Littleton Equipment Pads

Machines keep their own calendars. A standby generator exercises itself on a set day at a set hour, runs a few minutes under load, and shuts down. A heat pump cycles all afternoon in August and runs defrost cycles through a January cold snap. Pool equipment runs the same hours every day all season. A shop compressor kicks on and off dozens of times before lunch.

Each of those events is a small mechanical shock delivered into a square of concrete, and they run into the thousands over a year. That's the actual job of an equipment pad, and it's nothing like holding up a patio table. Get it wrong and you learn about it from a leaning condenser, a strained line set, or a tech telling you the machine is fine and the concrete isn't.

What the pad is doing while nobody watches

Level is the requirement people underestimate. Rotating equipment wants a tight tolerance, because bearings, compressor mounts, and refrigerant oil all assume the machine sits the way it was designed to sit. A pad that tips a fraction over two winters never announces itself. It shows up as a short service life on a machine nobody suspected was mounted crooked.

Access is the other daily reality. Somebody stands next to that equipment with a toolbox twice a year, pulls a panel, sets parts down, and in February does it through snow. So we size pads with working room on the service side instead of trimming tight to the footprint, and we set the top high enough above grade to stay out of puddles and drifts.

What we need from your installer before we pour

• Make and model of the equipment, with the submittal sheet if you have it
• Operating weight, including anything that fills with water or fuel
• Anchor bolt pattern and required embedment
• Conduit locations, sizes, and how high each stub-up needs to project
• Required clearances on the service side and any code-driven setbacks
• Whether the manufacturer calls for vibration isolators under the feet
• The install date, so the concrete has time to gain strength beforehand

What each machine does to its pad over a year

Conduit is where pads usually go wrong

Almost every pad we pour has something coming up through it. Power for a condenser or generator, a gas line, control wiring, sometimes fuel. Each one is a hole in a small piece of concrete, and holes are where cracks start.

So placement is deliberate. Stub-ups stay away from the edges, since a penetration near the perimeter leaves a thin ribbon of concrete holding nothing. We sleeve rather than casting rigid pipe tight into the slab, which leaves room for movement and a route for a future replacement. Steel gets tied around each penetration instead of stopping short. And the layout gets confirmed with your electrician beforehand, because a stub-up landing four inches off the cabinet knockout costs far more to fix than it ever cost to get right.

Timing a pad around the install date

Pads are small, so they're easy to fit into a schedule, and that's exactly why they get left until the last minute. The constraint isn't our calendar. It's strength. Concrete needs time before a heavy machine gets set and bolted down, and rushing that is how you end up with spalled anchor pockets.

Spring through fall is straightforward. Winter pads happen often, since equipment failures don't wait for April, and we handle them with a thawed subgrade, heated mix water, and blankets left on until the concrete is past the risk. One care item regardless of season: keep deicing salt off a new pad through its first winter, including whatever gets tracked over from the walk beside it. Shovel it, sand it, and leave the chemicals alone.

The pads that come back to bite people are never the ones that got poured too thick. It's always a two inch slab somebody floated on loose dirt so the unit would have something flat to sit on that afternoon.Straight from the crew