pressure tested with nitrogen

[hvac7]

I pressure tested lineset on an A/C unit with 300 psi of nitrogen for about 20 minutes. Is this enough time to detetmine if there is a leak or should it be longer? Like I have stated before I have mainly done nothing but rough-in installation and have not much experience with service. I thought I would never say this but I really like the side of the trade much better!

[ac rookie]

That should let you know. I usually use less pressure than that for about the same amount of time. While I wait I will usually go ahead and test with bubbles on all my connections.

[chicago installer]

plenty of time , usually you will find the leak, realy quick, with that psi

[hvac7]

I hope I am correct when I say 300 psi. What I mean is I use my high side gauge on my manifold set and pressurize the system till the gauge itself reads 300. Is this correct?

[HVAC Pro]

Could be a waste of good nitrogen. 150 psi. should do it. Check all joints with a liquid leak detector. If you can hold a 500 micron vacuum after checking your joints you should be leak free.

[hvac-tech-lane]

I used to think that a test like the one you are doing was fine but there can still be a small leak that the test won't show. I now always use some 22 tracer gas, boost it with nitrogen to about 120 PSIG and sniff the whole system wit my D-Tek. I've found some leaks with this method that the standing pressure test didn't show.

[big d tech]

Originally posted by hvac7
I pressure tested lineset on an A/C unit with 300 psi of nitrogen for about 20 minutes. Is this enough time to detetmine if there is a leak or should it be longer? Like I have stated before I have mainly done nothing but rough-in installation and have not much experience with service. I thought I would never say this but I really like the side of the trade much better!

The one problem that I have heard of when testing with that much pressure (300 psi)on a pre-charged system is that you run a risk of pushing nitrogen into the charge of gas if the valves are not totally tight. Now you have a non-condensible in your new system.

I would have to agree with hvac-tech-lane, a trace gas is really nice because if your leak is really small it is sometimes hard to see in a short time (20 minutes)by pressure loss alone. So if your not sure if your loosing pressure it sure is nice to have a trace gas to double check with. And having it in there the first thing saves blowing the straight nitrogen charge to put in a sniff of R-22 and re-pressurize.

But that's just my view :-)

[seatonheating]

To big D and hvac tech,

I agree with your thoroughness, but we must express that good brazing practices are the key. Most of the time I feel that a leak test isn't necessary ( I still do one), because of the fact I know I have done a good job brazing my line. Therefore, I only pressure test to maybe 150 psi for a few minutes, I know when the job is done right, this basic pressure test verifies that.
Josh

[sadlier]

SeatonHeating hit it on the nose. If each braze joint is puddled at the joint so that you can physically see that there is no leak then chances are there is no leak. Of course it's good to have an inspection mirror and flashlight for being able to completely inspect each joint. An ounce of inspection can save an hour of detection.

[hvac-tech-lane]

Originally posted by seatonheating
To big D and hvac tech,

I agree with your thoroughness, but we must express that good brazing practices are the key. Most of the time I feel that a leak test isn't necessary ( I still do one), because of the fact I know I have done a good job brazing my line. Therefore, I only pressure test to maybe 150 psi for a few minutes, I know when the job is done right, this basic pressure test verifies that.
Josh
I agree and disagree, so you're saying your batting 1000, why run the 150 standing test. Yes I hold a brazing certification and very seldom have a leak, however sometimes when you're standing on your head trying not to catch the building on fire, or bake a valve and only have 1/2 inch behind the joint and you're in a hurry, even with good practice my leak checks have saved me trouble down the road. Say a split system total charge was in the neighborhood of 6 pounds and you had a small leak that didn't show up with a standing pressure test, say 1/2 oz. per year of R-22 which my D-Tek will pick up quite well. How long until the system would manifest a problem that would generate a service call or be caught on the standard PM? If only one pound that would be 32 years,(I'll be retired by then hopefully) so it is quite possible that many systems could have very small leaks not detected with pressure tests. Not really trying to bust on you josh, just speaking from my experience and opinion.

[maxster]

if you did the full pipe up you know the joints that might of needed more attention when brazing,but for the condenser and AHU they should be tight from the mftr.then on the vac side pick up a good Micron guage,and that will double check your system.....its all in the routine of doing this that it becomes second nature.

[klyons20]

I never preasure check unless, I have to piece pipe together. I just make sure I do a good braze on both ends..
If it aint right the costumer will let you know in a couple of days. I rarely get a call back..

regards,
kelvin

[sadlier]

Originally posted by klyons20
I never preasure check unless, I have to piece pipe together.You better double check the codes. If the IMC has been adopted (including the residential equivalent) then you are not giving your customers what they paid for.

[klyons20]

What are you talking about?

My rule is to use only one pick to make the conection so, if I have a problem it can only be at the condenser or A coil. I dont piece pipe. The key is to make sure you have a good braze. Now if there is law that says you have to preasure check .. I would like to see it. I install 3 or 4 ton system by myself in 3 to 4 hours never get a call back.

regards,
Kelvin

[sadlier]

Originally posted by klyons20
Now if there is law that says you have to preasure check .. I would like to see it.IMC Section 1108, in particular 1108.1 and 1108.2. Whether it is law or not depends on whether it has been adopted for your area.

