HVAC REBUILD

[FellowTraveler]

HVAC REBUILD 1999 GMT400 K2500 SUBURBAN

I’ve been reluctant to purchase HVAC parts on line here’s the reason.

After ordering and waiting on three (3) different condensers all the same manufacturer “Spectra’ and same part number only one ‘the last one’ was the right one and it was from China.

The condenser to evaporator line was too short w/wrong bends so I spliced in a section of line and had to bend it for proper fitment….

AC compressor manifold and line/hose assembly issue either line/hose too short and/or wrong bends in hose ends etc. after lots of bending and fitting, deep vacuum, and Enviro Safe charge I now have the AC working nice and cold too.

However, I find HVAC parts prices are at a premium but the parts generally of poor quality and poor fitting…

While there have been ongoing debates on the safety of carbon based Freon substitutes I find it suitable for my use and 6 oz. of Enviro Safe is equivalent to 12 oz. of R134a.

 

[THEFERMANATOR]

I'm not looking forward to having to do any work to mine knowing how crappy parts are, and the fact many of these have been discontinued. Fortunately theres an A/C shop not far away that can do all the custom hoses I could need. And I haven't had any problems with R-134A, so no reason to try the new style refrigerants out there. 30 lb cylinders at SAM'S can be had for under $70 at the right time of the year.

 

[79jasper]

Hydrocarbon.
Aka propane. Lol
I've heard good things about the enviro-safe.
I wanted to use that when I recharged my ford, but I was on a role and didn't want to wait for shipping.

Sent from my SAMSUNG-SM-G935A using Tapatalk

 

[THEFERMANATOR]

It's not straight propane. Did some reading on it and it is a blend similiar to R-152A(AKA the stuff you buy to blow the dust out of computer parts and keyboards). Alot of peopel like it, and contrary to what many said, it is still here over 15 years later. And the next refrigerant coming out to replace R-134A that the yfound IS a greenhouse gas afterall happens to be a hydrocarbon based refrigerant as well. All of the sudden now HC's are safe for road use.

 

[FellowTraveler]

I'm not looking forward to having to do any work to mine knowing how crappy parts are, and the fact many of these have been discontinued. Fortunately theres an A/C shop not far away that can do all the custom hoses I could need. And I haven't had any problems with R-134A, so no reason to try the new style refrigerants out there. 30 lb cylinders at SAM'S can be had for under $70 at the right time of the year.

I looked for someone to do custom lines etc in my AO for my rebuild and had no luck.

 

[FellowTraveler]

It's not straight propane. Did some reading on it and it is a blend similiar to R-152A(AKA the stuff you buy to blow the dust out of computer parts and keyboards). Alot of peopel like it, and contrary to what many said, it is still here over 15 years later. And the next refrigerant coming out to replace R-134A that the yfound IS a greenhouse gas afterall happens to be a hydrocarbon based refrigerant as well. All of the sudden now HC's are safe for road use.

Propane and a small amount of iso-butane which you can mix yourself w/proper tools however too much iso-butane and freezing is the result. Another plus is that the Enviro Safe does not turn to acid if moisture somehow gets into AC system. I have an 8 HP 2 stage vac pump and it pulls deep and boils off moisture almost instantly..

 

[WarWagon]

HVAC REBUILD 1999 GMT400 K2500 SUBURBAN

I’ve been reluctant to purchase HVAC parts on line here’s the reason.

After ordering and waiting on three (3) different condensers all the same manufacturer “Spectra’ and same part number only one ‘the last one’ was the right one and it was from China.

The condenser to evaporator line was too short w/wrong bends so I spliced in a section of line and had to bend it for proper fitment….

AC compressor manifold and line/hose assembly issue either line/hose too short and/or wrong bends in hose ends etc. after lots of bending and fitting, deep vacuum, and Enviro Safe charge I now have the AC working nice and cold too.

However, I find HVAC parts prices are at a premium but the parts generally of poor quality and poor fitting…

While there have been ongoing debates on the safety of carbon based Freon substitutes I find it suitable for my use and 6 oz. of Enviro Safe is equivalent to 12 oz. of R134a.

Pay the GM dealer for condensers that fit. Updated design like thinner for dual air burbs (yuck), some years have a retrofit to R134a design.

