Is this 2 systems? 4 systems? 9 systems?
The foreground exterior condenser matches the two interior furnace/air handlers sharing one evaporator.
The three exterior condensers match the three interior furnace/air handlers sharing one evaporator.
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Twinning / Tripling / etc…
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I know it’s not your question, but I can’t help but wonder if there are not three individual evaporators in the plenum. Were you able to determine if there was in fact just one shared evaporator? I’m not familiar with these “sistered” systems.
You are correct. The 1st group has just one oversized evaporator with one refrigerant line.
In the second group, there are three refrigerant lines, thus three coils. However, the three evaporatos are inside one cabinet with one model/serial number.
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As far as the furnaces/air handlers themselves, I presume they all had individual SN’s? If so, I would count them as three separate units, regardless of if their controls were tied together and synchronized.
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Yes, individual serial numbers, which I will list in the report with individual ages and conditions.
The SoP I use for commercial systems requires describing the system first, then narrating the rest of the issues, etc. I will share my descriptive narrative with you in a second.
It was supposed to be a simple old bank. Less than 7K SF.
Here are the remnants of an old hydronic fan coil unit. There is a defunct boiler downstairs. They just kept modifying the existing. The electrical has a similar history.
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wow, thats a lot going on…
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Out of curiosity, what type of structure is this system being used on? Residential or commercial office space?
1975 commercial bank converted to an office call center.
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Thanks! Not that I can answer your question, but I can get a visual now on what you’re looking at. 
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I’m guessing there were 4 zones?
How many controllers were there?
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I think I have it. Feedback is welcome from the wrecking crew 
Heating and cooling are provided by three groupings of split systems:
Group One: One exterior condensing unit connected to two “twinned” natural gas furnace/air handlers, both utilizing a single shared evaporator.
Group Two: Three exterior condensing units connected to three “tripled” natural gas furnace/air handlers, all sharing one evaporator system.
Group Three: One exterior heat pump connected to two interior electric ductless air handlers.
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The twins were connected to one t-stat. The trips connected to another and the ductless had their little remote controls. The staff was fairly miserable. I saw one portable AC and multiple personal heaters and fans at each desk. Plus, they complained when to me when they could without being overheard.
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Probably would have been cheaper and in the long run a better option to keep the boiler system and install central air above. 
Sounds as though the system wasn’t performing properly, adequately, or both.
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Thinking realistically, an air handler is not what one considers a direct heat source so the evaporator would be the main source of Heat, Ventilation & Air Conditioning.
With that being said, I would consider this a combination commercial HVAC system for a report and list the equipment serial and model numbers. But that is just me.
I choose to use the term air handler appropriately. I added the natural gas furnace to the description to clarify and help the end user.
Here is what Goodman has to say about the terminology.
Parts of an Air Handler
Your air handler assists in regulating the circulation of indoor air and the temperature of the air in your home that you have set on your thermostat or control system. Your air handler consists of an evaporator coil, blower motor, air filter and the electrical and electronic components required to deliver enhanced levels of indoor comfort.
What is an Air Handler?
See, I posted my source
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I would list that as 9 systems. A bit more elaborate then anything I’ve had to deal with.
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Gees Brian, With all I’ve learned on this question I think it should count towards education credit. Great subject and Question!
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This property had a lot of those extra oh wow’s. Initially looking at it, thought it was going to be fairly uncomplicated. It had a little of everything. These smaller commercial properties we rarely see boilers (heating or for water) and even less that are operational. This boiler was not operational.
Unfortunately, we see this type set up often for commercial here in the south. I personally do not think pairing split systems that share ductwork is very efficient.
This building’s HVAC design was a hot mess.
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Since there’s five air handlers total, wouldn’t that be five systems?
How do you define a system?
If you are looking for a way to word it in the report, can’t you just say it broadly that the property had split systems in which the cabinets housing the compressor, cooling fan and condensing coils that were located physically apart from the air handlers with evaporator coils?