Hi all,
I have a Unitary Products Group 4-ton Condenser Unit Model BRCS0481BD. The serial number indicates it was made in 1998. Our AC has not been cooling well here in the Texas heat this year and I am trying to diagnosis if we have a R22 leak, or if the Condenser unit is just plain worn out (the fins are corroded). I would like to get through this summer and replace it with a new R410 efficient unit. But for now, I hooked up a gauge set to the LO and HI pressure line connections and found that the LO side was 76 psi and the HI side was 330 psi. It was about 95 degrees outside at this time. From reading around on the internet, the LO side should generally be 70 psi and the HI side should generally be no more than 250 psi. The design pressure on the HI side is listed as 350 psi, so it seems like the liquid HI side has too much pressure and I guess it was overfilled at some point.

Did a technican who serviced the unit in the past overfill it with R22? Maybe this is why the unit has not worked very well since we have been in this house - we were told back then this was a 3 ton unit and was undersized so we just lived with the problem since then. Any insight or assistance is appreciated so I will know whether this unit can operate better or not.

Thanks, dcay

When was the last time it got a good cleaning and serviced by a pro. Service tech?
Is the filter clean?
What is the temp. of supply air?(coming out the vents)
Are all the indoor vents open? Supply and return
How long have you lived there? And is this the first time you`ve noticed the prob. have you checked the sub cooling temps and superheat temps?

wmproop said it best... get it cleaned first.

Thanks wmproop and siberianair,

We have lived here 4 years and had the unit serviced the first summer when it did not seem to cool. The service tech said to my wife that it was charged OK - I was not home then and do not know if he actually checked anything else. Our house was built in 1987 and I thought this was an undersized builders' special - turns out it was actually a replacement unit. Later that first summer we then had another a/c professional come in to evaluate our house and discuss what we could do to make our house more comfortable a/c wise. He did not actually take any measurements or run calculations as I thought he might because he said he was experienced and knew what we needed. He discussed air flow and then wanted to upsize the unit outside and air handler inside and upsize all of the air ducts one size (+2"). He said the unit was a 3 ton and he wanted to install an upsized 4 ton system and a bigger air handler.

We could not afford the $16,000 he quoted for all of that work. I also wanted a whole house type of solution rather than brute force with just bigger equipment. After my recent research this week on my a/c unit, I found out that my unit is actually a 4 ton a/c afterall, not 3 ton as I was told before?! So this made me believe that this unit should have the capacity to adequately cool our house since it is a 4 ton size instead of a too small 3 ton unit.

We did only have one 20"x25" return register with a builder's 0.70 factor standard grill. We did install a second return register with two good 0.90 factor grills for 900 in^2 effective area, installed a sealed insulated door above the attic stairway, installed vent chutes all around the ceiling insulation and roof for ventalation and I installed an additional 6" R13 layer of attic insulation over the original R19 which seemed to have helped the next few summers - at least the unit would keep up with the heat. I am now installing a radiant barrier on the roof rafters (25% done) and planning on installing about 18 ft of ridge vents. It just seems that this year the a/c is not working as well and frequently gets behind the set temperature of 79 degF. It could just be the record hot temperatue here in Houston this year or I thought that it might be leaking freon and would still work to get through this summer. I think the fall would be much better to install a new system since it would inconvenience my family less and it would be easier to work in a cooler attic than the 140 degF it gets now. That would also give me time to research the best overall system for me. I'll be asking everyone here about that next.

The aluminum exchanger fins are clean but they seem to be corroded a lot. They bend easily when you press on them. The inside filters are clean and I measured the temperature of the air coming from the vents as 70 degF using my wife's digital cooking thermapen. I do not know what the subcooling or superheat temps are. Is this the temperatutre of gas freon line into the condenser (LO side) and the liquid freon line out of the condenser (HI side)? How do I check these values - just put my thermapen thermometer next to the line and hold a rag over it until a steady reading is obtained? If the aluminum heat exchanger fins are corroded and is keeping the air from easily going through them to cool the freon liquid - would that make the HI side pressure the 330 psig I measured? I guess if the liquid freon is not cooled enough then it would not get as cold when it was expanded in the evaporator. Does the LO side pressure of 75 psig indicate that there is good freon inside the system and this is not the problem?

If the problem is just an old condenser, a regular serivce call will not be able to help any and I will just live with the poor cooling performance anogther 2 months until the fall and change the system then. Is there anything else to check to tell if this is the case?

Sorry for the long write up and Thanks in advance for all of your help.
dcay

?? You said something about working in the attic,make me wonder ,is you airhandler in the attic? If so is the plenium/main trunkline insulated? If it's there and not insulated this could make a difference in the temp of your air,, attics get hot,even with the extra ventilation

Hi wmproop,
Yes my air handler is in the hot attic space. The (1) plenum from the house goes through about 10 ft of insulated ~22" flexable duct and the ducts are also insulated flexible ducts running through the hot attic space. I'll measure some temperatures directly in and out of the air handler and the condenser in and out lines.
Regards, dcay