[badbillr]

after brazing, always pressure test the system w/ nitrogen. you can add some tracer gas if you like. i use an ultra-sonic meter, no need for trace amount of freon. a quick pressure test will let you know if you have a sizable leak. once it passes the pressure check, then put it on a vacuum. really should have a micron gauge. if you can get the vacuum to 500 microns or less, you have no leaks. even the smallest of leaks won't allow you to achieve a 500 micron vacuum. i service & repair a lot of medical refrigeration equipment. those manufacturers want the micron rating to be less than 200 microns.

[johnl45]

Originally posted by klyons20
What are you talking about?

My rule is to use only one pick to make the conection so, if I have a problem it can only be at the condenser or A coil. I dont piece pipe. The key is to make sure you have a good braze. Now if there is law that says you have to preasure check .. I would like to see it. I install 3 or 4 ton system by myself in 3 to 4 hours never get a call back.

regards,
Kelvin What's a pick? Install new system including A coil, condenser and electrical by yourself in 3 to 4 hours (wow) can you post some pictures?

[klyons20]

I can do it in newely built houses only.

Dont have to change wire to t stat
Dont have to replace T-stat
Dont have to add condensate pump
Dont have to add fan center
Breaker box is up to date
Wide open basement makes it easy to run se cable
Also use se cable so you dont have to drill many holes..


you also have to be a good planner



[Edited by klyons20 on 06-12-2005 at 11:18 PM]

[websy]

For all the time it takes to pressure up a system and check the whopping 4 joints(linesets)....why the hell wouldn't you test?? Or are you using those precharged, self piercing line sets(more commonly known as plumbers linsets)???

Many times I have found leaks in brand new evaporator coils. Condensing units and Evaporator coils can all have leaks from the factory. More than once I have opened my valves on a new condensing unit only to see my vaccum dissapear then stop.


-websy

[seatonheating]

Hvac tech, I'm not saying that leak testing isn't important. But in my experiences with thousands of systems installed, and being the one who does the yearly maintenance( all systems holding charge I might add), I don't see it necessary personally to overdue it and waste alot of time. Keep in mind I do pull all my systems down to 500 microns, ensuring a quality job.

[klyons20]

What is the ICM?

[sadlier]

ICM is a rental company where you can get forklifts and scissor lifts. IMC is the International Mechanical Code (formerly known as the Uniform Mechanical Code).

[donphillipe]

I am new to leak detection but not general servicing. I am trying to find a leak on an old system I just inhereted for servicing. I had been told that 150 PSI was the maximum anyone should use for leak detection but since that showed nothing, today I gambled going up to 250 PSI and find I am losing about 2 lbs of Nitrogen psi per hour. (I see here that some people are using up to 400PSI to test???)

I have a spray bottle of 1/4 dish washing soap, the rest water and can't seem to find the leak. I have sprayed all the welded junctions on both evap/cond and welds along the line. Any insight on something more I can do with the equipment I have on hand?

Some questions:
- is this the best solution (soap/water ratio) to test junctions for leaks?
- should I crank up the Nitrogen PSI to 400 on this 15 year old system?
- should I expect a fairly obvious display of bubbles on a 2 lb per hour leak at 250 PSI?
- where else should I look for a leak?
- I have a D-Tek Inficon that would not detect this leak at any of these junctions either (previously when the system had a normal freon charge)
- will adding some of the freon back into the mix and then applying a high nitrogen pressure improve the sensitivity of the D-Tek?

[tinknocker service tech]

add a little freon and bring it to about 150 to 200 and look for your leak. 400 is way to much and you may make a leak you didnt have before. also if you have a weak joint and it lets loose at that presure it could cause a lot of damage or pain

[mark beiser]

I pressure test with around 115 psig of nitrogen so that I can use my compound gauge to watch for a pressure drop. Much better resolution on it than on the high side gauge.

I also have a Draco Systems ultrasonic detector that I set on its highest sensativity and check all my joints. I don't know what the smallest leak is that it will find, but I have found some very small leaks with the thing before.

After the pressure check, I evacuate the system to <500 microns, usually <400.

[hvac-tech-lane]

Originally posted by donphillipe
I am new to leak detection but not general servicing. I am trying to find a leak on an old system I just inherited for servicing. I had been told that 150 PSI was the maximum anyone should use for leak detection but since that showed nothing, today I gambled going up to 250 PSI and find I am losing about 2 lbs of Nitrogen psi per hour. (I see here that some people are using up to 400PSI to test???)

I have a spray bottle of 1/4 dish washing soap, the rest water and can't seem to find the leak. I have sprayed all the welded junctions on both evap/cond and welds along the line. Any insight on something more I can do with the equipment I have on hand?

Some questions:
- is this the best solution (soap/water ratio) to test junctions for leaks?
Check out Big Blue web site

- should I crank up the Nitrogen PSI to 400 on this 15 year old system?
Although it should be able to handle it it's not recommended, and shouldn't be necessary.

