Arkansas HVACR NewsMagazine January 2024

HVACR NewsMagazine January 2024

Tech News

to remember warm air holds more humidity. Just as SEER 2 and EER 2 doesn’t change the capacity of the equipment, the change in testing shows the real time shortcomings of the equipment when we skip over the facts. If you want to dig into the technical data, the following link will guide you through the process. Standards and Test Procedures | Department of Energy

criteria. It becomes costly and near impossible to improve air sealing at a final inspection. So, without Blower Door information you are guessing at the capacity necessary to dehumidify the space effectively, just like sizing HVAC equipment. It is not uncommon to find you need double the dehumidification that’s listed on the box and never rely on the square footage listed by the manufacturer. It is likely the test data reflect conditions that exist in the best insulated homes. As a final point, there has been discussion on the application of whole home dehumidifiers.

To sum up changes in general please reference the chart below.

Capacity Changes in Portable and Whole-Home Dehumidifiers Portable Whole Home Pre 2020 pints / day 2020 Post pints /day Pre 2020 pints / day 2020 Post pints /day

Some manufacturers recommend adding the load from the dehumidifier to the supply plenum. This may result in particular rooms picking up heat more than others due to placement of the dehumidifier discharge in the supply plenum. If the dehumidifier is within the envelope such as foamed attic,

30 40 50 55 60 70

20 25

80

70

100 120 140 160 200

85

30

100 115 135 170

30-35

35

40-45

90

55

So now that you are aware of limitations of equipment, and reduced capacity of dehumidifiers, what are the next steps? This makes it apparent to those that hate the words “Blower Door”, you will never be successful at sizing equipment and applying accessories unless leakage rates for the dwelling are determined. Large custom homes are very difficult to air seal and dehumidify unless blower door data is compiled as construction takes place. This data gives general guidance as to whether or not the home will meet final inspection criteria. I have spent time at a 10,000 square foot home that is awaiting a Certificate of Occupancy due to the Blower Door values not meeting inspection

dumping the supply from the dehumidifier in the attic can be acceptable if there is minimal access for return and supply air to circulate. As an alternative, where a foyer or staircase is present, it may be acceptable to oversize the supply boot or bucket and grille, reverse a wye to accept the conditioned supply and the dehumidifier duct. This will mix the warm load with conditioning supply in a relatively unnoticed area. Once again, this topic proves the job of the HVAC contractor requires skill, education, and the right tools to provide customers with solutions that improves comfort, affordability, and equipment longevity.