I have a 10 year old Lennox heat pump (outside unit) that requires repair or replacement. The current heat pump is a builder grade 1.5 ton Lennox unit. It is connected to a Lennox Elite CBX32M-018/024-230-6-04 air handler. This setup cools the apartment above my 2 car garage. My air handler is still in good working order. Although my current unit is 1.5 tons, there are only two AHRI ratings for this air handler. Both are for 2 ton units. One is the Merit HPX14 and the other is the Elite XP14. The 1.5 ton units in these series only match to the CBX32MV (variable speed) air handler.

I called Lennox's toll free number to find out the effect on the warranty, if I matched the 1.5 ton unit to my current air handler. I was told that would not qualify for the extended warranty. I had some other technical questions, and I was given a non toll free number to call. After waiting on hold for 45 minutes, a rep came on the line. We spent 45 minutes on and off hold, and I came away with no useful information. For example, I asked what the difference was mechanically between the Merit and Elite models. I was essentially told the weight and sound level - information that I already knew. I asked if the internal parts were different, and if so, what was the difference. The answer, they use different part numbers.

Therefore, I am hoping an HVAC pro can answer a few questions. Can someone tell me what the difference is mechanically between the Merit HPX14 and the Elite XP14? I know the XP14 is quieter and uses a different housing. Because this will be one of several HVAC units near my screened in porch, I prefer the XP14 for its quieter sound. Are there enough differences between the two units besides the sound that warrant paying a few hundred dollars more for the XP14? Do the Elite XP14 units hold up to the elements better than the Merit HPX14 units? I live near salt water, and the fins on one of my other heat pumps are heavily corroded.

What are the pros and cons of replacing a 1.5 unit that adequately cooled the apartment with a 2 ton unit? Will the electric savings gained by going to a 14 SEER heat pump be offset by going to a higher BTU heat pump?