Tandem Compressors

[Hitech]

First A/C post so take it easy :)

First of all I am an turbine engine engineer but have interest in all things mechanical.

I was wondering why The Tandem compressor sizes on my newly installed AC system (Ruud UASL-060JEC outside and RBHM26J inside) were chosen. Compressor "A" is +- 36,000 BTU and compressor "B" is +- 24,000 BTU. Compressor "A" is all ways stage 1 and "A" + "B" is stage 2. Is this just to simplify the control recognizing the limits of the TXV range? It would make more sense to me to have three stages, stage 1 "B", stage 2 "A" and stage 3 A+B. In our climate (SW Florida) we have about two months at the beginning of the cooling season (March-April and two months at the end of the cooling season (Sep-Nov) where the temperatures are moderate but the humidity is 80% +. I would think that if the expansion valve could be controlled to use the lowest capacity, it would enhance the moisture removal without excessive cooling.

[goshen]

First A/C post so take it easy :)

First of all I am an turbine engine engineer but have interest in all things mechanical.

I was wondering why The Tandem compressor sizes on my newly installed AC system (Ruud UASL-060JEC outside and RBHM26J inside) were chosen. Compressor "A" is +- 36,000 BTU and compressor "B" is +- 24,000 BTU. Compressor "A" is all ways stage 1 and "A" + "B" is stage 2. Is this just to simplify the control recognizing the limits of the TXV range? It would make more sense to me to have three stages, stage 1 "B", stage 2 "A" and stage 3 A+B. In our climate (SW Florida) we have about two months at the beginning of the cooling season (March-April and two months at the end of the cooling season (Sep-Nov) where the temperatures are moderate but the humidity is 80% +. I would think that if the expansion valve could be controlled to use the lowest capacity, it would enhance the moisture removal without excessive cooling.
Hi :

what type of unit are we talking about?
most units expecially the new ones have an exv that can adjust to either size as needed
i dont think your unit configuration falls under the category of tandem comps!
are your compressores inverter type, or regular ,or one of each?:)

[Hitech]

Well it has two scroll compressors in parallel with separate controllers. a single condenser and a single evaporator. The is a 5 ton split system.
This is typical current high efficiency design in the good old USA, stage 1 is 67% stage 2 is 100%. The compressors are single phase 230 volt 60hz.