Best Of
Re: Heating an Old House: Gas Heat Options
It all depends on what you want to spend and how the existing work is done. If you extend the existing ductwork to the 1st floor the ac will never be even between the floors unless you zone it. You could add ac to the first floor. You could add a hydroair coil to the existing furnace and control the blower to heat the second floor off the boiler. You could add hydronic emitters to the second floor and add either mini split or ducted ac to the first floor with a separate system. There are lots of options.

Re: Minisplit sizing - 1920’s Victorian in Northeast
You aren't even close to having enough information yet. With no wall insulation, this house is not a great candidate for heat pumps. Spend the money on tightening up the envelope and insulating and they will save more in the long run.
Re: Maid-O-Mist Failure Rate ?
Today they say "made in USA" on the box. There was a time a couple years ago when they didn't say that and I don't know if they were made overseas but I would think if your stuff was made in USA you'd proudly state it (as they do today).
Re: Clogged steam mains
Or a serious lack of main vents?
For Chicagoland, get in touch with @The Steam Whisperer .
Real efficiency gain potential vs sales fantasy vs as installed efficiency.
With regard to burning things and efficiency gains, the days of lots of low hanging fruit are limited. Finding a natural draft iron block serving a radiant slab is more and more rare where I am. New stuff that will save a substantial chunk of energy is less and less likely to be true.
Many boiler swaps are high efficiency for high efficiency with barely a real improvement in 20+ years. The physics of extracting heat from combustion are not going to change, the materials aren't going to change much either. 97% seem a reasonable peak to assume it won't be bested by much. Bean counters are pushing engineers to reduce costs. You can sell reliability or durability or repair-ability or even safety but selling new equipment has superior efficiency is most of the time, around here, sales talk nonsense. I was putting in 90+ equipment way back when and that's what's being replaced now. ECM isn't all that new anymore and isn't a quantum leap in savings.
New is more of just a re-up and not a substantial improvement in most cases. Yes a skilled tech can fetishist-ize efficiency with design and tuning, if the customer wants to pay for that. Most don't. New is simply a heat exchanger that's not plugged up or doesn't leak or components that don't have a million cycles on them or don't have an existing design/ build error or aren't rebreathing. Those pushing new gas burners as more efficient, better, high tech are either buying their own BS or are small cons. I know there are always some small gains on the table in addition to efficiency but it's diminishing returns at some point.
How high efficiency equipment is installed and used can make it very mid. and there's little honesty about that pre-sale. Efficiency tales are a bit of a contractors figs leaf covering up max. profit seeking and squelching repair. It's ok, it's natural to seek max. profit. Just be honest about it. Covering it up with half truths is shady.

Re: New Century House with Two Pipe Steam - Questions
It depends how tight the system is. If it is relatively leak free it can draw a vacuum but that is the least of your current problems.
There should be those vent traps at the end of each main and they all need to work. There also needs to be a way for the returns to vent because that is how the radiators vent. If it isn't venting it may compress the air enough to allow some steam in to some of the radiators.

Re: Leaking new vents?
Yes your boiler is rated for 391sqft but that is to be compared directly to your standing radiation, not the radiators + piping. The boiler rating already accounts for the piping estimate. So you are almost 50% oversized with all your radiators open. In my opinion you would be better off with slowing some of the radiators down getting a little more length out of a cycle to give the house a chance to heat up before all the radiators are filled and you start cycling on pressure.
Re: undersink water heater for dishwasher?
I would probably go with Bosch. I've heard that Miele is good too but i'd need corroboration on that. I have a bosch that is about 25 years old. I've had to repair or replace the water vavle a couple times and had to install a beefier relay for the heater. Oh and i had to get a slavaged rack because the coating was pretty easily damaged. If I had more space/less stuff i'd probably get a hobart built kitchenaid.

Re: Leaking new vents?
So true, and I tried to word my post not to infer that your suggestion isn't a good one. I just wanted to mention that there are considerations that must be, eh, considered. When manufacturers market a boiler with different burner configurations they have done that considering for you and are confident that the option is worthy of their "good name".
Re: What I think
The dystopia we are in is Brazil. I don't seem to recall them finding a solution at the end.
