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Klawman 09-01-2011 12:54 AM

Purge and Deep Vacuum?
I am 2/3 of the way through with a new Split A/C and Furnace intall and I am questioning what the installers are doing as far as what the contract calls "flushing of lines for R-410A Chageover" from an R22 system.

I didn't catch if the gauges were even used outside, but the tech clipped the lines set and pronounced that they there was notning in them. I later noted that some had leaked from the end of the severed upstairs line onto a duct. I have no idea how much, but more than a few drops.

I asked the tech about purging and he showed me an old can that of sometbhing that he said he shoots in the top of the lines for about 10 seconds. Later I approached him with my concern over what he was going to be doing as far as flushing the system and vacuuming the lines. He said he as going to do a vacuum but it wasn't necessary to do a long one, such as several hours, like was once thought.

Can someone give me an idea as to what a minimum purging and vaccum is like? It doesn't appear that the lines were fowled with burnt liquid.

This guy is saying they attach dryers to the lines that will catch anything and that is one reason I need not be worried about the lines being thoroughly purged/vacuumed. when I am told not to worry I start to worry.

I read somwhere that the lines need to be vacuumed to 300 microns. I didni't even see these guys set up a recovery bottle. I hope this makes sense.

This is all I know about a deep vacuum, that and one tech said he would vacuum the lines for 3 1/2 hours.

JJboy 09-01-2011 01:12 AM

An canister is enough. After you install filter drier, let AC running for a few days and change the filter drier again. Ask the tech to do a acid check. :thumbsup:

Klawman 09-01-2011 01:24 AM


Originally Posted by JJboy (Post 719148)
An canister is enough. After you install filter drier, let AC running for a few days and change the filter drier again. Ask the tech to do a acid check. :thumbsup:

These guys aren't talking about returning after they finish the intall tomorrow. After I told the guy I was concerned that they weren't doing a vacuum was when he said they were going to do one but it wasn't necessary that it was very long.

I also had the feeling that they were only going to use a part of a partially used up cannister.

JJboy 09-01-2011 01:37 AM

Ok, you don't need to do acid test if you're changing R22 to R410.
I think it's very important to use Nitrogen when welding.

JJboy 09-01-2011 01:41 AM

ask for triple evacuation:thumbsup:

Klawman 09-01-2011 02:07 AM


Originally Posted by JJboy (Post 719156)
ask for triple evacuation:thumbsup:

If there is not need for an acid test, because it is a changeover to 410 from R22, is there any point in changing the filter/drier after running the AC for a few days?

beenthere 09-01-2011 04:49 AM

No real need to use a chemical flushing agent. a high pressure flush using nitrogen is important. And then a good vacuum. Only way to know if the vacuum is a good one, is to use a micron gauge. A good vacuum could take an hour or a lot longer.

biggles 09-01-2011 06:37 AM

they were fly by night for sure:huh: and your asking questions made them rush it even more.they vented the R-22 charge into your recovery time on the 22...a nitro blow out won't hurt anything else is a waste of money and time change the dryer .a VAC pull would take all of 2 hours if tight to see 250 microns if there was moisture within the reading could be 1000 or 2000 and drop as it drys up...i won't even trust the newly charged freon...keep your paper work and all the invoices...some thing smells there:no: did they quote you total hours on the change out...

HVACDave 09-01-2011 08:01 AM

Pulling a vacumn is the important part before they open the refrigerant lines. I wouldn't worry about 250 microns (being summer and all). At even 1000 microns moisture boils at 32 degrees F, so if they reach that level, shut off the pump and the micron level stays there, the moisture should be gone, unless of course it is below 32 F where your piping and air handler are, (which I would highly doubt in this season).

Pressure testing with nitrogen after they have brazed in the unit would be advised to make sure that there are no leaks, then vacumn after that, then checking the charge using subcooling or aproach temps, depending on the unit recommendations, check temps across coil and air flow through evaporator, check amp draw on condenser.

Always bugs me when guys are in a hurry to get stuff done and don't take the time to do it properly, don't feel bad about checking up on what they are doing, you are paying good money to have it done properly and will be stuck with the resulting job for many years.

Funny, they always have to make time to do the job right the second time.

Klawman 09-01-2011 08:36 AM

Thanks to all. I barely slept last night as I didn't want to play the heavy if it wasn't warranted, but everything I have read and you guys have told me talked about the importance of a good flush; actually that replacing the lines was preferred.

Klawman 09-01-2011 10:40 AM

The crew is back and I talked about my concerns. They are pulling a deep vac. I asked about them using an old parially empty can of flush and they got a new one off the truck. They say they didn't evacuate the system bcause it was empty. I can believe that the little bit that dripped out of the cut lines in the attic was not much more than a couple of fluid ounces. Another guy bidding the job confirmed that the refrigerant didn't smell burnt by releasing just a tad from the valve. They have tanks of nitrogen, which I think is for welding, and "Yellow Jacket" digital gauges. They will also check for leaks. Overall, their work seemed pretty diligent and they know I am watching so I suspect thay will do a good job (especially with a $1,000 20 day holdback in the contract.)

Klawman 09-01-2011 10:46 AM

I guess purging only took minutes as they are welding the in line filter dryer to the outside line. Please tell me that the deep vacuum comes after that and not before.

hvac122 09-01-2011 10:50 AM

It comes after the welding.

Klawman 09-01-2011 11:24 AM


Originally Posted by hvac122 (Post 719342)
It comes after the welding.

Cool. They are just wrapping up the welding and seem to be taking good care.

Klawman 09-01-2011 02:06 PM

They ran the vacuum for 2 hours and knew I wanted to see it. Then the guy goes and "drops the charge" without getting me to see how many micons or pressure was pulled. So now we can't do the test. I am a little po'd. When they ran the furnace it really smelled. I am going to insist that they shoe me a leak test.

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