Aluminum Hydronic Radiators 5000 sqft. House

tbeach

I have a 5000+ sqft. house in mid-renovation state that has no existing heating system. It previously had a steam cast iron system but all of the hardware was removed. I would like to heat the home with hydronic radiators and have seen some nice-looking aluminum wall-mounted units that seem to be more of a European design and method. I have not found a local supply store (N. Indiana) that carries or has experience with these types of radiators. Not a huge problem since I can order everything, but I do have some questions with installation and system design. I will be heating around 3500 ft with the hot water and this includes a portion of the basement floor which already has in-floor heat tubing run throughout it. I was thinking I could do this as a two-pipe system in four zones.

Zone 1 - Main floor living room, dining, kitchen, etc extra areas (1400-1500 ft)
Zone 2 - Second floor three bedrooms and three bathrooms (750 ft)
Zone 3 - Second Floor master suite area (650-700 ft)
Zone 4 - Basement in-floor heat (500 ft, but low-demand area)
side note: I will also likely be using boiler water to heat a stainless steel domestic hot water tank.

One of my questions is the size of pex I need to run as my main heat supply lines. I was thinking 3/4", but can probably run 1" if necessary. My second question is how many units I can have on each zone. I'm planning on 45-50 BTU/ft.. I also will have gas fireplaces in the living and formal dining rooms to supplement, and the formal dining room will be a closed off space that can have a TRV set lower than the rest of the main floor as it will be used less frequently. My third question is if I need to watch what components I install with an aluminum radiator system. I know that cast iron and aluminum radiators cannot be mixed with the same water, but I would like to run my zone board and everything in the boiler room in copper and I didn't know if that's an issue on an aluminum system.

hot_rod

Why aluminum? Would steel work, a lot more choices.

So the radiators need to be sized to the heat load of the rooms they serve. Once you know the radiator size, then you can determine how many can go on one loop, and what size tube to feed to them.

Steel panel radiators typically have 1/2" connections, that dictates the BTU output to some extent. Maybe 3 panel rads on a 1/2" loop.

Some of the early aluminum baseboards had problems with the brass to aluminum connections corroding.

With a multi metal system I feel a good water fill, and a squirt of multi metal conditioner will protect all the metals. It needs to be an aluminum specific conditioner.

Runtal is a popular brand of baseboard and panel rads. I think you can order direct from them in MA.