Mitsubishi Gas leak? PURY P250 YGMA

[marc5180]

I got a call 2 weeks ago to a site where one of their VRF's wasn't working. I found the system short of refrigerant got a total of 11kg out instead of the 28.5kg there should have been in.
I put the system under pressure and found a leak on the outdoor condensor suction shutoff valve.
I checked all the indoor flare nuts and the BC flare nuts and couldn't find another leak.
I told the guy that i had found a leak and that i would like to leave it under pressure over the weekend (or that night) to be sure there were no more leaks.
He insisted that we run the system up rather than leave it under pressure again as it fed a medical store, i did believe that was the leak sorted as the pressure hadn't dropped since we sorted the leak but i decided to add some uv leak dye incase of any furthur leaks in the future.I then vacced out and recharged with 28.5 kg of R10a.

However i got a call yesterday saying it has gone off again. I went down and took out 4kg of r410a from the system meaning that it had lost 24.5 kg in 13 days, thats nearly 2kg leakage per day!!

It must have a major leak somewhere, however i pressure tested and leak checked all indoor units again and bc box and checked it for any UV dye leakage but nothing. Everything was dry and no signs of a leak. I stripped the condensor down but again couldn't find any leaks.
I pressure tested it at 9am this morning and i left at 4pm and it hadn't lost anything, the same as when i carried it out last time. I've left it on over the weekend but i am going to call in tomorrow just to check if it has lost anything but i don't think it will have.

It's as though it only leaks when the system is running, has anyone ever come across something like this because im lost:eek:

[eggs]

I've had it in the past.
Try testing at a lower pressure. It turned out that the nitrogen test pressure had closed up the leak on the pipe braze and the leak only showed up at about 10 bar.

It's worth a try.

eggs

[marc5180]

I tried it at 15 bar and couldn't find a leak then raised it to 30 bar.

It lost 24.5 kg + 17.5kg which is over 42kg, but there is no sign of a leak, it's as though there is refrigerant trapped in the pipework surely if it was a leak there would be some oil around or uv dye.

I turned power off to all of the indoor units to be sure the LEV's were open and weren't trapping any refrigerant in any of the evaporators. Not too sure about the solonoids in the BC box but i think these are open.

I'm expecting to see a big drop in pressure when i go back but if not then it must be leaking when the system runs up but how?

[Brian_UK]

Any underground or cavity pipe runs ?

[puddleboy3]

Drop the fan impellers out of the indoors and check for oil in the drip tray. I had same type of problem on a R407c multi system and found that one of the indoor unit heat exchangers was leaking at the header.

[marc5180]

There's no access to a lot of the pipework because it runs across ceilings and through rooms where they have been plasterboarded and painted.

None of the indoors are the 4 way blow cassette type they are either ducted (again with no access due to them being above a ceiling) or they are the single blow underceiling units.

I went back to the site at lunch time and found the pressures hadn't dropped at all but i don't see how that can happen when it is losing nearly 2kg of refrigerant a day when it is charged.

[raz5]

There's no access to a lot of the pipework because it runs across ceilings and through rooms where they have been plasterboarded and painted.

None of the indoors are the 4 way blow cassette type they are either ducted (again with no access due to them being above a ceiling) or they are the single blow underceiling units.

I went back to the site at lunch time and found the pressures hadn't dropped at all but i don't see how that can happen when it is losing nearly 2kg of refrigerant a day when it is charged.

Have you thought of using balloon gas for testing , it may be a molecule size problem and the ofn is too big, I hear what your saying about 2kg per day and i may be off mark but i have found 410a to be prone to this type of leak problem

[marc5180]

Have you thought of using balloon gas for testing , it may be a molecule size problem and the ofn is too big, I hear what your saying about 2kg per day and i may be off mark but i have found 410a to be prone to this type of leak problem
Yes i think if i go back on monday and still no leak then i will try helium. I have never had to use it before as i have always found the leak with OFN.

[Thermatech]

Try seperating the system up into sections.

If you have access to the BC box then you can pressure test each set of pipes to each indoor unit seperately & also test the BC box seperately & gas/liquid pipe to the outdoor unit seperately & the outdoor unit seperately.

