Part II: Importance of Maintenance and Upkeep for Maintaining Optimum Passive House Temperature Performance and Minimal Electricity Consumption

Maintaining Peak Mini-Split Heating and Cooling Efficiency
Having made some substantial improvements to our ventilation system we looked to our heating system.  I had suspected that our Fujitsu 9RLS2 ductless mini-splits were not performing as they should and had initially been under the impression that there may have been something going on with our outside units, but instead what I found was something vastly more simple that was to blame.

Just like I had been remiss with my upkeep of the ERVs, so it was with the mini splits.  Opening the covers up, I was shocked to find that the filters were completely "clogged" with dust build up.  I knew these things acted like vacuum cleaners for the air, but even I was floored when I saw how much these systems collected.

Dirt Filters Kill Mini-Split Heating and Cooling Performance
It was no wonder then why these units were performing so poorly, both with their heat output and with their air flow.  Here I was believing that I would need additional supplemental heat either by adding another mini-split (costly), an ERV post heating system (somewhat costly), or a number of space heaters (inexpensive) when all I really needed to do was to do some simply housecleaning maintenance of my minis!  I felt like an idiot that I didn't think to look at this possibility earlier.

One dirty filter!
Filter cleaning is very simple.  Once the replacement filters were put back in them supply temperatures returned to 120-130F and flow rates were way up.  Within a couple of hours the temperatures of the house rose 3-4 degrees.

Vacuuming the Condenser Unit with the Filters Removed
Here we were going through one of the coldest winters in recent memory and we weren't even bringing our A-game and our comfort and our wallet were paying the price.  No longer were the minis cycling frequently nor consuming 1500-2000 watts for extended periods of time without giving us much in return.

Big power consumption, little heat output!
Beyond the cleaning of filters, I noticed the condensers also appeared pretty gunky.  When these units were originally installed the home was still going through its finishing construction.  While the dry wall had been up, painting and sanding was under way and our on-site custom built stair case and railing system had been underway.  The amount of saw dust that was generated was staggering and even with the mini's filters in place plenty got past them.

I decided to disassemble wall units and give them a thorough cleaning.  I found a small toothbrush was every effective at cleaning the units along with spraying a blend of Clorox and water.  Fujitsu told me that it was not uncommon for the blow unit to get a build up of gunk, but I was unsuccessful at getting to this component.  I will leave that to my HVAC contractor.  Perhaps leaving that to an annual checkup.

Having completed my cleaning, I can say the units appear to be running much more efficiently and effectively.  They may even be operating at a level where I actually do not need any supplemental heat at all, even with temperatures below our design thresholds.

Both of these experiences have taught me the importance of system upkeep.  Passive houses certainly can have less complex mechanical systems in place that need servicing, but the ones that are there clearly require constant attention to ensure they are operating at peak efficiencies.  Having a house full of pets certainly adds to the dust factor and while the air is being "scrubbed" by the MHVR and the mini-splits, there is an increased stress on the filtering systems as a consequence.