- should I expect a fairly obvious display of bubbles on a 2 lb per hour leak at 250 PSI?
Not necessarily

- where else should I look for a leak?
Wherever there is refrigerant in the system.(I and many techs have found leaks in compressor cans.)

- I have a D-Tek Inficon that would not detect this leak at any of these junctions either (previously when the system had a normal freon charge)
- will adding some of the freon back into the mix and then applying a high nitrogen pressure improve the sensitivity of the D-Tek?
Yes i take a system up to about 20 psi with ref. then boost to about 100 with nitrogen.
Check your D-Tek so you know it works normally at your hose connection, then go after the leak with a can do attitude, its clearly there you'll find it. Give us a follow up.

[klyons20]

When checking a leak on an older system the first thing to do is to look for oil residue around the joints. If the unit leaks it will leave a sign. I find most of the leaks are around the service valve.

For example I went to a job to charge a system. I put my gauges on the system O psi. I noticed that the compressor had been replaced not mounted down properly, no valve cover, oily residue around the area, condenser very dirty.
This was a 5-ton unit with 7.5 pounds of Freon.

I charge nitrogen into the system about 200 psi. I start spaying everything with special bubble spray.

Bubbles start forming at top of suction service valve. I went back to the truck got some plumber tape and wrapped threads put back on cap tighten it down. Check again bubbles stop. Then notice freon coming out of strater valve on suction side I put a cap on that tighten with hand then 1/8 turn with pliers.

Leaks all sealed. Charge system. It took me 5 min to find leak.

Steps for leaks detection

Look for oil residue
Make sure caps on valves (some have a little gasket in side make sure that it is in place. In fact buy a bag of these caps so you will have them on hand.
Buy you a special formula for leak detection at the store.

Start spaying known joints. and all visible pipes even with installation on it. If it leaks it will show.

Its amazing the things that were hard. The more time you put in it becomes easy.

[stonewallred]

since we are talking abut leaks.

Yesterday spent two and a half hour looking for a leak.
Checked with sniffer, found refrigerant present, used ultasonic and couldn't hear it, used soap bubbles and couldn't find it.
Pulled a 400 micron vac on it two months ago and it held for over an hour while I ate lunch.
But had to add refrigerant to unit yesterday to bring it to proper charge and operation.
Sniffer goes shell shocked right at the cap manifold where they come off the the evap TXV. So I can visually check quite well and can not hear the leak or see soap bubbles.
Now what would be the deal here?

[jack david]

I normally pressure check with nitrogen because when I was a helper I remember more than 1 occasion (and different manufactures) where a leak was found in the coil. Point is it had nothing to do with the techs brazing skill.

[klyons20]

Most evaporators are charged with nitrogen. This helps keep it dry in side. and is a indicator that it holding preasure.

[oogene]

just found a leak in an air cooled condensor on a trailer reefer today. tried with 150 psig. no-go, 200 psig. no-go, 225 psig. no-go, bled system back down to 100 psig. to get manifold needles in the marks so I could monitor bleed off, decided to try more soap bubbles and found leak within a minute !!! (still want to get one of those ultrasonic detectors though)

[donphillipe]

I forgot to come back here to state where my leak was found, so I am thinking better late than never.

This system had many leaks. I had already quickly fixed the leaking king values by putting a super tighten on the caps and fixed the leaking service ports by using brass caps with o-rings. (I could not get the schraders out because previous tech had tightened the flare caps so tight that they could not be removed.)

The service valve area was the only location on the system that I saw any oil whatsoever. My D-Tec leak detector did not indicate anything when I tried inserting it in the evaporator drain for 10 minutes. I also went outside, covered the condensor with blankets and sniffed under there as well. Nothing.

I also used nigrogen to try various pressures suggested here, starting at 100 and going up to about 225. The leak "sped up" to about 1 psi per hour once I got to 200psi. At 100 psi, there was only about 1/2 psi lost in 8 hrs. Going to 200psi gave me the 1 psi per hour leak.

I used almost a quart of liquid leak detectant to no avail. I finally went with someone's suggestion here to look first at the evaporator. I pulled the evaporator, sealed it and put 200PSI on it. Sure enough it was losing about 1 psi per hour (same as I had seen on whole system pressure test). More Big Blue and still no indication to be seen. I turned it over on its side so the bubble liquid would pool on all the evaporator joints. I finally saw it! About 75% of the joints were leaking, all now showing microscopic bubbles. I didn't see any bubbles with 200PSI of nitrogen on the system and with the unit in its upright position.

A new evaporator and no more leaks! Thanks to everyone for all the tips.

[mark_aanr]

Must have been a Carrier evaporator coil......

Mark

[donphillipe]

Goodman :-)

[inturmoil]

You guys need to use 409 (yes, the cleaner)to search for leaks. It makes a nice foam on small leaks. . . . .leak searchng can really be a pain in the ass when you have a stack of calls!

[j-man04]

at 300PSI u will either find the leak or make one

[wannafreeze]

Originally posted by inturmoil
You guys need to use 409 (yes, the cleaner)to search for leaks. It makes a nice foam on small leaks. . . . .leak searchng can really be a pain in the ass when you have a stack of calls!

I checked the msds for this.Doesn`t sound good.