hey, I've put about 10 of these communicating furnaces in. Here's the story from goodman:
Because of a motor change, the required breaker size is being changed to 20 amps. The actually rating plate does NOT say "maximum circuit protection". It says "circuit protection: 20 amps." Which means as far as IBI goes, you need to have a 20 amp breaker with 12-2. According to goodman "when most installers look closely, they really have 12-2 wire running from the panel." Although I would disagree, that is their statement.
Now, on ACTUAL amp draw, if your running the blower at 4 ton speed (1600 cfm), your pulling 12-13 amps. Seriously, I've checked it. If you are running a 5 ton system though, you'll probably be over the 15 amp limit. That, and issues with the blower wheel getting dirty/worn and pulling more amps in the future will be a problem.
Anyways, the real question is: in a completely finished house, with no way to pull a wire, what do you do? Well, we always run the new wire + breaker. Only problem is we lose work because with rheem/lennox you don't have to run the wire, and our bid is alot higher :-\.
"Better tell the sandman to stay away, because we're gonna be workin on this one all night."
"Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."
"Just get it done son."
Dad adjusted