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Old 07-27-2012, 12:06 PM   #16
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So I want to replace the contactor in my outside unit


The contacts I thought perhaps burned from the frequent surges and power outages in my area recently, I'm confused about what you said about the contacts burning. Do you mean burned contacts could be causing the chattering but that burned contacts would not cause high line resistance?

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Old 07-27-2012, 12:26 PM   #17
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So I want to replace the contactor in my outside unit


High resistance somewhere could cause chattering.
Burned contacts may exhibit high resistance.
Contacts may burn because of relay chattering or old age.
Connections may become high resistance connections due to age or day/night temperature variations or incorrect install.
The connection resistance may vary with the current drawn or be constant.

It's like when your car solenoid oscillates because of a corroded battery connection.

You're looking for a connection that is supposed to carry heavy current.

You can check connection integrity with a DMM and a heavy resistive load rated for 240v and 10A or 20A but this procedure is a little bit beyond most DIYers.
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Old 07-27-2012, 01:46 PM   #18
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So I want to replace the contactor in my outside unit


My replacement contractor is in place now. Sadly, it chattered on start up.
The compressor ran for one minute, then heard a sound I suspect is a bypass of some sort, and then rather loud compressor complaining motor noise. (I shut it off of course)

All the troubles began after a three week ordeal with two major power outages and then a horrible heat wave - the capacitor blew. It seemed to work fine after two power restorations, but conked in the heat wave.

I thought the only problem that would need fixing was the capacitor. Service tech came out late on a Sunday. He only had two "spare" single caps of the right microfarads on the truck - but put in a dual capacitor the next day per my request. When he put in the single caps, the system seemed to start fine. Then as he was packing up, the contractor started opening and closing; its was very loud. On restart it smoothed out. He checked voltages and so forth and all was fine. He left with the system running. The service company called to put off the capacitor swap (for a new dual one) for a couple of days and I agreed. But I had to call them back:

Inside cool air seemed only to "ooze" out. The system then freaked out a couple of times. Once it cut out entirely, then restarted without issue. Then I found it with the fan going but no compressing going on, and just cool air blowing out of the top of the compressor. I turned the system off.

Another guy comes out with the new capacitor. He puts it in. The system chatters for him too, on first start up, but smooths out. This time it runs great guns for about 24 hours. Lots of nice cold air and joy for all the inhabitants within. He was supposed to check pressures on this visit, but didn't because it was just working brilliantly.

Then, it just pooped out. I go outside, and find the compressor is running but not blowing hot air out of the top.

On the third call the guy taking the pressures said the system was overcharged. The system pressures were "over the moon" - and higher on the low side. He said he'd never run into this problem before.
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Old 07-27-2012, 03:49 PM   #19
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So I want to replace the contactor in my outside unit


You may be having a line voltage problem from the transformer that serves your house. m ay want the power company to come out and check it.
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Old 07-27-2012, 04:21 PM   #20
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So I want to replace the contactor in my outside unit


Quote:
Originally Posted by sarahWW View Post
All the troubles began after a three week ordeal with two major power outages and then a horrible heat wave - the capacitor blew. It seemed to work fine after two power restorations, but conked in the heat wave.
There may be patterns of power quality problems that are especially harmful to HVAC equipment, e.g., rapid dropouts and restores.

The chattering smoothing out, if it was caused by a bad connection, implies self healing - what could that be about?

Your outage certainly opened a can of worms. I wonder if it totaled your AC. And how would you prove that?
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Old 07-28-2012, 09:44 AM   #21
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So I want to replace the contactor in my outside unit


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You may be having a line voltage problem from the transformer that serves your house. m ay want the power company to come out and check it.
Sorry to be slow to respond....but we lost power last evening, for about 12 hours. I know there was a broken pole in the area, though there wasn't any weather to directly cause such a thing. After the power went out there was a brief downpour, but loss of power preceded, there was no thunder, lightning, not even a stiff breeze. I speculate there was a transformer explosion, perhaps resulting from a surge.

I do want the power company to come check out the situation, especially since I've been reading other customers report some problems with some of the recent repairs.

One service tech did suggest voltage drops as a potential cause of trouble, though as I said, it "smoothed out"; his tests showed no abnormalities as he was observing, but he said it could be intermittent. When he left the system was working well and continued to work well for about 24 hours.


FWIW, I have no doubt we have dirty power in general in this area. I believe it has contributed to early deaths of other appliances over the years. And I think they have been "throttling" the power in the aftermath of outages in the intense heat wave.

I hope my AC isn't a total loss situation. I suspect it may be.
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Old 07-28-2012, 09:48 AM   #22
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So I want to replace the contactor in my outside unit


I was thinking of a "hail mary" with a hard start capacitor, or even swapping out the recently replaced (by service company) capacitor with a spare I bought, in case that one wasn't REALLY new or took enough beating to fail or was weak after being on the shelf too long.

