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Old 06-04-2015, 08:46 AM   #1
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Can't Detect R22 Leak


Hi Guys,

I have a 3 ton Carrier unit. Its about 6 years old. It has a N coil and TXV as the metering device. So, the coils were freezing over and the house was not getting cold.

I checked the the air filter to verify that it was clean. I then checked the subcooling and it was about 3 degrees. I then used an electronic leak detector to see if I could detect anything, but couldn't.

I then added dye to the system and ran the system for about 6 to 7 hours. However, I can't see a leak anywhere. I carefully looked at the evap coils, TXV, condenser, compressor lines, and the entire liquid & suction line run and could not find anything.

I also checked the service valves, and couldn't see a leak there either. I also tried the soap/water test on the service valves for bubbles, but nothing.

Could it be that I have not run the unit long enough for the leak to show itself? Its getting frustrating, since, I am not sure where else to look. Anybody has any advice or ideas?


Thanks,
John M.

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Old 06-04-2015, 10:20 AM   #2
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Sounds like you made a good effort. HVAC techs can have a hard time with pesky leaks as well. Did you use industry bubbles like Big Blue?

I think Carrier and many others had copper tube evaporator leaking problems around your time frame and they are switching back to aluminum. I would concentrate in that area with HVAC industry bubbles.

Warranty possible?

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Old 06-04-2015, 11:05 AM   #3
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Thanks for the response. Unfortunately, warranty is not possible, since the warranty was only for 5 years. I didn't try industrial bubbles, but will give it a shot.

By the way, one side of the N Evap coil doesn't have access(as shown with an arrow in the attached pic). Its impossible to see. I put my phone camera, with the yellow tinted glasses around it to see if I could detect a leak. I had the flashlight in one hand and the camera/glasses in the other hand. So, didn't get the best view. Is there anyway to take the coils out a little bit, without any damage? Or is there any other way to look at that side? It doesn't have an access panel for that side.


Thanks,
John M.
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Old 06-04-2015, 11:13 AM   #4
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You may have to wait longer. Small leaks can take quite a while to show up. Sometimes they only leak while running, and others only leak while the system is off. So give it another shot in a few days. Focus on compressor welds, anywhere the lines/coils can rub on anything, joints, and the ends of the coils.
Also what is the sub cooling? Amp draw if you have a meter? How's the blower running? Amp draw on that too? What is the super heat? How cold was it outside?

Last edited by supers05; 06-04-2015 at 11:15 AM.
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Old 06-04-2015, 11:31 AM   #5
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Quote:
Originally Posted by supers05 View Post
You may have to wait longer. Small leaks can take quite a while to show up. Sometimes they only leak while running, and others only leak while the system is off. So give it another shot in a few days. Focus on compressor welds, anywhere the lines/coils can rub on anything, joints, and the ends of the coils.
Also what is the sub cooling? Amp draw if you have a meter? How's the blower running? Amp draw on that too? What is the super heat? How cold was it outside?
I will run it for a while and hopefully the leak should show up...

The subcooling was 3 degrees. The blower is running fine. I will check the amp draw on the blower, but it didn't sound any different then normal. I didn't measure the super heat, since its TXV and not fixed Orifice. Do I need to measure the super heat?

Also, how do I check the amp draw on the compressor? I have a meter, but never did it.


Thanks,
John M.
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Old 06-04-2015, 03:25 PM   #6
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Let it run for a week or 2, then recheck.
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Old 06-05-2015, 07:36 AM   #7
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Quote:
Originally Posted by ashishm02 View Post
I will run it for a while and hopefully the leak should show up...

The subcooling was 3 degrees. The blower is running fine. I will check the amp draw on the blower, but it didn't sound any different then normal. I didn't measure the super heat, since its TXV and not fixed Orifice. Do I need to measure the super heat?

Also, how do I check the amp draw on the compressor? I have a meter, but never did it.


Thanks,
John M.
I edited my post after rereading your OP. I didn't see SC the first time. Anyways, I check the SH anyways, although it's not likely the problem. For amp draw, use a amp probe on AC devices. Clamp around one of the wires to the compressor while it's running. You won't have to remove any wires. If you don't have one, don't worry. The dye should work in a few days.
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Old 06-05-2015, 11:12 AM   #8
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Thanks for the info. I do have a the device you are talking about. Will try that out soon. Hopefully the dye works soon
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Old 06-05-2015, 05:25 PM   #9
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On the compressor , measure the amperage on the " common " wire .

Did you use the dye that shows up under UV light ?

If you can not find it , as preventative maintance , buy the device to change out Schrader valves and a package of schrader valves . Common source for leals .

Put the " caps " back on tight , but do not strip anuthing .

God bless
Wyr
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Old 06-06-2015, 08:24 PM   #10
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Quote:
Originally Posted by WyrTwister View Post
On the compressor , measure the amperage on the " common " wire .