16 oz in a pound. 6 oz can is equivalent to 16 oz of R134a. Not the short of a pound cans of R134a you are thinking of.

R1234yf flammability tests is a good youtube search followed by the same tests on R134a that doesn't light off. Oil from the AC system can light off no matter what refrigerant is in use. R1234yf is the replacement for the patent expiring on R134a. In this context all of a sudden the flammability risk isn't as bad as it was advertised to force us to use patented R134a over R290. Follow the money and flammable refrigerants are all ok now that R134a patients are expiring. Here comes the Global Warming Potential to make R134a bad as the expiring patient...

FWIW 600C is 1112F and my manifolds are known to get hotter than that. Loose the high side safety cut out switch and R134a will vent as the system blows up. (Did this several times on mine before I found the bad switch.) I do not know if R290's lower head pressure would keep the system from venting, but, it does trip the safety high pressure switch. R290 can cause a diesel engine to run away. Header wrap manifolds and turbo and cold air intake?

Envirosafe industrial reminds me of R12 with an A6 compressor cold and that's out of the R4 compressor... You should change the low side switch to one rated for R12 or an adjustable switch as the R134a switch cycles the AC clutch too much.

Kindly label the system so those of us that have a R134a reclaim/recycle machine know what we are dealing with.

 

[FellowTraveler]

Pay the GM dealer for condensers that fit. Updated design like thinner for dual air burbs (yuck), some years have a retrofit to R134a design.

16 oz in a pound. 6 oz can is equivalent to 16 oz of R134a. Not the short of a pound cans of R134a you are thinking of.

R1234yf flammability tests is a good youtube search followed by the same tests on R134a that doesn't light off. Oil from the AC system can light off no matter what refrigerant is in use. R1234yf is the replacement for the patent expiring on R134a. In this context all of a sudden the flammability risk isn't as bad as it was advertised to force us to use patented R134a over R290. Follow the money and flammable refrigerants are all ok now that R134a patients are expiring. Here comes the Global Warming Potential to make R134a bad as the expiring patient...

FWIW 600C is 1112F and my manifolds are known to get hotter than that. Loose the high side safety cut out switch and R134a will vent as the system blows up. (Did this several times on mine before I found the bad switch.) I do not know if R290's lower head pressure would keep the system from venting, but, it does trip the safety high pressure switch. R290 can cause a diesel engine to run away. Header wrap manifolds and turbo and cold air intake?

Envirosafe industrial reminds me of R12 with an A6 compressor cold and that's out of the R4 compressor... You should change the low side switch to one rated for R12 or an adjustable switch as the R134a switch cycles the AC clutch too much.

Kindly label the system so those of us that have a R134a reclaim/recycle machine know what we are dealing with.

I stand corrected on the amount of Enviro to R 134a I had posted as incorrect, thanks.....as flames go I can't think of anything under the hood that will not burn given the right chain of events except the metal. I don't do HVAC shops just DIY...so I'm sure no one will have an accident trying to recover anything from my system...

 

[THEFERMANATOR]

Propane and a small amount of iso-butane which you can mix yourself w/proper tools however too much iso-butane and freezing is the result. Another plus is that the Enviro Safe does not turn to acid if moisture somehow gets into AC system. I have an 8 HP 2 stage vac pump and it pulls deep and boils off moisture almost instantly..

I doubt you have an 8HP pump, that sucker would need a 40 amp breaker to run on 220 volts. I think mine is a 1/4 or 1/3 HP JB industries 2 stage industrial grade pump I picked up off of CL, and it will do the job NICELY. And forget about the problems of moisture contaminating the system, if you have moisture in the system, it will still freeze rendering your A/C useless.d

I looked for someone to do custom lines etc in my AO for my rebuild and had no luck.

Marks Air in Tampa will build you most anything you need as well as repair the infamous GMT-400 condensers when they strip off coming apart.ddddd

 

[FellowTraveler]

I doubt you have an 8HP pump, that sucker would need a 40 amp breaker to run on 220 volts. I think mine is a 1/4 or 1/3 HP JB industries 2 stage industrial grade pump I picked up off of CL, and it will do the job NICELY. And forget about the problems of moisture contaminating the system, if you have moisture in the system, it will still freeze rendering your A/C useless.d


Marks Air in Tampa will build you most anything you need as well as repair the infamous GMT-400 condensers when they strip off coming apart.ddddd

FERM, you caught my some-timers again thanks, 'it's 8 CFM, 1 HP, 40 MICRON, WT 45+ LBS. ROBINAIR 2 STAGE # 15800', yea I'm with you on the moisture content freezing.

