So can we install it ourselves? TL:DR: yes, we probably can! 
Ordered the one from Crappy Tire; should be pickupable Saturday. I await email. Too good a deal to pass up; if we can’t get it done, either return or ask Boyle to do or Martin?
This sort of humidifier might work on side of furnace; must confirm. link to install manual below
seems to me we should be able to install, as long as we can fit it.; goes on warm side output, but not on furnace itself. see pics below where I think there is already a hole pre-cut for this sort of thing.
electrical is no problem; might take this opportunity to run a proper socket in the laundry room? regardless, can use the furnace switched one. Remember to do other small electrical jobs while power is off.
control: will want the controller in the upstairs, near the thermostat. will need to run wire (AND PULL STRING) from landry room up to themostate. should slready6 be a cable in this route.
Canadian Tire $179 – seems same as the HD one, even cheaper!
This should mount on the warm air side of the furnance; conveniently, there is a pre-cut hole in this duct; i had to cover it with tape & strap ’cause it would leak air. this covers a hole ~8″x8″ (200mm x 200mm), which might be the size of the hole we need to cut. honeywell manual doesn’t say size. NO! see pics below.
2023-03-04 –
we need to run a wire from the furnace to the thermostat in the dining room. also need to mount a new humidistat next to the thermostat.
katherine: can you please remove the thermostat from the wall in the dining room. don’t disconnect the wires. it should have a bit of extra wire.
joan: we need to pull a blue network cable to the hole where the thermostat mounts. if we don’t have a fish, stiff wire should work. worst case, use existing furnace wire to pull a string back to furnace, then pull old+new.
katherine: mount new humidistat next to thermostat in dining room.???:
???: run water from bar sink filter to humidifier on furnace; we have lots of 1/4″ tubing.
???: check how to connect at bar filter end, with shut off?
???:
2023-03-04 – cut new hole or enlarge existing access hole?
need the following tools from the garage:
2023-03-04 – connecting water supply to bar sink filter; here are some pics; we need to T into one of the ougoing lines; there should be Y connectors in a bag with lots of other 1/4″ tubing & such in garage; bring all in.
2023-03-04 – temporarily patched up the AC; will replace this cover with something better later. maybe we have a pc of pc case or other alimnum to make a nice panel. or what dows 12″x12″ panel cover cost?
2023-03-05 – installed! and works!
Sadly, I spoke too soon. Looks like the bar sink water filter can’t supply enough water.
So we’ll temporarily use the cheap saddle clamp for testing; once it’s working correctly we’ll replace the saddle clamp before it inevitably fails.
Katherine: please set the furnace fan back to “Automagic”:
The dreaded, garunteed to fail in !10 years, saddle clamp. Sometimes called a vampire tap. 
The proper device, to be used at a later date.
2023-03-06 – Katherine sez water was shutoff to bar sink filter; I should have checked! so likely filter ran out of water, might be able to supply. test again. ~3:30pm, set furnace fan to “Always on” and humidifier set to 60%
:
OK, let us test again. turn the fan back to “Always on” now.
Whoops, the main water supply for the filtration system at the bar was still turned off! I turned it back on and turned the thermostat fan to ‘auto’ so the water reserve could fill back up. If we want to try again, I can turn the fan back onto ‘on’ tonight
OK, let us test again. turn the fan back to “Always on” now.
This is reply to youe comment, not a reply to my post. STOOPID COMPUTER!
OK, let us test again. turn the fan back to “Always on” now.
This is reply to you comment, not a reply to my post. STOOPID COMPUTER!