NY Guy First of all, I will say up front I know nothing about the Aerosys brand. I will assume by the model number this is a straight 2 1/2 ton AC condenser and that you heat by another source, probably boiler radiator heat. Carrier's FV series air handler has a high eff var speed blower motor. Rheem's RHBP (letters may be misplaced) is a high eff fixed speed X-13 blower motor. Either if used in correct application is certainly solid equipment. If you want more details on these air handlers, I suggest you go the respective website. I did take a quick look at the AHRI AC directory and surprise, I found the following matches. This gives you the tested performance/eff numbers. You will note these are with the Rheem air handler. 6032825 Active Systems AEROCON AEROSYS, INC. THDC-30RGASD RBHP-21J07SH2 990 28000 10.00 12.00 1 SCP-RCU-A-CB Yes 282 6032826 Active Systems AEROCON AEROSYS, INC. THDC-30SGA RBHP-21J07SH2 990 28000 10.00 12.00 1 SCP-RCU-A-CB Yes 282 6032827 Active Systems AEROCON AEROSYS, INC. THDC-30TGA RBHP-21J07SH2 990 28000 10.00 12.00 1 SCP-RCU-A-CB Yes 282 You should ask the dealer for the matching AHRI directory number. There was nothing listed with the Carrier air handler. That's all the info I can offer. IMO

On most heatpumps, the reversing valve is in the heat position at rest, meaning with no power to the coil that moves it. It you want the heatpump to cool, the 24vac must be applied to the coil of the valve to move it to the cool position. This is where "O" on your thermostat come into play. So... with everything off, 24vac comes into the thermostat at the R terminal. Its just sitting there waiting for you to turn on the heat or the cool. Now lets say you turn it to cool. Points close between the R on the thermostat and the Y on the thermostat & also the R and the O on the thermostat. 24vac flows from the R terminal into the Y terminal, out the wire that is attached to the Y terminal to one side of the contactor(makes the compressor come on). Power also flows from the R terminal of the thermostat to the O terminal, out the wire that is attached to the O terminal to the reversing valve, making it change positions for cooling. Power then comes from both the contactor & reversing valve back to the thermostat into the C terminal. Mind you, this is a very simple explination of a complicated process since there are many different H.P. t-stats out there with all different kinds of labeling. Hope this helps

bajau the 003 is the preferred air handler. and you want to ask for the "T" tin plated coil air handler mdl. see below. 1169025 Active Systems PERFORMANCE 15 PURON HP CARRIER AIR CONDITIONING 25HPA524H30 FV4BN(B,F)003 23600 13.00 15.50 24000 9.00 15200 1 1169075 Active Systems PERFORMANCE 15 PURON HP CARRIER AIR CONDITIONING 25HPA524H30 FV4BNF002 23600 12.50 15.00 24000 9.00 15400 what happened to the 2 1/2 ton system? I don't want to be borderline or undersized in hot, humid coastal SC. unless you just want to pay more bucks, forget the FE series Infinity air handler/Infinity stat and pair with appropriate Carrier thermidistat. IMO

Tigerdunes, thanks for the reply. The Trane heat pump (outdoor unit) was older. I'm not sure how old, but I think about 10 years old. Three years ago, the air handler was replaced and at that time, property management used a Trane dealer. The air handler installed was higher rated higher SEER so that in future when the heat pump is replaced, it could also be higher SEER (than existing 10 year old unit). In these last 3 years the Trane air handler has worked great with the older Trane heat pump. The HVAC contractor who installed the Ruud heat pump is not a Trane dealer and property management uses him now for some reason. He is the one who said the outdoor Trane heat pump should be replaced. He says that the Ruud heat pump is compatible (matched) to the Trane air handler. He said since the capacity (2.5 tons) and SEER rating are the same, they are matched, and said Ruud told him they would work together. He said brand name does not matter for match. What he is saying is that whenever the outdoor unit (Trane heat pump) went bad, it must have contaminated the coil in the Trane air handler and it should now be replaced, which he's offered to do "at cost". The Trane dealer tells me the Ruud heat pump is not compatible with the Trane air handler and the air handler is OK and the first guy should replace the air handler for free since he didn't match them correctly. Both guys are licensed HVAC contractors and both seem 100% sure. Which leaves me in limbo on what to do. What I'd like to know is, how does the HVAC contractor, or the customer, positively confirm that a heat pump and an air handler are matched? It's my understanding there is certain criteria, and brand name match isn't necessarily it. Is there any way I can get any type of documentation from any industry website or manufacturer website that will show the 2 units are mismatched? Thanks