single condenser / compressor construction is utilized. Since this article is all about TXVs, you might ask, "Why not just use two TXVs?" Well, this can get to be complex because remember, each TXV is fighting for control of the refrigerant flow and we don't want just one evaporator to perform well, we want both evaporators to perform well. This can require some special valves in order to pull this off and make them operate properly. The first valve we should talk about is the "bypass" Dianetti/Milliman Obviously using an orifice tube in combination with the TXV can be a bit odd but in some cases, this might be the best option. Take for instance some older automotive applications where two evaporators are used. The condenser / compressor architecture is the same as any other system, but the front and rear evaporators use different control devices (Figure 1). There are other cases of this in automotive applications where two evaporators are used and the Figure 2: Valves having nicked seats or bypass bleeds were designed to reduce oil drop out and pooling of refrigerant in rear or dual evaporator systems. October 2020 2 MACS Service Reports