I had tried w/o luck to get the bigger condenser from the 3500 cab chassis w/ambulance package it was an older style that could be flushed too.

 

[THEFERMANATOR]

That pump is beyond overkill. Mine is 3 or 4 cfm 2 stage 35 micron, and I've used it to evac a 4 ton house ac unit, and it did it in just a few minutes. Mine works great when my electric fan works, gotta get out and change it here soon with summertime temps returning.

 

[FellowTraveler]

That pump is beyond overkill. Mine is 3 or 4 cfm 2 stage 35 micron, and I've used it to evac a 4 ton house ac unit, and it did it in just a few minutes. Mine works great when my electric fan works, gotta get out and change it here soon with summertime temps returning.

Yea, I got a killer deal on it too, whats interesting is that as soon as I turn it on any moisture steams out almost instantly...

 

[Will L.]

Being a larger pump can bring the system to your max vacuum quicker. But no pump is capable of going greater than 29.92 in hg at sea level (full vacuum). Your altitude alters your max vacuum obtainable.

Getting rid of the moisture from a system is a combination of vacuum and time. If you have a pump that can achieve max vacuum for your altitude, you need to keep it under the vacuum for (iirc)10 minutes per pound of refrigerant the system holds to evacuate all the moisture.

Think of it as heat boiling off the water instead of vacuum. You can turn the flame up high enough to boil off the water instantly, but it takes time for the vapors to travel out of the system all the way to the vacuum pump. When you close the valves the moisture is trapped at the source of the vacuum. If you just bring it to a vacuum then close the valves in 2 minutes, where did the vaporized water go? Most of it is still trapped in the system.

I didn't get it until I saw a teaching system built from glass tubes. There was a fog in the lines for about 7-8 minutes. The system was only a 18oz set up, and just open to humidity of 20% for about 10 minutes.

That's how come small vacuum pumps can work. If it only gets to 15 in hg, you just increase the "cooking" time for it to boil off the moisture. When doing really large systems it is nice to have a larger pump to get you to your max vacuum quicker.

 

[FellowTraveler]

Being a larger pump can bring the system to your max vacuum quicker. But no pump is capable of going greater than 29.92 in hg at sea level (full vacuum). Your altitude alters your max vacuum obtainable.

Getting rid of the moisture from a system is a combination of vacuum and time. If you have a pump that can achieve max vacuum for your altitude, you need to keep it under the vacuum for (iirc)10 minutes per pound of refrigerant the system holds to evacuate all the moisture.

Think of it as heat boiling off the water instead of vacuum. You can turn the flame up high enough to boil off the water instantly, but it takes time for the vapors to travel out of the system all the way to the vacuum pump. When you close the valves the moisture is trapped at the source of the vacuum. If you just bring it to a vacuum then close the valves in 2 minutes, where did the vaporized water go? Most of it is still trapped in the system.

I didn't get it until I saw a teaching system built from glass tubes. There was a fog in the lines for about 7-8 minutes. The system was only a 18oz set up, and just open to humidity of 20% for about 10 minutes.

That's how come small vacuum pumps can work. If it only gets to 15 in hg, you just increase the "cooking" time for it to boil off the moisture. When doing really large systems it is nice to have a larger pump to get you to your max vacuum quicker.

Interesting thoughts, this pump has an exhaust muffler stack pointing up so when it boils the moisture you can easily see it as the vapor exits, when I turn the pump on it pulls deep right away (max vac) then the vapor (heavy) can be seen exiting the muffler for a few moments after the vapor visibly clears I run it another 5 minutes, so your saying there still is latent moisture I should run it anyway 10 minutes per pound of refrigerant I wonder if that holds true with the mixture I'm using or does that even matter?

 

[WarWagon]

'Nother trick is to run the HVAC blower to increase the temperature of the evaporators both for recovery and vacuum stages of repair. (Helps the recovery with the blowers running even occasionally.) Most of the time I watch a system come back up to 10-15 PSIG after my recovery/recycle equipment takes it to -10PSIG . I would guess from the dissolved R134a coming out of the oil. I have used a hair dryer on a system as the insulated accumulator had ice on it's outsides.

