Scheduling HVAC Equipment Manufacturing Through the Season

An HVAC manufacturer has two different scheduling problems in one plant: a stocked, seasonal, high-volume side that has to be built ahead, and a configured, date-driven side that competes for the same coil line and assembly bays. EDGEBIC by User Solutions plans the stocked models to a target position and schedules the configured orders against the same finite capacity, so build-ahead work and custom work share one honest plan instead of two competing spreadsheets.

The season is not the hard part. The hard part is that the two halves of the business use the same machines and nobody can see the collision until it happens.

Two Planning Modes, One Capacity Pool

High-volume residential units, standard coils, and common sheet metal parts are make-to-stock work. You want them built when the plant has room, held as inventory, and pulled through the season. Configured air handlers, rooftop units with option packages, and replacement builds are make-to-order. They carry a customer date and a routing of their own.

Set each product to the mode that matches how it is actually sold. The planning pass generates replenishment work for the stocked items against a target position, and the scheduler places that work on the same finite capacity as the configured orders. The mechanics are covered in make-to-stock versus make-to-order planning behavior and the switch itself in how to switch a product between make-to-stock and make-to-order.

The value is not the two modes. It is that both compete in the same schedule. A wave of custom orders in June shows up as pressure on the stocked build-ahead, visibly, in the plan.

Building Ahead Against the Curve

Seasonal build-ahead only works if the shoulder-month capacity is real. Look at a coil line that runs 3,200 hours a year and a season that demands 2,400 of them in five months. The other seven months hold 800 hours of demand and roughly 1,800 hours of capacity. That gap is the build-ahead budget, and it is a number you can schedule rather than argue about.

Because the replenishment orders are scheduled work, they occupy the calendar, they compete for the coil line, and they get rescheduled when something else jumps the queue. That is what makes the build-ahead honest. For the demand-side thinking, planning inventory for a seasonal demand curve covers the pattern, and seasonal capacity planning covers the capacity side.

Adding Shift Only Where It Helps

Peak season usually needs more hours, but rarely everywhere. The coil line binds. Braze may bind. Final assembly usually does not.

Shift calendars are defined per work center, so you can put the coil line on a second shift for eight weeks without touching the rest of the plant. Reschedule and read the result: how much of the backlog does the added shift actually absorb, and does the constraint move somewhere else? That last question matters, because adding hours to a bottleneck often just promotes the next work center to bottleneck. See adding a second shift to break a bottleneck and bottleneck migration.

For shorter adjustments, a daily capacity override changes a single work center on a single date, which is the right tool for a Saturday coil run rather than a permanent calendar change.

Pooling Interchangeable Lines

If you run more than one coil line, or several braze stations that can take the same work, bind the routing step to a work center group rather than one named line. At schedule time the engine expands the group and places the job on the member that finishes it soonest against live load. Members carry their own efficiency factor, so a faster line is modeled as faster instead of averaged into the group. Jobs already running stay on the line running them.

Configured Units Need Their Own Routing

An air handler with a heat recovery wheel, a different filter bank, and a custom coil circuit is not the base model with a note attached. Give configured units their own routing, or copy a base and adjust the steps that actually change.

Once the job is released, its routing is captured as a snapshot, so an engineering change to the master routing next month does not rewrite a unit already on the floor. That is described in why frozen routings protect in-flight jobs.

Quoting in Peak Season

Sales needs a date while the plant is full. A quote simulation schedules the proposed job against current live load and returns a promise date that includes the queue in front of the coil line. Nothing is committed and no existing job moves. If you want to see what accepting the order costs the rest of the book, insert it in a scenario and reschedule: the jobs that slip are flagged with their new dates before you sign anything.

A Worked Season

A plant with one coil line, planning for a May to August peak.

The 240-hour shortfall in the peak is visible in March, which is when adding an eight-week second shift is a hiring decision rather than a panic. That is the whole point of putting build-ahead into the schedule instead of a target document.

Tracking the Season as It Runs

Operators log start, stop, and quantity at a shop floor station, so the plan reflects what the coil line actually produced rather than the standard. Work already completed is never moved by a reschedule, so a mid-season replan does not disturb the record of what shipped. Over one season the logged hours become the standard you plan next season with.

Heritage in Volume and Configuration Together

User Solutions has built finite capacity scheduling since 1991, more than 35 years, for manufacturers running volume and custom work through the same plant: US Navy, GE, BAE Systems, and Cummins across 33 locations. The lineage behind EDGEBIC, including the RMDB heritage, drove GE Railcar on-time delivery from 30 percent to 90 percent. Balancing a stocked build-ahead against dated custom orders is that same discipline in a seasonal shape.

Where to Start

Classify your top twenty products as stocked or configured, set targets on the stocked ones, put your coil lines in a group, and schedule a full year with the shoulder months included. The build-ahead number will be the first thing you argue about, and it will be an argument with data in it.

For fundamentals, what is production scheduling is the plain-language start and capacity planning versus production scheduling explains the two horizons. The industry fit guide maps neighboring sectors, including consumer goods seasonal capacity, and EDGEBIC is the product hub. Ready to size next season's build-ahead honestly? Contact US for a demo.