LAARS Mighty Therm LO-NOx PH (Sizes 250/400) - Install and Operating Manual - Manual (Page 27)

Mighty Therm LO-NOx Hydronic Boiler Page 27
5.2.4 Testing the Manual Reset
Hi-Limit Switch
To test the manual reset hi-limit switch (see
Figure 39):
1. Touch the other lead of the voltmeter to both
terminals of the manual reset hi-limit switch. The
voltmeter should read 20 to 28VAC at both
terminals.
2. If no voltage is detected at one terminal, reset the
manual reset hi-limit switch by pressing the reset
button. Check the temperature setting.
3. If after pressing the reset button there is still no
voltage indicated at one terminal, replace the
manual reset hi-limit switch. An open switch may
indicate excessive water temperatures or
improper setting.
5.2.5 Testing the Flow Switch
The flow switch is a safety device that senses
water flow through the boiler. When the switch senses
adequate water flow, it closes, allowing the boiler to
fire. If the water flow is too low, the switch remains
open and prevents the boiler from firing regardless of
the temperature control setting.
The flow switch is factory mounted and wired.
Never attempt to repair the flow switch. If the flow
switch is found to be defective, replace the flow
switch. To test the flow switch:
1.
Remove cap from flow switch (see Figure 25).
2. Touch a voltmeter lead to each terminal of the
flow switch.
3. If the voltmeter reads voltage at each of the
terminals, the switch is good.
5.2.2 Testing the Transformer
NOTE: Keep the pump running.
Testing the transformer requires an AC voltmeter
with a 50 volt (V) range. Test the transformer using the
following procedures:
1.
Clip a lead from the voltmeter to the yellow wire
terminal on the transformer (this lead stays
connected to this terminal for all tests).
2. Touch the other lead to the red wire terminal (see
Figure 37). The voltmeter should read 20 to 28VAC.
3. If the voltmeter does not show voltage, check the
electrical power supply.
4. If the voltage is less than 20VAC, the electrical
circuit to the boiler may be supplying less than
103VAC. This could be due to high pump load or
air conditioners or other appliances on the circuit.
5.2.3 Testing the Electrical Power Supply
The electrical components of the HH and PH
boilers operate with supply voltage ranging from 103
to 126VAC at 60 Hertz (Hz). To test the electrical
power supply:
1. Measure the voltage at the hot and neutral
connections inside the boiler electrical junction
box.
2. Voltage outside of the required range may be due
to poor wiring connections, to other loads (e.g.,
air conditioners, compressors) on the circuit, to
high pump load, or to an electrical utility
company problem.
Figure 38. Testing the Transformer.
Figure 39. Testing the Manual Reset Hi-limit Switch.
OUT OF
PRODUCTION