As many of you have heard, new refrigerants for residential AC/HP (R32 and R454B) are on the way down the pipeline. For those in the industry, who lost some marbles when R410 was the new thing, I ask you this: "it really hasn't been all that bad now has it?"  

Hopefully this is being read by those who are curious and looking for insight to stay ahead of the curve. 

In all actuality, there is not a lot to be scared about when it comes to this change.  You may WANT to invest in new analog gauges and hoses for the new types, but don't have to (as long as you carry a PT chart). If you're using digital equipment, you should be all set. We of course, DO NOT want to accidentally MIX different refrigerants together, so a separate set of gauges and hoses may be in your best interest. 

Now, about the refrigerant itself, a lot of techs out there are overly concerned about suction pressure and high-side pressure. To this I say, "Your focused on the wrong thing". R32 and R454B will operate at very near the pressure that R410a does. However, what we really need to more concerned with is the temperature of the refrigerant at a certain pressure. STAY FOCUSED ON TEMPERATURE. 

We get this question quite a bit- "what should my pressures be on a day like today?" It's a bit of a loaded question because the focus is in the wrong place. 

For decades, air conditioning "design" by pretty much every manufacture, has always been, having an evaporator that runs approximately 35*F cooler than the return air. Or a 40*-45*F evaporator itself. Regardless of outdoor temperature, we still shoot for a 40 degree coil, because indoors is where the load is. EX:

(R22 @ 40* = 68.6 psi)  (R410A @ 40*= 118.8 psi)  (R32 @ 40*= 121 psi)  (R454B @ 40* = 112 psi) 

CFM across the evaporator will not change either, 350-400 cfm per ton.

Well what about the high-side pressure? Just as easy as low-side, we are still looking for a design CTOA ( condensing temperature over ambient) based on the seer rating of the equipment. Our condenser temperature (high-side pressure) CAN fluctuate a bit depending on outdoor load/temp. EX 1:  10-12 Seer equipment = 25* CTOA, 13-15 Seer = 20* CTOA, 16+ Seer = 15* CTOA.

EX 2: Lets assume its 90* outside, and we are running 13 seer equipment. Using our design CTOA, we can determine that our condenser temperature (high-side pressure) should be running about 20* warmer, 90 + 20 = 110. (R22 @ 110* = 226psi)  (R410A @ 110* = 365psi)  (R32 @ 110* = 375psi)  (R454B @ 110* 346psi).

Again, be more focused on the temperature of the refrigerant. If we maintain this "focus on temperature" mentality (40 degree Evap, Condenser CTOA, Super-heat temp, Sub-cooling temp), HVAC-life will be easy.

Carlos