Electronic leak teasting

[eggs]

Hi all
Could sombody help please?
I have just installed a freezer cold room and when it came to the pressure test, it was leaking.
I am loosing about 2 psi/hour.
The soapy water test came up blank.
I am going back in the morning with the electronic tester and the question is:

How much 404a do i need to mix with my nitrogen to enable the detector to detect ?

appx 4mtr pipe run of 3/8 and 7/8, and a working charge of appx 12kg. (the details are still on site).

Hope this is enough info

Please Help, it drove me mad yesterday.

cheers

eggs

[Brian_UK]

Before you start adding 404a to your test pressure a couple of questions/thoughts...

Have you tried testing in sections ? Condensing unit - liquid line - evaporator - suction line. Is the condensing unit precharged ? in which case - are the line valves holding, has the condensing unit pressure increased ?

Is your gauge set/hoses leaking ?

Is the TEV leaking around the head ? Is your soapy water mix good and strong so that the bubbles stay on the leak and are not blown away ? Try building up your test pressure in stages so that you get an indication of when the leak starts, this can sometimes point you towards the likely size of the hole; bear in mind that an increase in pressure can push two pieces of tube together and partially close a leak off.

Anyway Eggs, I wish you well.

[eggs]

The trouble is the job is in a prison and we only have very short working times, because the freezer is next to the excercise yard and all tools have to be locked away before one group of convicts get banged back up and the next load of rabble go for their walkies.So we only get about 45 mins to seperate the system to test the seperate parts.

Another frustrating day ahead me thinks !!!


cheers eggs

[Jasper]

Is your gauge set/hoses leaking ?

Sounds like the cause to me

[chemi-cool]

Hi Eggs.

We have discussed the leak test using Helium.
From what was said there, I am using today as Andy suggested 85% OFN and 15% helium.

No need for any electronic gadgets, just soapy water, you will find the leak in seconds, check the gages as well.

Good luck.

Chemi

[eggs]

Found the bloody thing !
Right in the middle of the evaporator coil.
Funny thing is, when i opened up the system to install the pipes, there was pressure there ???
Must have been the increase in pressure that opened the hole it up.
Anyway "Warranty Claim"

Cheers for the thoughts


eggs

[adam]

why helium? how does it work in helping find a leak?

[chemi-cool]

Hi adam.

Helium molecules are smaller then OFN and therefore escape from smaller holes in the pipework so its easier to locate a leak.

Of course you need to use soapy water or buy a special Helium leak detector (very expensive).

Hope this answers your question.
The best, have a go. You will be surprised from the results.

Chemi