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SULTAN
03-06-2007, 07:33 PM
I am a hvac student in my 1st year. I am having a problem with my own central ac at home. I did a soap test and i found some bubles forming on the suction line near the evap coil in the furnace...
Is there any simple solution as to fixing this leak? What are the steps involved briefly fixing the leak?

What i think i need to do is.
Pump down the system.
Suck all refrigerant out..
Re-braze the area where its leaking from.
Fill up with nitrogen and do a pressure test.
Do vacum test
If its hold's the charge then open the liquid line and ON the unit.

Am i following these steps properly?

LRAC
03-06-2007, 08:27 PM
evap coil in the furnace...


what on earth is a furnace doing in your house.
regards
Lrac

Karl Hofmann
03-06-2007, 08:42 PM
what on earth is a furnace doing in your house.
regards
Lrac

It is the way that they heat and cool their homes over there. They prefer to use forced air heating which involves a furnace, rather like the warm air heaters that we use in industrial units here.

Over there, wet central heating systems using radiants and underfloor are not so popular

digi-finger
03-06-2007, 09:41 PM
depending on refridgerant it you may have to reclaim all gas and re charge according to manufacturers guidelines, reclaiming all refrigerant would be my prefered method particuarly with zeo blends r407c r410 ect

Karl Hofmann
03-06-2007, 10:07 PM
And don't forget to pass a trickle of Nitrogen through the system WHILST you are brazing to help prevent flakes of oxide forming inside of the tubing

marc5180
03-06-2007, 10:09 PM
I am a hvac student in my 1st year. I am having a problem with my own central ac at home. I did a soap test and i found some bubles forming on the suction line near the evap coil in the furnace...
Is there any simple solution as to fixing this leak? What are the steps involved briefly fixing the leak?

What i think i need to do is.
Pump down the system.
Suck all refrigerant out..
Re-braze the area where its leaking from.
Fill up with nitrogen and do a pressure test.
Do vacum test
If its hold's the charge then open the liquid line and ON the unit.

Am i following these steps properly?

That sounds fine by me..:D

Dr._Fleck
03-06-2007, 10:11 PM
Put your gauges on, set on cooling and shut the liquid line valve. When the suction pressure reaches 5psi kill the power and shut the suction valve.

You then must ensure there is no pressure in the evapoator before starting any brazing. The way to do this varies depending on what type of suction valve you have.

Next run some weld over the holes, dont get it too hot, back the torch off so the weld stays thick (the same consistancy as washing up liquid i like to think)

Lastly give it a vac, open the valves, leak test the area with suds, top up the refrigerant.

If the system performs poorly, replace all the refrigerant, but you should be ok:)

taz24
04-06-2007, 01:49 PM
Put your gauges on, set on cooling and shut the liquid line valve. When the suction pressure reaches 5psi kill the power and shut the suction valve.

You then must ensure there is no pressure in the evapoator before starting any brazing. The way to do this varies depending on what type of suction valve you have.

Next run some weld over the holes, dont get it too hot, back the torch off so the weld stays thick (the same consistancy as washing up liquid i like to think)

Lastly give it a vac, open the valves, leak test the area with suds, top up the refrigerant.

If the system performs poorly, replace all the refrigerant, but you should be ok:)

Are you suggesting that he does not pressure test the system?

What about any gas already lost?
Zeotropics will leave the wrong mix behind so a full recovery would be nessesary?

taz.

Dr._Fleck
04-06-2007, 05:44 PM
He can pressure test if he wants to.

I would not bother as it is not a new install and he has found the leak:).

About the wrong mix: run the system, see how it performs and as i said maybe you'll have to replace the refrigerant.

digi-finger
04-06-2007, 06:34 PM
He can pressure test if he wants to.

I would not bother as it is not a new install and he has found the leak:).

About the wrong mix: run the system, see how it performs and as i said maybe you'll have to replace the refrigerant.


To be 100% safe,time/energy efficient reclaiming all refridgerant is the best idea, pressure test for a minimum of 24 hrs and tripple vac before weighing gas in. This is definately the best option for a 1st year student if you wanna get anywhere that is!

Dr._Fleck
04-06-2007, 08:37 PM
I suppose it's more by the book for a student yes(although more cost involved), i just explained how i would do it.

By the way, i'm not being funny or anything but there is no "d" in refrigerant.

digi-finger
04-06-2007, 08:55 PM
good at some things bad at others!

monkey spanners
04-06-2007, 09:03 PM
At least start off doing things by the book. If you start cutting corners now, who knows where you'll end up.

Cheers Jon

SULTAN
04-06-2007, 11:12 PM
Thanks for all the help guys. No they didn't teach as anything but theory in class rooms. And due to stupid laws for insurance policies, the teachers dont let us play with refrigerant :)

Anyhow...My question now is.

During pump down when there is 5psi left in the suction line, I shut down the system.
Questions...
1. How will i recover that 5psi of refrigerant? Should i just go straight to vaccum or recover that **** all in cylinder?
2. How do you determine how much nitrogen needs to be pumped into the lines /evap coil?

