buddy got natural gas ran to his house, took out a 3ton carrier heat pump (6 years old) and gave it to me. i'm gonna hook it up but I don't want the electric heat strips hooked up. I have a propane furnace already in the house, can I move it up on the ductwork and put the heat pump on the end to make the line set shorter? figure i'll need two thermostats in the house, one for each system. comments?

Let me start by saying I have been an HVAC contractor for over 20 years. Definitely going to need more information to get you in the right direction. I already know you have a gas furnace and would like to keep it. Good choice by the way. Do you already have A/C with the furnace and if so what ton is it? What type of freon is in the unit your buddy gave you? It's either R-22 or 410A. If you have A/C what type of freon does it have? Did he give you the inside and outside or only the inside? Once I know the answers to those questions will I or any other HVAC guy be able to point you in the right direction unless of course they are standing there. I can tell you that if the answers come back for it you might be looking at the best of both worlds.

no a/c on gas furnace. 410a on the gas, I got both units, inside and out.

OK you have 2 options. actually 3. You can purchase a 3 ton cased coil that is 410 compatible and put it on top of your furnace. Also get the piston size that matches the outside. The old may work. Next option take out the furnace and replace it with the electric air handler that your buddy gave you and upgrade your electrical because your furnace is 110 and the electric one is 220. Or you can take the coil out of the electric one. Build an insulated box that it will fit and put it on top of the furnace and tie it to the duct work. A last option would be to gut the electric one except for the coil and put it on top of the furnace and connect it to the duct work but WOW what a lot of work and fitting. OK. For the good news. If you do manage to get a coil on top of your existing coil you can use the furnace as your auxiliary/emergency heat. A lot of contractors don't know about it or how to go it. It's called DUEL FUEL and it is really very simple. You are going to have have to upgrade your thermostat and thermostat wire anyway to use a heat pump. I use 6 strand for both inside to thermostat and from inside to outside unit. At the furnace tie the orange t stat wires together. Put both the yellow wires on the Y terminal in the furnace. put both the red wires on the R terminal in the furnace. Put both the white wires to the W terminal in the furnace. Put both the blue wires to the C terminal in the furnace. Put the green wire to the G terminal in the furnace. Follow the wiring instructions in the thermostat. Out side I would have to know what color wires Carrier uses. When you do this you are using your furnace as the blower for the A/C and the Auxiliary/Emergency heat for the heat pump. Best of both worlds efficiency of a the heat pump in winter and the efficiency of the furnace when the heat pump needs help' Sorry its long winded.

he gave me the t-stat with it. i'll have to check r.e.micheals for a coil. might be the easiest way to go.

A cased coil in the correct tonnage is definitely the easiest and frankly best option. Shop around just make sure it is 410 compatible. Also make sure you get the correct piston for that coil to match your outside unit. You will need the Model number from the outside unit to get that. Take the dimensions of the plenum that is on the furnace now and try to get a cased coil as close as possible to it. That will make it a lot easier to install and match everything up at the furnace side and the plenum side. When I say plenum it is nothing more than the duct coming off the top of the furnace. Your friend did you right giving you the heat pump thermostat. Feel free to ask any questions as they come up because there will be some. You probably already know you are going to have to run a drain and have someone weld the copper. You will also need to get access to a set of 410 gauges and a vacuum pump. Be figuring all that out in the meantime especially how you are going to do the condensate drain from the coil. As I said there will be questions and there are many options for the drain depending on your situation.

being a plumber the brazing the lineset is no problem. its a Ducane 92% furnace so the drain line is already there. i'll hook it all up and have a local hvac company come and charge the line.

Duct sized big enough for A/C,blower big enough,Ductwork insulated so it doesn't sweat and stain your ceilings if in the attic.