Seems to me that the longer a filter goes unchanged, the better it filters. What is the depth of the filter in your Berkeley photo?
I don't know the particulars about the filter in the Berkeley photo (not my photo, not my project.)
While it's true that the dirtier the filter, the better it filters (particulates above some size), the dirtier it gets the greater the static pressure that it imposes on the system, and the lower the total air flow in the system. Dirty filters are a common reason for air conditioner evaporator coil icing, low efficiency, and lower cooling capacity in cooling systems. Also, filters that are unable to filter out things as tiny as mold spores can grow mold and mildew in the material that it is clogged with, spreading those spores around the house.
As I stated last month, the current system does run on R22. Seems like somebody would have invented a good cleaning system by now. When R410A is outlawed, will the lineset need to be changed again?
I depends on what replaces the R410A. Lubricants compatible with R410A are compatible with R32 (which has only about 1/3t the 100 year global warming potential of R410A, and one of the likely contenders), given that R410A is simply a 50/50 mix of R32 + R125. Originally R32 was the logical higher efficiency choice for replacing R22, but part of the industry balked at the (albeit low) flammability of R32. Mixing it with R125 retained most of the properties as a refrigerant, but also suppresses the flammability.
Do you happen to know why a lineset would audibly vibrate in heating mode but not cooling mode?
Yes.
I suppose you want to know too, eh? Very well...
In heating mode the system is sending hot liquids directly into the indoor coil via the usually fatter "suction line" in a cooling only application and the flow is metered
after the coil, sending the post-metering gas down the usually skinnier "liquid line" in a cooling only application. The mass and velocity of what is in each line changes depending on which mode it's operating in, so it's not surprising that it might vibrate more or differently with the flow in one direction than when flowing in the other.
heating mode
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cooling mode
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The BBNW tool calls for minimum possible (3 inch) ducts to 3 out of 5 rooms. That seems awfully small to me, appropriate only for bathrooms. Does it seem small to you?
That would be on the small side for a low-static air handler system, but common enough in high-static high velocity systems with moderate to low room loads. Minimum is minimum, not optimum. It's generally good practice to keep duct velocities <<400 fpm wherever/whenever possible to keep the static pressures and noise at bay. Low duct velocity increases the duct size. While there is such a thing as
too low a duct velocity, the duct would have to be pretty ridiculously oversized to get there.
More here (from the folks in Decatur, GA).
The duct design part of the BBNW tool isn't the greatest tool for newbies, but people who have run their fair share of Manual-D by the book can make it useful.
The BBNW tool says that the bedroom over the garage has a heating load of 8,345 btuh and a cooling load of 4,313 btuh. Do you still think it's a bad idea to give it its own individual 1/2 ton Mitsubishi minisplit? If so, suppose that room's occupant refuses to dress appropriately for the seasons and insists on wearing summer clothes in winter and winter clothes in summer. Could they be satisfied by embiggening the duct diameter to that bedroom?
With a design heating load of 8345 BTU/hr @ +25F an -
FH06 or -
FS06 is a decent choice due to it's very low (but still COP 4+ efficiency) 1600 BTU/hr minimum modulation level @ +47F, with plenty of spare capacity at 25F.
Bonus rooms over unconditioned garages are often hard to make work well when zoned with the rest of the house, and as long as there is sufficient load to make it run efficiently (=TRUE, in this case) a standalone single zone minisplit works. However, and FS06 married to a MXZ multi-split in this situation is usually a recipe for comfort &/or efficiency failure unless all other zones cassettes/heads are similarly appropriately sized relative to their loads (=FALSE, in the "ductless head for every room" approach.)
Back on the filters & static pressure issues,
this guy is a bit hard to listen to (unless you are accustomed to sipping from a firehose- feel free to pause, back up, and grab an espresso before restarting), but even a MERV 8 x 1" filter can bring a low static system to it's knees if allowed to get dirty. He did test both a 2" & 4" filter along with the many 1" filters, as well as an unrated 1" filter that would block particles bigger than a cat (but not necessarily cat hair, and
definitely not cat
dander.)