cause a transformer to fail?
Not much. Rarely happens.
a transformer do?
Simply said, it takes incoming power (primary) and
reduces to a lower power (secondary). You have only one
primary but you can have several secondary output
voltages. Most boards only use one secondary but some
Its purpose is to take the incoming power and
lower the power to a voltage the board and other components operate on. So the
primary can be 115v or 230v depending on the spa. Note that some spas that
operate on 230v have a 115v primary transformer. Don't assume your spa is 230v
The secondary is the lower voltage. Most output
to boards are around 12-15vac. This operates the board and often the outside
How to I
test a transformer?
Testing a transformer
should not be performed by someone who is not
experienced and comfortable with electricity. If you are
not qualified, have a licensed electrician do the test.
What you need to test is the incoming power to
the transformer and the output. In general, incoming power travels through the
board to the transformer and back. So look for your two primary wires from the
transformer plugged into the board. Note: This test can only be done on spas
with a separate transformer from the board. Boards with onboard transformers can
not be tested this way.
Again, concern is this test has to be performed
while power is being applied to the spa. See picture. You identify the 2 primary
lines and slide your meter's probes down the wires until they touch the metal on
the plug. You should get either 115v or 230v depending on which voltage the
system is designed for.
If proper primary voltage is present, test one or
two pairs of secondary voltage. They should be decreased into the 12-20vac
range. If they are, the transformer is good. If not and you do have proper
incoming power, the transformer is bad.
Let me say that since 1995, I probably have
replace 2 bad transformers. They are highly reliable.
On picture below, I'm checking the primary
voltage for this spa; in this case, white and black wires. I'm sliding the
probes down the wires until the lightly touch the metal clips inside the actual
plug. This gives me a 230v reading which is correct. The incoming power to the
transformer is good.
On many systems, its is HARD to get to those
metal clips because the plastic/wires are tight. But you need to do so to check.