Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-13-2009, 09:05 PM   #1
Member
 
Join Date: Jun 2009
Posts: 48
Rewards Points: 25
Default

AC stops cooling when it rains


I have a problem that I would like some additional help on.

My AC works fine when it is dry out. I've had a tech out here just two days ago to confirm that my coolant levels are good, the compressor works fine and gives me appropriate pressures, power draw is within spec, I'm not icing up the evaporator, and I'm getting a normal air temperature differential across the evaporator. In other words, the system works.

However when it rains, the system stops cooling. I get warm air out of the register and the compressor unit outside stops rejecting heat (it's just blowing air through the fan, but the air is not appreciably warmer, as it should be) while the fan continues to run. Usually it takes half a day or more of letting the system sit idle after rain stops before the system will blow cold air again. On more than one occasion, the system has gotten to this state and continued to run, only to eventually trip a breaker at the air handler.

I suspect this is some sort of electrical problem, but I need more information or to hear from someone who knows more about this stuff.

Emfuser is offline   Reply With Quote
Old 06-13-2009, 09:17 PM   #2
as seen on tv
 
Join Date: Mar 2009
Location: pa
Posts: 205
Rewards Points: 150
Default

AC stops cooling when it rains


I would have your contractor return and inspect and test wiring. Possible to have something bare and shorting due to water.

qbert is offline   Reply With Quote
Old 06-13-2009, 09:38 PM   #3
nap
You talking to me?
 
nap's Avatar
 
Join Date: Dec 2007
Location: sw mi
Posts: 5,407
Rewards Points: 2,000
Default

AC stops cooling when it rains


can you yourself check the evap coil? If so, I would check it while this is happening. I suspect your evap coil may be freezing up when the rain acts as an additional heat transfer medium, which is more effective than the air, and causing the evap coil to freeze up.

Instead of waiting for the rain, I would think a sprinkler would simulate the rain.

a dirty evap coil will is also more prone to freezing up as well so if the evap coil is dirty, this would add to the situation.
nap is offline   Reply With Quote
Old 06-13-2009, 09:47 PM   #4
GC/Master Plumber/Mech
 
Join Date: Feb 2009
Location: Hays, KS
Posts: 1,472
Rewards Points: 504
Default

AC stops cooling when it rains


If the breaker tripped one time I would start looking at the electrical connection between the disconnect and condenser. I would also inspect the low voltage wire from the furnace to the condenser.

When you start to inspect the electrical connection make sure you turn off power to the condenser. If the is a bare wire or short you don't want to be the newest short to ground.
Plumber101 is offline   Reply With Quote
Old 06-13-2009, 10:01 PM   #5
Member
 
Join Date: Jun 2009
Posts: 48
Rewards Points: 25
Default

AC stops cooling when it rains


Quote:
Originally Posted by Plumber101 View Post
If the breaker tripped one time I would start looking at the electrical connection between the disconnect and condenser. I would also inspect the low voltage wire from the furnace to the condenser.

When you start to inspect the electrical connection make sure you turn off power to the condenser. If the is a bare wire or short you don't want to be the newest short to ground.
I'm real good with industrial safety since I started my professional career as a nuclear power plant non-licensed operator. I basically do my own home red-tagging program, and do live-dead-live testing on electrical stuff I work on.

I pulled the side panel off of my outside unit and I may have found some corrosion on the main power relay to the compressor, but the wiring looks good otherwise. I'll keep you all posted after I clean this bit up. I'm going to have to bring it inside.
Emfuser is offline   Reply With Quote
Old 06-13-2009, 10:20 PM   #6
GC/Master Plumber/Mech
 
Join Date: Feb 2009
Location: Hays, KS
Posts: 1,472
Rewards Points: 504
Default

AC stops cooling when it rains


You may have a contactor going bad
Plumber101 is offline   Reply With Quote
Old 06-13-2009, 11:14 PM   #7
Member
 
Join Date: Jun 2009
Posts: 48
Rewards Points: 25
Default

AC stops cooling when it rains


Well, that didn't change anything. The contactor works fine, the resistance across it was less than 1 ohm, and it shut clean when the demand signal to start the outside unit came on (after I had re-installed it).