Also rotate the compressor to help anything in it's cylinders out in full vacuum.

No kill like overkill - I would love a vac pump like that. (Right until I have to pull the rope on the generator to start/run it that is!) However don't take shortcuts and vacuum the system for the full 15-30 min. Also replace the accumulator if you leave the system open for more than 2 min. I sometimes take a hose and clamp it on the accumulator connections with a new one out of the system say after I flushed a system. I then hit it will full vacuum, add a snort of R134a and then take it back down to 0. Then put the new accumulator in the system, make sure it holds a vacuum for 15 min, charge and leak check. In this way I don't ruin a new accumulator instantly.

As mentioned above, but, worth saying again: It's not the ice that blocks the FOT when you have lots of moisture in the R134a system that you worry about. It's that little bit of moisture...

 

[FellowTraveler]

'Nother trick is to run the HVAC blower to increase the temperature of the evaporators both for recovery and vacuum stages of repair. (Helps the recovery with the blowers running even occasionally.) Most of the time I watch a system come back up to 10-15 PSIG after my recovery/recycle equipment takes it to -10PSIG . I would guess from the dissolved R134a coming out of the oil. I have used a hair dryer on a system as the insulated accumulator had ice on it's outsides.

Also rotate the compressor to help anything in it's cylinders out in full vacuum.

No kill like overkill - I would love a vac pump like that. (Right until I have to pull the rope on the generator to start/run it that is!) However don't take shortcuts and vacuum the system for the full 15-30 min. Also replace the accumulator if you leave the system open for more than 2 min. I sometimes take a hose and clamp it on the accumulator connections with a new one out of the system say after I flushed a system. I then hit it will full vacuum, add a snort of R134a and then take it back down to 0. Then put the new accumulator in the system, make sure it holds a vacuum for 15 min, charge and leak check. In this way I don't ruin a new accumulator instantly.

As mentioned above, but, worth saying again: It's not the ice that blocks the FOT when you have lots of moisture in the R134a system that you worry about. It's that little bit of moisture...

That idea of rotating the compressor is interesting...

 

[Will L.]

It does not matter what the refrigerant is that your running. To get out the moisture you hold it under the vacuum 10 min per pound.

Also getting the most out of your system is getting the widest difference between high and low gauges is key. When it says 28oz or 39oz that is a generic amount. Get to 10% of the amount and watch the gauges go to 5% over and notice the peak of the curve. Get it back to that point.
Be careful on some of the "micro" systems that use less than a pound. Only go to 2% over.

 

[FellowTraveler]

It does not matter what the refrigerant is that your running. To get out the moisture you hold it under the vacuum 10 min per pound.

Also getting the most out of your system is getting the widest difference between high and low gauges is key. When it says 28oz or 39oz that is a generic amount. Get to 10% of the amount and watch the gauges go to 5% over and notice the peak of the curve. Get it back to that point.
Be careful on some of the "micro" systems that use less than a pound. Only go to 2% over.

Truthfully, I was not aware w/big pump that I should pull vac for that time, I assumed it could be shorter, but you what they say about assuming! Thanks

 

[Will L.]

AssUmed- something about a proctologist, right?
It does save time on the getting to max vacuum for sure. And I'm sure hits a complete vacuum for any altitude, which also saves time. Then the cool factor of having more power than the average guy wins extra points, always.

 

[THEFERMANATOR]

You can only pull down to whatever atmospheric pressure is. I want to get a micron gauge one day to test my pumps to see what they actually do. The fastest vacuum pump I have ever seen is a snap on air one. It can pull my 4+ lb system down to 30 on my gauges in well under a minute, but it does sliw way down pulling the gauge down to 32. I've seen several electric pumps that can't pull either of my gauge sets to 32, but that little air one can. My electric one is slightly slower at 1st, but goes faster once the vacuum gets down to 30 and it kicks to the 2nd stage. A bigger pump just means it pulls a system down to atmospheric quicker, but it still takes x amount of time to boil out any moisture or remaining refrigerant(please for the love of GOD! DON'T CALL IT FREON! IT'S REFRIGERANT!) left in the system. Need to get out and pull mine down so I can put my fan pressure switch in to actuate my electric condenser fan.