OK, first I'll say I don't know much about A/C function, but do have an idea how it works...

Last Fall I got a new Central A/C system from a guy that owed me money. (His Dad owns a HVAC shop)

The guy since skipped town, but I did manage to get the system installed, but not running 100%.
Electrically, everything works fine. It comes on, goes off as it's supposed to.

The problem is, it doesn't get as cold as it should...
When I had it charged with R22, we used a vacuum pump to suck down the system before opening up the service ports on the outside compressor unit...
After it sat with a 30hg vacuum for 1/2 hour or so, we opened up the service ports assuming it was "pre-charged" from the factory...
Started it up and ran it for a few minutes with a set of guages on it.
The high side was only at 100psi, and the low side was around 30psi. (If I recall correctly)
We decided it was low on R22, or had none at all, so we charged it, and got the pressures up to 300psi high side and 80psi low side...

STILL no cold air...

I did notice that both lines to the evaporator were the same temp, and cold to touch.
Checked them with an IR temp guage and it said they were only @ 72 degrees F...

When I got the unit, it came with a piston kit, which I did not install.
The piston that was "pre-installed" was .059", and the extra piston supplied was .065"...

My buddy that charged the system said he was afraid to use the bigger piston, as it could "flood the evaporator"...

It was getting dark, so we just left it as is, and my buddy went home...

The next day, I went outside, closed the service ports, and changed the piston kit to the bigger .065"...
When I opened the line to install the piston, I got what I thought was an UNUSUAL amount of oil out of the line...
The piston is installed just above 4 capillary tubes, and it just seems like the excessive amount of oil could have been clogging the tubes, or creating a problem some how...

Any Advice ?

I don't feel like calling a contractor, and paying several hundred dollars for 1 hour of work I could do myself.

Thanks in advance.

If the high side is 300 psi you have a blockage somewhere.
How was the copper line brazed? Some people use silver bearing soft solder and they use to much and it gets into the line set. Hence clogs things up.

Rick

It was silver soldered, and done quite nicely...
Another buddy did that for me. (He's a plumber)

I think the blockage may be the excessive oil in the system....

When I opened it up at the evaporator to change the piston kit, I got damn near a coffee cup full of oil out of it...

Could that cause a problem ?

Right now, the lines are depressurized and empty, but the compressor unit outside is still pressurized since I closed the service ports before opening up the system...

Would it be OK to open the ports and recapture whatever is left in the compressor, then recharge with R22 from scratch ? (Without adding any more oil)

what brand of equipment is it?

300 is a tad high for most systems but not uncommon. If you blower is not working correctly that also will bring up the pressure, the wrong size duct work will also cause a lot of problems.

Condensors are typically overcharged so when you open up the ports the freon will fill 20' of line set. If you have something like 50' of copper line set you will have to add freon.
The freon gets absorbed into the oil. Read on the condensor what type of freon it takes.

Well I gotta go to work...hopefully this will help you out till I check back later.

Rick

Word of advise...don't get caught dumping freon.
If you hook up a powerful vacuum to it it will bring the oil to a gas state and evacuate it. you will need to read the instructions to get the proper oil/freon level. They are all different.

Rick

Actually, the lines from the outside to the inside are only about 4ft long...

The ductwork is sized properly, and is also new...

Basically, the biggest problem is getting the evaporator cold...

I always remembered the lines were opposite temps when things were running properly...

Big line gets ice cold and is insulated, small line gets hot, and is exposed...
In my case, both lines are about the same temp...

Everything is new, and unused up to this point...
I keep thinking there was too much oil in the system...
Maybe enough oil for 25ft of line, but I only need enough for 4ft...

IM sent!

BigDozer66

IM sent...

House is approx 1400sq ft.
House is 65 yrs old, and has little (no) insulation...


Both inside and outside units are the same mfg...
The Mfg is:

Goodman Mfg. Co. LP
Houston, TX 77008


System specs are as follows:

Evap is labeled:

Mod# U29
SN. 0111458946
R22
design pressure 90 psig
test pressure 150 psig


Outside unit labeled:

Mod# HDC24-1AB
SN. 0102456605

Compressor RLA- 12.8 LRA-61
Max working pressure 400psi
Factory test pressure LOW-150 HIGH-300
Factory charge 40 oz R22



It also has a sticker on the side of the evap unit that says:

"When the desired system capacity is 2.5 tons, the piston kit supplied must be installed"

The only thing I can tell you right now is I suspect a small blockage some where. The smallest point in the system is the piston .059 and the 4 calipallary tubes that run from the piston area. The condensor was made 02-2001.
Another question...is a line dryer installed on the 3/8 liquid line? Has it ever cooled correctly? Goodman/Janitrol/GMC products have a standard 5 years all parts warranty...10 years if its a 12 seer or higher. It may pay to have a HVAC tech out for a visit.

