[jerryk1234]

Hello all!

I spent some time on this forum last year - got excellent help & advice with fixing the HVAC system in my house - which had been mostly removed by a tenant when the house was foreclosed.

At that time, I had cracked the books, passed the EPA test, bought two condensers, an evaporator and a furnace.

Put together the upstairs system, got the AC working. Then winter came, and AC became less interesting and the whole project hit the back burner. In fact, my permit expired and I had to go get it extended. They only give one extension, so I better finish it up this year.

Putting together the downstairs system I will have to braze up the suction line to the evaporator. The evap is a Goodman 3030-something. I am worried about heat. The suction line disappears into the cabinet and there is insulation on it inside. I pried out the rubber grommet....

Does one remove the panel to get at the innards and shield the insulation etc? Or just stuff in a wet rag and braze away?

I have refined my procedures a bit since last year. Now I have a proper adapter for my nitrogen purge setup, consisting of a brass airbrush fitting ( 1/4 IPS on one end, and a little tiny hole at the other end ) - brazed to a piece of 3/8" line, and the other end swaged so it slips over the tubing that I'm brazing. And a 3/8" to 3/4" adapter that I brazed and swaged up out of scrap tubing. The tiny hole makes it easier to set a reasonable
flow rate that won't use up all my nitrogen.

I also got a little tiny welding torch - the kind the sell at Harbor Freight. This thing is so little and so light, it's like holding a welding pencil. Yet it brazes 3/4" tubing with sil-fos no problem. You have to be a little patient, but it does do it. And it's easy to get behind the tubing to the blind spot.

So if somebody could supply me with a clue as to how to braze up that
evap, I'd appreciate it....

- Jerryk1234

 

[yuri]

stuff a wet rag in and braze away BUT the trick to successful welding is to do it FAST enough so the rag does not go dry or catch on fire. also the faster U do it the less time for heat to conduct down the copper and damage stuff so I prefer to use a oxy/acetylene torch and do the welds quickly which means using a fairly large tip also. everyone has their preferences but turbotorches are good for quick jobs but tend to burn everything around the weld and are slow. most journeyman I know use oxy/acetylene on commercial jobs/installs so there U have it.

 

[jerryk1234]

stuff a wet rag in and braze

*** Done. Used the big oxy torch. Didn't burn anything . Now for the fun part.
Pressure tested it with my nitrogen rig for an hour, then hooked up the vacuum pump.
250 microns and falling....

- Jerry

 

[jagans]

You all mean Brazing right? Shouldnt the lines be charged with nitrogen first?

 

[beenthere]

Its best to flow nitrogen or another inert gas while brazing.

 

[jerryk1234]

You all mean Brazing right? Shouldnt the lines be charged with nitrogen first?

*** Of course. Charged and brazed. With the Oxyacetylene torch.

Had a nasty surprise when I went to fill the torch. "One exchange MC cylinder, please".... "That'll be $37.00" Sacred Excrement!

Second nasty surprise - checking Ebay for R22 - Yikes, the stuff has more than doubled in price since last year!

- jerryk1234

 

[jerryk1234]

It's morning. Hooked up the vacuum pump for another few hours. Got it down to
70 microns. Guess that's enough. Now to see how much it rises....

- jerry1234

 

[yuri]

Too bad you did not keep a video diary of your "projects". You are probably the most thorough highly skilled DIYer on installing your own AC by now.:thumbup:

 

[jerryk1234]

Too bad you did not keep a video diary of your "projects". You are probably the most thorough highly skilled DIYer on installing your own AC by now.:thumbup:

*** Why thank you, Yuri!

Unfortunately, I was not feeling so swift yesterday. I learned an important lesson:

* When you charge an AC, ALWAYS WEIGH YOUR CYLINDER FIRST AND WRITE IT DOWN. Do NOT depend on the fancy "TARE" feature of your scale!!!!!!!!!!!!!

Guess how I learned that.... The Tare lost its noodles, and I was left with vague
guesses as to how much I'd put in.

So what about the numbers? Here's what we have ( R22 ):

Suction Line: 93.5 PSIg, 37.4 degrees F.
Liquid Line: 99 PSIg, 58.1 degrees F.

Huh?

I've never seen a refrigeration system with such a small difference between input and output. Like there is no pumping going on.

Yet refrigeration is obviously happening.

