Get Your RTU Replacement Right the First Time

When your rooftop HVAC unit (RTU) gives out, it’s immediately noticeable—employees notice how hot it’s becoming inside the building, and customers won’t stick around in a hot environment. As a building owner, you need to address the problem quickly so your staff and customers can get back to business as usual.  You’re going to need a contractor, one who is licensed to work on ACs and refrigeration equipment. Due to the pressurized gases and other hazardous materials related to RTUs, each state requires schooling and testing before issuing an HVAC license.

The contractor comes out to your place of business to assess the situation. They check out your setup and give you an estimate to fix the RTU or replace it. When replacing an RTU, a curb adapter is commonly used to keep the existing rooftop access point and curb in place while accommodating a new air conditioning unit, and proper fitment and efficiency are dependent on exact measurements. Before you enter into a contract for RTU replacement, make sure that your contractor has followed these critical steps in preparing for the job.

Measure the Roof Curb

The contractor should take exact measurements the length and width of the curb the RTU sits on top of. They should also take photos of the RTU from multiple angles for added reference.

Take Photos of Model Number

It’s a good idea to take a photo of the RTU brand and model number. Make sure the label isn’t occluded by dirt or grime before taking the photo. It’s very common to accidentally transpose a number or letter when writing a model number down (or when relaying a number over a phone call), and occasionally models are only a letter or number apart from one another. This simple mistake can drive costs skyward in terms of remaking an adapter, crane costs, added labor hours, and so forth.

Photograph the Entire Rooftop Environment

The contractor should take pictures of the whole situation on the roof from multiple angles. This will help the curb adapter designer adjust for any obstructions or roof features near the curb, including cosmetic walls, gas lines, drainage lines, vent pipes, etc. The curb adapter may need adjustments from a standard design to accommodate obstructions, and the RTU’s maintenance panel needs to be accessible for future servicing including filter changes and programming adjustments.

In one example, we built a curb adapter for a unit which was two feet away from the roof of the building—we didn’t know that, so the equipment was hard to maintain. The maintenance tech would have to hang off the side of the building to service the RTU!

In another example, there was an electrical box near one unit that was unknown to Curbco prior to building the curb adapter. Once discovered, the design had to be adjusted, the adapter remade, and a crane had to be hired out a second time. In addition, the building owner was saddled with an extra curb adapter, which they will probable never have a use for or be able to resell.

Assess the Area Beneath the Equipment

The contractor should assess and document the area between the RTU and the curb. RTU forklift rails should be hanging over the sides of the original curb, and if they’re not, that’s an indication that there’s something in between, like a curb adapter or a vibration-isolation rail, both of which should be known by the curb adapter designer.

Ideally, the contractor should document the dimensions of the duct openings for the air supply and return. That way, all parties can check produced drawings against actual dimensions.

Ensure a Curb Adapter Isn’t Already in Place

The contractor needs to ensure that there’s nothing in between the current RTU and its curb. If there is already a curb adapter between the unit and the curb, another solution will need to be explored. It’s never a good idea to “stack” multiple curb adapters. They are not designed to support additional weight or to route extra airflow, and safety and efficiency concerns will quickly emerge. Think of a curb adapter like a soda can—you don’t want it to fold.

Get it Right the First Time

Taking the time to document the entire RTU setup thoroughly will cost extra time on the front end, but the costs of getting the measurements wrong can be high. Make sure to account for all variables before your replacement, and the total time to fulfillment will be as short as possible, allowing your staff and customers to breathe an air-conditioned sigh of relief.