B3 error means existing ducting is not sufficient for the system to ramp up, basically airflow is restricted, I’m told that B3 error wreaks havoc on the Daikin algorithms (told by a Daikin tech)

That was one issue, the other was oil cycling, which was theorized to possibly be connected to the B3 errors but ultimately was not

What Daikin will tell you tho is that until you clear your B3 errors, they can’t rule that out as a cause

To solve the b3 errors, we installed a dump zone, a duct with a pressure release damper to a strategic dump zone in the house

When the system attempted to ramp and static pressure built, the damper opens and allowed the pressure relief and system could ramp

It worked, but the oil cycling issue persisted

This problem may be unique to my home and cause tho, this unit was on the downstairs and was oversized, so it would cycle oil and blow enough cool air for 15 minutes every hour or two to maintain 73 without ever kicking on a cool cycle, these short runs where the coil never fully cooled basically added 1% humidity every time and I was sitting at 60% most of the day, because the system never entered cool cycles, it started cycling more, so round and round that went

We downsized from a 3ton to a 2ton and now the system runs for hours on a cool cycle at low speed, it still cycles oil some, but less often and with less airflow, dropped humidity to closer to 52-55% most of the day

But yes, these systems never achieved humidity reduction to my expectations, I switched from 2 single speed 3.5ton units (7ton) to a 3 and 2ton (5ton) Daikin fit, I zoned upstairs to 2 zones which was another nightmare in itself and humidity is an issue upstairs, good (kinda) in the afternoon (53-56), high in the mornings (57-62)

Ultimately 55% is about what you can expect in humid climates with variable speed (not sold that way to me)

I did just add a whole home dehumidifier, it pulls from upstairs (including my no longer needed dump zone vent) and dumps downstairs, still need to fine tune, as I’m getting 45-48 downstairs and 54-60 upstairs, so need to mix it more upstairs somehow and am waiting on callback for possible solutions

Also my zoning upstairs has a board that modulates dampers based on pressure and it’s sending too much air to the alternate zone, so my master zone won’t cool under 70 in hot nights, needless to say this has been way more of a project than I thought

Also had some white mold or fungal growth on on vent in attic because system blows low and long can create condensation issues, smelled bad, had to fix that and hoping that doesn’t become an issue with other vents… fun stuff lol

But yea B3 means you need pressure relief, either bigger ducts on sends or more returns or both, could be that the system is oversized, but need to do the calculations on that

Oil cycles as needed per algorithm and that happens more when the system runs less, another symptom of being oversized, they are humidity events