I know its alot of work to set this test up but 9/10 it will prove which pipe has the leak & all you need is good access to the BC.

[marc5180]

That's a good idea, the BC box is probably the only bit that we do have full access to all of the flare nuts and pipework.
I'm just worried that this is going to be a very time consuming job, the customer wants it on asap but he will just have to wait.

If it hasn't lost anything on monday then i will have to try the helium but like i said above, i've never come across a leak that i havn't found with OFN.

[Brian_UK]

As you have ducted units try using a leak detector in the downstream side of the units.

Run them, put the detector in and then turn them off; this reduces the airflow but allows any refrigerant to concentrate.

[AbsoluteWDJ]

Try seperating the system up into sections.

If you have access to the BC box then you can pressure test each set of pipes to each indoor unit seperately & also test the BC box seperately & gas/liquid pipe to the outdoor unit seperately & the outdoor unit seperately.

I know its alot of work to set this test up but 9/10 it will prove which pipe has the leak & all you need is good access to the BC.


I agree with this marc. On the majority of pressure tests i carry out i'll shut service valves so that outdoor and interconnecting/indoor pipes are divided. Pressure test both sides at equal pressure. Leave it for a weekend and hopefully it narrow down where to start leak checking. It sounds that your situation could take a bit of time. Hope your customer understands this!! Oh yeah be aware of tiny cracks in flare nuts. Good luck

[Brian_UK]

I'm just worried that this is going to be a very time consuming job, the customer wants it on asap but he will just have to wait.They always want it yesterday don't they ;)

[andy c]

I have been to two of these units very recently, which have held a pressure test, but lose refrigerant over a period of about a month. Both leaks were found on the internal pipework of the bc box, at the point where the pipe splits from one to two. Its very easy to re-braze these, once the bottom cover, electric box and drip pan are removed. I found them by pulling a wire of the compressor and switching the power back on, to energise the solenoids in the bc box. Hope this is of use. Regards, Andy C

[airconadam]

Is their no way to open all the valves on the system from the outdoor board? I have had a similar problem with daikin and you can open all the valves in bx boxes and the outdoor unit to ensure all the pipework is open,this also ensures a full recovery and a correct vac.

adam

we also spoke to mitsi and they said power down everything and that will open all the valves???????

[marc5180]

The power to the condensor has been turned off as well as power to all indoor units on this system. I haven't tried turning power on and disconnecting the compressor yet.

Went back to site today and the needle hadn't moved at all indicating no leak...
I went out and picked up some 99% helium and cut the pipework coming out of the condensor and braized in schraeder stubs so both the condensor and pipework could be tested independantly.
Pressure tested both to 25bar with the helium and waited for 2 hours with no drop again.

Theres no signs of oil anywhere or uv dye, it's as if there is no leak. I have never come across a leak like this before.

All i can think now is that it only happens when the compressor starts and begins to vibrate something in the condensor, hopefully when i go back tomorrow the condensor will have lost some pressure or im off on long term sick :D

[Brian_UK]

I know that you said you can't see any dye but is it possible that the leak is from the access port fittings; they're tight when your manifold lines are connected but leak with a cap on...

[marc5180]

No we have checked and double checked them, 100% sure it isn't them.

[andy c]

When i carried out the pressure test to both systems, (0n two different sites) they held a nitrogen pressure test of 24 Bar for the whole weekend. This had me confused at first, because the systems lost 18Kg of refrigerant in a month or so. They had both also held under a vacuum, which also suggested no leaks present. The leak wasn't identified on both occasions, under normal procedures. But after disconnecting the CN Plug from the board for the LP device, to stop the compressor from being able to run, I powered up the system whilst under nitrogen pressure, and within a few minuites, the leak could be heard within the bc box. I don't know whether the solenoids are energised with power or de-energised, but on both sites it worked for me. The second site i attended, was after two of my colleages had also carried out the pressure test, and been unable to find a leak. A possible tell tale sign is to have a feel in the bottom of the drip tray of the bc box for oil. Regards, Andy C

[marc5180]

But after disconnecting the CN Plug from the board for the LP device, to stop the compressor from being able to run,

I'll try that tomorrow but i did remove the bottom cover of the BC box and i could see through to the solonoids but couldn't see any oil or dye.

