How to Leak Test an AC With Nitrogen Pressure

in this video i want to talk about nitrogen pressure testing and leak detection it's a pretty simple seaming subject but it's an area that a lot of mistakes are made because again the nitrogen pressure test is the place that we confirm that we don't have any leaks especially after we've brazed in all of our copper connections made all of our flared connections or other types of mechanical connections and so it's really important that we pass or fail so that way we know if we have any additional leaks it's a super important part of a clean dry and tight system which is what allows a new air conditioning refrigeration system to last a really long time [Music] all right step one before you're going to pressure test anything or do any further leak detection you want to make sure that there are not any leaks at your schrader course now again depending on if this is a brand new system or if you've made a significant repair or whether you're walking up to a system for the first time this is going to vary how this is going to go but if you walk up to a system that has any signs of oil around the schraders you're going to want to go ahead and address those right away so generally speaking the best bet would just be to go ahead and pull out the old schraders and replace them to eliminate them as a potential problem also make sure that your caps have seals any hoses you're going to connect for your nitrogen pressure test should have nice new seals in them and then another thing to keep in mind is when you are bubble testing a best practice in bubble testing is to put a cap over the port with no seal in it and then spray bubbles on the cap rather than spraying bubbles straight into the schrader port if you get soap in there obviously we don't want that in the system so putting a cap over it with no seal will kind of act as a dust cap but will still allow anything to leak out and that's just kind of a good practice if you are going to bubble test them you can also bubble test your actual hoses or any of your connections after you're under pressure before you're going to pressure test you want to purge nitrogen through the system now that's different than flowing nitrogen flowing nitrogen is done at a super super low pressure something like three to five scfh purging can be done at a much higher pressure this image here is showing the western nitrogen regulator that has the purge mode right on it but generally speaking i'm going to purge it's something like 100 psi and that's just purging through one side and allowing it to flow out the other side and this just ensures that we displace as much air and oxygen as we can before we pressurize then we're going to attach pressure probes to each side of the system i'm showing here using two crts core remover tools with the pressure probes on the sides you can use a different strategy using a manifold if you like just keep in mind that the more connections that you place into the system the more likely those connections themselves are going to be the leak point also commonly with manifolds the actual gauge where it attaches to the manifold body is a possible leak point so you're going to want to make sure all of those are leak free as well next you're going to pressurize the equipment with 250 to 600 psig of nitrogen that's typical again you want to follow the manufacturer's recommendations generally speaking if you are going to be pressurizing the low side of the system you're going to use the low side test pressure if you're working on something like a vrf or vrv system that's where these higher pressures would come in and those are recommended by some manufacturers once you get up to your desired pressure range then you're going to valve off the nitrogen from the system this is a nice way you can use crts because they give you nice easy ball valves the good quality ones that are designed for vacuum also hold really nicely with their design you also do want to make sure that you are not leaking out of the end and again that's where you can once again use that technique use a cap with no seal in it cap it and then bubble test it around that cap rather than spraying bubbles right in the end of a crt just to make sure that you're not leaking there especially when you're using these higher pressures like 500 or 600 psi next you're going to let it stand typically for 30 to 60 minutes that's going to be a very standard residential type of test pressure time frame if you're doing something like a vrf or vrv system where you have much higher internal volumes a lot of piping and you have to make sure you do not have leaks then sometimes they're going to have you sit 24 even 48 hours so that's why i mentioned you know do it according to manufacture specifications if you see any drop that's where you want to start over again start over and make sure that you test everything either way i'm going to use soap bubbles on any field fabricated joints especially any braised joints or any flares that we made while you're under this pressure test and just checking for small micro bubbles if you are going to perform an electronic leak detection you would have had to put a little bit of trace refrigerant in first and again that varies quite a bit there is no standard guideline i can give you of how much to add that's one of the common questions we get how much trace refrigerant do you add um you're not going to add a lot generally speaking on a residential system it's going to be well under a pound and you're just going to put it in the vapor phase it's just so that way you can trace and find it with an electronic leak detection once you have passed or failed now you release the nitrogen you proceed with whatever else you're going to do if it's a new system or you've replaced a component the next step would be the vacuum generally if it does fail then you again start over use your soap bubbles or use your electronic leak detection methods now one thing i also want to mention is using a nitrogen pressure calculator if there is a significant change in temperature so let's just use an example let's say we put in 300 psi which would be a very standard pressure to use if the temperature started off at 90 degrees and then the average temperature dropped to 70 degrees over the period of time of the pressure test my pressure would drop to 288 psig again you also see here i calculated the atmospheric pressure at sea level so you would also need to calculate that and so it is normal for nitrogen pressure to change within the system if there is a significant change in temperature but keep in mind that temperature change relates to both the inside and outside if you've got a split system and the evaporators inside and the condenser is outside and you're pressurizing everything that's going to be an average of everything both inside and outside and that can be a tricky business and so just recognizing primarily that there will be a change in pressure if there's a change in temperature generally if you're doing a 30 minute to an hour type of pressure test there's not going to be a big enough change that it would matter if you're doing a 24 hour or 48 hours something really long like that there could be a significant difference and using a nitrogen pressure calculator can really help so that's it that's some of our best practices for nitrogen pressure testing make sure you use a good quality regulator make sure you have no leaks try to keep it as simple as possible and monitor that pressure on both sides another thing to keep in mind that i've mentioned in previous videos is if you are pressurizing on the liquid line and you're watching your suction side come up which is what i generally suggest put it in the liquid line watch the suction side come up if you're doing higher pressures and you have a hard shutoff txv you'll hit a point where it will stop flowing through because that hard shut off txv closes off and so that's something to think about and when you get to that point you would have to pressurize from both sides in order to get up to those higher pressures if you are pushing through a hard shut off txv all right that's it thanks for watching we'll catch you on the next video thanks for watching our video if you enjoyed it and got something out of it if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click the notifications bell to be notified when new videos come out hvac school is far more than a youtube channel you can find out more by going to hvacrschool.com which is our website and hub for all of our content including tech tips videos podcasts and so much more you can also subscribe to the podcast on any podcast app of your choosing you can also join our facebook group if you want to weigh in on the conversation yourself thanks again for watching you

Channel: HVAC School

Views: 150,843

Keywords: How to Leak Test an AC With Nitrogen Pressure, nitrogen pressure test, nitrogen pressure testing, nitrogen leak test procedure, ac leak test, nitrogen test ac system, nitrogen pressure test gauge, Leak test ac unit, nitrogen pressure test air conditioning, ac test, hvac school, vacuum test ac system, bryan orr, hvac, how to, pressure test, heat pump, air conditioner, heat pump troubleshooting, nitrogen, air conditioning, hvac training videos, ac system troubleshooting, Txv

Id: JaSUDn2VU04

Length: 8min 0sec (480 seconds)

Published: Tue Jan 19 2021