The unit still is not rejecting any appreciable amount of heat, though, and thus not cooling. This is really puzzling.
Emfuser is offline   Reply With Quote
Old 06-13-2009, 11:17 PM   #8
Member
 
Join Date: Jun 2009
Posts: 48
Rewards Points: 25
Default

AC stops cooling when it rains


Quote:
Originally Posted by nap View Post
can you yourself check the evap coil? If so, I would check it while this is happening. I suspect your evap coil may be freezing up when the rain acts as an additional heat transfer medium, which is more effective than the air, and causing the evap coil to freeze up.

Instead of waiting for the rain, I would think a sprinkler would simulate the rain.

a dirty evap coil will is also more prone to freezing up as well so if the evap coil is dirty, this would add to the situation.
The one time I crawled under the house and opened the panel on the air mover (right after I had shut the system down during one of my investigations), I found the evaporator wet but not frozen. The condensate drain line was also clear, and no water was pooling. The evap was pretty clean, also.

I really hope this doesn't come down to TEV or compressor replacement, but what gets me is the whole business about the system failing ONLY when it rains.
Emfuser is offline   Reply With Quote
Old 06-13-2009, 11:21 PM   #9
GC/Master Plumber/Mech
 
Join Date: Feb 2009
Location: Hays, KS
Posts: 1,472
Rewards Points: 504
Default

AC stops cooling when it rains


What I thought when I first read this thread was the maybe when weed eating you might have nicked the low voltage line and when it rains some how they are shorted together causing just enough voltage lost and not pull in the contactor.

Does the condenser come on and run when the concern is happening?

If it is

I'd want to know what the amps reading to the condenser is when this is happening. Low amps=fan running High amps=fan/compressor running

Want to know if the compressor is running or not.

To me this is an outside wiring issue
Plumber101 is offline   Reply With Quote
Old 06-13-2009, 11:28 PM   #10
Member
 
Join Date: Jun 2009
Posts: 48
Rewards Points: 25
Default

AC stops cooling when it rains


Quote:
Originally Posted by Plumber101 View Post
What I thought when I first read this thread was the maybe when weed eating you might have nicked the low voltage line and when it rains some how they are shorted together causing just enough voltage lost and not pull in the contactor.

Does the condenser come on and run when the concern is happening?

If it is

I'd want to know what the amps reading to the condenser is when this is happening. Low amps=fan running High amps=fan/compressor running

Want to know if the compressor is running or not.

To me this is an outside wiring issue
Unfortunately I do not have the inductive ammeter that the recent tech did. My multimeter can't handle that sort of amperage.

The only indicator I have whether or not it's fan or fan/compressor is the heat rejection, and that's pretty easy to tell the difference on. When the tech was out the other day and the unit was properly rejecting heat, it was drawing about 10 Amps.

I think it is safe to assume that the compressor is not running, based on the lack of heat rejection. At least that's what I have to go on until I can purchase or borrow an inductive ammeter.

I'll get out there tomorrow when it's daylight and have a session with the wiring diagram, following the wiring to look for anything erroneous.
Emfuser is offline   Reply With Quote
Old 06-13-2009, 11:31 PM   #11
Member
 
Join Date: Jun 2009
Posts: 48
Rewards Points: 25
Default

AC stops cooling when it rains


Thank you for your insight, btw.
Emfuser is offline   Reply With Quote
Old 06-14-2009, 06:27 AM   #12
Member
 
biggles's Avatar
 
Join Date: Jan 2008
Location: Long Island
Posts: 3,630
Rewards Points: 2,000
Default

AC stops cooling when it rains


doubt it is the wetness of the rain i think it is more the temperature drop with the rain cooling the condenser.might want to check the stat for comptressor on/off time adjustment...you might be short cycling the compressor after the last run and the pressures haven't equalized so it goes to restart and trips the breaker.the flag there is that the condenser fan is running but the compressor isn't... you have only one contactor that powers both on a call from the stat so the compressor is going off on internal limit with that short cycle.if your stat has no configuration for compressor on and off cycle you can add a adjustable time delay out on the condenser control wiring going in. http://bestbuyheatingandaircondition...e=r-compressor

