DIYbanter - View Single Post - Blew another damn transformer on my Trane XB80

David Nebenzahl

On 4/9/2011 6:11 PM spake thus:

On Sat, 09 Apr 2011 14:42:39 -0700, David Nebenzahl
wrote:

On 4/9/2011 2:30 PM A. Baum spake thus:

An amp meter goes in series with the secondary (or primary) of
the transformer. You can convert amps to volt-amps by multiplying
volts times amps. 24 volts times 1 amp = 24 volt-amps. I don't
remember if transformers are rated differently for the primary or
secondary or which one is usually used. It might be in the
technical data usually packed with the transformer or stamped on
the transformer somewhere.

Using the primary side would be more conservative (= a bit safer),
since it will include any losses between primary and secondary
sides. But it really doesn't matter. And I'd much prefer to measure
current on the secondary side, rather than deal with 120-volt
juice.

He still has the problem of finding an AC ammeter, since a DMM
won't handle AC current.

As noted previously, this is NOT the case. An AUTOMOTIVE DMM might not
have an AC current scale, but virtually all general purpose meters do.
They generally have a "third terminal" used with the common for the
high range, which will be what he wants to use since the low range
that uses the standard (vom) connections generally tops out at 300ma,
more or less.

Well, all I can say is that *none* of my 3 general-purpose multimeters
(2 analog and 1 DMM) have AC current settings. But apparently this is a
non-issue in this case, as the OP's meter definitely has AC current
capability.

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