[Tally Wacher]

I have been doing some work on my parents' house in preparation for late Spring/Summer in Houston. I have installed soffit baffles, air sealed the attic, blown in cellulose to R44, cleaned the condenser and evaporator coil, and replaced the Tstat.

They have a Heil condenser model CA9060VKD2/AH060GA2 and an American Standard coil TXH054A4HPA1. I think the system is about 18 years old. They have all rigid ducts except for one flex and to the best of my knowledge have been insulated.

I go to call for cooling and it does produce cool air but the temperature difference between the air coming out of the vents and the air going into the return varies from the 0-9 degrees lower. How does one proceed? I was thinking about borrowing a friends AC manifold to see if the system needs charging. I really can't access the lines in the attic anymore due to the blown in insulation so it is hard to check for leaks there. I will check at the condenser. If I find that the system needs charging, I would try to use an AC sealing kit and then recharge with R22. BTW I don' have a license, but my buddy does and can get the refrigerant. Thanks.

 

[roughneck]

Is the compressor coming out on? If so, what is the operating pressures, superheat and subcooling?

 

[Tally Wacher]

I believe the compressor is coming on. Don't have the manifold gauges to get superheat or subcooling yet.

 

[Tally Wacher]

Not sure why I can edit my posts, but I wanted to clarify that the temps I was getting was with a infrared thermometer at the return vent and registers. I did not take the temp post coil, so I don't know the temp difference across the coil. The unit has a TXV so if need be I will charge using subcooling.

 

[WyrTwister]

Take the air temps with something like this .

http://www.harborfreight.com/1-inch-pocket-thermometer-46586.html

God bless
Wyr

 

[Tally Wacher]

Buddy brought over the wrong manifold set, but the low side was 20 psig and high side was 175 psig. Temp on the lines were in the mid 80s. He went ahead and charged it with r22 and the system is working well. Post charge pressures were 50 low side and 190 high. He said that he was being conservative with the charge as the system was old. He let me borrow his halogen hawk to see if I could pin point the leaks. He wasn't too thrilled about the idea of using leak freeze.

 

[yuri]

190/50 is good as with that old school unit a 4:1 compression ratio is very good. However a 18 yr old unit in Houston has as many running hours and miles as a 30 yr old unit in my area or less hot areas. Sounds like the compressor is not badly worn or you would not get a good ratio. Sounds like the charge is OK to me and you are lucky it lasted that long.

Nobody I know of likes or uses those leak seal products as they can wreck your gauges and can cause problems internally. Works for a few people but I avoid it like the plague.

 

[WyrTwister]

Does it have florescent dye in the system ?

Schrader valves are inexpensive . So are the " caps " with O-Rings .

https://www.johnstonesupply.com/storefront/product-view.ep?pID=B14-812

http://www.grainger.com/product/JB-INDUSTRIES-1-4-SAE-Cap-w-Gasket-3DXG2?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/3DXG2_AS01?$smthumb$

On my own equipment , I consider them to almost be preventive maintenance , when I have a leak .

What was the outside Air Temperature when the pressure readings were recorded ?

I would not use a leak sealant .

God bless
Wyr

 

[beenthere]

Buddy brought over the wrong manifold set, but the low side was 20 psig and high side was 175 psig. Temp on the lines were in the mid 80s. He went ahead and charged it with r22 and the system is working well. Post charge pressures were 50 low side and 190 high. He said that he was being conservative with the charge as the system was old. He let me borrow his halogen hawk to see if I could pin point the leaks. He wasn't too thrilled about the idea of using leak freeze.

50 PSIG low side is too low for R22. Your indoor coil will freeze.

 

[user_12345a]

Needs to be above around 58f to not freeze.

Properly charged/operating r22 may be anywhere from 60 to 80psi depending on many factors, but you have to get your buddy to check the super heat and go from there.

 

[yuri]

I can easily run 50/175 where I am and see that in cool weather. Not something you want to run for several hours but for startups is OK. All depends on the outdoor temp and house temp at the time. 60-65/200 is better.

 

[Tally Wacher]

Does it have florescent dye in the system ?

Schrader valves are inexpensive . So are the " caps " with O-Rings .

https://www.johnstonesupply.com/storefront/product-view.ep?pID=B14-812

http://www.grainger.com/product/JB-INDUSTRIES-1-4-SAE-Cap-w-Gasket-3DXG2?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/3DXG2_AS01?$smthumb$

On my own equipment , I consider them to almost be preventive maintenance , when I have a leak .

What was the outside Air Temperature when the pressure readings were recorded ?

I would not use a leak sealant .

