Gas and Oil Home Heating Furnaces - 2.5 TON CONDENSING ,3 TON EVAP

CAN YOU MAKE A 2.5 TON OUTSIDE UNIT WORK WITH A 3 TON EVAP COIL DO I NEED TO CHANGE THE PISTON KIT AND IF I DO WHAT SIZE DO I NEED , THANKS MARK

Yes you can. It is a common practice. It raises the SEER slightly and humidity removal is increased. Change the piston. A three ton piston will give you a lower head pressure, which can cause problems on lower temp/high humidity days. Your condenser should come with the correct piston for it. An average 3t piston is about .072. You can make your things even better by installing a TXV valve using a subcooling temp of 10 to 12 degrees.

I DO NOT HAVE THA CORRECT PISTON TO CONVERT THE 3 TON EVAP COIL TO WORK WITH THE 2.5 TON COND UNIT. WHAT SIZE PISTON KIT SHOULD I GET? HERS THE PROBLEM , I INSTALLED A 3 TON EVAP COIL ON 2.5 TON COND UNIT AND VACUMED IT DOWN , AND CHARGED IT UP AND IT IS STILL NOT COOLING AND THE LOW SIDE KEEPS JUMPING UP TO 90. THAT IS WHEN I SAW THAT YOU HAVE TO MATCH UP THE PISTON KIT TO THE COND UNIT BUT I DO NOT KNOW WITCH ONE TO GET I HAVE A CONVERSION CHART BUT I DO NOT KNOW WHAT SIZE PISTON IS IN THE COND UNIT . THE ONE IN THE EVAP COIL RIGHT NOW IS B17898-65 , WITCH I THINK THAT MIGHT BE TO LARGE, THANKS FOR YOUR HELP ,MARK

B17898-65(65=piston size .065) is a Goodman piston number for a 2.5 ton condenser. A B17898-71(.071) is their 3.0 ton condenser. Your piston is sized correctly. If this is a straight condenser(not a HP), sounds as though you got an inefficient compressor. If HP you may have a bleeding RV.
High suction/low head are classic syptoms of bad valves in a compressor. Check you compression ratio it should be about 3:1.

[Edited by fjrachel on 04-22-01 at 08:33]

The York 2.5 ton condensing unit is only 2.5 years old. It is not a heat pump. How do i test the compression ratio to get 3:1? The unit was cooling good before I put the bigger evap coil. The old one just had a leak. So could it also be the compressor? Thanks, Mark!

If it was cooling before... Have you physically pulled the piston? And actually looked at the size? If not, do.. If it's too big you should be showing a negitive superheat. And compression ratio is head pressure PSIA=suction pressurePSIA. Check that superheat.....Have you ever done this before? And are you certified to handle refrigerant?

Hi,

If experienced and EPA certified for handling refrigerants,I would do the following:

1-Check Discharge/Head Pressure
2-Check Suction Pressure
3-Check Superheat (Evaporator and Total)
4-Check Subcooling
5-Check Amps (Compressor and Total)

Post these and we'll have a better understanding of unit operation as it is at this time.

Is it possible that you could of had a Liquid Line Restriction and thinking it was undercharged,kept pumping refrigerant trying to raise Suction/Head Pressure and now it is overcharged?

Inefficient Compressor = Low Head Press.,High Suction Pressure,High Superheat,High Subcooling and Low Amps.

Liquid Restriction = Low Head,Low Suction,High Superheat,High Subcooling and Low Amps.

Overcharge = High Head,High Suction,Low Superheat,High Subcooling and High Amps.

Hope this helps.Take Care.

CoolBreeze

HEY , GUYS , THANKS FOR ALL YOUR HELP ON MY UNIT PROBLEM . I FOUND A BLOCKAGE IN THE CAP TUBES . I CLEANED IT AND VACUMED IT DOWN AND CHARGED IT UP , IT IS COOLING LIKE DREAM, THANKS FOR ALL YOUR HELP , AND I DO HAVE EPA CERTIFICATION , MARK

Hi,

Glad you got her cooling. Always remember if the suction won't seem to rise when charging after install/change-out,check for restriction before pumping more refrigerant into it,otherwise,more often than not,you'll still be restricted plus overcharged.Take Care and Good Job.

CoolBreeze