HVAC split systems: Commercial VS Residential? Important differences?

Other than the size of the components and the amounts of fluids they’re capable of handling, they seem pretty much the same to me, but I don’t yet know a lot about commercial.
Are there crucial differences that those learning need to know about? The system component types? General installation?

Ken, I do approx. 30 commercial inspections a year but I am not a licensed HVAC contractor. In my experience, they are the same. Splits are used when package units do not align with the building use or size. Such as splits are typically used with smaller buildings or multi-tenant buildings. The largest split I have seen is a 10 ton heat-pump. Thermostats, sensors, zone control and power management varies. Often the air handlers are suspended above ceiling tiles which makes things so much more fun.

Multi splits are something you need to be aware of. The largest systems today can get up to 36 tons.

1 Like

Wow, I am looking forward to coming across one of those. I have seen some tandem units but even those have not reached that size in my years.

This is a typical setup, from a Manhattan hotel.

1 Like

That is a cool set-up.

Yea, there are economizers; You need to understand enthalpy controls.

There are low ambient controllers;
Fan controllers.
Hot gas by-pass.
Variable speed controllers (compressor and fans).
Compressor uploaders (reduce capacity when not needed).
Condenser fan controllers (not all fans run all the time).
Compressor controllers (not all compressors run at the same time).
Commercial A/C needs to operate summer and winter.

There are oil pumps on large commercial compressors (not sumps as in residential).

There are smoke detectors inside commercial units.

Do you understand three-phase electrical when it comes to rotating equipment?

Thermostats and zone control equipment are not the same.

Now the little RTU’s that most of you see are more like a residential unit are closer to residential, but those are in fact just big residential units if they don’t have any of this extra stuff. Just because the building is commercial, does not make it a commercial unit…


Kenton …

We commonly see things like a strip shopping center with 20-30 split systems OR a 75,000-100,000sf bldg with 40-70 ton RTU’s, or Chillers, etc. The strip center splits are like a household unit … The others NO


I think I’ve covered RTUs (package and year-round units)and cooling towers well enough.

I wasn’t able to figure out a whole lot about chillers, and it seems that unless they have a background in them, many of those doing commercial inspections leave chiller inspection to an HVAC guy. I left it at basic description, look for leaks, excessive vibration, excessively hot/cool shell, and check the log for anomalies.
I don’t know what narratives to write about the things David mentioned, they’re just beyond me.
Most of the books out there are for contractors and don’t have much on inspection, and the same for what I find online.

The same with multi-splits.

I guess when the air handlers are hung above suspended ceilings the mounts ought to be checked, along with the typical things like corrosion and leaks, squeaks, excessive noise & vibration, belts, pulleys, damage, ductwork, etc.

1 Like

I use ASTM E2018 -15 as my standards of practice. Everything @dandersen stated is out there. But, a lot of that is beyond baseline scope. Sometimes I will bring in an HVAC expert, Elevator Expert, Fire Sprinkler etc. On an as needed basis.

What you just described for a typical PCA would work well in my opinion for split systems.

1 Like

For me in my narratives: 1st I describe what’s there, age and apparent condition. Then was it operational. Then any visual deficiencies with recommendations.

There so many types of systems, the possibilities are endless. Your original question was about splits. I find the problems are very similar to residential.

1 Like

Your question was:

Are there crucial differences that those learning need to know about? The system component types? General installation?

I did not know why you were asking but these are the differences. The Commercial Inspector does not need to know how to evaluate these things, but they must know what they are and what they do. They are in charge of the building assessment and must know about these things so you know what to ask for and provide some facts to the HVAC.

ASTM standards are a whole lot easier to comply with than a Home Inspection that is controlled by Realtors and State Gov’s.

Kenton- basically if the Inspector does not know what they are looking at and know what stuff does they should be working with the Tradesman that does. It would be a big help to know about what I listed to retain your integrity as a Commercial Building Inspector.

On my first job interview in HVAC, I was asked by the boss what turns on the fans on a cooling tower. I answered “Temperature”. After calling me a dumb-ass he informed me it was “Refrigerant Head Pressure”. Well, what the hell causes an increase in head pressure? Heat dumb-ass…

Commercial clients are not the same as residential. They know more about the buildings and equipment than any Home Inspector. You need to be able to talk the talk if you want to walk the walk. If anyone is not aware of the things on my list, it would behoove you to brush up on or at least know what they do.

Economizers; are the number one defect in HVAC Inspections. You will find cut wires and 2x4’s stuck in the damper to keep it shut. Someone complains they are cold in winter or hot in summer and facility maintenance goes up and finds the unit sucking in outdoor air, and guess what they do because they know not what they do? This is also the main reason schools fail Radon testing.

Kenton- you are free to call me about this stuff if you need. I just sit around the office evaluating IR Drone scans someone else takes these days…


David, I’m working on a commercial version of the InterNACHI Narrative Library, so I’m compiling narratives covering defects/deficiencies commonly found during commercial/light industrial inspections, not preparing to actually perform commercial inspections.

I have a pretty good feeling for the differences between home and commercial inspections, and I’m going through the entire library adjusting the language for just that reason.

A number of inspectors have been generous in giving me copies of their commercial reports, and those reports have things in common, but they also differ in some ways, and even those that claim to comply with ASTM 2018-15 don’t really, mostly because they generally stick to identifying the problems.

I’m trying to complete the Commercial HVAC section, but have no background in it, so identifying and writing narratives for deficiencies commonly found with those systems has been challenging. I thought I had done a pretty good section on economizers, but cut wires and 2x4s… you don’t find those problems doing online research, so it’s my lack of personal experience that limits what I produce.

I’ve worked hard at it for a long time and will have it vetted before I release it. I’d love to spend a little time on the phone with you, you’re one of the most highly qualified inspectors I know. Maybe early next week?

I’ll say! I’m just trying to create a collection of narratives most commonly encountered during commercial/light industrial inspections.

1 Like

@kshepard I agree with Dan on the splits.

That would be fine except for Monday. I’m tied up all day working on the Stegeman Coliseum project.