THRU WALL UNITS 

Thru wall units are an excellent choice for many warehouse applications. They do not require any floor space. Typically, the units are mounted in shipping/receiving areas to address the cold air gain at the dock doors. 

For manufacturing areas, due to the presence of overhead cranes, thru wall units are frequently not a viable option. The clearance required for an overhead crane at the side wall typically does not allow adequate room to install a thru wall unit. 

The heater may have an external gas train. The gas train should be positioned such that the equivalent distance from the outlet of the gas train to the inlet of the heater does not exceed 4 feet. Usually the best location is to place the gas train perpendicular to the side of the heater, so it can be piped directly into the heater’s gas inlet, as illustrated in the S-Series Technical Manual. 

Servicing the unit is another potential problem if overhead cranes are present. Accessing the unit via a boom lift or scissors lift will entail entering crane space. This usually means that the work cannot take place until the crane(s) is locked out or other measures (such as a blocking crane) are taken. Locking out of cranes may seriously affect production, so it should not be taken lightly. 

Servicing the units utilizing a ladder is frequently not an option due to requirements for safe ladder use. In addition, it is difficult, if not impossible, to access several of the heater’s parts from a ladder. 

If a location for a thru wall unit is found, then consideration should be given to the impact on local work stations. What will the mounting height of the heater be? How will the air be distributed? Double deflection grilles are extremely effective when fine tuning air flow. 

Another potential safety issue is whether plant personnel will be regularly traveling or working beneath the suspended load. Additional safeguards may be needed to secure the heater. 

Installing the unit may require barricading the floor area where the installing crew is working. Plant vehicle & pedestrian control must be considered. Flag men may be required. These aspects will need to be covered in the safe work plan. 

Below are installations of thru wall units that were installed several years ago. As always with retrofit installations, final mounting configuration and placement depends on “what the building gives you” with which to work. 


The Cambridge Air Solutions' Applications Engineering Team is available to discuss custom solutions for your project. Have your local rep engage this team for any specific needs you have!

In new construction, the primary source of moisture entering the building is most likely from the newly poured concrete slab.

The National Ready Mixed Concrete Association (NRMCA) describes the ‘What’ and ‘How’ of concrete slab moisture in their 2004 Concrete in Practice publication CIP 28-Concrete Slab Moisture. Potential sources of concrete slab moisture include:

  • The floor slab is in contact with saturated ground. Moisture moves to the slab surface via capillary action or wicking.
  • Water vapor from damp soil will diffuse and condense on a concrete slab surface that is cooler and at a lower relative humidity due to a vapor pressure gradient.
  • Residual moisture in the slab from the original concrete mixing water will move towards the surface.
  • It may take anywhere from six weeks to one year or longer for a concrete slab to dry out to an acceptable level under normal conditions. Reference: Bruce Suprenant,  Concrete Construction, November, 1997.

The topic is also dealt with in depth by the U.S. Environmental Protection Agency in their publication EPA 402-F-13053. Moisture Control Guidance for Building Design, Construction and Maintenance. December, 2013. Topics include: moisture control in buildings, basics of water behavior, designing for moisture control, constructing to prevent moisture problems, and operating and maintaining moisture-controlled environments.

As manufacturers of HVAC equipment, Cambridge Air Solutions has no input regarding the numerous factors involved in concrete work that affect the moisture in the slab. However, when moisture problems arise, we are often involved in looking for remedies to deal with the moisture. Some of our contractors refer to the procedure “IAQA flush-out, REQEQ2,2r1”, required by LEED and published by the U.S. Green Building Council. https://www.usgbc.org/credits/reqeq22r1-0. This flush-out, as required by LEED, is intended to rid the building of moisture as well as “off gassing” of building materials.

Requirements

Select one of the following two options, to be implemented after construction ends and the building has been completely cleaned. All interior finishes, such as millwork, doors, paint, carpet, acoustic tiles, and movable furnishings (e.g., workstations, partitions), must be installed, and major volatile organic compound (VOC) punch list items must be finished. The options cannot be combined.

Option 1. Flush-out (1 point)

Path 1. Before occupancy

Install new filtration media and perform a building flush-out by supplying a total air volume of 14,000 cubic feet of outdoor air per square foot (4 267 140 liters of outdoor air per square meter) of gross floor area while maintaining an internal temperature of at least 60°F (15°C) and no higher than 80°F (27°C) and relative humidity no higher than 60%. OR

Path 2. During occupancy

If occupancy is desired before the flush-out is completed, the space may be occupied only after delivery of a minimum of 3,500 cubic feet of outdoor air per square foot (1 066 260 liters of outdoor air per square meter) of gross floor area while maintaining an internal temperature of at least 60°F (15°C) and no higher than 80°F (27°C) and relative humidity no higher than 60%. Once the space is occupied, it must be ventilated at a minimum rate of 0.30 cubic foot per minute (cfm) per square foot of outdoor air (1.5 liters per second per square meter of outdoor air) or the design minimum outdoor air rate determined in EQ Prerequisite Minimum Indoor Air Quality Performance, whichever is greater. During each day of the flush-out period, ventilation must begin at least three hours before occupancy and continue during occupancy. These conditions must be maintained until a total of 14,000 cubic feet per square foot of outdoor air (4 267 140 liters of outdoor air per square meter) has been delivered to the space.