I've read somewhere that the outdoor AC unit needs to be leveled. My outdoor unit is a bit slanted due to the floor not being completely flat (pic below). However, I don't see any obvious structural issues. Is this something I need to correct? Perhaps by sticking a small piece of wood on one side?
Take a look at the installation guide for this Lennox condenser unit. It actually specifically points out that the slab should either be leveled or maintain a slope of 2 degrees.
Page 8 mentions, "PLACING UNIT ON SLAB When installing unit at grade level, the top of the slab should be high enough above grade so that water from higher ground will not collect around the unit. The slab should have a slope tolerance as described in figure 5, detail B"
https://resources.lennox.com/FileUploads/31c2ac16-919c-41a1-ad0c-515f8351eccbLennox_14ACX_IOM.pdf
It should be as level as possible. The previous posts make good mention of rubber mat 6x6" squares and careful approach to only tip the unit as little as possible not to kink any lines. If you don't hire a professional and aren't confident by yourself to address the issue, having a second person watch the lines while you tip can save much potential trouble. Previous information from these posts also generate ambiguity over the importance of having the unit level in regards to the compressor. Leveling the unit will terminate any ambiguity. An additional concern not previously adressed is the compressor and/or fan bearings. An off level unit will put additional unintended mechanical stress/strain on these rotating components long-term. Therefore for best performance and longevity of your unit, level it and take special precautions in the process.
Refrigerant needs to flow through the coils evenly without too much interference from the slope of the unit. A level concrete slab with rubber pads between the unit and the concrete is what the manufacturers recommend. "Mostly level" is probably okay for a residential unit. Get a half-inch thick outdoor rubber mat and cut it into 6"x6" squares. Put single pieces on the high side and stack several pieces under the low side to bring the unit closer to level. Be careful not to kink or damage the refrigerant piping to the unit when you do that. If you damage the lines when you raise the unit to insert the pads, you will wish you had left it alone.
Outside A/C compressors are typically supported on a concrete pad, concrete blocks, or a vinyl pad such as the one shown in the photo at page top. The air conditioner compressor support pad should be level and secure against movement.
Compressors which are badly out of level may fail to function properly and need adjustment. Tipping and moving compressors can also cause can cause leaks in refrigerant lines, leading to costly air conditioning service calls to evacuate and recharge the system after repairing the refrigerant leak.
Do not try to move your A/C compressor yourself as you might cause a refrigerant leak or may otherwise damage the equipment.
For slightly-tipped air conditioning compressors we generally leave them alone but we add support as needed to avoid further movement.
Check the installation specs for your unit to see if it is supposed to be level (most likely) or slightly pitched. There are some ACs (large Rheem units for example) that are supposed to be installed with a slight pitch towards the condensate drain. If you aren't having any trouble then leave it alone. If you are having trouble, then call a pro sooner than later. Routine maintenance on an AC is much cheaper than having to replace one.
For a professional appearance it should not appear to be set without a thought to anything but function as if a war time situation where getting online asap is the priority. The thought that an AC unit must be absolutely level or its wont work or work well is based on absorption type systems RV's used in the old days that used ammonia and a flame rather than a compressor. Technically speaking, no it matters not if its level or even close to it, it can be at a slant but will look weird.
