Select your language

Humidity control

The importance of solving this kind of problem allows to offer an installation with an optimal air quality. For this there are ideal strategies and technologies.

by Alfredo Sotolongo*

The most economical energy to produce is the one that is saved!

In recent years we have had in our industry a tendency to improve indoor air quality and this movement has pointed to humidity as one of the main causes affecting air quality in the conditioned area. Many colleagues have contacted me to once again concentrate on solutions to this very harmful and common problem.

- Publicidad -

In our countries, mainly between the tropics of Cancer and Capricorn, the outside air we use for ventilation contains high enthalpy values. If this air is not properly controlled it causes mold, condensation on surfaces, allergic reactions, etc.

When selecting units dedicated to handling 100% outdoor air, the purpose is to control humidity without using additional energy, only the energy needed to cool and compensate for the thermal load. It is that the air entering the cooling coil must be cooled to the saturation point where both the dry bulb and the wet bulb are  as close to 55°F as possible. 

This is the ideal point in the psychometric table so that when applying sensitive heat it brings the air conditions to those of neutral air. The air is discharged from the cooling coil with as much water removed as possible, but saturated at 100% relative humidity. When reheating the air, applying pure sensitive heat, in the psychometric table follows the horizontal line until it reaches the point of neutral air 75°F and 50% relative humidity. Under these conditions is that the ventilation air that is delivered to the rest of the air units of the building must be, which prevents them from requiring greater thermal capacity.

In addition, it is about using energy recovery units to exchange  the energy of the exhaust air with the ventilation air, with the purpose of reducing the capacity of the units of 100% outdoor air. With this system, the outside ventilation air enters the cooling coil at less critical conditions is achieved.

In our experience, the most effective way to reheat the air out of the cooling coil, without expending additional energy, is by using hot gas reheating. Originally, manufacturers of 100% outdoor air units designed their units using a two-way, two-position solenoid valve that directed the hot gas-shaped refrigerant into the reheating coil installed at the air outlet of the cooling coil instead of directing it to the condenser. In this design, the thermostat controlled the cooling coil while a humidistate controlled the solenoid valve.

As this solenoid valve was not modulating, the humidity problem was partially controlled, but many other problems continued, such as:

a) Poor control of the amount of overheating.

- Publicidad -

b) Sudden changes in the temperature of the supply air.

c) Temperature and humidity values that are not acceptable especially in units of 100% outdoor air.

Companies like AAON have designed the units with the components and controls that allow them to continue removing moisture from the conditioned area even when the dry bulb has been satisfied, but supplying the exact amount of overheating to compensate for the dehumidification requirements (See diagrams that appear next to this article).

How has AAON managed to achieve the ideal conditions to allow the balance between temperature and humidity? It has achieved this with a one-of-a-kind design, adding to the reheating coil a modulating valve to proportionally control the hot gas and another modulating valve in the condenser and electronic control. 

For example, if one valve opens 20%, the other closes 20% and both receive the signal from the control system that uses thermostat that controls the compressor and humidistat that controls the hot gas valves.

- Publicidad -



 

The most important advantages of this design are the following:

a) If the temperature control value of the dry bulb is satisfied and the humidistate continues to ask for relative humidity to be reduced, the valves would modulate the maximum amount of hot gas that would pass through the reheating coil at any given time.

b) The control system also consists of a temperature sensor to be installed in the supply air that modulates the temperature of the overheating.

c) When the hot gas passing through the reheating coil is modulated, the system supplies the exact amount of reheating necessary to meet the conditions of the conditioned area.

d) The occupants of the conditioned area will be satisfied with the comfort achieved because there are no sudden changes in the conditions as in the case of two-position solenoid valves.

The main purpose of the unit dedicated to handling 100% of the ventilation outside air is to contribute to improving indoor air quality and at the same time achieve it without spending any additional energy.

Very often we find units that handle 100% outside air without having  the necessary thermal capacity to lower the outdoor air conditions to as close as possible to 55°F/55°F saturated air and thus, remove as much water as possible (grains) and also, without any overheating, which creates serious problems  of relative humidity in the conditioned area and therefore, unacceptable indoor air quality. Whenever 100% of outdoor air is handled, it is imperative that the thermal capacity of the unit is sufficient to bring the air as close as possible to 55°F/55°F and it is necessary that there is reheating that is applied without additional energy consumption.

