Nitrogen leak testing

[atikovi]

I got a nitrogen regulator and bottle for checking leaks. What pressure should I use? How long to let the system rest with no drop in pressure to call it good?

[70monte]

I've been told several times and read a few places to go to 150 psi. That is what psi I use. I usually let mine rest 30-60 minutes but I know some people let it sit overnight.

[Tim]

I've been told several times and read a few places to go to 150 psi. That is what psi I use. I usually let mine rest 30-60 minutes but I know some people let it sit overnight.

That is what I understood as well. Something I read a long time ago, evap cores are designed for burst pressure of 150psi.

[atikovi]

I pressurized the system and sprayed down the lines to check for leaks. Found the upper condenser fitting leaking,



I replaced the o-ring and pressurized it again to 175 psi at 7:30 pm yesterday with 76°F. Do I still have a leak or are these readings normal?

9:30 pm 72° 145 psi
11:00 pm 71° 145 psi
7:30 am 67° 140 psi

I can assume the overnight drop of 5 psi is from the drop in temperature. What about the 30 psi drop in the first 2 hours? Is that just the nitrogen migrating throughout the system?

[70monte]

I've been told several times and read a few places to go to 150 psi. That is what psi I use. I usually let mine rest 30-60 minutes but I know some people let it sit overnight.

That is what I understood as well. Something I read a long time ago, evap cores are designed for burst pressure of 150psi.

Yes, the evap seems to be the weak link as far as pressures go for testing purposes. 150 psi seems to work fine.

[70monte]

I pressurized the system and sprayed down the lines to check for leaks. Found the upper condenser fitting leaking,



I replaced the o-ring and pressurized it again to 175 psi at 7:30 pm yesterday with 76°F. Do I still have a leak or are these readings normal?

9:30 pm 72° 145 psi
11:00 pm 71° 145 psi
7:30 am 67° 140 psi

I can assume the overnight drop of 5 psi is from the drop in temperature. What about the 30 psi drop in the first 2 hours? Is that just the nitrogen migrating throughout the system?

I would think that you shouldn't have any significant drop if you don't have a leak but since it didn't drop much for about 10 hours, I don't know. The temperature drop is not that much during the 12 hours time period so I wouldn't think it would cause the 35 degree total drop.

[atikovi]

Well, at 10 am it was still at 140 so I vacuumed 2 hours and then charged. Will see how long it lasts.

[Cusser]

Well, at 10 am it was still at 140 so I vacuumed 2 hours and then charged. Will see how long it lasts.

I think you made the logical choice.

For that area, you can test for leaks with soap bubbles.

[tony1963]

A 5 psi drop at rest wouldn't be a way to measure if you lost some refrigerant. I would attribute that to a temperature change.

The soapy water test is a better way to test than with dye. I prefer an electronic leak detector but would be fine with soapy water in lieu of.

Nice job diagnosing.

[Q451990]

Here's a nitrogen pressure calculator. I have found that it follows what Fieldpiece uses for their temperature compensation in their gauges for their "tightness test."

https://www.oceanhvac.com/nitro.php