Have an old (23yr) heat pump system, inside unit is time bomb with rusted, leaky drip pan, clogged/moldy coils, and high vib. fan. Live in MD. Outside unit is newer (est. about 8 yr old). Want to go to dual fuel option -- either heat pump with gas furnace or heat pump with hydronic boiler for heat and DHW. Water heater is also 23 yrs young, electric. Have gas newly piped to mechanical space for possible boiler, furnace.
A few questions and issues come to mind from the few quotes I have received thus far, and looking for general guidance (and perhaps ground truth on a couple).
1. Replace entire system to include the outside unit. Most money, but can then get a matched system, more efficient system (current outside unit is 10 or 13 SEER, no one can tell me yet) with more warranty. Go with new gas hot wtr htr.
2. Keep current outside unit, get new gas furnace/air handler, new inside coil. Use as AC/heat pump until outside unit fails then replace both inside and outside unit with 15/16 SEER R410 equipment. New gas Hot wtr htr.
3. Keep outside unit as AC only and get new gas furnace, inside AC coil. Convert to dual fuel heat (heat pump) when outside unit dies. New gas hot wtr htr
4. Go hydronic option. Dual fuel heat pump, gas boiler for heat (hot water coils above air handler) and DHW. Advantages for this is one gas appliance. Disadvantage is price and complexity. Looking at Munchkin or Triangle Tube boilers. Have one recommendation for Quietside on demand HW heater with storage tank but have not heard good things about that product.
Know that is a lot to process but am looking for some general pros/cons.
One specific issue that I would like to throw out there concerns the 5/16 inch Heat pump line running btwn inside and outside. The "newer" outside unit had a 3/8" connection but the 5/16" inch line is brazed/welded. Should this line be replaced/upgraded to 3/8" (what about for R410). Other line is 7/8". How much efficiency is lost to that missing 1/16" if a 16 SEER Heat Pump system is installed. Replacing the line is doable by only digging into finished basement drywall cieling, about a 40 ft run.
Thanks for any help,
Searching for info John