Rick

Art, I am an HVAC tech.  The 4' line set is part of your problem, the oil gets blasted out of the compressor and settles out where to Freaon boils off, which is the evap.  300/100 sounds like a combo of overcharge and maybe a restriction.  I'd call GMC and ask them which piston to use with the evap/cond unit thatyou have.  IS the evap higher or lower than the condenser unit?  What size copper tubing did you  use?  With a correct charge and system, the air going thru the coil shoudl drop about 20 degrees.  What speed is the fan running?  You have what sounds like a 2.5 ton evap and a 2 ton coil.  The instruction manual should tell you which piston to use with that setup.  If it gets out of hand i will pay a visit.  Ops.

 Edited to add:  With a cold liquid line, it sonds like a restriction in the line somewhere.  make sure the service valve is fully open and check to see if the shrader valve got melted on the end when you buddy soldered it.  

300/80 High side/low side pressures??

OVERCHARGED! Back that baby to a 55# low side and you should be OK.

I have a goodman system too. works great! a little noisy but shit if its running and the windows are closed , I dont hear a thing.

Cant be a restriction, low side pressure is too high.

General rule:

high side: low, low side: low = low charge, leak
high side: high, low side: low = restriction
high side: low, low side: high = compressor inefficient
high side: high, low side: high = overcharged

55# may be low depending on the load, Doc, you know that.  Usually the evap will run between 35 and 40 degrees colder than the return temp, so do the math and convert the temp to pressure for R22...   I amy just have to talk Art into a grilled burger and a personal visit.  Ops

Yeah but he is in PA not AZ or NV where the temps are probably what? 80? better to be undercharged then top off than to overcharge and cause potential damage. However this one has me curious. If you check it out, keep me posted

Well, after talking to several people, reading this thread, and doing a little work on the unit, I've come to this conclusion...

First and foremost, it appears as though the outside unit was NOT properly charged from the factory, or it was discharged and refilled with air or nitrogen.

After I installed the .065 piston, I went back outside to open the service ports and recapture whatever was left ...
Guess what ?
NOTHING but air pressure...
No cold stuff, no freon, no frost...nada.
Just 10 minutes of clean fresh air.

When we originally vacuum'd the system down, we left the service ports closed.
We assumed it was factory charged with 40oz of R22 like the label indicated...
After sitting at 30hg for a half hour, we opened the service ports, and ran the compressor.
Again, we assumed it was charged from the factory.
The pressures were only around 100/30, so we hooked up a bottle of R22, and filled it to 300/80 or so...
It never got cold, so we just called it a night since it was getting late.

The next day, I started this thread looking for answers...


I also learned that 4ft of line is part of the problem.
This is sorta unavoidable, due to space constraints.
The outside and inside units are right next to each other, but on opposite sides of a wall...

If I had to make an educated guess without using a tape measure, I'd say the evap is between zero and six inches above the compressor...

The inside fan speed is set on the highest setting.

I have 3/8 copper and 5/8 copper tubing...
The outside unit mounts the lines with 3/8 & 5/8 flare fittings, and the inside unit is silver soldered.

The evap unit has a sticker on it that says:
"When the desired system capacity is 2.5 tons, the piston kit provided must be installed"

I assumed this meant to install the .065 piston, so I did...

Right now the whole system is empty.

I think I either need to re-route (lengthen) my copper lines using a detour method, or just fill what I've got with R22 and start over...



Whatch 'yall think ???  

Since you have such a short line set and removed a little bit of oil....go ahead and recharge the system. If you can read the charging chart on the inside cover use those figures. It will be around 200 to 225 on the high side 70 on the low at ambient temp around 75 degrees. This will be an average...use the chart.
Charge is very important...to low it freezes to high you could lock the compressor.

Rick

No, there is no dryer. Just copper line to and from...

No it has not cooled properly yet.
This is a new installation, and hasn't seen service yet...

Saddle-up your horse...
You don't need to talk me into a visit...
I'll feed you grilled burgers 'till you puke.
I just need my A/C to work... [:D]


Actually, I left a message on my buddy's machine today...
Told him to get back over here with his gear...