The MG Pony
05-06-2007, 05:08 AM
Well whats the service port access like? Ideally you want the refrigerant out of the pipe and then have it flooded with N2 at slightly less then atmosphere, make the repair, put in 100psi and soap test the spot and let that sit for say 20 minutes whilst it cools the rest of the way, then after confirming no more leak, vac out the line to as deep of vac as you can practically get it then open up the valve, don deal.

use a nice SS wire brush to clean the oxide off the joint too, will help expose a bad joint, or, make it look purdy as well! Trick I'd do with small home made systems where you can see the piping, polish off the joints then put clear nail varnish on them, keeps them shiny and protects them from future oxidization.

frank
05-06-2007, 09:34 PM
pressure test for a minimum of 24 hrs and tripple vac before weighing gas in.
We've had this discussion before. Why do you need 3 attempts at achieving a good vacuum?

BigJon3475
06-06-2007, 12:22 AM
1. Pump down the system as stated above.
2. Close off service valves.
3. Braze the leak. (use water and rags to protect the service valves and put a liquid line filter dryer also at minimum)
4. Pull a vacuum using a vacuum gage to below 250 microns (however long it takes and preferably less than 250 or however you attempt with triple evac or just letting the pump do it's job)
5. Open service valves.
6. Put gauges and thermocouple on liquid and suction valves to check for super heat and subcooling.
7. Check and make sure your evap coil is clean and the condensing coil is also clean.
8. Turn system on and check charge using superheat and subcooling method. (check amperage draw if possible)



Also for the folks saying you need to recover all of 410A this is not the case unless it all leaks out to atmospheric pressure.
http://www.refrigerants.dupont.com/Suva/en_US/pdf/h47125.pdf
Note pages 4 and 5.

analog
06-06-2007, 02:51 AM
1. Pump down the system as stated above.
2. Close off service valves.
3. Braze the leak. (use water and rags to protect the service valves and put a liquid line filter dryer also at minimum)
4. Pull a vacuum using a vacuum gage to below 250 microns (however long it takes and preferably less than 250 or however you attempt with triple evac or just letting the pump do it's job)
5. Open service valves.
6. Put gauges and thermocouple on liquid and suction valves to check for super heat and subcooling.
7. Check and make sure your evap coil is clean and the condensing coil is also clean.
8. Turn system on and check charge using superheat and subcooling method. (check amperage draw if possible)



Also for the folks saying you need to recover all of 410A this is not the case unless it all leaks out to atmospheric pressure.
http://www.refrigerants.dupont.com/Suva/en_US/pdf/h47125.pdf
Note pages 4 and 5.




You guys are so new.

Let me tell you how we do it on the island.

#1 dump the *****

#2 weld up the leak

#3 put the system in a vacuum, but forget about the micron gauge, your hoses leak anyway.

#4 weigh in the factory charge.


#5 Stay in school, just say no to drugs.

SULTAN
06-06-2007, 09:30 PM
1. Pump down the system as stated above.
2. Close off service valves.
3. Braze the leak. (use water and rags to protect the service valves and put a liquid line filter dryer also at minimum)
4. Pull a vacuum using a vacuum gage to below 250 microns (however long it takes and preferably less than 250 or however you attempt with triple evac or just letting the pump do it's job)
5. Open service valves.
6. Put gauges and thermocouple on liquid and suction valves to check for super heat and subcooling.
7. Check and make sure your evap coil is clean and the condensing coil is also clean.
8. Turn system on and check charge using superheat and subcooling method. (check amperage draw if possible)



Also for the folks saying you need to recover all of 410A this is not the case unless it all leaks out to atmospheric pressure.
Note pages 4 and 5.

wow those are alot of steps....how much do contractors charge for doing a simple leak test and patching it up for?(if leakk was on copper tube) for a residential r22 ac system?

sinewave
06-06-2007, 10:10 PM
Dr Fleck


Do you own a Ten Gallon Hat and some Spurs by any chance? :p

Dr._Fleck
06-06-2007, 10:11 PM
£36 per hour, plus milage @50p mer pile, plus as much as you dare charge for parts.

Sub contract rates are a bit lower though.

What's the point of going to college if there is no practical side? That's mad, i thought Britain was the only country with no common sense:)

The MG Pony
06-06-2007, 10:33 PM
Some do some don't, BCIT here you spend more time learning in the shop building and repairing units then you do in a class room.

BigJon3475
06-06-2007, 11:20 PM
wow those are alot of steps....how much do contractors charge for doing a simple leak test and patching it up for?(if leakk was on copper tube) for a residential r22 ac system?

Most of it is basic for a leak repair. The checking for clean coil and evap is a must if it is going to be charged and also the air flow. If it's not moving enough air it won't be able to be properly charged.

analog
07-06-2007, 02:54 AM
wow those are alot of steps....how much do contractors charge for doing a simple leak test and patching it up for?(if leakk was on copper tube) for a residential r22 ac system?



