On Feb 12, 9:39*pm, The Daring Dufas
wrote:
On 2/12/2012 7:22 PM, gregz wrote:









The Daring *wrote:
On 2/12/2012 10:52 AM, Jules Richardson wrote:
On Sun, 12 Feb 2012 00:50:46 -0600, The Daring Dufas wrote:
Most of the HVAC techs who have a capacitor tester carry this
one or a similar one:

http://preview.tinyurl.com/6p7c8ld

My own test gear tends to be more elaborate thus more expensive since I
also do circuit board repair work on a lot of different things.

So do motor capacitors typically fail in a way where it's only the actual
capacitance that drops, rather than the ESR which climbs (the latter
being what often causes problems* in electronic circuits)? *The
description of the meter in the link you posted doesn't seem to make any
mention of ESR, so I assume it's not relevant in motor appications?

* the real issue being that the capacitance can still check out OK on a
meter, but the high ESR will affect the circuit and cause it to fail.

cheers

Jules

Motor run/start capacitors are an extremely inexpensive commodity and I
tend to look at them like disposable batteries here lately because so
many of the Chinese caps fail. It seems like every little hit from a
voltage spike coming from the electrical service punches holes in the
dielectric of the darn things. A simple test on every service call is the
prudent thing to do because of the nature of the equipment. I have
seen sources for very high quality American manufactured capacitors but
they're very expensive. o_O

TDD

Last year I got some kind of surge/ spike that took out the suppressor I
had on my compressor line. I installed a new one again. Ac is ok.

Greg

That's why I recommend surge arresters on HVAC equipment. Around here in
the summer months is when we have a lot of thunderstorms and the
darn lightning strikes occur when the AC is running wide open. Voltage
spikes travel a long way from a strike and of course power may cut in
and out a lot so I always install a anti-short cycle timer to protect
the compressor from slamming on and off when under load. Most electronic
thermostats have the timer built in but there are a lot of mechanical
thermostats out there.

TDD

Picked up a new cap today and changed it out. Checked the cap and it
was 4.8uF out of 5. I can measure within 1%. It did need changing
though but not for the reason the tech mentioned. The rivet holding
the connectors was sloppy loose. Also found the wire dress a mess.

Jimmie