Drama-Free HVAC Retrofits
Drama-Free HVAC Retrofits
HVAC retrofits seem simple enough. They can be, but careful planning is key. Knowing exactly what to plan for and doing the work up front will ultimately determine how smoothly the project goes.
Below are the specific elements of any HVAC retrofit. Each has a certain timeframe and cost associated with it. These points can be modified to fit almost any type of equipment—rooftop units, split systems, chillers, boilers, cooling towers and so on.
In commercial buildings, it’s common to find that the space has been renovated or changed use since the original HVAC equipment was installed. So the first thing to do is to get a mechanical engineer to evaluate the space and determine if the equipment and systems comply with building code and the use of the space.
We once received a call from the parent company of a popular Florida restaurant. Apparently, the restaurant was muggy, ninety degrees, and customers were leaving before their meals were served. Engineering revealed that the restaurant was 160 tons short of cooling. It turned out they had recently enclosed their large, outdoor patio in glass without factoring in the additional cooling requirements of the space. While this is an extreme example of a common theme, it illustrates the need to take this point seriously.
The amount of heat generated inside the space is probably the single most important determinant of comfort. A human body generates approximately 300-600 BTUs of heat per hour, so a high-occupancy space will require more tonnage cooling capacity. Computers, servers, lighting,refrigeration and cooking equipment all generate a sizeable amount of heat. The intense afternoon sun and corresponding solar gain can also be uncomfortable for people who work or shop in the space, especially with western-facing windows. Geographic location and altitude can drastically affect the heat load calculations so they should be done by a local mechanical engineer familiar with the climate. All these factors affect the comfort level and therefore must be considered.
With rooftop and split systems, specifications may include the SEER rating or efficiency of the unit, economizers for outside air exchanges, smoke detectors, EMS controls, humidification, hail guards, coated coils and new electrical disconnects. A mechanical engineer cannot always make those judgement calls for you, especially regarding efficiency and controls.
How long will it take to get the job scheduled and the equipment to the site? If you are replacing a common item, it may be in stock. On the other hand, equipment ordered from the manufacturer can take multiple weeks to ship from the factory. Items that may need to be special ordered include chillers, cooling towers, boilers, make-up air units and certain types of rooftop units.
If you are switching your rooftop unit to a different brand or model, you’ll likely need custom-built adapt-a-curbs between the unit and the rooftop so that the supply and the return air align with the penetrations in the roof. Adapt-a-curbs are usually custom made and require some lead time.
If you aren’t replacing like-for-like equipment, the project will likely require structural engineering and possibly structural reinforcement. The weight of the new and old equipment, as well as additional weight from adapt-a-curbs, will determine what is required. City building codes will usually dictate if structural reinforcement is necessary. If so, it will typically require reframing of the joists, or welding in structural steel. Again, this takes time, and, of course, money.
Is there enough power to handle the new unit? This is especially important if you are adding new equipment but may also come into play for change-outs. Some of the electrical issues that you may encounter include new fusible disconnects, single- or three-phase power, GFI outlets, wiring, panel upgrades, and sometimes, working with the utility company to upgrade service.
Very large buildings such as shopping centers or distribution centers may require a specialized crane or even a helicopter to set the unit. You’ll need to determine where the crane can set up on the property so that it is both safe and doesn’t affect your business. Also, for safety reasons, the building may need to be unoccupied when the crane sets the unit(s).
If the unit being installed has a rating over 2,000 CFM, the unit’s smoke detectors will need to be tied into the main fire panel and may need additional sensors, controls or programming.
If it’s required, always pull permits. Volumes could be written about the economic ruin suffered because someone thought they could skirt the issue. Proper permitting takes the liability out of your hands and places it somewhere else. In order to get a permit, the city may require you to bring unrelated items up to code. Depending on the neighborhood’s zoning, you may need to install a fence around the project. These kinds of things can add to the duration and cost of the project.
Some other issues that could affect your project include roofing, piping, natural gas, welding, height of the project, core drilling, or test and balance.
There are many things to consider when it comes to HVAC upgrades or replacements. Preparation and planning will keep your HVAC system where it should be—humming along like background noise. Keep all of these things in mind and you’ll be on your way to delivering your capital project on time, on budget, and without drama.