Why is it that portable dehumidifiers are not built with an external window tube venting system to cool the compressor coils, similar to a portable A/C with window vents? As it is, the dehumidifier will heat the room causing discomfort and/or unnecessarily loading the Central A/C system.

@Terry wrote: “…wouldn’t it be useful for the DOE to do at least 1 other rating of whole-house dehumidifiers for situations where the dehumidification is focused on dehumidifying incoming ventilation air…?”

Dehumidifier capacity is largely a function of inlet dew point. If you duct outside air directly to the inlet as you suggest, the DoE test procedure as it currently exists would no longer apply, as you’ve gone well outside the assumptions baked into the procedure (and not just the incoming air metrics). It’s relatively rare to see a whole-house dehumidifier set up this way, but the next time the DoE updates its DH test procedure, maybe this will be a thing…?

In any case, I come back to my original point: official rated capacity should not be used for sizing. Moreover, as I’m sure Allison will cover in his forthcoming article on sizing, DH capacity is only part of the puzzle — designers must also calculate moisture loads. This gets rather involved when the equipment is configured to directly condition outside air. This is the norm for commercial mechanical design.

BTW, I would argue that designing to maintain RH below 50% in a humid climate, especially if t’stat is set below around 75F, imposes unnecessary expense, both in terms of first-cost & lifetime energy costs. The comfort range is generally accepted to be from 40% to 60% RH. To wit, most folks are equally comfortable at 55% as they are at 50%, and don’t tend to lower the t’stat to compensate until RH exceeds ~60%.

@Terry, no test procedure can ever be sufficient for sizing compression based systems due to the wide performance variation depending on operating conditions. As with AC and heat pump ratings, dehumidifier ratings are intended as a basis for making product comparisons, not for sizing equipment for a specific project!

Mechanical designers should always refer to manufacturer performance data when sizing equipment. The fact that so many contractors don’t know any better (or don’t care) is indicative of how dysfunctional the residential HVAC industry is!