Rooftop Unit Replacement

What a rooftop unit replacement actually involves

A packaged rooftop unit is the whole system in one cabinet: compressor, condenser coil, evaporator coil, blower, gas heat section or heat pump, and the controls, all sitting on a curb over a supply and return opening in the roof. That makes a replacement simpler than a split system in one way, since there is no refrigerant line set to run through the building, and harder in another, since the new cabinet has to land on the old opening, on a roof, by crane.

A complete changeout covers the new unit, a curb adapter when the footprint has changed, the gas connection and a pressure test, the electrical disconnect and whip, the thermostat or building controls, condensate drainage, the crane lift and rigging, and disposal of the old unit. Then it gets commissioned: refrigerant charge verified, gas pressure set, airflow and static pressure measured, economizer and safeties proven, and the whole unit run through a full heating and cooling cycle before anyone signs off. A rooftop unit that was set down and wired up is not finished. It is installed when the numbers say so.

Signs the unit is at the end of its useful life

Most rooftop units give fifteen to twenty years of service. Salt air, restaurant exhaust and a thin maintenance history shorten that. Age alone is not the decision. The pattern of failures is.

• A cracked heat exchanger, which is a safety problem and not a repair candidate
• A failed compressor on a unit past ten years old
• Refrigerant leaks that come back after every recharge, especially on R-410A equipment now that the refrigerant is no longer produced
• Rusted-through cabinet panels or a base rail that no longer sheds water
• Repeated control board, blower motor or gas valve failures on the same unit
• Staff or tenants who have stopped calling because they assume it will never hold temperature

When the repair estimate approaches a third of the replacement cost, or the unit runs on a refrigerant that is going away, the honest answer usually points toward replacement. We put both numbers side by side and tell you which one we would choose if the building were ours. If the numbers favor fixing it, our rooftop unit repair page covers what that visit looks like.

Sizing and selection happen before the crane is booked

Like-for-like is the most common mistake in commercial replacements. The original unit was sized for the building as it was built, not for the tenant using it today. A retail bay converted to a fitness studio, or an office that became a dental practice, carries a completely different load.

So we start with a load check on the space as it is now: occupancy, equipment heat, ventilation requirements, hours of operation, and what the existing ductwork can actually move. Then we match tonnage, heating capacity, voltage and phase, and the supply and return orientation to what is on the roof. Gas heat versus a heat pump comes up more often now, because cold-climate heat pump rooftop units hold their capacity in weather that used to rule them out, and utility programs in parts of this footprint reward the switch. We will tell you when that math works for your building and when it does not.

What moves the price

Tonnage and heating capacity set the base. Everything else is your specific roof.

• A curb adapter versus reusing the existing curb as it is
• Single-phase versus three-phase power, and whether the existing disconnect and feeder can carry the new unit
• Options such as an economizer, hail guards, coated coils for coastal sites, a duct smoke detector, or a building automation tie-in
• Crane size and placement, which depends on how far the unit sits from the roof edge and where the crane can set up
• Gas piping changes when the input of the new unit differs from the old one
• Roof condition around the curb, which a roofer may need to address before we set anything on it

We price the job in writing before the crane is scheduled. There are no allowances that turn into change orders on the roof. If the electrical service needs work, our electricians quote it in the same document, and if the gas line has to change, our gas fitters handle that too.

How replacement day runs

Most single-unit changeouts are one day. The crane is scheduled early, before parking lots and traffic fill in, and the lift itself takes minutes each way once the rigging is set. While the old unit is being cut loose, the electrician is on the disconnect and the gas fitter is on the piping, because they are our team members and not a second contractor waiting on the first one. Your business stays open. Heat or cooling is typically back the same afternoon, with the inspection following on the schedule of the local inspector.

Multi-unit replacements get sequenced so the building never loses more than one zone at a time, and we plan around your busiest hours rather than ours. When the new thermostat or controls go in, we walk your manager through them before we leave the site.

Why building owners here call High Ground

We have more than 260 packaged and rooftop units in our service records across New Hampshire, New Jersey and southern Maine, from Carrier, Trane, Lennox, York, Rheem, Daikin and the rest. Our technicians have been on those roofs for spring and fall maintenance for years, so we know how these units fail in this climate before we quote the one replacing yours.

One licensed team does the whole job: HVAC, electrical and gas. Every replacement carries our Lifetime Workmanship Guarantee. If our work is not right, we come back and make it right. High Ground is veteran-owned, the mission is giving the trades a good home, and the crew on your roof intends to be the same crew doing your maintenance next spring. For everything else we do for businesses, see commercial HVAC.

Related Heating & Cooling services

• Rooftop Unit Repair
• Commercial HVAC
• Heat Pumps
• HVAC Maintenance
• Thermostats
• AC Install