It's something else for me to try though so thanks.

[laf100]

I too recommend dropping the bottom of the BC box to check for leaks more closely, I have had leaks here twice. I also swear by my Fluke digital pressure gauge, it will show you to .1 psi resolution, and more often than not you can see it dropping. Neither of these explain your 2kg per day loss though!!:D

If you dont have full access to all your fan coils or pipework, you could be waisting your time!:confused:

[nike123]

Check this manual:
http://www.refrig.com/LeakDetectionManual.pdf

[marc5180]

Thankd for that Nike:D

[Goober]

I have to agree with laf100, if you can't get to all the pipework you may be wasting your time. Also with all the pipework insulated the leak dye may not be visable. Tried cutting the insulation in random places to see if any oil/dye present?

[marc5180]

Went back to the unit today and found the needle on my gauges hadn't moved indicating no leak.

I cut open the ceiling to get full access to the bc box and i removed the electric box and tray so i could see inside.

I turned power on to the condensor and ran it up with the compressor disconnected. No signs of leaks at all in the Bc box or anywhere on the condensor. :confused:

[laf100]

I do feel your pain marc5180 :eek: !!!

As you have the "luxury" of good access to the BC, my next step would be to dis' all the branch pipes, and cap off the pipe connections of the BC using flare nuts & bonnets. You have then approximatley halved your system, and can p/test the CU, main pipework & BC box, without actually having to cut/re-braize any pipework.

If no joy, then test each branch pair & AHU individually from the BC access point. I have only had to do this once...and it ain't fun! :rolleyes:

[airconadam]

I still cant see us finding a leak tho after 4 days of the system under pressure???? with helium and nitrogen! its as if the system only leaks when the unit is ran up?? maybe its a case of running the system up and using the electronic leak detector??

adam

[marc5180]

I do feel your pain marc5180 :eek: !!!

As you have the "luxury" of good access to the BC, my next step would be to dis' all the branch pipes, and cap off the pipe connections of the BC using flare nuts & bonnets. You have then approximatley halved your system, and can p/test the CU, main pipework & BC box, without actually having to cut/re-braize any pipework.

If no joy, then test each branch pair & AHU individually from the BC access point. I have only had to do this once...and it ain't fun! :rolleyes:

If we had a drop in pressure then this is what i would have done but we have had no pressure drop in over 5 days.

[Goober]

Breath, and breath, and breath. Patience is going to win this one. you'll get there.

[AbsoluteWDJ]

Just out of curiosity. How old is the system? and has it had any previous faults of this kind. Might be clutching at straws but has there been any works carried out in or around where the pipework runs. I have had a couple of occasions where a builder has put a screw straight through refrigerant pipe!

[AbsoluteWDJ]

Just out of curiosity. How old is the system? and has it had any previous faults of this kind. Might be clutching at straws but has there been any works carried out in or around where the pipework runs. I have had a couple of occasions where a builder has put a screw straight through refrigerant pipe!


In saying that you would still expect to see a pressure drop....Stick with it my friend....Is the whole system under pressure?

[sinewave]

Does the system leak in cooling or heating?

Sometimes leaks only happen on a specific cycle.

[marc5180]

Update; got back to the system today and the pressure still hadn't dropped at all.
I decided to vac out and recharge with the intention of running the system up and checking for the leak with the sniffer.
Put system on vac and got it down to 1000 microns (1Torr) and turned the vac pump off and waited for it to rise but it didnt at all.

I recharged and ran it up. I put all 7 indoors on cooling and checked the condensor with the sniffer, then went to the BC box, then all indoor units.
All of them were cooling and there were no signs of a leak again, so i put them all into heating.

Again checked the condensor, the BC box and all indoors. If there is a leak then it has me beat because i have spent 5 solid days trying to find it.

