Roof Curb manufacturers use a lot of 1″ Duct Liner. They also use a lot of adhesive to adhere the liner to the metal and then a much higher than normal % of weld pins to secure the liner to the metal. Why so many weld pins? After all, In a typical HVAC Duct shop the usage of Weld Pins to Liner might be 1.5 weld pins per square foot of liner. In a Curb Shop it’s probably closer to four weld pins per square ft of liner.
That’s because Curb Shops make a lot of something called Curb Adapters. Curb Adapters are large, square or rectangular structures made of 18 ga Galvanized, internally lined with insulation, and with about a half dozen varying angles and bends that end with pass thru openings that will mate with the supply and return design of the new Rooftop Unit (or RTU) and also match up with the openings in the roof that were cut out when the original unit was installed. Because the duct liner is adhering to various angles and bends, it’s pieced onto the curbs interior in strips cut out to match the dimension to which it will be secured.
Why the PBF520?
Because Curb Adapters are large, a pinspotter with a Long Gun Cable is a necessity as is it’s mobility around the shop since it’s a lot easier to move a portable pinspotter than a Roof Curb. And because Curb Adapters are 18 gauge Galvanized, this portable machine with a Long Cable has to have a lot of power. The PBF Pinspotter, with a 16 ft Gun Cable, heavy duty Caster Wheels and the largest transformer of any of Duro Dyne’s weld pin machines is designed with Curb Adapters in mind.
Tip: To get peak performance out of the PBF (or any Resistance welder), use a heavier wire when connecting to the electrical panel because the voltage will drop as the machine is moved farther away from the power source.
How has the PBF Pinspotter changed over the years?
The old style PBF pinspotters had the Gun and Ground Cables wired directly into the Unit. The New style has a Cam lock which makes them easy to repair or replace. The old PBF 14 had no wheels; the PBF510 came with wheels which made moving around shop easier; the PBF520 improved those into heavy duty caster wheels. The 16 ft standard Gun Cable is unchanged but there’s also an option of having extensions to 24 Ft. Finally, the 520 machine features a more Ergonomic weld Gun.But, to get the peak performance out of your PBF520, just as you did with the PBFS-14, a heavier gauge wire should be used when connecting to the electrical panel, especially when there’s a significant distance from the machine to the power source . A heavy enough gauge of wire ensures peak performance out of the machine . This comes into play when using 2″ or 3″ weld pins, less so when using 3/4″ weld pins thru 1″ Liner unless welding to 14 gauge.
Curb Adapters always mount to the Original Roof Curb
Most commercial buildings are made with flat roofs for the benefit of installing the numerous and large HVAC units on top of the roof rather than taking up valuable real estate inside and alongside the building. When the building was constructed it included new Rooftop Units (RTU), each mounted on its own roof curb. These Roof Curbs were supplied with the Rooftop Unit and cut into the roof During the construction of the roof. RTUs have a typical life span of 10 to 15 years at which time they are replaced with a new RTUs. But since the roof curb to which the original RTU is affixed doesn’t mate with the new RTU, a Curb Adapter is custom built to mate with the New RTU on top and connect with the original Roof Curb on bottom. When times passes and that second Rooftop Unit gets replaced, so does the Curb Adapter. Curb Adapters are always mounted to the Original Roof Curb, never to other Curb Adapters One RTU per Curb Adapter per Roof Curb.