The system is a brand new 2.5 ton Goodman condenser driving a brand new Goodman 2.5 ton evap through a TXV.

I remembered that TXV systems often require a hard start kit. In fact, I had bought one when I spec'd the system. Dug the hard start kit out of the junk, installed it. No difference.

At one point, I was messing with the connections to the charging manifold. Turned the nut a bit, there was a *click*, and the gauge started making a bit more sense. But now I can tighten it as much as I want, nothing changes.

My HVAC contractor friend suggested measuring the electric current pulled by the pump to get a better idea of what's happening. To him, the numbers mean one of two things: 1 - A "partial pumper" - when a compressor is all worn out, it may run without moving much refrigerant. Probably not, this one is brand new. 2 - a bad connection or connections to the meters, such that they don't show the real pressures.

Could it just be so grossly undercharged that the condenser is unable to liquify the refrigerant?

- Jerryk1234

 

[yuri]

Get or borrow another set of refrig gauges and report back. sounds like something is very wrong with yours. gotta start with the simple things first. your 37 deg suction line is normal and should read 64 psig which is normal (could be if charged properly). both liquid line readings are out of whack. your report card is dropping to B-.:laughing:

when you get new readings we need to know the house temp, outdoor temp and humidity inside. should be at least 70F outside and inside B4 charging any AC unless you got 5-10 yrs experience or weigh it in properly. even then we have to adjust for line length etc etc. if you have a contractor friend then definetly buy him some beer and get him to fine tune it as we cannot do that over the net. will make a huge differnece in the long run with oil return etc etc.

 

[jerryk1234]

Get or borrow another set of refrig gauges and report back. sounds like something is very wrong with yours. gotta start with the simple things first.

*** Makes sense. How about if I unscrew the high side gauge and connect it to an air compressor? Just to check it out. I do have a second manifold, but that's an
R-134A one, and the connectors are all different. We're not talking about high
accuracy here, just see if it shows 100PSI as 100PSI - not 50.

Unfortunately, my AC contractor buddy is 160 miles away, well beyond "free beer" distance.

- Jerry

p.s. I don't have a wet bulb thermometer. But the local airport does. They report the temperature and dew point every hour. I understand that
I can calculate the wet bulb temp and relative humidity from that. For example, right now, it's temperature 14C, dewpoint 11C.

 

[yuri]

I don't know what you got going there and for me trying to imagine etc is beyond my abilities now.

 

[jerryk1234]

I just connected the manifold to my nitrogen purge setup. Each gauge is
accurate to within a couple PSI, as checked against the output gauge of the nitrogen regulator. The nitrogen setup is a very high quality piece of equipment. Medical
grade.

The local gas store pissed me off no end. They gave the top cover of my tank to somebody else. MY top cover was spun stainless steel. They looked around and gave me a crappy mild steel one. Gray on the outside, rust on the inside.

- Jerry

 

[beenthere]

Excessive flood back(grossly over charged) to a scroll can cause the scrolls to separate and and loose the ability to move refrigerant, or move very little.

 

[jerryk1234]

OK, Things are looking much better. I fiddled with the hoses and the Schraders and now have:

High side: 115 PSIg, 19 degrees C ( 66 F )
*** Just about at saturation.

Low side: 58 PSIg, 48.7 degrees F
aka 16.7 degrees of superheat.

Sounds like the charge is low.....

- Jerry

 

[JScotty]

OK, Things are looking much better. I fiddled with the hoses and the Schraders and now have:

High side: 115 PSIg, 19 degrees C ( 66 F )
*** Just about at saturation.

Low side: 58 PSIg, 48.7 degrees F
aka 16.7 degrees of superheat.

Sounds like the charge is low.....

- Jerry

Yeah 115 psi on the high side seems a bit low. The trick to charging TXV systems is to compare the liquid line (the smaller one) temp to the saturation temp of r-22 at the give pressure. Follow the needle down to the r-22 scale that tells you the saturation temp at that pressure. The line temp should be about 10 degrees less than the r-22 temp on your guages. Or if you want to get real accurate look for a target subcooling on your unit & the difference should be that number, 10 is just kind of a basic guideline.

 

[jerryk1234]

Yeah 115 psi on the high side seems a bit low. .

Update: Added some more gas, and all of a sudden the numbers started making sense. 8 degrees of subcooling, 8 degrees of superheat. Gentlemen, we have AC!

- Jerry