1 stage or 2 stage A/C system?

Question

I live in Northern Virginia in a three story, 1950sq ft, 10 year old townhouse. Historically, as with many townhouses, I have had problems cooling the upper floor in the Summer, and heating the lower floor in the winter.

My question is whether I should replace my existing system with a 1 stage or 2 stage system. I have not been able to verify that a 2 stage system would help my townhouse problem, but it does seem superior. But is it worth the significant cost difference?

Answer 1

A two stage system may be more energy efficient, but won't solve the problem of differing temperatures from downstairs to upstairs. That's most likely a ducting problem. You may want to consider a ductless mini split system for the upstairs. That would be less expensive than replacing the entire system, and would help cool the upstairs and keep a more even temperature.

The heat's another issue. You should try letting the system blower run continuously to see if it helps even out the temps. Depending on your layout, strategically placed ceiling fans may help as well.

Answer 2

uncledjm is on the money. Your house's two-story design is the main problem as far as the overheating goes. As you know, "heat rises." Well, it's rising - right into the bedroom levels.



Adding the mini-split system will work, but in my experience those things are neither attractive nor quiet, regardless of what the manufacturers say. The do, however, tend to be ridiculously energy efficient compared to other systems.



If you are committed to replacing your system, this is what I would do if it were me:



1) Definitely go for the two-stage system. It saves money in the long run. They spend most of their time running at the lower speed which is also quieter, and it's surprising just how many things make noise in a house. Wouldn't it be nice to turn some of that down?



2) Gain access to the ductwork and make whatever changes are necessary to add dampers that will permit the upstairs to be heated and cooled separately from the downstairs.



3) When installing the new system, also switch in a new thermostat that will:

a) Permit setbacks so the system is off when no one is home

b) Add a 'stat upstairs to signal the zoning panel

c) Add a zoning control panel to operate the zone dampers

All these functions require a level of hardware not often seen in a conventional home. You're definitely going to need a tech unless you are a seriously advanced amateur.



Zoning control allows you to treat a larger home as if it were a couple of smaller homes if you aren't using the entire space all the time. If you are using the entire space all the time, you may be better off adding a separate system to treat the upstairs.

Answer 3

What's the make and model of your AC unit? If it is less than 90,000 btuh it is probably one stage. ALso, How many wires are available to connect to the T-stat?