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phs
17-05-2011, 10:04 AM
hi iv got a question for all you pro's might be able to help me with this unit is at my house installed by me 2 years ago leaking only on heating mode not under test pressure, now i am licensed to install domestic spits so im not a home handy man,..... so ill start from the start .............

noticed oil on flashing a few months back turned it on heating tested found leak back of head unit on 5/8th line recovered gas (R410A) loosened 5/8 comp nut applied oil and tightened nut back up tested with nitrogen at 550psi with gauges connected at 550 psi for 5 hours valves open, no leaks. evacuation was for 1.5 hours with a 75/lt pump got it to 330 microns turned hose valves off for 10 minuets after the test time the digi vacuum gauge had creeped to 370 microns, thow atmospheric temperature was rapidly dropping as when i started vac in it was 16 deg c and by the time it tested it was 12 deg c.

is there a leak or is it the temp change ? and why so long to get it to 330 microns ? its a 10 m run of pipe 5/8th and 1/4. has it got to do with the feron oil in the lines?

any input would be great as i dont want to stuff around with it again . i also have a infacon tekmate sniffer so i can check once gas it in and operating but rather get more info before going further

cheers

phs
17-05-2011, 01:00 PM
well i continued vac in the system down for another 2 hours, got it to 200 microns closed gauge valves test for 10 mins. over the test it creeped up to 230 microns. the out side temp had dropped to 6.8 deg c. is it even possible to get it as low as 200 microns with a leak ?

yorkman_gr
17-05-2011, 01:32 PM
nitrogen having not effect in pressure changing in this temperatures the P= constant with nitrogen, maybe u have more leakage's or to much ***** remain in your oil and is dumping out

monkey spanners
17-05-2011, 02:01 PM
If you had a leak the vac reading would be in the thousands to tens of thousdands, as you say disolved refrigerant in the compressor and lines can effect the time it takes to get a good reading. Sounds ok to me!

I always like to make a new flare on some fresh pipe and braze it in to replace leaky flares, though if i'm pushed for time due to needing to get the plant running again asap and the original flare looks ok i'll heat it up till red hot and let it cool and clean it up, this will soften the copper again and help it seal nicely.

chemi-cool
17-05-2011, 08:46 PM
If there is a leak only in heating, then its on the low side pipes connections.
Open them, redo the flair, put some oil on the copper and nuts, close and vac.

Trying to tighten nuts not always help.

phs
17-05-2011, 10:01 PM
Thanks for the replys. So on nitrogen there was no drop over 5 hours , the leak was on the suction line on heating the flare. I un did the nut inspected the flare it was fine it was covering 95% - 100% of the flare And it was done with a rothanburger ratchet 410a flaring tool. I think it was nt tight enough . I applied oil and re tightened.

As for the vacuuming , so u don't think with a small leak that it would suck down any where near 200 microns ? is the presure rise of 30 microns over 10 mins acceptable considering the temperature change ?

monkey spanners
17-05-2011, 10:19 PM
I wouldn't worry over a 30 micron rise, i'm doubtful the vac gauges are that acurate at such a small pressure difference anyway.

phs
18-05-2011, 02:17 AM
Ok cheers I'll charge it up in a few days get it running and I'll just go over all the joints with the tek-mate to sniff any leaks , but yeah just wanted to be sure before I go any further ... Thanks

Magoo
18-05-2011, 05:26 AM
If using the heavy wall thickness pipe use the correct flaring tool and reflare the connection, plus use the torque wrench spanners as well. Have you checked the vacuum pump actual performance.

phs
18-05-2011, 02:19 PM
Yeah mate if you read one of my earlier post I stated I used the best 410a ratchet flaring tool on the market and the flare was good simply was not tight enough and no oil was used as lubricant . So the flare is ok ,I have put the gauge st8 on the pump it get down to 10 microns fairly quick and a few weeks back I used it on a slightly smaller system and it got 50 microns in about an hours less time . But it was a new install , this one I'm having trouble with has had ***** in it previously . Im not sure if that is the cause for the system taking so long to get to 200 microns ?

joeydc
20-06-2011, 02:14 PM
If you had a leak the vac reading would be in the thousands to tens of thousdands...

Hi, Guys.

I've never posted on this board, but I am an active participant in HVAC-Talk and HVACProtech.

A leak that is detectable via a sniffer will not necessarily show up on a micron gauge. It all depends on system volume and leak size. Please see:

http://hvac-talk.com/vbb/showthread.php?t=849872

or, if you have access:

http://hvacprotech.com/viewtopic.php?f=196&t=15960

In this case, a leak easily identifiable by an H10, and soap bubbles, did not result in an appreciable rise in pressure (or an inability to bring the pressure down quickly).

So, when in doubt, use a good sniffer and/or soap to confirm no leaks.


I wouldn't worry over a 30 micron rise, i'm doubtful the vac gauges are that acurate at such a small pressure difference anyway.

There is one. It is called the BluVac. In the video above, it is the only of the gauges that increases (by 23 microns) during a 10-15 minute period.

Full disclosure: I am the inventor and manufacturer of the BluVac gauge. I am not intending to spam here. I thought this information would be useful to the discussion. Take it for what its worth and delete this post if necessary.

Tradewinds
20-06-2011, 02:56 PM
Hi PHS,
In the UK we only need to get to 2 Torr which is 2000microns. When leaks are as small as you are refering to, they can often be down to the manifold gauge lines. So it's best to go vacuum gauge direct onto pipework and copper lines to vac pump.

Nitrogen does change pressure with ambient temperature which I think is approximately 7psi per 'C.

It may also be worth mentioning that leak detectors must have a sensitivity of 5g/year to meet the F Gas regs, so a lot of the standard detectors in the wholesalers shouldnt be used.

Hope that helps.