Triple evacuation on split system

[batfink]

Hi Guys,

Sorry, I have been reading through the forums and found loads of interesting stuff :) My lastest thoughts are towards triple evacuation on split ac/heatpump systems? All of the text I have read states triple evac takes place on the plant low and high side valves, but split systems like daikin only have a service valve on the gas side, so is a triple evac really necessary? Is the standard, from what I have seen, chuck you vac pump on, leave it for as long as you can method really suitable? Of course these guys strength and leak test first :)

many thanks,

B

[multisync]

Most splits are up to 5/8 + 3/8 new clean pipe. -what are you expecting in there that needs a triple evacuation?

Read what Daikin say

Up to 50 feet -not less than 10 minutes
over 50 feet -not less than 15 minutes

http://www.daikinac.com/residential/documents/3P141697-4C_EN.pdf


Multisync
London

[paul_h]

Leaving it on for as long as you can does no good if there's a leak, you need to be able to measure the vacuum otherwise you may just be sucking in air through a bad flare or I/U leak.
Get a digital vac guage, evac until 700 microns.
Basically anything below 1000 microns means you can be fairly sure there's no leaks.

[batfink]

cheers guys, thats my question rearly is a triple vac needed? As you say nice new pipe with sealed ends shouldn't need it. I would imagine triple vac's are required of multi-splits, VRV's ... ?

15 mins thats not enough surely? I am limited in the installs I have completed as we have a company install for us, but a 5 meter run will vac down in next to no time but may take a while or a few goes until the torr gauge holds at a torr or so.

As said before, vac down after a strength and leak test, as you say otherwise whats the point :)

[Brian_UK]

We assume that you are only talking about new installations.

What are your feelings on existing plant being repaired.

As regards only having a single access point, are there any more under the covers?

[taz24]

Hi Guys,

Sorry, I have been reading through the forums and found loads of interesting stuff :) My lastest thoughts are towards triple evacuation on split ac/heatpump systems? All of the text I have read states triple evac takes place on the plant low and high side valves, but split systems like daikin only have a service valve on the gas side, so is a triple evac really necessary? Is the standard, from what I have seen, chuck you vac pump on, leave it for as long as you can method really suitable? Of course these guys strength and leak test first :)

many thanks,

B


Tripple vac are an excelent way of dehumidifying systems and removeing non condensables.

If you have time constraints then the tripple vac can be quicker than a deep vac on large systems, but on a small split with short pipe runs one deep vac would be sufficient. You have to be careful of pulling a deep vac too quick, if you pull a deep vac too quickly it can freeze moisture in the pipework and not boil it off as vapour.



Leaving it on for as long as you can does no good if there's a leak, you need to be able to measure the vacuum otherwise you may just be sucking in air through a bad flare or I/U leak.
Get a digital vac guage, evac until 700 microns.
Basically anything below 1000 microns means you can be fairly sure there's no leaks.


In the UK we do not use a vacuume to prove integraty. We pressure test first with OFN and when we are sure the system is safe and no leaks are pressent we vac the system. the vac is only used to remove moisture and non condensables. If a vac is used for leak testing it can actualy give you false information. A system under pressure has different stress exerted on it than a system in a vac.


Cheers taz.

[paul_h]

Tripple vac are an excelent way of dehumidifying systems and removeing non condensables.

If you have time constraints then the tripple vac can be quicker than a deep vac on large systems, but on a small split with short pipe runs one deep vac would be sufficient. You have to be careful of pulling a deep vac too quick, if you pull a deep vac too quickly it can freeze moisture in the pipework and not boil it off as vapour.





In the UK we do not use a vacuume to prove integraty. We pressure test first with OFN and when we are sure the system is safe and no leaks are pressent we vac the system. the vac is only used to remove moisture and non condensables. If a vac is used for leak testing it can actualy give you false information. A system under pressure has different stress exerted on it than a system in a vac.


Cheers taz.True, but the problem with splits is it's not a good idea to pressurize too high. If the service valve leaks, you get nitrogen in the system and have to reclaim the whole charge. The solution to this to only pressurising to 800kpa, and if you do that then you might as well not bother with nitrogen. May as well open the liquid for static pressure leak test with leak detector.
Experience has told me any leaking system will not go below ~1300 microns, so if I can vac well under 1000 microns, the install is good in my opinion.
If I was welding a system, I'd test with nitrogen as I would be using nitrogen while welding, so I'd pressurize before connecting a precharged system for a test, so I'd not be relying in the service valves to stop nitrogen getting into the system.
If I'm doing a small split with flares, I'm just going to test with vac, saves the hassle with getting out the nitrogen, gives me a reliable test without the chance any of the service valves not holding.

edit: If I'm reclaiming a leaking system, yeah, then I'm all for 3500kpa leak test with nitrogen. I just dont trust some service valves after finding at least 20 faulty ones while doing waranty service.
I've had difficult leaks not show up if you used under 2000kpa nitrogen presure, but they always failed the vac test. So tesing with nitrogen at 1000kpa is not as good as evacuating to 1000 microns IMHO. Of course 3500kpa often shows a leak and also tells you where it is, unlike a vac test.

