What is a 410A 3 1/2 ton air-conditioner low pressure at 80 degrees

The outside ambient temp has little effect on the suction pressure. The indoor temp is what will slightly effect the suction pressure. In the trade we say we want a 40 degree evap coil, this means approximately 125psi. This is when the indoor temp is around 74 to 78 degrees. The hotter the house, the higher the pressure. I like to see a 50 degree evaporator when the indoor temp is above 80. Charging by subcooling is the way to go!!

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EPA regulations: Freon 22 units are no longer available, Units that are compatible are available They come pre charged with nitrogen It must be dumped. If there is freon in the old system it should be pumped down into the condenser unit before the inside unit is removed, Close the high side king valve and run the unit until the low pressure reads near O Close the low pressure king valve. and turn unit off. 410A freon units are readily available. Most if not all 2 ton air handlers will work with any outside 2 ton unit though some building codes will not allow a mix. Their reason: if something fails who is to blame:

low side 68 psi or 40 degrees at the coil

highside 25 30 degrees above ambient air (outside air)

bad motor

150 is low for high side pressure. may have to add more r-22 to system. if you had a blockage high side pressure should be higher. have you turned both service valves at condensor ccw completely?

Hello, the unit is a 3 ton and was built in 2004. 0z R22 stands for R-22 refrigerant. Not sure why he told you 410a but if the unit says R-22 than that must be used.

Hi ,I am an Hvac tech as well,check to see if ductwork sizing is capable of handling 1200cfm.sounds like system is low on airflow and u are slightly overcharging.need to be at least 115 back and 290 I head at 80 degree ambient

It sounds like you are low on charge. I think you have a thermostatic expansion valve and you need to check the subcooling, you should have 12 to 15 degrees at 95. At 95 degrees your head should be about 280# for a 12 or 13 SEER unit or higher depending on the effeciency. At 78 to 80 degrees indoor depending on the humidity, that is normal. The valve will open to try to fully feed your indoor coil and it sounds like your head pressure is to low to force enough refrigerant thru the coil.

No you dont have to charge it manuelly as All units come fully charged and tested– direct from the factory.

Square footage is how you determine what size of an AC you need, say two bedroom house with 1500 square feet would require a 3 ton unit but I would go to a 4 or 5 ton depending on brand and what you may do in the future, Like adding a bedroom or bathroom and how many people will be living in the house, a heat pump normally last longer the bigger it is and is more efficient than a smaller size. Just think like this, a 3 ton will run 30 minutes to an hour longer to cool the same space as a 5 ton so if the five ton does it 30 minutes faster it will not run as long. And when it has to pull down the temperature again it will do it much faster. So less run time means faster heat or cooling and less energy is used. I have found that the bigger units are made better and last longer as a general rule. And to understand the 3-ton and 5 ton let me say that it means how long it takes 3 tons of ice to bring the temperature down 10 degrees, the old BTU’s British thermal units. However the bigger the unit the more well built it is normally and the less maintenance required. 5 tons of ice would get it cooler faster. But one thing to keep in mind a heat pump is only good for 20 degrees temperature range, for instance if the high range is 80 then the low side would be 60 in order for it to be efficient so if you have it set in the house at 72 degrees on the high side and low side would be 52 degrees. But the larger the unit the less time it would take it to recover from the heat differential.