I cant see it being on pipework because helium would find the leak over a weekend so it must be on something that is expanding and contracting like some sort of a seal but i can't think where.

I'm going back tomorrow to check it again and see how it is running, i'm even dreaming about it at night. I woke up in the middle of the night last night saying "i've found it" my girlfriend told me.:eek:

[marc5180]

AbsoluteWDJ,
the system is about 2 years old and no building work has been going on that i know of.

Sinewave,
I've tried on both heating and cooling mode now and still no signs of a leak.

[El Padre]

I have had this before and put it down to the BC box, changed the box and solved the problem, I think that a joint was leaking only when all the units are in heating mode, as you can exclude the condenser and pipework from being at fault that is the most likely culprit!

[AbsoluteWDJ]

I woke up in the middle of the night last night saying "i've found it" my girlfriend told me.:eek:[/quote]

What exactly did you find!!!
My fingers are crossed for you mate.

[marc5180]

I have had this before and put it down to the BC box, changed the box and solved the problem, I think that a joint was leaking only when all the units are in heating mode, as you can exclude the condenser and pipework from being at fault that is the most likely culprit!

I haven't found any leak on the BC box or anything to indicate that there is a problem with it, so i don't want to change it until i do. I'm going to go back tomorrow and put all indoor units on heat and stay with it for a few hours and monitor closely.

[marc5180]

I woke up in the middle of the night last night saying "i've found it" my girlfriend told me.:eek:

What exactly did you find!!!
My fingers are crossed for you mate.[/QUOTE]

Haha, i'd been dreaming that i had found a pin hole in the pipework, then woke up and realised i had been dreaming:mad:

[rude]

i hate waking up in the middle of the night thinking about work.

[nike123]

This is one of perfect examples why I hate even think about direct expansion systems in place of good old hydronic systems.
Another one is their unnecessary complexity.
Don't forget, everything leaks!:( So many joints, to many leak potential.

[El Padre]

Update; got back to the system today and the pressure still hadn't dropped at all.
I decided to vac out and recharge with the intention of running the system up and checking for the leak with the sniffer.
Put system on vac and got it down to 1000 microns (1Torr) and turned the vac pump off and waited for it to rise but it didnt at all.

I recharged and ran it up. I put all 7 indoors on cooling and checked the condensor with the sniffer, then went to the BC box, then all indoor units.
All of them were cooling and there were no signs of a leak again, so i put them all into heating.

Again checked the condensor, the BC box and all indoors. If there is a leak then it has me beat because i have spent 5 solid days trying to find it.

I cant see it being on pipework because helium would find the leak over a weekend so it must be on something that is expanding and contracting like some sort of a seal but i can't think where.

I'm going back tomorrow to check it again and see how it is running, i'm even dreaming about it at night. I woke up in the middle of the night last night saying "i've found it" my girlfriend told me.:eek:
At least she did'nt wake you up saying that she's found it!!:D

[dannycool]

A long shot, but another thing to consider is the presence of other engineers, i have experienced other engineers obviously being out of gas and stealing it from other systems, and a couple of times they have recovered from our equipment by mistake.
If it is a shopping centre or multi-occupancy office check the vistors log book around the time of your call outs

[airconadam]

I called into the site today tested every unit on heat and cool and all worked fine with no problems touch wood we wont get called back but surely its not fixed itself???

adam

[marc5180]

A long shot, but another thing to consider is the presence of other engineers, i have experienced other engineers obviously being out of gas and stealing it from other systems, and a couple of times they have recovered from our equipment by mistake.
If it is a shopping centre or multi-occupancy office check the vistors log book around the time of your call outs

We had thought that someone could be tampering with it so we had marked the caps on the condensor.

It took 2 weeks before we were called back to it and that time is up next thursday. I have my fingers crossed and everything else for that matter:D
Only time will tell now.

[Suffolk Fridge]

a mate of mine has just found a leak on a pury-p250ymf-c system that took him nearly a week to find. It was a hairline crack on a refnet in the bc box. Refnet only leaked on running, due to expansion/contraction. He only found it out of sheer desperation by dropping the bc box out of the ceiling (no mean feat with this particular box) capping all the connections and pressure testing it on the floor at 38 bar. even then it only showed up a tiny amount with leak spray.
In my experience i have found that putting dye in a city multi system is pretty ineffective as the oil separator is so good, it doesnt even leave the condensing unit. Fingers crossed for you mate i have been there many times.