If I don't hear from him, I'd gladly compensate you for your time Ops...

I'm not working right now, so I'm available "whenever".


*edit to add...

I changed my email addy if you tried to email me.

New email is: [email][email protected][/email]

You are onto something with the nitrogen charge.  I'd change the piston to match the condenser, which is a 2 ton.  Just put a coil of copper tubing in the basement, no one will see it there.  The 5/8 OD tubing is OK for a 2 ton unit.  Change the piston, evacuate and recharge.  Keep me posted, I need something to do next week.  Ops

Do I need to lengthen both lines ?  or just the smaller 3/8 line ?

Should I coil it above or below the evaporator ? (I'm thinking below to act as an oil trap)

Line length don't mean squat except for total charge if done by weight,

Call Janitrol and find out which piston to use.  I suspect the smaller one is correct as they are matched to the condensing unit, not  the evap.

Best way to cahrge is by weight; eliminates one variable.  Second best way is SUPERHEAT.  SH is the difference between suction (large) line temp and the temp represented by the low side gage.  Needs to be 20 degrees or so at the compressor or near to same.  If you can not do one of the above, pay for the service call!!  Low side needs to be above 32 degrees saturated, ie about 58 pounds.  Anything less and the coil will freeze.  Hi side temp should run 110 to 140 degrees condensing or some 30 degrees over ambient (rough numbers) assuming no headpressure control.  Temp of small (liquid) line depends on WHERE the piston is located.  All lines downstream of it will be cool / cold.

The oil in the system is NOT a problem!!  Do NOT remove any or you are in for trouble.  Checking oil levels in welded compressors is a PIA that requires you remove  the compressor!

Elevation differences of 10' or less between evap and cond unit are a non issue as well.

So in all likelyhood, the whole problem was a result of having the outside unit charged with something other than R22 ?

All I need to do is put the original .059 piston back in, and charge it ?

Maybe I'll just call and get a service guy out here tomorrow...

How much could it possibly cost ???

Around my area...45.00 for the call 5.00 a pound for R22. Should be there no more than a hour.

Rick

My bill would be something like this:

Service call (includes 1st hour)  $ 64.00
2nd hour (likely)                  $64.00
About 6 LB R-22                   $ 33.00
Vacume pump                       $  7.50
+ sales tax @6%
Total would be about $178.61

Any additional problems found or parts equired would be extra.  Add $64. if any refrigerant needs to be recovered.

Hope this helps......

I guess I'm to cheap.
Without any problems.....
1 hour should be able to vacuum & charge.
3lbs freon 15.00...only 6' of line set.

For 178.00 I'll drive to you from TN.

Rick

I guess I'm to0 cheap.
Without any problems.....
1 hour should be able to vacuum & charge.
3lbs freon 15.00...only 6' of line set.

For 178.00 I'll drive to you from TN.

Rick

With all due respect, but if you know nothing of HVAC how do know the time required to do the job?  To pull a PROPER vacume on a system put in under questionable circumstances it a time thing that can not be estimated.  It  may achieve 200 microns in 10 min or it might take all day.  Just depends how much moisture is present.  There is also the time for travel - not an issue here because we are two states apart but I find 30 min is a decent guess.

I do not know how much gas your unit holds.  Quite often it is on the data plate so you should have better info on that than I do because you have the unit.  I charge by weight, based on nameplate data if available.  There would be a few ounces of deduct due to short LL.  I look that up on a chart so do not know off the top of my head.  Need exact size of tube to do that task.

Granted refrigerant costs less than $5.50 a LB.  I need to make a profit and that is one of the ways I do it.  I can buy it wholesale, you can't.

Finally, keep in mind the thing don't work.  It is the cheapest, lowest quality equipment on the market.  Anything is possible.  I can fix it (but do not travel THAT far!!), you can't.  Kinda leaves you at my mercy doesn't it?

This little rant may help a few people understand why I no longer do residential work......

I just bought fifty 30lb jugs of R-22 at 34.00 a jug.
Thats puts it at about 1.25 a pound.

Actually I can charge a cheaper rate since I own all of 150,000+ dollars worth of tools and equipment. The only payment I have is to the bank for my commercial building at 360.00 a month.
I'm licensed for automotive, residential and commercial. Right now I'm so covered up it not funny. So I guess I can buy wholesale.

Just having fun.
Rick