Lack of flexibility can be another drawback of combination units. “If you are working on an expansive jobsite and you have a guy on one end who needs a welder and another guy 300 ft. away who needs a compressor, you are suddenly limited and find yourself in a situation where one guy is waiting on the other,” says Leisner.

“The combination machines are also typically larger than the standalone units, so moving around a jobsite, if not truck mounted, can be slightly more difficult,” Leisner acknowledges. “We’ve found ways to engineer these machines so that they are not much bigger than a welder/generator.” This ensures performance is not compromised due to size limitations of the “box.”

“Having said that, most workers on different ends of a jobsite will still require the functionality of multiple pieces of equipment,” he notes. “Having all functionality in one compact unit that is relatively easy to move may provide an advantage. In this case, it may also make sense to have multiple combination units.”

Assess Output requirements

“When IMT developed the CAS35WG, the welding, generator and air pressure capabilities were all based on customer input,” says Worman. “Customers told us that a 250-amp welder, 5,000-watt generator and 35-cfm compressor would be ideal to meet their wide variety of application needs.”

Even so, such systems may not offer all of the capabilities you require. “If you have serious requirements for air or welding... individual units are better options,” says Gilbert. “If you regularly use a lot of compressed air, for example, an underhood compressor is going to give you more air and it is one less engine to maintain.

“Having right-sized equipment can save a lot of waiting time and avoid frustration,” he adds. “It has to be realized that these units are typically large and heavy, so you are giving up payload and space to carry around all of these options, whether you use them or not. If you are never or rarely going to use some of the functions, you are going to be spending money to drive those items whether they are used or not.”

In this case, it can make more sense to go with an individual unit. “If you are going to be using a lot of air tools, it is better to buy a system specifically designed to be a high-output air compressor,” says Gilbert.

If multiple functions are regularly required, however, a combination unit should be seriously considered. “If your equipment is truck mounted and you will use all three functions (or four functions in the case of the Trailblazer 302 Air Pak with battery charger/jump starter), it’s a no-brainer — go with the combination machine,” says Leisner. “You will save on weight, space and fuel. Especially if you work in MRO, you can’t lose. There are also industries such as structural steel erection where all three functions are used consistently. Two or three separate machines in these applications are not efficient.

“If you find yourself in a job where you only need air a small percentage of the time, then a standard welder, generator or combo welder/generator will work for you,” says Leisner. “Also, if you will have workers needing different functions on opposite sides of a jobsite, separate units (or multiple combo units, depending upon the work) may make more sense.”

“When weighing whether to purchase a separate welder, generator and compressor or a combination unit, consider the benefits realized when you avoid adding an engine-driven welder/generator to the floor of the mechanics truck body,” Worman advises. “A combination unit can be mounted to the top of a side pack, freeing up the load bed and increasing payload while eliminating maintenance costs associated with a separate drive engine.”