[R1976]

This thread is great! It's like a gripping series for RAC engineers and I can't wait for the outcome!

Sometimes these series do go on though, I got bored of Lost on series 87.:D

Seriously though, Leaks like this are a nightmare and I wish you luck. I have had cracked flare nuts that only open on heat mode.

[jteixiera]

Just a quick question. are the indoor units powered? Hopefully yes as The indooor units have electronic LEVs

[marc5180]

Mitsubishi told us that the indoors had to be powered down, then we rang back up and the guy told us to leave them switched on which we did. Everthing had power apart from the condensor.

[airconadam]

all the indoor units were powered up also spoke with mitsi and they said powerdown to open the LEV??? we tried both!! no difference!

adam

[jteixiera]

I think you must cut the system into sections(i.e.) pressure test the condenser on its own, isolate each fan coil unit from the BC box and pressure test each unit with the associated flow and return pipe work and pressure test the bc box on its own. I have found a few leaks in the bc box solenoid valve heads. once you take the pc board off the bc box you can get to all the solenoid valves and really appreciate what the bc box does.

[robin r33 gtr]

I think you must cut the system into sections(i.e.) pressure test the condenser on its own, isolate each fan coil unit from the BC box and pressure test each unit with the associated flow and return pipe work and pressure test the bc box on its own. I have found a few leaks in the bc box solenoid valve heads. once you take the pc board off the bc box you can get to all the solenoid valves and really appreciate what the bc box does.



I cannot see the point in cutting the system into sections if it is holding pressure for 4 days.

If there is also dye in the system it should show a leak by now.

Even loosing that much refrigerant a few times with no dye would show signs of oil.

Can you get to all of the pipework?

Have you found all the units on that system and not left one out hiding in a cupboard or on another floor as I have seen this before.

[Goober]

What's happening with this job? Did ya find the leak? Huh? Huh? I think movie rights are being sought for the telling of this story, Brad Pitt being lined up for the starring role.....

[Suffolk Fridge]

come on guys i am itching to know where this leak is now.....

[marc5180]

Hi sorry i haven't updated but as of yet we haven't found the leak but.....

We went back to site and recovered the refrigerant that we had put in and found that it had lost some.

Against what some people suggested, we cut the system up into sections and pressure tested, starting with each indoor unit. Again there was no fall in pressure.

Next we cut the flared connections at the BC box and tested the pipework and the condensor.

We left it for a few days and went back and found the pressure had dopped 10 bar:D.
So now finally there is signs of a leak.
All i can think is that by running it has disturbed the seal/hole/bend/leak (wherever it's leaking from) and it is no showing signs of a leak, which as you can imagine is great news for us.

We split the condensor and pipework into sections yesterday to prove wether it is the pipework or the condensor that is leaking and i will be going back on tuesday to check it.

If it is found to be the pipework then i will have to seperate the pipework into sections as there is not much access to it. At least this way i should be able to narrow it down rather than ripping all the ceiling down to check the pipework but it is going to take time.

The customer is aware that it is going to take time now but at least now there is light at the end of the tunnel.

I'll update when i find anything more.

Thanks guys

[1torr]

This is better than hwo shot JR

[airconadam]

The leak has now been found am sure marc will be along shortly with the details and maybe a pic.I will keep you all in suspense for now,untill marc posts

adam

[robin r33 gtr]

I have been checking everyday for the answer.

[Goober]

Oooooooooh! The Suspense! The Suspense!

[marc5180]

Went back to site Wednesday and found that the liquid pipework from the condensor to the BC box had lost pressure. Both the liquid and suction had been cut at the BC box and at the condensor so each pipe was being tested individually.

Knowing that the leak was on the liquid i cut the pipework again and braized in 1/4 schraeders to test both sides of the pipe. 1 side was testing from the 3rd floor down and the other was testing the 3rd floor and onto the roof.

