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Befuddled by Big Baseboard

Hap_Hazzard Member Posts: 2,849
I have an eight-foot fin-tube baseboard unit in a 10'x12' room. It gives off a decent amount of heat, so I never paid much attention to it, but I've been gathering information about the size, type and venting of all my radiators so I can estimate the total EDR and balance the venting, and basically just understand the system better. When I got around to calculating the EDR of this baseboard, I was in for a surprise.

According to this article <a href="http://www.heatinghelp.com/article/322/Steam-Radiators/162/Fin-tube-Radiation-for-Steam-Heating">http://www.heatinghelp.com/article/322/Steam-Radiators/162/Fin-tube-Radiation-for-Steam-Heating</a>, a 2-inch fin-tube baseboard "is rated at 5.7 sq. ft. EDR per foot." My baseboard has two 2-inch elements with 91" of four-inch fins, for an EDR of 86 sq. ft. This surprised me because it not only makes this baseboard ridiculously oversized for the room it's in, it's also 17% larger than the next biggest radiator, a 24-section 6-tube, 25" thin-tube radiator in the living room. It also makes it about 20% of my total EDR.

Probably the only reason this baseboard doesn't make the room unbearably hot is that the supply runout is one-inch copper. Surprisingly there's no water hammer when the condensate tries to run back down that one-inch runout, but it has a slow vent and about 650 cubic inches of air to push out, so it never gets close to filling.

So what I have is basically an oversized, underutilized baseboard. I was thinking of removing one of the tubes and possibly installing it elsewhere, but then I got this crazy idea. One of the shortcomings of fin-tube baseboard is that they aren't as massive as a cast iron radiator, so they don't stay hot as long after the boiler shuts off. Since the rest of the house is heated by radiators, the thermostat doesn't cycle until they cool off, and by then the baseboard is stone cold. But I could use the second tube of this baseboard as a heat reservoir by filling it with deoxygenated boiler water and capping it off.

My enthusiasm for this dimmed a little when I did the numbers. Eight feet of 2" pipe holds about 1 1/2 gallons of water, which weighs about 12 pounds. I figure the baseboard (16' of 2" pipe + fins & fittings) weighs about 64, so that would only be about a 19% increase. Even accounting for the higher specific heat, it would only increase the heat capacity by about 22%. But if the choice is between this or removing a tube and using it elsewhere, I'd actually be more than doubling the heat capacity I'd end up with. Removing one of the tubes would leave me with a more appropriate EDR, but it would cut the current heat capacity in half, leaving me with roughly the equivalent of a 22-section, 4-tube, 25" thin-tube radiator that only weighs about 32 pounds. (Filling one tube with water would make it roughly equivalent to one weighing 78 lbs.)

So this is my quandary: Should I

a. remove a tube and use it elsewhere? (very low heat capacity but appropriate EDR in two locations)

b. fill the upper tube with water? (appropriate EDR, 22% improvement in heat capacity)

c. leave it as it is?

I should mention that I do have a spare 36 sq. ft. radiator I can probably use in the other location if I decide not to split the baseboard.
Just another DIYer | King of Prussia, PA
1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
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