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Adding Radiation- Wonder if Piping Is Adequate

PGB1 Member Posts: 81
Hello All!
In a bathroom, we have 4 feet of 1" copper baseboard with steel fins. It is in the cast iron bathtub's apron.
I'd like to add a 600mm x 600 mm flat panel radiator to the room. The chart for the radiator shows 3,673 btu/hr at 160-F (GPM not specified).

The question I have is if the existing 1/2" copper tubing is an OK size to run both units in series.

This zone is piped with 3/4" copper and each radiation unit is fed with a monoflow tee and 1/2" to each unit. There are four monoflows in the zone. One is before the bathroom for a toe space kitchen heater, then the bathroom and there are 2 more monoflows downstream, feeding copper fin tube radiation.

The fin tube in the apron will come first in the room's piping. Arriving water is usually between 158 and 162-F. The fin tube return will feed the new radiator. The panel radiator's return will go back to the 3/4" loop.

The pump is a Taco 007. The pump's rated GPM is 23, but I don't know the actual GPM after the 3/4 x 3/4 x 1/2" monoflow to the bathroom.
I can reverse and feed the panel radiator first, but that will add ca. 11 feet of pipe and 4 more elbows, with the resultant restriction.)

Before the fin tube, the room used to have an upright radiator that was 3 column, 3 section. (32" high, 17" wide, 9-1/2" deep). It more than adequately heated the room on the coldest of days, even with the balancing cock partly closed.

I don't know if this is enough information to help decide if the 1/2" copper tubing will supply enough BTU/Hr for the two radiation units. What do you all think?

Plan B: Another 3/4 x 3/4 x 1/2 monoflow off the main loop, adding about 18 feet of piping and 8 more elbows.

Thanks For Helping!


    EBEBRATT-Ed Member Posts: 15,835
    edited February 2023
    Yes 1/2" will handle 1.5 gpm @ 10,000 btu/gpm so it's good for 15,000 btu but if your running it off a monoflow you have unknown flow.

    But since the same pipe fed the old rad and it heated the bathroom you should be fine
  • PGB1
    PGB1 Member Posts: 81
    edited February 2023
    Thank You Very Much Ebebratt-Ed for the very helpful information. (Plus the common sense you mentioned that I didn't think of: The same pipe fed the old radiator & heated well).

    Panel radiators provide quite a bit of resistance to flow, starting with the thermostatic valve's small opening. With that in mind, I'll pipe to the unit with the fewest elbows as possible and use pairs of 45's instead of 90's. I'd imagine keeping PEX out of the loop is a good idea, due to the restrictions at the fittings. But, if I remember correctly, too much flow to a panel radiator is very loud.

    Despite the too many details I put in my question post, I forgot to mention that all of the mono-flow tees on this zone are backwards- on the supply side of each radiation unit. We lose the venturi effect that counteracts some of the resistance. (They're scoop tees, not the cone type.)

    If the flow isn't adequate, I can always swap tees for this loop, putting the mono-flow on the return. (This zone was here when I bought the house. I'd imagine the dead men who designed the system calculated flow with the tee locations in mind.)

    Thanks Again For Helping Ebebratt-Ed , I very much appreciate it.