What HVAC contractors should tell the crane company

One: The Weight, and Which Weight

Operating weight is the number we need. Shipping weight, dry weight, and operating weight can be meaningfully different on the same unit, and a spec sheet will often list more than one.

The other trap is the old unit. On a change-out there are two picks and two weights. A twenty year old unit with a heavy gauge cabinet and an economizer bolted to it can outweigh the new one that is replacing it. If we plan on the new unit's weight and the old one is heavier, we planned the wrong pick.

Then there is what is attached. Curb adapters, economizer hoods, roof curbs coming off with the unit, and accumulated debris all add. So do units that were rained into or that have a sump full of water. If the old unit is coming off with anything on it, say so.

A model number is the most useful thing you can send. From a model number we can find published weights ourselves and stop guessing.

Two: Where the Crane Can Set Up

This is the one that changes the machine and the price of the whole day, and it is the one contractors most often assume is obvious.

The crane needs a place to sit with room to spread outriggers, ground that will hold, and no overhead lines above the swing. On a commercial property that might be a parking lot, a service drive, a loading area, or the street.

The details that matter are unglamorous. Whether the parking lot has a drainage structure under it. Whether the property manager will let us take a fire lane for an hour. Whether the loading area will be occupied by a delivery truck at eight in the morning. Whether the gate to the back lot is wide enough for a boom truck.

A photo from the setup position looking at the building answers most of this in one image, and it takes less time to send than describing it.

Three: The Distance to the Curb

Radius is the horizontal distance from the crane to the unit, and it is what determines whether a job is straightforward or marginal.

The thing people forget is the building depth. If the crane sits at the front of a building and the curb is in the middle of a large roof, the radius includes the whole distance across that roof. The unit may be light and the pick may still be substantial.

Parapets and roof height add to it. A tall parapet means the load has to be lifted higher before it can come inboard, and high plus far is where reach gets used up.

Pace it off, or measure it on a satellite view. An approximate number given up front is far more useful than an exact one discovered on site.

Four: What Is Already Up There, and What Is in the Way

Roofs accumulate. Other units, condensers, exhaust fans, satellite dishes, solar arrays, conduit runs, gas piping, skylights, and safety rails all occupy the space the load has to travel through or land beside.

Solar in particular has changed a lot of rooftop work in this town. An array between the setup side and the curb means the load has to be brought in over it, and nobody wants a unit swinging above panels.

Skylights are a safety issue rather than a lifting one. They look like part of the roof and they are not, and a crew member stepping onto one is the worst thing that can happen on a roof.

In the flight path outside the building, the usual suspects: service drops, light poles, trees, and the neighbor's building. Send a photo of the roof if you have one, even a bad one from your phone.

Five: Who Is Receiving It

Somebody has to be on the roof to guide the unit onto the curb and confirm it is seated. That is not a crane function. The crane brings the unit to within a few inches and holds it while somebody with hands on it does the last part.

So the question is who, and will they be there at the start time. On a coordinated job that is your crew and they are already up there when we arrive. On a job that was scheduled loosely, everybody arrives at once and spends thirty minutes getting organized while the crane waits.

The related question is what state the old unit will be in. Disconnects pulled, gas secured, refrigerant handled, fasteners out, unit broken loose from the curb. If that work has not happened, the crane is watching it happen.

Ideally it happened the previous afternoon. That single change does more for a summer rooftop schedule than anything else on this list.

• Model numbers for both the old and the new unit
• A photo from the proposed setup position toward the building
• A photo of the roof showing the curb and anything around it
• Approximate distance from setup point to curb
• Building height and whether there is a parapet
• Confirmation that disconnect and break-loose work will be done beforehand
• Who will be on the roof and what time they arrive
• Where the old unit goes after it comes off

The Thing Nobody Plans For

Where does the old unit go. It comes off the roof and then it is a large object sitting somewhere, and somebody has to have decided where.

On the ground in the parking lot is fine if it is getting picked up. On a trailer is better if the trailer is there. Left in a fire lane because the scrap truck comes Thursday is a problem for whoever manages the property.

It sounds trivial and it regularly adds twenty minutes to a job while people work out an answer. Decide it before the day.

What We Do With the Information

All of it feeds three decisions: which machine comes, where it sets up, and how long we block out. Get those three right and a change-out is a short, calm visit.

Get them wrong and the failure is usually total rather than partial. A crane that cannot reach cannot half reach. That is why we would rather over-ask on the phone than under-ask, and why a contractor who sends four photos and a model number gets a much more useful answer than one who asks whether we can do a rooftop unit.