[Grizzly]

Taz and Paul.
Without meaning to state the obvious,
I think what either of you say makes good sense.
And have used either approach to good effect.
When you refer to "pressure testing" with nitrogen taz,
surely you really mean " leak test".
I know that you are very knowledgeable on these issues taz!

What is being taught nowadays regarding using nitrogen on a part charged system?
I was always taught minimise the risk of cross contamination wherever possible.
But then again the bulk of my work is on existing installs.
grizzly

[Will]

not less than 10 minutes
not less than 15 minutesFunny stuff.

The only time 'time' comes into play performing an system evacuation is when your waiting for a micron reading reaction.

[paul_h]

Taz and Paul.
Without meaning to state the obvious,
I think what either of you say makes good sense.
And have used either approach to good effect.
When you refer to "pressure testing" with nitrogen taz,
surely you really mean " leak test".
I know that you are very knowledgeable on these issues taz!

What is being taught nowadays regarding using nitrogen on a part charged system?
I was always taught minimise the risk of cross contamination wherever possible.
But then again the bulk of my work is on existing installs.
grizzly
I've been told by manufacturers not to pressure test with nitrogen to an amount you exceed the static charge of the refrigerant. Which is normally 800kPa, (in case the valves leak), which is a joke considering the system will run at ~3500kPa on heat.
Which is why I don't use nitrogen at all unless welding.
So I rely a) good flares, b) just a vacuum test.

For me it's just personal experience, seen heaps of faulty valves, I've seen heaps of leaking systems, I've correlated the two, and found most leaking systems don't get below ~1300 microns.
I also have seen heaps of leaking valves because I was in a city wide warranty support role so I've seen the worst that can happen. You guys over there look after your installs, as I have said before, it's handled differently here. I, as well as ~15 other people handled all faults in my city with a 5 yr warranty, installers got to walk away the second they got payment, so I've seen a lot since I was the most experienced guy.

But then again, if you are going to leak test a evap/pipework not conected to a pre-charged split, or trying to find the leak on a system that needs reclaiming, I'm all for the high pressure nitrogen test. I think I was the highest user of nitrogen at any workplace that I was at, I love high pressure testing :D I just don't trust service valves after what I've seen and what manufacturers told me. Vacuum testing is the safest way for a pre charged system.

Edit; Not the best I agree, but if you wanted the best way, It would be flared unions on the evap pipe run and prssure tested before you hooked up the pre-charged condenser. Then if it passes that test then hook up the condenser and vac.
But split systems are installed here in under 2-3 hrs, so everybody does things in the quickest way.

[taz24]

True, but the problem with splits is it's not a good idea to pressurize too high. If the service valve leaks, you get nitrogen in the system and have to reclaim the whole charge. The solution to this to only pressurising to 800kpa, and if you do that then you might as well not bother with nitrogen. May as well open the liquid for static pressure leak test with leak detector.
Experience has told me any leaking system will not go below ~1300 microns, so if I can vac well under 1000 microns, the install is good in my opinion.
If I was welding a system, I'd test with nitrogen as I would be using nitrogen while welding, so I'd pressurize before connecting a precharged system for a test, so I'd not be relying in the service valves to stop nitrogen getting into the system.
If I'm doing a small split with flares, I'm just going to test with vac, saves the hassle with getting out the nitrogen, gives me a reliable test without the chance any of the service valves not holding.

edit: If I'm reclaiming a leaking system, yeah, then I'm all for 3500kpa leak test with nitrogen. I just dont trust some service valves after finding at least 20 faulty ones while doing waranty service.
I've had difficult leaks not show up if you used under 2000kpa nitrogen presure, but they always failed the vac test. So tesing with nitrogen at 1000kpa is not as good as evacuating to 1000 microns IMHO. Of course 3500kpa often shows a leak and also tells you where it is, unlike a vac test.


Taz and Paul.
Without meaning to state the obvious,
I think what either of you say makes good sense.
And have used either approach to good effect.
When you refer to "pressure testing" with nitrogen taz,
surely you really mean " leak test".
I know that you are very knowledgeable on these issues taz!

What is being taught nowadays regarding using nitrogen on a part charged system?
I was always taught minimise the risk of cross contamination wherever possible.
But then again the bulk of my work is on existing installs.
grizzly


I think we all agree on the same thing, we've just explained it differently :p

I agree with the fact that you have to be careful when putting OFN in the system, if the valves are weak on the system then it has been known to put nitrogen into the refrigerant charge and bugger the refigerant charge in the system.

Who said refrigeration was easy??? :D

Cheers taz

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