LAARS Mighty Therm VW-PW (Sizes 175-400) - Installation, Operation and Maintenance Instructions - Manual (Page 26)

LAARS Heating Systems
Page 26
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.
2. Touch the other lead to the red wire terminal (see
Figure 35). The voltmeter should read 24 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 heater 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 VW and PW
heaters 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 heater 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 36. Testing the manual reset hi-limit switch.
Figure 37. Testing the fusible link.
Finding a loose connection or a charred wire can
save a lot of time and money.
5. Check the fuse inside the black, twist-lock fuse
holder. If it is burned, replace it with a 2-amp
fuse (Part No. E0084400). If there is a short, the
cause of the short must be found and repaired.
Do not jumper or bypass the fuse.
6. Make sure the electrical circuit to the heater is
on.
7. Make sure the toggle switch on the right side of
the heater is on.
8. Make sure the temperature control is set high
enough to call for heat.
9. Make sure the manual reset on the safety controls
(e.g., low water cutoff, hi-limit switch, etc.) has
not tripped. If it has, reset it.
If the pump is circulating water, and the rest of
these items check out all right, the trouble could be in
the heater control system.
Caution
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
5.2.2 Testing the Transformer
NOTE: Keep the pump running.
Red
Yellow