God bless
Wyr

There is no dye in the system. Outside temp was about 78 degrees F indoors was 80. I think I'll just continue charging the system once a year instead of the leak freeze until the parental units decide it is time for a new system. The caps still had the rings but will probably get new caps/rings

50 PSIG low side is too low for R22. Your indoor coil will freeze.

Needs to be above around 58f to not freeze.

Properly charged/operating r22 may be anywhere from 60 to 80psi depending on many factors, but you have to get your buddy to check the super heat and go from there.

I'm going to get my own manifold and do some more learning. So far it has been very educational and interesting. Going to go sniffing for the leak this weekend and probably add a little more R22 and shoot for 70 psig low side then.

This is a great forum and I've learned so much. Thanks to everyone.

 

[roughneck]

Pressures are only part of the equation. SH/SC is very important.

 

[user_12345a]

Edited post, wouldn't mind if mods could delete original one 30 minutes exceeded...

Needs to be above around 58f to not freeze.

Properly charged/operating r22 pressures will greatly vary depending on many factors - you have to get your buddy to check the super heat and go from there, charge based on required superheat using chart, wetbulb return air, outdoor temp.

Could have a low side pressure anywhere from 58 to 80 and be properly or improperly charged depending on the conditions.

Pressures alone aren't reliable for charging, at least in theory. Some guys may know what they should be for a certain machine in certain conditions after many years of experience, but you'll be better off doing it properly.

 

[user_12345a]

I'm going to get my own manifold and do some more learning. So far it has been very educational and interesting. Going to go sniffing for the leak this weekend and probably add a little more R22 and shoot for 70 psig low side then.

You are not inflating a bike tire.

So many things can cause low suction pressure including low airflow. In fact you could dump lots of refer in, get the suction pressure up, think it's cooling fine but the compressor gets damaged by liquid returning to it, system overcharged, cause not recognized.

All you need is suction line temperature minus saturation temp - saturation temp is on the gauge.

It's temperature rise above boiling, basically when all the liquid refrigerant in the evap coil has finished boiling off, it's all gas and the gas continues to absorb heat, warm up.

You need 100% vapour coming back to the compressor.

Chart tells you what it should be.

Can be used to diagnose problems; for example a suction pressure of 50 but zero superheat --> to me that automatically indicates very low airflow, plugged coil - without that reading it would be misdiagnosed as low charge

Subcooling - same thing but on the condenser. Saturation temp minus liquid line temp.

Tells you how much liquid is stacked in the condenser (higher = more liquid), can help diagnose restrictions, metering device problems.

Theory is an amazing tool - better to understand why than to memorize what. With an understanding of why no one don't have to memorize anything, look for specific things.

 

[yuri]

If it was 78 outdoors and 80 inside then you are probably way low on charge. Should be running 65/225 or higher. Impossible to quote you numbers but that is a rough guide for a new unit with proper airflow.

You also need to know about the superheat or subcool if it has a TX valve.

However for future readers and yourself the best layman's way to check is to stick a accurate cooking thermometer in the supply duct after the coil (1-2 feet downstream if possible ) and then subtract that temp from the return air temp or house temp. If you are getting less than a 15 deg F drop you may have a worn compressor or be low on freon. 15-20 is normal. Do this test between 8-10 am before the sun gets too high.

Where I am we can run 70 F in the house and get a 50-55 F supply when it is 70 F outside. Our humidity is rarely above 50 RH.

There are other factors like how high a SEER rating the unit is and airflow but for a 15-20 yr old unit those temps work.

 

[beenthere]

There is no dye in the system. Outside temp was about 78 degrees F indoors was 80. I think I'll just continue charging the system once a year instead of the leak freeze until the parental units decide it is time for a new system. The caps still had the rings but will probably get new caps/rings





I'm going to get my own manifold and do some more learning. So far it has been very educational and interesting. Going to go sniffing for the leak this weekend and probably add a little more R22 and shoot for 70 psig low side then.

This is a great forum and I've learned so much. Thanks to everyone.

Shooting for 70 low side can cause a gross over charge. Systems should be charged by super heat and subcool.

50PSIG is a saturation temp of 26°F for R22.

At 175PSIG for the high side, the outdoor temp shouldn't have been higher then about 73, for a 10 SEER condenser.

 

[yuri]

You cannot shoot for any reading. How clean the indoor coil is and the amount of airflow over it plus how clean the outdoor coil is will affect your pressures. There is a critical tipping point where adding more freon will cause liquid to slug back to the compressor and damage it. That could be 50 psig or 55 and 5 psig can make a huge difference and start slugging.