I returned the following day and found the piece that was going back onto the roof had lost all its pressure so i knew it was somwhere on this pipwork.

I cut all cable ties off and unclipped the pipework and began stripping off the lagging to check all joints but couldn't find anything.
I traced it back as far as i could then it disappeared through the wall. I went back onto the roof and checked the pipework there but again nothing. I noticed that it disappeared through some cladding and into a roof void to which there was no access and there was about 30m of pipe inside somewhere.

I spoke to the manaager and explained that we needed to get in there so we began to try and take the cladding off. (see pics)

As soon as we had the cladding off the first thing i saw was the pipework then i noticed oil and UV dye everywhere.

We climbed inside and saw that the pipewas was resting on the head of a nail that was sticking out of a joist by about 5mm.

All i can imagine is that over time the pipework has been rubbing against the nail and caused it to wear the coper away.
The hole in the pipework was quite big about 3mmx5mm and the nails head was wedged inside the hole.

I should have took a picture of the nail but didn't. The pics are where the pipework was and getting ready to braize it up. Notice the oil all around and the uv dye if you look closely.

[AbsoluteWDJ]

Went back to site Wednesday and found that the liquid pipework from the condensor to the BC box had lost pressure. Both the liquid and suction had been cut at the BC box and at the condensor so each pipe was being tested individually.

Knowing that the leak was on the liquid i cut the pipework again and braized in 1/4 schraeders to test both sides of the pipe. 1 side was testing from the 3rd floor down and the other was testing the 3rd floor and onto the roof.

I returned the following day and found the piece that was going back onto the roof had lost all its pressure so i knew it was somwhere on this pipwork.

I cut all cable ties off and unclipped the pipework and began stripping off the lagging to check all joints but couldn't find anything.
I traced it back as far as i could then it disappeared through the wall. I went back onto the roof and checked the pipework there but again nothing. I noticed that it disappeared through some cladding and into a roof void to which there was no access and there was about 30m of pipe inside somewhere.

I spoke to the manaager and explained that we needed to get in there so we began to try and take the cladding off. (see pics)

As soon as we had the cladding off the first thing i saw was the pipework then i noticed oil and UV dye everywhere.

We climbed inside and saw that the pipewas was resting on the head of a nail that was sticking out of a joist by about 5mm.

All i can imagine is that over time the pipework has been rubbing against the nail and caused it to wear the coper away.
The hole in the pipework was quite big about 3mmx5mm and the nails head was wedged inside the hole.

I should have took a picture of the nail but didn't. The pics are where the pipework was and getting ready to braize it up. Notice the oil all around and the uv dye if you look closely.

Nailed it! Well done....:D There great systems VRF/VRV but a pain in the backside and not to mention time consuming, when your looking for a small leak!

[robin r33 gtr]

How many days will you be billing for that job? At least you got there in the end.

[laf100]

Good work Marc.
:cool:

[pie man]

Nice one that was a great read, glad you solved it!

[Brian_UK]

Well done Marc, the customer should be happier now with less callouts to come.

We all have 100% hindsight but don't you kick yourself for not pushing harder to get at the invisible pipes earlier ?

[marc5180]

I don't know what's going to happen regarding the cost of the job, thats not up to me.

The customer is very happy that it's fixed. This is the prime example of why access is needed to pipework and indoor units and BC boxes and this is why it has taken so long because there was no access.

I hope i never see another leak as long as i live.:p

[rude]

Well done!! i hate leaks like that where you cant find them, but u persisted and it worked out!

[Brian_UK]

I can see the headlines now in the trade mags.

Student of the Year finds hidden leak.

Global Warming risk removed.

:D:):D

[Suffolk Fridge]

well done mate sounds like a job well done, one for the memory banks hey?

[marc5180]

I can see the headlines now in the trade mags.

Student of the Year finds hidden leak.

Global Warming risk removed.

