HVAC guys. How do these pressures sound for my house a/c?

thedarkwolf

Diamond Member
Oct 13, 1999
9,000
110
106
75psi low side and 290 high side. The air coming out of my vent is around 50 degrees. Seems like this year my a/c is running pretty much all day if the temp is over 80 and can't maintain the temp once it reaches 90+. I only have it set at 76 so I don't think it should be struggling this much. Whatever the sticker on the outside of the a/c said faded years ago and is unreadable. This is an older r22 setup.
 
T

Tim

Check into having a real energy audit done by a reputable HVAC company in your area if you'd like to know how you're really doing.
 

richardycc

Diamond Member
Apr 29, 2001
5,719
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my upstair central AC is like that this year, had a guy came over and did a recharge, it is a little bit cooler, but still running a lot longer that it used to, and the vent air is only 62degree, thats kinda warm. I think my problem is the my air handler is up in the attic, which is a dumb place for it. Maybe I need more insulation or a turbine vent up there.
 

thedarkwolf

Diamond Member
Oct 13, 1999
9,000
110
106
Well my house is all one story so don't have that problem. I just don't remember it running this much before and I thought the air was always cooler. I have all the tools and the right freon to re-fill it myself. I just don't know what kind of pressure I am suppose to be seeing and don't want to remove or add any till I have some idea of what to look for. I'd rather not pay somebody $100 to come out here and tell me my a/c is old and should be replaced. I already know that but I don't feel like spending $3k rightnow since I would have to replace the furnace at the same time. I just want to limp it along for a while longer.
 

drnickriviera

Platinum Member
Jan 30, 2001
2,416
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You have gauges and R22 but you don't know how to charge the system? capillary tube or expansion valve? If you don't know the difference. Leave it for someone more experienced.
 

Rubycon

Madame President
Aug 10, 2005
17,768
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Pressures are not very useful without RAT/SAT of evaporator/condenser. At least your compressor has good valves!
 

thedarkwolf

Diamond Member
Oct 13, 1999
9,000
110
106
Originally posted by: drnickriviera
You have gauges and R22 but you don't know how to charge the system? capillary tube or expansion valve? If you don't know the difference. Leave it for someone more experienced.

Never learn anything that way. I can read what the differences are and I don't remember seeing a thermal expansion valve but I'd have too look again to be sure. Its dark now. Thanks for the link fossilburner.
 

drnickriviera

Platinum Member
Jan 30, 2001
2,416
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I'm all for DIY, but you can damage your system if you don't know what you're doing. I service all the units at my rentals, but I have the benefit of having a retired HVAC guy as a neighbor. Anything that seems out of wack, he gets a call.

Few years back, one of my tenants wanted to add some charge to the unit of the rental he was in. He installed commercial hvac units so I didn't think anything of it. Looks like he overcharged the unit. Liquid got into the compressor. Pop goes the compressor throws junk into the a-coil and clogs it.

If you insist on doing it. Add a little at a time, if the pressures and temps are going in the direction they should. Stop.
 

thedarkwolf

Diamond Member
Oct 13, 1999
9,000
110
106
Starting to just think my problems are all in my head anyway. I got rid of my straight out of the 70s rotary thermostat that was way off last year. I think my new digital thermostat that actually shows the correct temp is just making me think the a/c isn't working as well as it should. My pressures seem fine from what I can figure out on the net and the temp coming out of the vents are right on for the pressure it does have.
 

AlienCraft

Lifer
Nov 23, 2002
10,539
0
0
Originally posted by: thedarkwolf
Well my house is all one story so don't have that problem. I just don't remember it running this much before and I thought the air was always cooler. I have all the tools and the right freon to re-fill it myself. I just don't know what kind of pressure I am suppose to be seeing and don't want to remove or add any till I have some idea of what to look for. I'd rather not pay somebody $100 to come out here and tell me my a/c is old and should be replaced. I already know that but I don't feel like spending $3k right now since I would have to replace the furnace at the same time. I just want to limp it along for a while longer.

The truth shall set you free. :D

Then you've already checked all the old taped up joints on that air handler in the attic and made sure you're not leaking anywhere along the duct line and at the registers? Using new tape , zip ties or foil?
And have proper attic venting so the air handler doesn't get to be a dutch oven?

And new filter and cleaned off the coils? Of course you have, those are the basics. :roll: :)

Seriously, check at the registers. Make sure they are tight to the duct and there is insulation around them properly. Can't cool down what you keep heating up.

 

thedarkwolf

Diamond Member
Oct 13, 1999
9,000
110
106
My setup isn't the norm. Mine is a combo gas furnace and a/c unit that sits outside so everything is just right there. Its clean well other the all the rust, its old :). I haven't crawled around under the house yet to check the duct work but all the vents seem to be getting the same amount of air flow including the returns. The furnace side is what usually give me problems. This year the induction fan motor died and I had to rig up a new one since you couldn't even get one for this without being licensed and then it was $250 + whatever the service guy would have charged to install it.
 

thedarkwolf

Diamond Member
Oct 13, 1999
9,000
110
106
Yeah my friend was saying his is running around 60psi. I think my biggest problem is my attic insulation and lack as far as I can tell of any in the walls. Think I'll make replacing the attic insulation my next project. Walls are too much of a PITA and my gas and electric bills aren't bad anyway.
 

Vette73

Lifer
Jul 5, 2000
21,503
8
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A couple things to check...

1. How is the duct work run and if in the attic how is the insulation around the duct work? Even if the AC works correct and blows cold air, if it can't get from the AC air handler to the room then it will never work no matter how good the cold the handler gets.

2. Have you cleaned the evaporator coils in the air handler area? The old owner either used the cheap filters and when we had dry wal installed a lot of dift/dust got to them and clogged them up. I did not have a service port so I just cut a hole and cleaned the coils and then cuta peice of sheet metal and put some mastic on it and screwed it down over the smaller hole.

3. Air filter? I know it sounds simple but I have seen a lot fo them clogged. The best ones to use for most is the cheapest pleated one. The plain spun fiberglass ones, the older type, don;t catch enough dirt (see #2) and the higher end pleated ones work to well in that they slow down the air flow to much IMO. So the cheapest pleated ones seem to be a good middle ground. The catch more dirt but also don;t hurt air flow to much.


My dad does AC work and I am replacing all my attic duct work from the air handler. I am using either 6" or 8" round tubing from Lowes/HD and putting insulation around that with mastic to seal up the connections with screws as well.