached to the yellow wire on the transformer.
4.
Place the second lead on the "W" connection on
the terminal board. Turn the wall thermostat high
enough to call for heat. If the meter fails to
register 24V, the thermostat or its circuit may be
defective.
5.
Make sure thermostat is set high enough to call
for heat. Place second lead on the "A" connec-
tion on the terminal board. If voltage is evident,
skip to step 6. If no voltage, test the circuit
between the red wire on the transformer and
terminal 4 on the pump relay; from terminal 6 on
the pump relay and the "A" connection on the
terminal board; and from the purple wire termi-
nal on the pump relay to the "W" connection on
the terminal board. If no output is found, the
connections or the pump relay could be defective.
6.
Place the second lead on the orange wire termi-
nal on the hi-limit switch. If no voltage across
the switch, check for defective hi-limit, open
circuit due to excessive water temperature, or a
low temperature setting.
7.
Place the second lead on the orange wire termi-
nal on the blocked vent safety switch. If voltage
is present, the vent damper is open. If voltage
isn't present, connections or the vent damper
could be defective.
8.
Verify the voltage across the blocked vent and
roll-out safety switches.
9.
On JVT boilers, test for voltage at the "TH"
terminal on the gas valve. If none is found,
follow steps 1 through 8.
10.
If it is determined that there is voltage to the gas
valve, the pilot is lit and the thermocouple is
properly positioned, and the thermostat is set
high enough to call for heat, the gas valve or the
pilot thermocouple may be defective
11.
There are two tests necessary to make sure the
problem is not in the pilot thermocouple. The
first test can be performed by unscrewing the
compression fitting on the gas valve, and placing
one millivoltmeter lead on the center post of the
tube and the other lead on the copper tubing. If
the meter shows a reading of approximately 30
millivolts, proceed to the second test. If it
doesn't, replace the pilot thermocouple. The
second test requires the use of a Millivolt Read-
ing Adapter to test the thermocouple under load.
Once again, remove the pilot thermocouple
compression fitting from the gas valve. Replace
it with a Millivolt Reading Adapter, and screw
the thermocouple fitting into the end of the
adapter. Attach one lead from the millivoltmeter
to either side of the adapter and the other lead to
ground. Light the pilot and set the wall thermo-
stat high enough to call for heat. With the boiler
firing, take a millivolt reading. It should be in the
15 millivolt range. If it isn't, replace the pilot
thermocouple.
Caution
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