There is no such thing as a simple leak test. They are all a bitch. The key is the homehowner supplied information concerning the loss of refrigerant. For example, " I just paid some trodder 200 Euros to top off the charge 2 yarn ago"


Residential systems all leak, it's a fact of life. The trick is not to let some under-educated rogue scare you. It's not his fault, all new service guys are trained to increase income by the severity of the repair. The more they bring in, the better they look to their bosses.


Good luck on your repair, I just wish that I was there to fix it for you, but alas, I can't be.

BigJon3475
07-06-2007, 03:27 AM
I just consider it removing factors that destroy systems. If one of the coils is clogged or it's over or under charged they all have effects on longevity not to mention it affects performance. If you don't pull to a deep vacuum and install filter dryers you should just go ahead use your gauges for pulling your vacuum and charge with your hand and waiting for the cold. IMO it's just guessing if you don't look at actual performance #'s. In the end doing it right in the first place will save money in the long run. There is never time to do it right the first time but always time to do it twice.

JohnJRambo
08-06-2007, 01:35 AM
Have to go with the full reclaim, proper pressure test and evacuation with a torr gauge followed up with weighing the charge in (especially if it is a blend).
:D

TIGA
08-06-2007, 09:47 AM
Close the liquid line,start the machine to cool,Run the machine until yr gauges read 3-5 psi.

Switch off the machine and close the suction line immediately.Before doing any brazing make sure there is no any refrigerant in the Evaporator.
Braze the spot and pressurize the system with dry nitrogen, check the system for leaks if ok then vaccumise the system open the liquid line gently then the suction line.
And topping up of the gas may be necessary if the machine lost alot of refrigerant.

Makeit go Right
10-06-2007, 01:27 AM
Great information. Seems there are two schools of thought on how to deal with leaks: a) Pump down, repair, and top-up; or b) Change this blended gas for a new perfect charge, as part of the repair work.

Reading through pages 4 and 5 of that link from BigJon3475, http://www.refrigerants.dupont.com/S...pdf/h47125.pdf, it really questions whether changing the gas is simply a waste of engineerís time and customerís money.

Has anyone got more to say on that?

Meanwhile, I have summed up the above tips and advices for these two tasks, in case it draws in any other tiny tips that could be added into these sequences:

Leak Repair - Pumping down a system:
1. Put your gauges on,.
2. Run system and set system on cooling mode
3. Shut the Liquid Line valve.
4. When the suction pressure reaches 3-5 psi, switch off system and shut the suction valve.
5. Make repair(s). Use water and rags to protect the service valves and similar items. Run the welding rod over the holes, donít get it too hot, back the torch off so the weld stays thick (the same consistency as washing up liquid). Clean up external joint with wire brush/wool
6. Install a liquid line filter dryer.
7. Test to 100psi for 1-hour minimum (24-hrs is best). While the test is on, put some washing liquid onto the repair joint(s) to check that area is sound.
8. Meanwhile, check/clean the coil and evap. (If there is inadequate airflow you canít charge it properly.)
9. Vacuum out the system, using a vacuum gage to below 250 microns (however long it takes). You can triple-vac or just let the vac-pump do it's job.
10. Open the liquid-line gently, then the suction-line.
11. Put gauges and thermocouple on liquid and suction.
12. Turn system on and check charge using superheat and subcooling method. Also check amperage draw.
13. Add top-up refrigerant gas as necessary.

Leak Repair Ė Change Refrigerant Gas for New:
1) If refrigerant gas has leaked from a system do not try to reuse the existing refrigerant charge. Zeotropics will leave an uncertain blend of the three different remaining gases:
2) Reclaim refrigerant from system into reclaim bottle(s) using a Reclaim Unit (not simply connect up a bottle and take what comes, vac'ing the rest go to atmosphere).
3) Flood system with OFN2.
4) When/while brazing, trickle in OFN2 tohelp prevent flakes of oxide forming inside the tubing and causing damage when system up and running.
5) Make the repair(s). Use water and rags to protect the service valves etc. Run the welding rod over the holes, donít get it too hot, back the torch off so the weld stays thick (the same consistency as washing up liquid). Clean up external joint with wire brush/wool
6) Install a liquid line filter dryer.
7) Test to 100psi for 1-hour min (24-hrs is best). While the test is on, put some washing liquid onto the repair joint(s) to check that area is sound.
8) Meanwhile, check for clean coil and evap. (If there is inadequate airflow you canít charge it properly.)
9) Vacuum out the system, using a vacuum gage to below 250 microns (however long it takes). You can triple-vac or just let the vac-pump do its job.
10) Re-charge system with new refrigerant gas: Calculate pipe length and add up refrigerant needed for pipe+condenser load Ė weigh in exact refrigerant required.
11) Double-check the charge using superheat and subcooling method. Also check amperage draw.


BigJon3475 also chipped in the best TIP Iíve heard for a while:
ďThere is never time to do it right the first time but always time to do it twice.Ē

I think I can see myself using that one with a few of my customers in the future, when discussing some needful repairs. Very useful, that.