Humidifiers and Dehumidifiers for Air Handling Units (AHUs)

Q: Is there a rule of thumb for calculating humidity load?

As an approximate rule of thumb, for every 1m³/s of fresh air, approximately 25kg/hr of humidity is needed.

Q: What factors determine humidifier selection?

The main elements that need to be considered are what energy is available, what level of humidity control is acceptable, are there any physical constraints on size or location, what is the water quality like and what level of maintenance is acceptable. Details to these questions will help inform correct humidifier selection.

Q: How far away from the AHU should a steam humidifier be located?

To maintain efficient operation, a steam humidifier should be located no more than 4m from the AHU. This is to minimise any condensation that might form in the steam hose. Steam hose condensation can reduce efficiency, lower output capacity and increase energy use.

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Benefits

Working with Condair on your next humidity control project has many benefits.

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World Leading Technology

Continuous product innovation keeps Condair at the forefront of the industry

Comprehensive Range

Being able to offer all technologies allows Condair to always offer the best solution

Humidifiers and dehumidifiers for air handling units

Top of page Benefits Use Cases References FAQs

System selection and design

Condair provides expert advice and guidance to air handling unit manufacturers and consultants specifying humidifiers, dehumidifiers or evaporative cooling systems for AHUs.

Many factors need to be considered to correctly design a humidity control system and have it deliver the required environmental control. Some are obvious, such as the available energy source and required accuracy, but factors such as water quality or the cost of maintenance should also be considered.

Condair offers free technical support on:
- Psychometric and load calculations
- Absorption distance calculations
- Run cost analysis and comparisons between systems
- System selection including all associated components

World leading technology and innovation

For more than 75 years Condair has been innovating in the field of humidity control. The electrode boiler steam humidifier was invented by Condair in the 1960's and has been the most widely used commercial humidifier technology ever developed.

Today, Condair manufacturs the most comprehensive range of commercial humidity control systems in the world. Through continued investment in R&D, Condair's products remain the most efficient, hygienic, user- and maintenance-friendly systems available.

Evaporative cooling partner for AHU manufacturers

Alongside expert advice and an extensive range of humidity control systems, Condair empowers air handling unit manufacturers and OEMs to innovate and deliver customised solutions for end-user success.

Evaporative cooling offers significant opportunity to the HVAC sector to reduce cooling energy use and deliver a more sustainable built environment. Condair’s experience in manufacturing evaporative media and in-duct evaporative systems ideally positions it as the supplier of choice for manufacturers wanting to develop their own evaporative cooling products.

Condair’s flexible approach to project management and its global footprint enables it to support its AHU and OEM clients no matter where they or their projects are located.

Use Cases

Chiller pre-cooling

Chiller pre-cooling combines the natural heat-absorption properties of water evaporation with mechanical chillers for economical cooling.

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Projects and References

Weatherite, UK

When Weatherite needed to develop an innovative cooling solution that didn't rely on man-made refrigerants, it turned to Condair's adiabatic cooling expertise. The partnership resulted in Weatherite's innovative AdTec-D direct cooling system, which is now a highly proven free air-cooling unit, used by leading telecoms and data centre clients.

A cool recovery with Konvekta

The Condair ME evaporative humidifier is being used by energy recovery specialists, Konvekta, as one of its standard adiabatic cooling solutions. As an example, a recent installation at a clinic in Tyrol, Austria, resulted in a confirmed annual energy recovery across the Konvekta systems of 92% for the building. A single Condair ME humidifier contributed more than 60,000kWh/a of cooling during this period from just 3,800kwh/a of consumed electricity.

AERA Air Conditioning and Ventilation

Indirect evaporative cooling for packaged AHU

Condair evaporative humidifiers have been selected by AHS (Air Handling Systems) to provide evaporative cooling in the innovative OptEvent™ air handling unit. The humidifier cools the return air with low energy cold water humidification in this packaged heat recovery system that has been independently verified by BSRIA.

Frequently asked questions

How are humidifiers sized for an air handling unit?

To size a humidifier for an AHU project, a psychrometric chart is used to determine the amount of water required to increase the humidity from the initial level to the target level for one kilogram of dry air. This value is then multiplied by the total air volume. The starting condition is typically based on the coldest and driest expected situation, often corresponding to the outdoor conditions on the coldest winter day.

Is there a rule of thumb for calculating humidity load?

What factors determine humidifier selection?

What is the absorption distance for steam in an air handling unit?

Absorption distance will depend on the humidity level, air temperature and velocity. Typically, at 2.5m/s, 20°C and 50%RH the absorption distance will be around 1m. This can be shortened by up to 70% with the use of advanced short evaporation steam lance manifolds.

To avoid condensation, nothing should be located in this absorption area with no duct bends or transitions. If submicron filters are used after the humidifier, the absorption distance should be x2.5, to avoid moisture being removed by the filter. If sensors or high-end humidistats are placed in the duct, the absorption distance should be x5 to ensure proper mixing prior to the stat.

Is there a low energy humidifier?

To change the state of liquid water into a gas requires the same amount of energy if the water is being boiled to create steam or evaporated from a surface or aerosol. When it's evaporated, the energy comes from the air itself rather than from a heater. The result is an evaporative cooling effect that occurs during the process, as the air's thermal energy is used for the water's vaporisation, which chills the air.

So different types of humidifiers will use approximately the same amount of energy to achieve the same output. To achieve "low energy" humidification, it is advisable to review system efficiencies, such as correct installation or operating practises, along with any possible sources of waste heat that might be used for the vapourisation process.

How far away from the AHU should a steam humidifier be located?

Get Free Expert Advice

If you’re exploring options for humidity control, Condair’s expert sales engineers can visit your site, review your project requirements, and provide tailored recommendations.

Prefer to connect remotely? Our team is always available for a phone call or online meeting to discuss your needs, answer questions, and provide complimentary technical guidance.

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