Did you use the dye that shows up under UV light ?

If you can not find it , as preventative maintance , buy the device to change out Schrader valves and a package of schrader valves . Common source for leals .

Put the " caps " back on tight , but do not strip anuthing .

God bless
Wyr

Thanks Wyr. Yes, I used the dye that shows up under UV light. Is there a specific color of the "common" wire? How do I identify it?

I thought that the leaks would be at the schrader valves also, but I tried the bubble test, and nothing happened. I can't rely on the dye at the schrader valves, because the dye was added via the schrader valves and it doesn't matter how much you clean, its impossible to inside these valves.


Thanks,
John M.
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Old 06-06-2015, 08:42 PM   #11
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I will give you my take on the problem and it is not to say others are not correct.

First of all did you check the freon last year? Is this a leak that has been happening slowly. Leaking a ounce or more a year. That can happen and finally it froze up. If so it is a VERY small one and may be very difficult to find. Not sure what your sub cooling should be as I don't have the SEER or chart but 3 deg may be borderline freezing level not a major leak situation. Should be a bit higher but the whole idea is to have liquid in the bottom 2 rows of the condensor and cool it. Any subcooling is good. That means you have liquid there not gas. If it was very low it would just be gas.

You may have a VERY small leak and all it needs is topping up. With those tiny leaks the way I do it is to remove all the charge and then pump it up to 250 psig or higher with nitrogen and a trace amount of refrigerant. Sometimes they don't show up well w/o 250 psig pressure or more. Also you can leave it and see how fast it is leaking.

You may have just had a leak on the valve caps. I would remove them and make sure the inside valve is backseated snugly if it has that design. Parker did a lot of them with a cone shaped inside and the valve needs backseating ( metal to metal, bronze to bronze seats well ) and lots of techs did not seat them well. Then seal the caps with nylog and snug them well. Check the schraeders with Nu Calgon leak soap and the other joints. Soap and water is next to useless. Not bad for natural gas but with freon you need soap that clings to the joint.

No need for amp readings. If you don't have a nitrogen tank etc then you are going to have a very hard time. Also you may not have to do a great major search if it was just a slow leak over several years. One of the schraeders may have not seated and leaked and unless you got brass flare nut caps or good quality brass caps with rubber seats the plastic ones are useless. I use the spit test when I remove my gauges or Calgon soap. May be a fluke and you have no leak if it was just a schraeder valve fluke leak. Sometimes they don't seat and just need to be popped once with a small screwdriver to seat properly.

http://www.refrig.com/Product/Sealan...ylog_blue.html


http://www.nucalgon.com/products/gas-leak-detectors
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Last edited by yuri; 06-06-2015 at 08:59 PM.
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Old 06-06-2015, 08:58 PM   #12
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I use amp draw as an extra indicator. It's helpful but not necessary.

I too think it's a very small leak. It could take days or weeks to show up. Look for oil stains, but sometimes you won't see them. (my last leak was right in the middle of the spot weld on the compressor. So the panel had an oil strain but the compressor didn't. We had to use a refrigerant sniffer to find it.)

If the schraders are old, I always change them, and replace the rubbers in the caps. (or replace the plastic caps with new metal caps.)

Cheers!
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Old 06-06-2015, 09:03 PM   #13
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Yeah, this may be a wild goose chase. Remove the charge. Pump it up to 200-250 psig with nitrogen and see if it holds. You MUST have good gauges with good rubber seats in the hoses or quick connects that use o-rings as at those pressures they may leak and you get fooled.
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Old 06-06-2015, 11:26 PM   #14
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Wow, thats a lot of good info!!!

I never checked last year, as only this year(3 weeks ago) I noticed it not cooling. It was cooling for about a month or so this year. I will try the Nu Calgon leak soap and also I have plastic schrader valve covers. I will replace them with brass flare nut ones. Any specific type to get?

Yuri, I don't know what the subcooling should be as it is not mentioned anywhere. However, info online states that it should be between 10 - 12 degrees. So, isn't 3 extremely low? Shouldn't it be more closer to 12? Also, the way I noticed the issue was that the house wasn't cooling down and when I checked the evap coil, it had ice on it.


Thanks,
John M.
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Old 06-07-2015, 02:25 AM   #15
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3* does sound low but I've also seen it work just fine with that. If it's cold outside while it's still running, it can freeze up too. It's a problem we get here. (+90* high, dipping below 35* a few hours later. You end up with units that are still running, freezing up or locking out.) If you can find any, you might want to install a freezestat. It would prevent another freeze up while looking for the leak. If you're jurisdiction allows it, you may have to top it up, for it to run better while waiting for the dye to show up. (We can't here)

My supplier only has one type of cap. It's textured on the top to help tighten them by hand. They come with new rubber o-rings. If you get the type without o-rings, you need to use a wench to tighten them. (make sure you use a counter wrench also)

Cheers!

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