1. Determined by the manufacturer of the equipment. It's all in the manual.

2. Seems that should be up to the installer....if they are qualified.

Here ask this question to the installer: "Are you willing to absolutely guarantee there will be no issues and feel comfortable doing it that way?"

After all, the installer will be the person coming back if there are problems.

3. Call Honeywell and tell them your thinking about purchasing this unit and ask them......or your installer.

User manual: https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-1815EFS.pdf

Also see below for installation.

Refer to this similar question: http://hvac-talk.com/vbb/showthread.php?1262861-Which-Hooneywell-Best-for-XR-16-TAM7-VisionPro-IAQ-or-Profile-IAQ

Here is a link that might be useful: Vision Pro iaq installation manual

This post was edited by audiomixer on Tue, Feb 19, 13 at 1:44

I could be wrong, but I don't see any harm having a line set which is the next size larger than the minimum. The manufacturer usually will specify the minimum diameter. The diameter needs to increase in size for long runs.

If the lineset is easy to replace, then I recommend to spend the money and replace it. This solves the problem on what is the proper method of cleaning. It also puts all the responsibility on the contractor in case there is a leak. The manufacturer will specify how the lineset should be cleaned if you do decide to keep it.

The Vision Pro thermostat can control a 2-stage AC condenser. If you live a area with high humidity then spending the extra money on a 2-stage condenser is worth it in my opinion. I would use the humidity control on the thermostat. It is probably more accurate than your current humidstat.

If you replace, save the old lineset, clean it up if needed, and take it to a scrap metal dealer for it's scrap copper value. Might give you a nice dinner for two.

IMO