HVAC Control Board Build-to-Print

NOTICE TO BUYERS:

We are a Professional Electronics Contract Manufacturer (EMS).

We do NOT sell retail or off-the-shelf ready-to-ship replacement boards.

All products shown are custom manufacturing cases protected by client NDA.

To get a formal quotation within 24 hours, please provide:

• Gerber Files (RS-274X)
• Complete BOM List (with manufacturer part numbers)
• Estimated Order Volume (Prototype or Mass Production)

Where the Design Gets Hard

An HVAC controller is rarely a difficult board in terms of density. Its difficulty is coexistence. The same PCB carries a 24VAC control interface and switched mains for compressors, fans, and valves, alongside millivolt-level analog front ends reading NTC thermistors, pressure transducers, and humidity sensors. Add an inverter compressor drive nearby and the board is also living inside its own switching noise. Getting each function to work in isolation is straightforward. Getting them to work while the compressor ramps is the engineering problem, and it is the reason these boards are built with more layout discipline than their component count suggests.

What We Build

We produce indoor unit controllers, outdoor unit control boards, thermostat and wall-controller assemblies, and the interface boards that link a unit to a building management system. Scope is usually a single board or a matched indoor/outdoor pair produced against one shared drawing set, so pin assignments and firmware conventions stay aligned across the two halves of a system. Where the customer supplies the enclosure and harness, boards can be delivered as tested assemblies with connectors fitted rather than bare PCBAs. Firmware flashing, parameter loading, and serial number programming are available so boards arrive ready for line assembly rather than for a programming station.

Mixed-Signal Layout

Separation is the governing rule. Analog sensing runs are kept short and away from switching nodes, with ground returns arranged so sensor currents do not share a path with relay or triac return currents. Relay and triac outputs sit in their own copper zone with slot isolation where creepage to the low-voltage side must be maintained. Boards typically run four to six layers with a dedicated ground plane, high-TG FR-4 for units exposed to rooftop and plant-room heat, and copper up to 3oz where relay current or compressor drive demand it. Sensor inputs carry RC filtering and TVS protection, and the 24VAC interface is laid out for surge and transient tolerance rather than for the nominal waveform. Finish is ENIG or lead-free HASL, held to IPC-A-610 Class 2 or Class 3 as specified.

Build and Test

The process challenge is the mix itself - fine-pitch microcontroller and sensor packages on one side, power relays, terminal blocks, and heavy through-hole connectors on the other. SMT runs first with solder paste inspected before every lot and reflow profiles tuned per board thickness and copper load; through-hole parts are then attached by selective or hand soldering at controlled temperature. AOI covers 100% of boards, with X-Ray on fine-pitch and BGA areas. Functional testing is where HVAC boards earn their value: sensor input simulation across the full temperature range, relay and triac output verification under load, communication loop testing over RS-485 or Modbus, and where specified, EMC pre-screening. Conformal coating is applied for outdoor units and humid plant rooms.

Where It Goes

These controllers run in split and multi-split air conditioners, ducted and rooftop packaged units, heat pumps, VRF systems, ventilation and ERV units, chillers, and building automation sub-controllers. Environments range from sealed indoor cabinets to rooftop enclosures exposed to sun, rain, and temperature swings of forty degrees or more across a season.

Reliability Notes

HVAC electronics fail on the installation side more often than at the bench. A board that tests perfectly can still fail from a lightning-induced surge on the 24VAC line, from condensation during a seasonal shutdown, or from thermal cycling at a rooftop location. Layout that respects creepage and isolation, protection devices sized for the actual surge environment, and coating applied where moisture is expected address the majority of these. Lots stay traceable from bare board through finished assembly, so a field return can be isolated to a production window. TECOO has manufactured industrial and appliance electronics for 24 years.

FAQ

1. Can I buy this board as a spare part?
No. It is a manufacturing example only; every board is produced from the customer's own Gerber and BOM.

2. Do you build both the indoor and outdoor unit controllers?
Yes. The pair can be produced against one drawing set so pin assignments and firmware conventions stay consistent.

3. Can you handle the 24VAC interface and mains switching on one board?
Yes, with creepage, clearance, and slot isolation laid out to the working voltage between the two sides.

4. Is functional testing with sensor simulation available?
Yes. Sensor input simulation, output verification under load, and communication loop testing can all be included.

5. Do you program firmware before shipment?
Yes. Programming, parameter loading, and serial number writing can be added to the build.

6. What do you need to quote?
Gerber (RS-274X), BOM with manufacturer part numbers, and an estimated order volume.

Send your Gerber, BOM, and volume forecast. Our engineers will review the layout for mixed-signal and isolation issues and come back with DFM notes and pricing within one business day.

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