:D:):D


I wish, sadly i was the runner up
but yes the global warming risk has been removed
:D

[jdunc2301]

and thats why im always mysteriously ill or busy when a VRV/VRF comes in showing signs of SOG :)

[sinewave]

Still strange though why the system was continualy holding OFN pressure testing levels over days with such a big hole? :confused:

[Contactor]

Phew, get some sleep now then...

[al]

Still strange though why the system was continualy holding OFN pressure testing levels over days with such a big hole?

Cos ofn has a larger molecule size i think??

al

[marc5180]

But it was tested with OFN and helium and showed no signs of a leak until we ran it up again.

[nike123]

We had thought that someone could be tampering with it so we had marked the caps on the condensor.

It took 2 weeks before we were called back to it and that time is up next thursday. I have my fingers crossed and everything else for that matter:D
Only time will tell now.


Last fall I was commissioned one MHI VRF, and portion of pipes was buried in floating concrete floor (estrich). Floor is made from wooden beams and planking on which I layed pipes from distributor to floor standing FC. Than I made pressure and leak test and leaved pipes under pressure. Than builders are poured concrete layer at insulation above planking (and pipes).
Cople month later I was at site to mount Fan coils and found no pressure in pipes.
I pressurised pipes and after lot of searching found nothing. Then I decidet to go back in midle of the night when no one is in builiding and sorounding is quiet. And after lot of walking like ghost, I finaly found hardly to hear hissing above my head in one room. Hissing is so quiet that you need absolute quietnes in sorunding to be able to hear it. That is why I conducted my search in midle of the night, no mater what object location is on one of Islands and far from city noise.

Then I localised place where hissing is coming and found that hiss coming somwhere from above where pipes, which feed floor mounted FC in room above, are layed.
Next, I needed to demolish concrete above from FC to point where hissing is heard.

After some diging I finaly found that screw (3,5 X 35 mm Knauf screw, very sharp tip) which holds flexy ducting holder from ventilation mounted below is screwed in one of pipes wich feed FC and that on that place I cannot separate pipe from floor. Hising is realy quiet, and only when I unscrewed screw hising has amplified somewat.

When I checked how much N2 pressure I lost during searching (whole day and main portion of night) i found that it drop less than 1 bar, which you could easy assign to pressure drop becaouse of temperature change.
Therefore, I considered myself wery lucky guy.:rolleyes:

Finaly, I cut and and repalaced portion of pipe to FC.
Later it was pressurised again and I pronounced piping healty after it is been at right pressure (corrected for temperature change) for 7 days.:eek:

Nedless to say that, when I mounted pipes, I strictly said to construction supervisor, that NO ONE CANNOT SCREW NOTHING in floor or in ceiling without my supervision (I photographed whole instalation).
And best ting is, that guy from team which I supervised in ventilation mounting and whome I explained that he cannot screw anything in planking, only in beams, is rensponsible for that "scr ewing" and that he (of course) did not mention to anybody that he done that crapping.:mad:

I hope someone could learn something from this example. I certanly did!:D

[marc5180]

That sounds like a nightmare, having to demolish the concrete to get at it as well.
Rather you than me :rolleyes:

[ukcragrat]

It just proves that this job is never boring, frustrating sometimes, but in this case very rewarding. Well done Marc.

[1torr]

I had a 11/8th suction ball valve leaking from the body where its screwed together on a Sanyo once. It held ofn at 41 bar,sprayed with leak spray no leak. Put 8 bar R410a in and bubbled up straight away.

[jteixiera]

I think you must cut the system into sections(i.e.) pressure test the condenser on its own, isolate each fan coil unit from the BC box and pressure test each unit with the associated flow and return pipe work and pressure test the bc box on its own. I have found a few leaks in the bc box solenoid valve heads. once you take the pc board off the bc box you can get to all the solenoid valves and really appreciate what the bc box does.

i did mention to cut the system apart a few weeks back.

well done got their in the end

[fridgemagnet]

Well done mate for finding the leak should help keep the hole above my head (here in NZ) a bit smaller for a bit longer.

:off topic:
One thing you guys might want to considder is UV dye is not permitted in city multi units (any mitshubishi for what thats worth) reason being is causes plating on the compressor bottom bearing when used with R407b and R410A. end result complete failure of compressor and the next and the next .........

