The control layer that runs the mechanical system — and ties it into the building's electrical and automation systems.
What We Provide
Thermostats to full DDC and building automation — here is what our controls work covers, and how it ties into the electrical scope we already run.
The Basics
Strip away the acronyms and a DDC system is a short chain: sensors measure, controllers decide, actuators act — and every link in the chain is visible from one screen.
Electronic sensors read temperature, humidity, duct static pressure, and CO₂ throughout the building. Those readings feed microprocessor controllers running programmed logic — the sequences of operation — and the controllers drive the outputs: damper and valve actuators, compressor and fan stages, relays, and speed commands to variable-frequency drives. Every input and output becomes a data point that can be scheduled, trended, alarmed, and adjusted from a front end instead of a screwdriver.
Compare that with what it replaced. Pneumatic controls ran on compressed air through copper tubing — they drift out of calibration, they leak, they keep a compressor running around the clock, and they cannot tell anyone what they are doing. Standalone thermostats are one control loop each: no coordinated scheduling, no reset strategies, no record of what the equipment did last Tuesday. A building still running on either is not just harder to operate — it is invisible.
Sequences of Operation
A sequence of operation is the written specification for how the mechanical system behaves. A building performs only as well as the sequence actually running in its controllers — not the one on the drawings.
A building runs for decades on whatever logic was loaded during start-up week. If the programmed sequence quietly diverges from the design — a placeholder setpoint left in, a reset never enabled, an interlock jumpered out to survive one hot afternoon — the drawings say one thing and the building does another, and nobody can see the gap from a thermostat. That is why we verify sequences during commissioning: every point proven end to end, every mode exercised, and the as-left program documented for the owner. Where a project calls for it, we build on ASHRAE's published high-performance sequences (Guideline 36) rather than inventing logic from scratch. Our start-up and functional-testing work is covered under HVAC service and commissioning.
Free Cooling
An air-side economizer opens the outside-air dampers and cools the building with outdoor air whenever that beats running compressors. In Tucson that is a real resource — if the controls actually work.
The desert gives economizers more useful hours than most owners expect. Tucson's dry air and large day-to-night swings mean spring and fall afternoons — and summer nights that fall out of the hundreds into the seventies — deliver outdoor air a rooftop unit can use in place of compressor cooling. And because the air is so dry, a properly set dry-bulb high limit does the job that humid climates need enthalpy sensors for: the controller compares outdoor temperature against the lockout setpoint and closes the dampers before the unit starts importing 110°F afternoon air. Set the high limit wrong in either direction and you either give away free cooling or pay to condition the outdoors.
Then there is the broken-economizer epidemic. Field studies keep finding that a large share of installed economizers simply do not work — dampers seized, actuators failed or unplugged, sensors drifted, lockouts set so low the dampers never open. The failure is invisible: compressors pick up the load, the space stays comfortable, and the only symptom is a power bill nobody traces back to a stuck damper. Tucson adds its own accelerant — monsoon dust cakes damper blades, bushings, and linkages every summer, and an economizer that is never stroked and verified ends up frozen in place. Newer editions of the IECC require fault detection and diagnostics on economizers for exactly this reason.
Schedules & Setbacks
Conditioning an empty building to occupied setpoints through a 110°F afternoon or all night long is pure waste — and it is the first thing a controls system fixes.
Unoccupied setback lets the space float well above the occupied cooling setpoint after hours, within limits that protect finishes, electronics, and product. An optimal-start routine then works backward from the schedule: the controller learns how fast the building recovers and starts the equipment just early enough to hit setpoint at occupancy — not three hours before. Weekend and holiday calendars keep a Monday-through-Friday building from cooling an empty Saturday, and in our climate night pre-cooling can pair with the economizer to flush the building with cool, dry desert air before the sun comes back up.
Scheduling also shapes demand. Commercial rates in southern Arizona typically bill on the month's peak draw as well as total consumption, so staggering equipment starts and keeping large loads from stacking on top of each other matters as much as runtime. Scheduling and setback are one leg of a broader efficiency strategy — our energy, solar, and EV work covers the rest.