My coils aren't awful-looking but I thought I might wash out the outside. I'd clean the evaporator coil with self-rinsing foam if I could get everything running again, but otherwise won't bother.
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Old 07-28-2012, 09:55 AM   #23
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So I want to replace the contactor in my outside unit


try this testing...shut the disconnect outside for the condenser then remove the stat off the subbase and jump R to Y.this is a direct jump for cooling that sends 24V constanly to that contactor..when you go out the contactor should bein(no fan.comp )with disconnect OFF leave it off.no break one of the low voltage wires coming into the condenser..so th contact open touch it it closes do it a dozen time open/closed...open/closed...again and again...i want to see if the transformer is weak from the 208V pole spike.. if i chatters with th wire touched push it in see if it stays? lets here back...eithet a loose connection or the control module with the stat inline(jump removes that load) is draining the VA on that furnace TR..easy fix...see if you have a local GRAINGER around..what type of stat are you running solid stat LED type? 40/50/60-VA....115V-208V-24V check all connections on the low voltage side and stat terminals... http://www.grainger.com/Grainger/WHI...BaseItem=3TZ67

Last edited by biggles; 07-28-2012 at 10:04 AM.
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Old 07-28-2012, 07:41 PM   #24
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So I want to replace the contactor in my outside unit


Your predicament brings up some ideas.

For $20 in parts (a "window comparator" and LM555 timer) a device could be wired into your power line and thermostat that would shut off your AC within 0.015 seconds when it detects an out of bound voltage and then waits a minute or 10 minutes until the power surge is gone.

For considerably more than $20 you add a neural network that learns the pattern of your Poco's glitches and turns off your AC in anticipation of a glitch.
You could have it wired into one of these detectors that detects nearby lightning strikes for additional security.

This is all existing technology. If the market demand is there some company may already make these things. Searching patents online may be a good place to start.

Or you may be able to get insurance against these kinds of things. These events are not exactly "Acts of God" and insurance companies know how likely it is that your Poco will wreck your appliances in your area.

Last edited by Yoyizit; 07-28-2012 at 07:44 PM.
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Old 07-29-2012, 12:41 PM   #25
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So I want to replace the contactor in my outside unit


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Originally Posted by Yoyizit View Post
Your predicament brings up some ideas.

For $20 in parts (a "window comparator" and LM555 timer) a device could be wired into your power line and thermostat that would shut off your AC within 0.015 seconds when it detects an out of bound voltage and then waits a minute or 10 minutes until the power surge is gone.

For considerably more than $20 you add a neural network that learns the pattern of your Poco's glitches and turns off your AC in anticipation of a glitch.
You could have it wired into one of these detectors that detects nearby lightning strikes for additional security...
Interesting idea. Over the years I've wondered about some kind of whole-house surge protection but never seriously investigated the possibilities. We get dips, sometimes throttling, too. If I end up having to sink $ into altogether new system, it would only make sense to try an protect it given the fragility of our local grid.
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Old 07-29-2012, 01:33 PM   #26
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So I want to replace the contactor in my outside unit


Biggles:


I speak less HVAC "jive" than I'd like to.
I would like to try what you suggest, but might have to ask for some steps to be translated or to ask exactly how to do something.
Would you be willing to describe things to someone who's not done much of this before, and talk me through it?
*
I can* capture pics and vid and post it here or link to youtube

Last edited by sarahWW; 07-29-2012 at 02:12 PM. Reason: Edited to direct comment to Biggles
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Old 07-29-2012, 03:45 PM   #27
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So I want to replace the contactor in my outside unit


the reason for shutting the condenser disconnect is so your not banging it off/on checking that 24V control circuit being called in from the stat and furnace...the line voltage has nothing to do with the contactor action opening or closing out at the condenser.call the stat to cool and break the control wire at the contactor touch nd retouch it see if it chatters or holds..might need a new TR in the furnace?sorry for the ramble but that is how a service tech is when he is banging you for
$200 repair plus unneeded parts.like he is doing magic...
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Old 07-29-2012, 07:09 PM   #28
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So I want to replace the contactor in my outside unit


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the reason for shutting the condenser disconnect is so your not banging it off/on checking that 24V control circuit being called in from the stat and furnace...the line voltage has nothing to do with the contactor action opening or closing out at the condenser.call the stat to cool and break the control wire at the contactor touch nd retouch it see if it chatters or holds..might need a new TR in the furnace?sorry for the ramble but that is how a service tech is when he is banging you for
$200 repair plus unneeded parts.like he is doing magic...

There are terms I don't know the shorthand for. Does "stat" refer to the t-stat, or some other control? Also, what is TR shorthand for? I don't recognize the abbreviation.

My furnace isn't a furnace - I have a boiler separate from the AC (hot water baseboard heat), though they share the thermostat. I select cool or heat mode

There is also relay in place that allows me to run the continuous fan mode in the air handler and the boiler at the same time.
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Old 07-30-2012, 06:45 AM   #29
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So I want to replace the contactor in my outside unit


Sounds like you've got an intermittent short somewhere, which is a very difficult thing to track down.

You could also have troubles with logic boards, transformers, etc etc - in cases like this, you are often better off leaving this to a competent service company - although they will have a difficult time fixing a problem if it's not occurring during the visit.
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Old 07-30-2012, 08:25 AM   #30
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So I want to replace the contactor in my outside unit


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Sounds like you've got an intermittent short somewhere, which is a very difficult thing to track down.

You could also have troubles with logic boards, transformers, etc etc - in cases like this, you are often better off leaving this to a competent service company - although they will have a difficult time fixing a problem if it's not occurring during the visit.
Exactly, though the hourly diagnostic fee will be, like the last service tech described my "overcharging" system, "over the moon". Also my service company, sadly, is rather interested in getting me to replace my system. (Not until next year.) Any relatively simple tests or lower-cost part swaps that don't involve removing or adding refrigerant or blowtorches, I am willing to attempt.

Failing that, learning about what MIGHT have gone wrong and what will be tested, will help me deal with the service company, and understand what they tell me.

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