New tech, leak check question

[LordoftheFreon]

I've done 3 leak tests so far in my new career. At first I trusted the tools I am using and now I don't. I've heard that the leak is almost always in the evaporator coil, and that is where I have thought it was every time so far, and so far it's seemed to work out, but i think that may only be because of the fact that it is USUALLY is there. I don't think I'm finding the leak.

We have a sniffer and I use the UV dye. When I did my leak test today, I turned off the light in the attic and used the goggles, the UV light AND the sniffer. I saw a faint line of green on the evap coil... but I thought it should be brighter than that. Also, when I put the sniffer to it, even on high sensitivity, the sniffer didn't make the rapid "leak beeping." But the sniffer DID indicate leaks... only seemingly randomly... it never beeped in the same place twice. This guy's unit was a block of ice when I showed up (I came back after thawing) and my gauges read low pressure, freezing evap coil when I came back. I checked the coils, both were reasonably clean, both fans were running fine, this is why I did a leak check.

However, I definitely don't want to replace his evap coil only to find out he has a leak in the condensing unit, so I head out there. The UV light seems USELESS in daylight. I use the sniffer. It goes NUTS near the compressor... but won't REPEAT this. Even though I try to replicate it over and over. So I cup my hands around my goggles, use the UV and try and see if there is any green in that area. I see nothing.

I'm convinced the sniffer is garbage. I'm afraid I've diagnosed a leak in the evap coil on low evidence... and am still not confident there isn't a leak outside somewhere, considering I no longer trust my tools.

Am I nuts?

[beenthere]

Some leaks are hard to find. And need to have the system recovered except for a few ounces as trace gas, and then nitrogen used to bring the system up to a high pressure and checked.

Most leak dyes need to be put in and allowed to circulate for several days. How long was the leak dye in the system?

[LordoftheFreon]

It was only in the system about an hour. I was going to come back the next day because I noticed that seems to be what everyone else does... but after I read the package of the dye, it said to "leave the system on for 30 minutes to circulate) and the homeowner was quite desperate for answers, so I came back an hour later. After reading the package and believing it only needed 30 minutes, I thought everyone else must be coming back the next day because of scheduling conflicts. We are very busy all the time pretty much.

Do you think this is what I did wrong? Though, I still think our sniffer doesn't work.

[beenthere]

The dye travels with the oil, which travels with the refrigerant.

Its a relatively small amount of oil that travels with the refrigerant, so not much oil or dye circulates in 30 minutes.

Myself, I prefer to add the dye, top off the system, and then come back the following week to look for the dye. That gives the system plenty of time to circulate the oil and dye, and enough dye to come out to find it easier.

Since the leak rate is unknown, I never assume the dye will show in a short amount of run time.

If your area is a high heat area, and the unit will run a lot, 3 days may be enough time.

[Snapperhead]

My sniffer hasnt come out its case in 3 years , it drives me Nuts

If I dont see oil residue outdoors , or on the line set brazes , line set isn't rubbing anywhere , shraders dry , its in the evap

I will look for traces of oil in evap real quickly , or rubbing capillaries , then Im calling it the evap

I have found a few caps rubbing and brazed those

[garyed]

You have to be careful with detecting small leaks in the condenser especially if you already put your gauges on it first. Sometimes you can be detecting gas just from using your gauges on the system. Unless it's an obvious big leak at the condenser I always come back double check it. If you have a slow leak under an accumulator it's hard to pinpoint. Some of these new aluminum coils will drive you crazy too. I've had the same coil set my leak detector off like crazy one day & then not even show up a leak the next day. I think there is some type of expansion & contraction going on that I've never experienced before. Using more than one leak detector is a really good idea because until you feel it or see it bubble the only thing we can do is trust our leak detector & hope its right.

[FlyersFan]

I don't have any experience with dye so I can't help you out on that front. As far as electronic detectors go: practice, practice, practice. And get a good leak detector. If a detector won't sound off in the same area twice, it's likely not leaking there. I agree with bumping up the pressure with nitrogen to help find a leak, and I've even gone so far as running the heat to warm up the joints in the evap coil so they might leak a little faster.

[leslie cook]

I have had a few condensers leak under high pressure when running but not under static pressure.

[Hurst11]

I have had a few condensers leak under high pressure when running but not under static pressure.

I know for sure that is possible but nobody ever seems to think it’s possible around my area. It absolutely drives me nuts when I bring that up and people go yea your full of chit. Glad to have finally found someone who had seen it too.