If you need more information on any of the topics covered in this column, please contact me at the email [email protected]

* President of Protec, Inc., is certified as a professional engineer in Puerto Rico and the state of Florida; has more than 40 years of experience in the application and sale of systems and equipment for energy conservation. He is a member of ASME (American Society of Mechanical Engineers), AEE (Association of Energy Engineers), ASHRAE and was president of the Miami chapter of that association.

No comments

• If you're already registered, please log in first. Your email will not be published.

Leave your comment

In reply to Some User
Building Automation Days 2025 in Bogota marks a milestone for the KNX standard in Latin America

Building Automation Days 2025 in Bogota marks a milestone for the KNX standard in Latin America

Colombia. With more than a hundred attendees and the participation of six high-profile exhibitors, Building Automation Days by KNX LATAM, Colombia edition, established itself as the most relevant...

Design Envelope Technology Hits 750 gpm Fire Pump Segment

Design Envelope Technology Hits 750 gpm Fire Pump Segment

Canada. In response to the growing demands of the fire protection industry, Armstrong Fluid Technology announced the expansion of its Vertical-In-Line pump line with the addition of the new 5x4x10PF...

Greenheck Launches New RV-220 Model and Expands Its Line of Dedicated Outdoor Air Systems

Greenheck Launches New RV-220 Model and Expands Its Line of Dedicated Outdoor Air Systems

United States. Greenheck announced the addition of the RV-220 to its line of dedicated outdoor air systems (DOAS), a solution that responds to the growing demand for equipment with greater outdoor...

Embraco enters the HVAC market with new scroll compressors and aims to become a full-service supplier

Embraco enters the HVAC market with new scroll compressors and aims to become a full-service supplier

Brazil. Embraco announced its official entry into the heating, ventilation and air conditioning (HVAC) market following the acquisition of the specialized company Xecom, and the launch of a new line...

SIGMAN GROUP and Carrier-VRF reinforce technical training in the HVAC sector in Ecuador

SIGMAN GROUP and Carrier-VRF reinforce technical training in the HVAC sector in Ecuador

Ecuador. An intensive week of technical and commercial training brought together key players in the HVAC sector in Quito and Guayaquil, thanks to the joint initiative of GRUPO SIGMAN and...

AHR Expo Mexico 2025 returns to Monterrey with its most ambitious edition yet

AHR Expo Mexico 2025 returns to Monterrey with its most ambitious edition yet

Mexico. The event returns this year to Monterrey with an unprecedented edition. The exhibition, dedicated to air conditioning, ventilation, heating, refrigeration and filtration solutions, promises...

Fujitsu Launches New AIRSTAGE Multi-Position Air Handler with R-32 Refrigerant

Fujitsu Launches New AIRSTAGE Multi-Position Air Handler with R-32 Refrigerant

United States. Fujitsu General America announced the launch of its new AIRSTAGE Multi-Position Air Handling Unit (MPAHU), designed to provide greater application flexibility by easily...

HVAC project at the Javeriana University, finalist in the CALA Awards 2025 in the HVAC category

HVAC project at the Javeriana University, finalist in the CALA Awards 2025 in the HVAC category

The HVAC system installed in the building of the Faculty of Sciences of the Pontificia Universidad Javeriana, in Bogotá, was selected as a finalist in the HVAC category of the CALA Awards 2025. The...

Concord Project in La Lima Free Trade Zone, finalist in the HVAC category of the CALA Awards 2025

Concord Project in La Lima Free Trade Zone, finalist in the HVAC category of the CALA Awards 2025

The HVAC system project carried out by MultiFRIO for the company Concord in the La Lima Free Trade Zone, in Cartago, received the final prize in the HVAC category of the CALA Awards 2025, a...

HVAC project at the Universidad Santiago de Cali, finalist in the CALA AWARDS HVAC category

HVAC project at the Universidad Santiago de Cali, finalist in the CALA AWARDS HVAC category

The air conditioning project of the Auditorium Building and the Technology Center of the new campus of the Santiago de Cali University was chosen as a finalist in the HVAC category of the CALA...

Free Subscription
Remember Me
SUBSCRIBE TO OUR NEWSLETTER
DO YOU NEED A SERVICE OR PRODUCT QUOTE?
LASTEST INTERVIEWS
SITE SPONSORS










LASTEST NEWSLETTER
Ultimo Info-Boletin