Existing Buildings
Most existing buildings do not need new equipment. They need the controls they already own restored to doing what they were designed to do.
Buildings drift. A schedule gets set to run around the clock during one long-ago event and never gets set back. Setpoints get walked apart one complaint at a time until adjacent zones heat and cool against each other. Sensors fall out of calibration, valves leak by, and overrides pile up until nobody remembers what the system was supposed to do. None of it announces itself — the building still gets comfortable; it just spends more every month doing it.
Retro-commissioning is the systematic fix: pull the trends, functionally test the equipment, find where the running logic and the design intent parted ways, and restore — or rewrite — the sequences to match how the building is used today. On most buildings it is among the least expensive efficiency work available, because the hardware is already bought and installed. What is missing is enforcement.
Building Automation
The building-automation system is where all of this comes together — and the protocol decision made at the first controller determines who the owner gets to hire for the next twenty years.
We design toward open protocols — principally BACnet, the building-automation standard published as ASHRAE Standard 135 — so controllers and devices from different manufacturers can share data on a common network. On an open system, the next chiller, the next tenant-improvement floor, or the next service contract does not have to come from whichever vendor installed the original panel. Proprietary systems trade that freedom away quietly, and owners usually discover it at the worst possible moment: bid time.
Integration is the other half. HVAC is one occupant of the automation backbone — lighting and energy-management controls ride the same network, and metering feeds it — so schedules, alarms, and trends live in one front end, with remote access for the people who run the building. Because our controllers, control power, and network pathways come from the same shop as the mechanical scope they serve, the integration is designed in — not negotiated between trades in the field.
Where It Applies
From Tucson, our HVAC controls work lands in office buildings, schools, and industrial plants that need sequences that run as written.
The Design-Build Advantage
Controls wiring, control power, and the panels they land in all come from one shop here. There is no gap between the controls contractor and the electrician — we're both.
Back to HVACFAQ
Straight answers on DDC, economizers, and building automation — the questions owners and facility managers ask us most.
Direct digital control replaces pneumatic controls and standalone thermostats with electronic sensors, programmable controllers, and actuators on a network. Every reading and command becomes a data point you can schedule, trend, and alarm from one screen — so the building can be operated deliberately instead of guessed at.
Usually, yes. Most rooftop units, air handlers, and split systems can be retrofitted with DDC controllers and sensors while the mechanical equipment stays in place. The work is largely control wiring and programming, so it can be phased and done in occupied buildings — and it is often worth doing before deciding whether the equipment itself actually needs replacement.
Yes — more than most owners expect. The desert's dry air and big day-to-night temperature swings produce plenty of hours in the shoulder seasons and overnight when outdoor air can cool the building for the cost of running a fan. The catch is that economizers fail quietly: stuck dampers, failed actuators, and bad lockout settings are common everywhere, and monsoon dust makes regular verification essential here.
There is no single right number — it depends on what is in the building and how quickly the system can recover the space. The principle is to let unoccupied spaces float well above occupied setpoints, within limits that protect contents and finishes, then use an optimal-start routine that brings the space back just in time for occupancy instead of hours early. At 110°F design temperatures, those unoccupied hours are where a large share of the cooling budget goes.
It is the written specification for how the mechanical system behaves: operating modes, setpoints and resets, staging order, interlocks, safeties, and what every device does on a failure. The sequence is what turns a collection of equipment into a system — and verifying that the programmed logic matches the written sequence is a core part of commissioning.
BACnet is the open communication standard for building automation, published as ASHRAE Standard 135. Controllers and devices that speak it can share data regardless of manufacturer. For an owner, that means the next expansion, replacement, or service contract is not locked to whichever vendor installed the original system — a position worth protecting from the first controller onward.
It depends on the point count more than the square footage: how many pieces of equipment are controlled, how many sensors and actuators each one needs, whether existing controllers and wiring can be reused, and how much integration and graphics work the front end requires. A controls-only retrofit prices very differently from a full BAS on new construction — tell us what the building runs today and we will scope it in a bid. Request a bid to get started.
Tell us how the building runs now. We'll come back with a controls plan and the sequences in writing.
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