I’m guessing this is an ignition system of some sort, it fired off what sounded like burners. I don’t know why a modern ignition for a gas water heater would have to be so much bigger than a modern ignition for a gas furnace, but I’d like to know what this is.
-Kent
It is a high efficency gas WH the box is sealed and the combustion air comes from the bottom of the unit. It still needs the 18"'s and blocking.
Those lower covers easily lift right off by pulling upwards.
If you didn’t remove these covers, how’d you inspect the water heaters?
Its my understanding that the 18 inch height is not required if the unit has the sealed burner chamber. Since it may require having the owners manual to determine this I still mention it in the report.
Whats the manufacturer and model number? (Ya got that, along with the S/N, right … 
)
It’s not in a garage it’s in the mechanical room so no 18"
I didn’t know what it was so I didn’t start pulling it apart.
I know it’s a high efficiency water heater from the induced draft. My question is, what are those metal boxes over that access to the burners chamber?
They are protective covers. As I stated earlier, they’re easy to remove.
The lower cover just lifts up and towards you. The top cover is secured with two philips head screws. I remove these covers regularly.
Why two forty gallon W/H’s?
“High end home”…I’ve seen them with 2 heaters plus 1 near the master suite and another at the guest quarters. All of them were heating water beyond low or vacation settings and two people living in the home. We can’t be waiting for hot water.
Actually, I installed an extra one in parallel when I lived with a few women. Everyone working, on schedules, had to keep moving, in and out. Come to think about it, I added a extra bathroom too. 
Oh well, maybe it wasn’t because it was a “high end home”. 
That looks to me like a couple of water heaters with electronic / electric ignition systems . (no gas open pilot lights) Ga$ $avings
(Flamable Vapor Ignition Resistance ) water heaters which also have electronic ignition would have a orange wire coming from the burner chamber and sealed burner chambers ( NEVER… open the sealed chamber since you will be paying for new seals) Per MFG…$$$ 
This (guessing here) are not sealed burner chambers and most likely have to be considered like standard cat 1 natural draft units and have to be elevated 18" above the ground .
Looked at the web site for State Industries and found the installation manual. High-efficency Direct Vent Water Heater.
http://www.statewaterheaters.com/lit/media/im/res-gas/184333-001.pdf
These are housings. The upper housing protects what appears to be a quick disconnect switch, the lower protects a surface-mounted control box and the access hatch to the burner compartment, so David’s right, OK to remove.
Kent
Now you really didn’t think I was making this up, Did you?
IMO, its worth taking a close look at page 25 of that manual - might avoid a mistaken diagnosis of problems with the unit.
No David, I just wanted to know what was behind doors number 1 and 2.
Well come on down…!
-Kent
Door #1 contains a pressure switch that prevents ignition in the event that the induced vent blower is not working. No draft, no ignition.
Door #2 has the electronic controller/ignition control.