Think I've finally got the new HVAC tuned where I want it

[LoneRanger]

by "tuned" I only refer to settings on the smart thermostat. No messing with anything else such as wiring changes to fan speeds.

AC is maintaining indoor humidity @ 45 - 55% range now. I used staging differential threshold (stage 2 lockout) set for 1.5 degrees from thermostat set point and CPH set to 2 to finally achieve my aim: longer run times with the system staying primarily in Stage 1 cooling which is stage 1 compressor mode and low blower fan speed on the air handler. Can hear a satisfying trickle of water from the evap coil drain pipe now. Stage 2 compressor mode still kicks in from time to time and the air handler will ramp up to higher speed I guess when it determines Stage 1 is at 90% load (?...) But so far that's not happening a whole lot and she's remaining in Stage 1 for run times of about 20 - 25 minutes.

Yes, I think the estimator may have slightly over sized us on capacity is why at default settings (Honeywell Prestige IAQ thermostat) it wasn't running long enough to manage indoor humidity efficiently, because it was going right into Stage 2 cooling within minutes of start-up. I knew I had to lock that behavior out, if possible, by playing with the staging differential and cycles per hour (CPH), which seems to have got it done. So far , so good !!

 

[Fitter30]

Most two stage compressors low speed is 25% to 30%. As for as being over sized it hasn't got hot yet. What is so nice about low speed it pulling out humidity and not really over cooling the space.

 

[CourierDriver]

turn on your ceiling fans in reverse blowing upward, will save on heat load in summer and u will feel cooler...

 

[greenjp]

I went all the way and set my CPH to 1. I wasn't quite educated/brave enough when we replaced ours and I let 'em stick with the same size as the original (3.5). At least a half ton oversized, maybe a full ton. Anyway here in MD it's humid so I set the dip switches in the furnace to the lowest speed (350 cfm/ton I think?) and set it up for dehumidification which reduces it another 20% or so if the RH is over 50%. It works well.

On the ceiling fans, blowing up is the recommended winter mode so you circulate the warm air down without the feeling of having air blown on you. In the summer you do want the air to be blown on you for the cooling breeze effect. Also helps move the hot air to where the AC return can get it if you don't have a ceiling returns.

jeff

 

[AZjeff]

so you've "tricked" the unit into thinking it's smaller than it is so it runs longer. You'll have more even temps throughout your house as well. Nice job puzzling that out.

This is what HVAC pros recommend that most people reject.

 

[LoneRanger]

Originally Posted by AZjeff
so you've "tricked" the unit into thinking it's smaller than it is so it runs longer.


Colloquially stated but spot-on.

 

[AZjeff]

Originally Posted by LoneRanger

Colloquially stated but spot-on.

I resemble that remark.

Had a friend who was a residential HVAC estimator. He would get frustrated regularly after going through the calcs and telling the customer the proper size unit and the customer would reject the size as too small, especially when it was smaller than what was in the house.