For everything I have read, yes it makes sense that the orange wire replaces the white wire for a heat pump configuration. The white wire is used to turn on the furnace for heat, and the yellow wire enables the condenser for cooling. But you have a heat pump, therefore when you are in heating mode, the thermostat will turn on the condenser (yellow), but it must also enable the reversing valve in the proper direction. The orange wire is used to control the reversing valve. Call the Hunter technical support line at 1-888-830-1326 from 8am to 5pm Central time. They should be able to review this with you and guide on which thermostat is appropriate for your set up.

Petey may be a bit cranky here because we DO get a fair number of people here who want us to bless their code violations as some kind of special case for which an exception is justified. There are a few regulars here who sometimes do that where it makes sense and where there is reasonable precedent - just check out this thread. However, I agree with Petey that this isn't such a case. The code is clear-cut and rational on this point. It shouldn't be a significant burden to comply. In Jeremy's case it just means a little more fishing. To me this is, if nothing else, a matter of good workmanship and pride. Some of the code requirements for ranges were relaxed during the second world war when saving copper was a national priority. That's why the code allowed only 3 conductors instead of 4 for ranges. However, that rule persisted for 50 years after the war! Finally somebody noticed. ;-) I do recall seeing the NEC allowance for connecting both a cooktop and a wall oven to a 50 amp circuit, instead of having separate circuits for them, but I don't remember that the code allowed a smaller tap for each. I could be remembering wrong though, and I don't have the code here to check. But in any case I'd suspect that this ruling was originally another copper-saving measure - which is now no longer really needed. (I know, copper's scarce and pricey right now, but we have aluminum instead. ;-) I don't mean to suggest that I speak for Petey here; he can certainly speak for himself. Nor do I mean to impugn Jeremy's motives. I'm just explaining why some of us (including myself at times) now and then get annoyed with posters who come here for advice (which, I remind you, is free ;-), and then get sore and complain when they don't get the answers they had hoped for. After a while maybe some of us can get a little touchy about this, that's all.

Is there anyone on this thread still? Here is my issue. Bought an older 2 person tub. It has a 4 wire seemingly 220 wire coming from tub--goes in to a timer box where the terminals are dbl and tripled up going through those circuits--then the plug for that box coming out of it is a 110 plug and that is the only plug giving power to the tub through the timer box. Has this tub effectively been already wired for a 125 /110outlet and I can just plug and play? Am I safe considering the 125 plug does have a built in ground through it?

Replace the cord with a 4-wire cord. There will be a green screw in the disconnect of the rang tying the neutral to the chassis of the stove. Remove the screw. The two hots go to the screws marked for them. The neutral goes to the same block to the neutral screw (usually between the two hot screws) and the ground is connected to the chassis.