Last edited by biggles; 06-14-2009 at 06:30 AM.
biggles is offline   Reply With Quote
Old 06-14-2009, 07:58 AM   #13
Member
 
hvaclover's Avatar
 
Join Date: Oct 2008
Location: Suburbs of Detroit Mi
Posts: 3,704
Rewards Points: 2,000
Default

AC stops cooling when it rains


No body get's it During a rain shower the weight of the water slows down the cond fan mtr. Cond fan is weak.
__________________
Just slow, not stupid.
hvaclover is offline   Reply With Quote
Old 06-14-2009, 08:41 AM   #14
nap
You talking to me?
 
nap's Avatar
 
Join Date: Dec 2007
Location: sw mi
Posts: 5,407
Rewards Points: 2,000
Default

AC stops cooling when it rains


Quote:
Originally Posted by hvaclover View Post
No body get's it During a rain shower the weight of the water slows down the cond fan mtr. Cond fan is weak.
that should not appreciable change the cooling ability of the system though since if there is that much water, the cond coils would be getting washed down with the rain as well. Additionally, it takes 1/2 day or more on non-use to rectify.


For some reason, I figured the OP knew if the compressor was running or not. Apparently my mistake. Unless you have a very quiet compressor, you should be able to tell if it is running or not.

If the comp is not running, then, to me, it could be something along the lines of what plumber was shooting at or even what biggles was aiming for.

emfuser:

can you operate the unit with the cover off and observe the compressor. Even without a ammeter, you should be able to tell if the comp starts or not.

You can place a hand on the comp and tell if it is running. Safety check possible circuit pathway for shorts first though.

If the comp is not running, you need to determine why.

Is power reaching the comp? If so, a bad comp or a bad Klixon switch or bad capacitor. Biggles hit on something there as well. If a bad comp or bad klixon, or cap, a short cycle could cause a problem along these lines. If you have any of the noted problems, a short cycle may cause overload of the comp and any of the three could cause a no comp start.



Bottom line; you need to be able to determine if the comp is running and then attempt to repeat the scenario while observing.

biggles; the fact it takes upward of 1/2 a day or so would generally remove just a simple short cycle problem that a time delay would help with. There has to be a bad part to be causing long term problem such as this.

when testing I would look for an attempt to start and then comp shut down. Then, if it attempts again in a minute or so, I would look to a capacitor or a system problem allowing too high of head pressure or even liquid slugging.

If it does not try to start, I would look towards the klixon switch.


if all else fails; call an AC guy that knows more than simple gauge pressures. A "tech" that knows there is a problem under certain situations and only checks while things are expected to be working normally and leaves when things appear to be fine is not a tech.
nap is offline   Reply With Quote
Old 06-14-2009, 09:49 AM   #15
GC/Master Plumber/Mech
 
Join Date: Feb 2009
Location: Hays, KS
Posts: 1,472
Rewards Points: 504
Default

AC stops cooling when it rains


Quote:
Originally Posted by hvaclover View Post
No body get's it During a rain shower the weight of the water slows down the cond fan mtr. Cond fan is weak.

I thought of the Been but I would think that it would have to be reduced by atleast 25% of more rpm to see what no cooling.

I mean I have seem as I'm sure you have seen where a condenser coil is so plugged that air flow is reduced but it still cools a little.

I'd like to put a set of gauges on and so the sprinkler thing someone here proposed

Plumber101 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Help! Just changed my Fan Controler (ICM 275) now system "false starts" when cooling redmachodevil HVAC 4 01-26-2011 03:21 AM
cooling coil formulas? Tinman_iii HVAC 8 06-05-2009 08:33 PM
My air conditioning (cooling) has gone away guptaalok HVAC 4 05-20-2009 12:43 PM
Finding Crown Stops for Hitachi FCH Mitre Saw andonyx Tools 4 04-16-2009 12:36 PM
Geothermal cooling loop help stuartm HVAC 2 09-29-2008 10:18 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.