Should I be worried about what I am observing and hearing (radiant heat install in process)?

Kaos

Heat load divided by room sqft.

Most manufacturers show data for standard house setup. That is 3/4" subfloor with either tile or hardwood over it. Even if your subfloor is 7/8" planks, it won't change the heat transfer enough to worry about. So if your flooring close enough to standard, you don't need to worry about R value.

Most manufacturers also show how much insulation they want under the emitters to meet required btu output.

You can use the data from tables the manufacturer provides for loop spacing and number of emitters. I would aim for 140F water at design time which should get you good efficiency out of a condensing boiler.

It never hurts to add more emitters than required, this will only bring down the water temperature required which again helps with efficiency. It doesn't change how hot the floor will feel so not much drawback except a bit more material cost.

RenovationWontEnd

thank you. i will take a look at the manufacturer tables.

since I had all the numbers handy, I also did a calculation using the spreadsheet @hot_rod pointed me to. attaching below…i assume i would ignore the altitude adjustment. i did not add the roof details in this calculation.

RenovationWontEnd

I made some changes to measures I added to my heat loss; didn’t change much. i wanted to see room level heat loss so opted to update the online calculator. i also added the zones and floor r values in a spreadsheet (using this https://www.heatizon.com/installation-manuals/r-values-building-flooring-subfloors)

I used the MrPex tubing Heat Output charts for the HTP and in slab installations as a reference. I used the BTU/SF I calculated to approximate the SWT based on the floor r value (also added to the spreadsheet).

The boiler installed is a ALTA 200 combi boiler; the ratings and specifications are here:

The things I am thinking through now (and would be grateful for guidance) are:
1)How would I choose between heat transfer plates vs ultrafin for 2nd floor (if I could)? What should my considerations be? Some of my current considerations (correctly or incorrectly) are:

A)Is it desirable to have less difference in swt in the slab and in joist across zones? Or does this not matter.

B)Some joist spaces are small (sistered 2x6 in some areas, 2x8s in others) would this make it hard to get right level of insulation for effectiveness of ultrafin?
C)Some pex touching electrical wire, cat6, cat5 wire and combi boiler vent (thinking high swt could be a problem)
D)Some pex touching nails protruding through subfloor (that will need to be addressed, regardless of which direction we go); some pex looks too close to toilet plumbing (would wax ring melt?!)

2)Does it seem reasonable that contractor choose this combi boiler given our heat loss? We have two full kitchens (3 sinks total and 2 dishwashers), 1 washing machine, and two bathrooms with showers (no tubs). The thing I’m noticing is the heating input is 20-150 for the boiler, though most of our zones are under 20 BTUH.

hot_rod

The smaller boiler would have been adequate, a lower turndown would be helpful also. There are probably control options to derate the boiler firing if you notice short cycling, that is the boiler running less than 10 minutes, often.

But the larger boiler was probably chosen based on your hot water needs, it is a Combi correct? The smaller one would give you a bit over 2 gpm of hot water. Probably 3 or more with the model you have. Is the hot water production adequate for your needs? I have gotten by just fine with 120 combis.

The UltraFin will be an easier install, and would cost you a higher operating temperature. You may get enough output from it to still run the boiler in condensing mode. Check the Ultra Fin output charts.

Your load loads in that mild climate give you options to have a workable system.

I'd use a foam type, radiant friendly closet bowl seal to be safe. Wires are not an issue. nails may be if the tube can rub on them.

Kaos

With a design load of about 25k, a unit with a min fire of 20k is not the best fit. Except for the coldest of days if would be cycling.

With your low load, something like this might be a better option (I think there is some other similar units out there):

https://www.laars.com/products/product/combi-heat

You can also use a regular combi rated power vented water tank with a plate heat exchanger or a Taco xblock for your space heat. These run in the mid 80% range efficiency when used for space heat and even a standard burner will easy supply both your hot water and space heat.

A combi modcon only makes sense if you are very tight on space.

If you must have a boiler, I would go for one of the smaller units that can modulate down to 8000BTU.