[Hurst11]

Number one thing is a quality leak detected and learn it like the back of your hand. After a while you will get a feel for if it’s going off randomly or if it is something worth looking closer at. Gotta be careful when looking in the condenser after putting the gauges on cuz that gas that comes out can linger down low in the machine and in the coil for a long time. Also carry you some bubbles and when ya start picking something up with the detector,spray some bubbles to confirm yea or na Be careful with the bubbles tho cuz some of them will set the detector off as well. Your right in 9 times outa 10 it’s in the coil but ya still gotta find it to cya. The longer ya do this you will learn all the different equipments most common leak areas and you can check them easy and quick

[LordoftheFreon]

Thanks so much for the replies guys, I had to do another leak test YESTERDAY. I put in the dye and won't be back for four days to check. I will also bring some soap bubbles. And I won't give up on my sniffer yet. I want to know I'm finding whatever leaks there may be for sure.

[catmanacman]

why was the HO desperate for answers , how low was the unit , how old is the unit . i personally won’t use dye i will run the heat if it’s gas heat or a heat pump then re sniff.

[rquave33]

Leaks are a pain. Honestly if it's the frist time I go to a job and the leak rate is unknown and the customers says it's been a long time since it's been service and the uint is only slightly low I do a quick once-over and charge it and make them sign that they have a leaky system and I can't guarantee it unless they let us perform a leak test...9/10 go for the just put some gas in it. Also I would say 75% of leaks are in the evap also check your dryers. The fact you see any green means it leaking though but as others said you really need to let it run for a bit with the right charge in it.

[Saturatedpsi]

What leak detector do you have, what refrigerant are you trying to detect and what is the rate of loss, approximately?

[gbfromsd]

Definitely an art leak search is. Get good at it and they will call only you. Electronic detectors hit on a leak every time the tip passes through the flume. Use your fingers to direct the flume and angle the tip to stay on the flume. If it doesn't repeat every time, it's not a leak. Always keep in mind detectors zero out on the ambient concentration so remove your tip to clean air often. Soap works well down to the very small but you have to leave it for a few minutes to see a cocoon. Large leaks will blow through the soap, wrap a finger around the joint to see bubbles from behind or large leaks. Soap isn't what it used to be though. Where did Big Blue go?? I've had good success with ultrasonic. Funny to find a leak in a lineset from 20ft away

[3.14]

I have had the same issues over the last 20 years or so... to the point that I rarely use an electronic leak detector. I’m sure some would disagree, but in my experience I have had more success by looking for signs of oil and then spraying soap solution all over the place. If this doesn’t work I will run a leak detector around to see if I can get any “clues” (usually resulting in what you have described, “random hits”). My next step is dye and then a full blown isolation test.

I honestly can’t say that an electronic leak detector has ever given me anything other than clues as to where a leak is.

I spent a week once looking for a phantom leak, finally resorting to an isolation test and found a very leaky liquid line on a 7.5 ton commercial system with piping under slab (an approximately 125 ft. line set). We replaced the refrigerant lines overhead and the problem was solved.

To summarize, if you can’t hear or see the leak you probably won’t be able to smell it either... at least not pinpoint it. Maybe I’m wrong but I have spent WAY too much time fooling around with electronic leak detectors only to finally pin it down with an isolation test.

Another note, make sure you rule out leaking service valve stems early in the process... I have repaired many leaks to find I could still not pull a good vacuum, only to find the service valve o-rings were leaking... SO frustrating.

I know isolation tests are a pain in the a@@ but they are also extremely dependable.

[garyed]

Everybody has their way of doing leak tests that they find works the best. For me when it comes to an electronic leak detector I "don't leave home without it". I use mine as much as I do a volt meter. It is true they are not good at pin pointing leaks but they can sure save a lot of time getting you close. I use soap bubbles to pinpoint once I get close. A lot of times you don't need to pinpoint the leak but just get in a general area.
I can't count how many times I've had a leak in an older system & found it with my electronic detector in 5 minutes in the condenser or evaporator, then sold a new system without ever having to pinpoint the leak. When you have an old system with a leak, the main thing is to determine whether the leak is in the equipment or in the line set. I've never used the ultrasonic detectors but i heard they are pretty good too. Line set leaks happen but they are pretty rare & I would guess that I probably do an isolation test about once every two years. My advice to any tech would be to invest in a good electronic leak detector & keep soap bubbles with you. Now what's a good electronic leak detector is a whole other discussion, especially since they got rid of the H-10G.

[Hurst11]

I use my a lot. On the equipment I work on ya mostly know all the easy common places they leak. Very first thing I do is visually look for oil first and if I don’t find anything I’ll pop the coil door off and if it’s oily I use my detector to get me close then soap to show exactly. After I’ve forund it I’ll have the homeowner come up and show them what is going on. I have found most homeowners really like for ya to show them where it is. I started doing that on all of em after I had a customer who wouldn’t believe me it was coil leaking because some other person didn’t know what they were doing and sold him a coil that turned out not to be leaking. That was at his previous house so when he wouldn’t believe me bam right here it is sir. I can put ya a new coil in tomorrow. New customer for life.

[LordoftheFreon]

Thanks everyone again, I learn a lot from what everyone has to tell me. I'm determined to get better at this and will probably try EVERYTHING lol