Comments on: What Is a Properly Sized Air Conditioner?

By: Stanley Okumura

Stanley Okumura — Thu, 04 Apr 2024 17:54:57 +0000

The problem of oversized heat pumps could be a non issue if thermostats had a turn on and turn off temperature settings. Usually they have a swing/differential/deadband/delta fixed setting of 0.5 to 1 degree which can be very energy inefficient with wear and tear of your heat pump. There are a few thermostats on the market that let you set the turn on temperature and the turn off temperature. For instance, I would prefer setting the AC to activate at 78 degrees, cool down the house to 72 degrees, then turn off and stay off until the temperature rises to 78 degrees again.
The inverter heat pump seems to avoid this problem by adjusting its speed to the needs of the house and runs much quieter as it idles and gradually speeds up or slows down.

By: Paul Szymkiewicz

Paul Szymkiewicz — Wed, 07 Feb 2024 19:16:19 +0000

Allison, congratulations on your anniversary! There is no manual J or S for that!

The daily swings in indoor relative humidity from low 50%’s to low 60%’s were maybe a bit high. But that depends on the building envelope (including the basement underbelly), human activity, and outside conditions. I can see that your indoor de-humidification effect on average started between 8-10am. Was your system cooling that early in the day?

By: BruceB

BruceB — Wed, 07 Feb 2024 18:19:11 +0000

Would you have better humidity control with another brand of heat pumps such as the Carrier Greenspeed that claims to do better?

By: David Power

David Power — Wed, 07 Feb 2024 17:33:17 +0000

We followed your guidelines when we installed our new heat pump a year ago. It did have a bit of an issue with the humidity control at first, we set it for 50% humidity as the Lennox system has a dehumidification mode and allows you to setup the limits of over cooling to get the humidity where you want it. Then we replaced our 40 year old sliding glass door and dog door.
It keeps it within a couple percent of 50 without a problem now.
Your news letter comment struck home as well. Because of health issues we wanted better than a merv 13 filter which I had been running for at least a decade. During the design I requested a merv 16 filter which Lennox and Traine both offer. The engineer properly sized the new ducts and blower for this. It’s a 4” filter and box. The pressure drop across this is still very low and according to the particle counters I have in my house the air has never been cleaner. This combination along with a fresh air duct has made significant improvements it the air quality that’s important to me as I was born with chronic lung issues. As this design was right in the middle of the big Covid lock down we also had UV-C led systems put in the return and supply’s ( in metal work as the uv-c will degrade the standard piping). The difference in comfort, air cleanliness and energy usage couldn’t be more different. In a record setting Houston summer heat our utility bill never exceeded $125. It’s cool, comfortable, dry. The unexpected surprises were bread now takes weeks to mold rather than days and the house stays much cleaner. This with the rising cost of electricity has made it a very worthwhile investment. Thanks for all you do.
David

By: WIlliam Hullsiek

WIlliam Hullsiek — Wed, 07 Feb 2024 17:08:28 +0000

Hydronic systems also benefit from being undersized. You want to always have water circulating through the heat sources (in-floor or panel-rads) to create a balanced energy exchange. Things are more comfortable when the system is just able to keep up (or being slightly undersized). If you keep the water temperature below 9F5 for heating or above 48F for cooling- you can achieve COP of your heat-pumps in the 4-5 range.