Gas and Oil Home Heating Furnaces - Air Conditioning Question

I have read some of the posting and you guys are very hopeful

I have two air ruud conditioners units a 2 tons unit downstairs and 3 ton unit upstairs.

The downstairs house size is around 1400 square feet and open when I put a thermometer at the register to see how cold the air is it is 55 degrees coming out. The downstairs area is cooling fine.

The upstairs unit is 3 tons and the square footage is around 1900 this unit runs all day and never goes below 76 degrees
last night it was 77 degrees outside and the air coming out of the register was 71 degrees and not blowing as hard as it was ealier in the day the returns are located on the second floor hallway and the air being sucked in was 78 degrees. Somene told me there should be a 20 degree difference between the registers and the return. Also they said the air coming out of the registers should be at least 60 degrees

When I checked the unit upstair there is a brass pipe going in to the ref unit and it was frozen and water was dripping from it. The unit is unit is 2 years old and this cooling problem as been a problem from the start.

Also my attic is finished and the unit sit on the outside of the finished area. I have an exhaust fan but the temp inside there is 110 and 130 degrees depending on the temp outside.

I change the filter monthly and the guy who installed it says everything is fine but he always comes on days when it is cooler outside.

If anyone can offer me some things to check I would really appreciate it. ALSO I AM TO TECH WIZ so be gently :-)

Since the brass pipe (compressor out) was cold, it means the compressor is working. However, check the brass pipe on the other side of the compressor (intake). It should be warm to hot.

An A/C works by having a compressable gas in a sealed system. The gas is compressed to a liquid. When that chilled liquid is sent into the evaporator in your house the heat 'boils' the liquid into a gas and absorbs the heat in your house. That gas is now warm and sent back to the compressor which when compressing the gas, drives out the heat.

Perhaps the brass pipe is crimped somewhere and it cannot make a cycle through the system. If the compressor intake is cool too, then there is probably a constriction somehere.

Call in a service person.

If this was happening from the beginning why didn't you complain to the installer?

I'm no professional, so this is just a semi-educated guess.

I had to deal with a central a/c system at work once that always froze up when it got really hot out.

Usually it's because the unit runs for so long without shutting off. Generally that happens when the system is not powerful enough (in btu's) to do the work you're asking of it quickly enough. Or you're running it with the door/windows opened.

After a while of what normally would be just a little frost on the evaporator turns into a big block of ice. Which allows the evaporator to cool off even more and make more ice. All the while it's not exchanging the heat from the air to the refrigerant (giving you the bad vent temps and probably bad flow).

A quick fix is to turn the a/c off and put the blower in the climate control system to "fan on". Allow it to blow the room temp air over the ice and it'll thaw. (Wait until you feel lots of airflow through the vents and the water stops pouring out of the drain tube)

Then turn the a/c on but only at about 2 degrees below the actual room temp. Let the system cool the area off a little at a time giving it time to shut off and thaw for a while.

Perhaps my employer was just too cheap to pay somebody to come check the refrigerant level, but I was able to get pretty good results just nursing it like that. You may want to consider a higher btu unit for upstairs.

In my world (of automotive a/c) a low refrigerant charge wouldn't result in anything being frozen.

Hi JAZJOH....You've given some pretty good info for the problem, which is pretty much typical, but I must say first that 1900sf generally takes 3 1/2 tons. This isn't cut and dried, since its based on your heat load and the number of cooling days for your area. Since the system is only 2 yrs old its doubtfull the ID coil and/or blower, is plugged with dirt, and can assume all registers and returns are open. Frosting on the larger suction line (copper) out of the unit indicates either you've a leak in the system or the expansion device is restricted. The latter is only a possibility, unless the installer allowed outside air to enter through poor workmanship. If this WERE the case, then you need to have a licenced HVAC tech check it out. My guess would be, you're just short of gas due to a leak, probably at a copper joint. Wherever the leak is, you will probably see indications of oil. I suggest you remove the units' panel at the coil and see if there is icing. If so, put the panel back on turn the heat/cool switch OFF and the fan switch ON.Let the fan run for 3-4 hours then turn the a/c on. For best results, check the temperatures AT the air handler for accuracy on the TD. Anything between 17 and 21oF is good, after 12-15 minutes running time. Anything more or less than these numbers is the beginning of a problem. As for the attic temps at the unit, use your exhaust fan. Your ductwork is insulated as is the cabinet, so there shouldn't be much heat gain, maybe a degree or two at best. Installations like this are typical, at least here in Florida. So look around for an oily spot and check the TD. If you're short of gas, tell your service tech to fix it right ,and bear in mind, you may be a little shy on capacity.

[QUOTE]Originally posted by jpeskoff
Since the brass pipe (compressor out) was cold, it means the compressor is working. However, check the brass pipe on the other side of the compressor (intake). It should be warm to hot.

An A/C works by having a compressable gas in a sealed system. The gas is compressed to a liquid. When that chilled liquid is sent into the evaporator in your house the heat 'boils' the liquid into a gas and absorbs the heat in your house. That gas is now warm and sent back to the compressor which when compressing the gas, drives out the heat.

Perhaps the brass pipe is crimped somewhere and it cannot make a cycle through the system. If the compressor intake is cool too, then there is probably a constriction somehere.

Call in a service person.

If this was happening from the beginning why didn't you complain to the installer? [/I did complain to the installer but I live in PA and it is not always hot. Everytime he would come it was always on a cool day. He would check something outside come inside run the system. But since it was cooler outside it seemed to work. I have contacted the builder who is sending someone else. {today it was 90 degrees when the system cut on the air coming out of the registers was 67 degrees. The builder spoke to the guy who is coming and he said one problem might be that there is not enough vents which is causing a backup and might be freezing the line. He did not do the install and he has not seen the system. I will try the stuff you laid out for me and I will post my results......QUOTE]

Thanks for the replys I have requested the builder to send someone different to look at the system as well as me hiring some from the authorizer dealer to also look at the upstairs unit. I will post the findings.

Anyway thanks again for taking the time out :)

:) Well the new hvac guy came today he said the upstairs unit was low on freon more like almost empty. I told him that the guy who installed it, added freon last year (mind you the system is only 2 years old) He said there is likely a leak and they will have to try and find it or install a new line if they can't find it. The unit is outside and the ref unit is all the way up in the attic. That's alot of joints to check. I guess the guy who installed also knew there was a leak but chose not to say anything just put more freon:mad:

He also said there is not enough air flow I have 2 returns on the 2nd floor the filter size is 14 X 20 X 1 he said that my upstairs area is large and the air is being bottled up and freezing. I also have a finished attic and there are 2 vents up. He is going to install another return to increase the airflow he is going to put it in the attic.

If you guys get a chance to read this please let me know if this makes sense.

Thanks Again