Might be time to read those manuals before we add aditives to systems. :confused:
I was involved as an independant engineer for mitsy on why thy had a string of commpressor and diode fails on a city multy entire waranty claim got declined du to UV Dye in the system. The buildup causes continous high current draw wich is just under the safe limit of the system diodes when the compressor seizes the time delay is too long to protect the diodes wich were basicly running at their max the entire time, normaly they are overrated by 35% to prevent this from happening.

Get an infrared sniffer its a God sent tool they detect leaks as small as 3g per year dont get affected by wind like the old cold and hot cathode sensers. Next leak you have and find in one day with your brand new IR Sniffer you can thank me :p

[dellapureneed]

Oh hell, I think I've got the same type of problem about to occur!!
So far my system hasn't been ran up, it is only 16 units of mix between wall mount & cassettes. All pipe work is internal to/from Box & is available to get at. Except where it follows through bulkhead to studding wall for wall mount & to ceiling bulkhead for cassettes as this is now decorated & there are only 2 brazed joints above per room. All the flare joints were made off good, so I was told & brazed joints were alledged to be good too!. The pipe was ran in coils from box area down a corridor & peeling off left right per set to each room. The longest is 30 metres & no other joints or additions were made & it is only 1/4" & 1/2".
The pipes serving box are ready for final penetration to plant deck area & as no condenser is on site. I have closed off the 2 serving pipes to the box & put schraeder access on both. I introduced OFN slowly & checked 5bar-10bar-15bar-20bar-& up to 41.5bar. It took a very long time than normal to get up to 41.5bar but no leak apparant heard in the rooms at access points to flared connections! building was vacant & no noise disturbance.
1 hour with whole lot capped & sealed a drop to 40bar, so I topped up back to 41.5bar thinking there would be some settlng to equalisation.
1 hour later drop to 40 bar again & no temperature drop that day or opening doors or windows to rooms etc etc.
Next morning 18bar!!!! OH DEAR leak imminent.
checked all flares with bubble test nil found
My thoughts are that the very limited space that the 'design' had to install the CMB Box has 16 units sets of pipes all brazed all sweeping under the box then up towards port connection stubs. So I can ony see if the leak is inside this box then oh hell it will all have to be disconnected to get inside & cap off all 32 stubs & re test. I know for a fact this box had OFN factory shipped inside & was still there when 1st cut off retaining cap.
Now only assuming the pipes were actually brazed up well & the flares were good, then if these prove still leak tight & the box is proven good too.
Can it then be a pipe fracture in a bend or a split in the tube? this would be less of a chance I know but has occured before with even quality pipe!
I do hope it can be found easy I may have to ask the builder to remove sections of MF ceiling around the corridor where the likelyhood of bends are & cut the armaflex lagging & have a good listen and bubble test.
If this still cant be traced then I might have to look at the indoor units themselves!
It may be more a suspect than you think! I do suspect some heavy handed manipulation by the lads on the wall mount pipe tails to exit them 180 degree back in the opposite direction. This has been found before with the pipe from manufactured as it connects to the coil, once reversing of the bend & even though the 'spring' stops most over zealous collapsing/crushing it could be just one weak point or braze there that could be the leak failure.
I have found on a wall mount VRV from Toshiba that the brazed on brass flare union to pipe was a 'dry' joint & leaked as low as 5bar!! That was supposed to have been tested at factory? Unlikely. We re brazed it & was fine then.

Any comments welcome
Dellapureneed.

[marc5180]

If the system is loosing pressure then with regards to actually finding the leak then this can only be a good thing.
The quickest way I have found to find a leak on these systems is to pressure test the whole system as you have done and check all indoors/BC box flare nuts etc.

If no leak found then split the system up into sections ( I know it's a pain but in the long run it's quicker)

I'd separate the consensor from the pipework, also if the run to the bc box is quite far then test this then test the BC box with all 16 units.

If it drops with the 16 units on the you will have to begin separating the indoorsas well.

Good luck

[martinw58]

have had leaks in side bc box where pipes conect on big pipe