Augmenting A/C

[pennyv]

We currently have a York split-system heat pump, 1.5 tons, providing A/C to our kitchen and dining-room, installed by previous owner when he extended the kitchen. The air exchanger is in the attic of the single story attached garage.It's probably 25 years old, but the heat pump is only 2 years old (original one failed). We never use the heat function as we have a natural gas furnace with radiators for the whole house. We now want to add A/C to the rest of our 2 story 2,000 sq ft house (in Massachusetts). 2 contractors have determined it can be done, feeding ductwork from the main attic thru upstairs closets to the first floor. But they disagree on whether to simply add a second independent system (A/C only, not heat pump) sized for all the remaining rooms, or to instal one new system (again A/C only) for the whole house (rendering our existing equipment obsolete).

Adding a second system will obviously be somewhat cheaper to purchase and instal, but what are the long-term pros and cons? We plan to have a 14 SEER unit, whatever its size, while the existing is only a 10 or 12, and the new unit will use the newer refrigerant. Are running costs likely to be greater for 2 units, assuming we aim for the same degree of cooling throughout? Will the 2 systems interfere with each other? (The new system will have the air return on the ceiling of the 2nd floor, while the existing is in the kitchen ceiling).

Or is it a good idea to have 2 independent systems, effectively giving us 2 zones?

Or is it better to replace all the old stuff, bearing in mind that the equipment in the garage attic is 25 years old, even though the condenser is only 2 years old.

Whatever we decide, we probably won't go with York. The contractors are offering Carrier and Lennox - are these brands comparable as regards performance and reliability?

Any comments will be gratefully received. Thanks.

[BaldLoonie]

I'd leave the existing unit. Pretty sad that the indoor unit wasn't changed with the outdoor unit :( Don't use that dealer!

Here's the skinny. With gas prices going through the roof, I'd consider a heat pump. Investigate local prices and if electric isn't that bad on price and I know in the NE it can be, a heat pump would provide cheap heat in mild weather. If you need a bit of heat on a nippy morning, a little bit of heat pump running is SO much cheaper that firing up a boiler and getting all the piping & radiators hot.

Running costs for 2 units would be similar. You are paying to remove heat regardless of how many units. I wonder if a 14 SEER is a wise economic move with a mild cooling season. That's where if you consider a heat pump, a 12 SEER pump may not be much different in price than 14 SEER cooling only and have a considerable payback.

[pennyv]

Thanks for your suggestions. We are definitely not using the earlier contractor. The 14 SEER actually will not cost us much more to purchase as there are energy rebates available. But both new contractors did not think much of heat pumps in our area. Perhaps they aren't very common as oil heat was always so much cheaper than electricity, and most older houses were built with radiators and not forced air. Now more people have converted to gas if it's available in their town, and there may be a smaller difference in cost between gas and electricity in the future.

Would be pleased to hear opinions on heat pumps from others in the NE.