My parents recently had to have an outdoor unit replaced. About a month later the house was not getting warm enough and we thought it might be the old thermostat in the house so we replaced it. That didn't fix the problem so we called the business that installed the unit and they said only licensed individuals can change thermostats and we had hooked it up incorrectly which damaged parts of the outside and inside unit. We know it was hooked up correctly because we followed all the directions and we had previously installed one in our home. Is there any ruling that says a homeowner can't change a thermostat without being a licensed HVAC installer? Also would it be inappropriate for an installer to put in a unit that user R22 knowing that the freon is going to be pahased out?

Replacing thermostats in not a licensed activity. Why would they sell them at home Depot and now even Radio Shack.

Yes, you run the risk of damage. That damage is usually damage to the thermostat and/or damage to the control board. If your lucky a fuse blows. If your not, a transformer blows. The consumer stats do have few options. Is this electric or conventional? Is this a heat pump?

There are a lot ore questions than that and a LOT more configuration options. Carrier's stat can autoconfigure. Sometimes you have to tell it the size of the outdoor unit in tons or BTU/hr.

I believe an honest installer, should have informed you of the R22 rules and possible tax credits that are available for higher efficiency unis.

The reality of the situation is that R22 is either all or mostly coming from recycled R22. I forget the date that they are no longer able to manuafacturer it. We may already be at the point where you cannot by an R-22 system, but R-22 parts will be avialable for warranty claims.

Simple answers. It comes down to a pay now or pay later with R410 units being more expensive and physically larger. R410's oils are not compatible with R22 and thus the lines must be replaced or flushed.

By monkeying with the system, you may have essentially voided the installer's warranty. Not, say the heat exchanger warranty from the manufacturer.

When you had a problem within a month, you should not have tried to fix it yourself to avoid warranty issues.

The decision to repair or replace is always a tough one, but I might expect the replaced unit to be serviceable for 10 years. Your current inside unit depends on when it ceased to be manufactured.

I do believe it wasn't an informed decision unless I'm missing something like current age of inside unit, efficiency of inside unit, condition of inside unit, financing etc.