On Sun, 19 Sep 2010 17:14:49 -0400, wrote:

On Sun, 19 Sep 2010 20:00:41 GMT, (Doug Miller)
wrote:

In article , Sam Takoy wrote:
On 9/19/2010 1:32 PM, Molly Brown wrote:
On Sep 19, 10:24 am, Sam wrote:
Hi,

Yesterday, for the first time I saw what was inside a baseboard
radiation: 3/4" copper tube with fins. I see how the fins can be
efficient at releasing the heat. But the volume of water is minuscule.
Over an 8' run, the amount of water in the tubing is

pi*(3/8)^2*8*12*0.0173160173 = 0.734398282 quarts

But how much heat can be contained in less than a quart of water?

Many thank in advance!

Sam

How many GPM are you re-circulating?

I don't know. I've always assumed (incorrectly?) that the pump stays on
just long enough to replace cold water in the system with hot water.

Why would you assume that? In fact, the pump continues to run as long as the
thermostat is calling for heat.

So I figured in one cycle, the water in the fin tubing get replaced just once.

The obvious absurdity of that conclusion should have told you that your
premise was incorrect.
And in a zoned system, the pump runs as long as ANY thermostat is
calling for heat.

*AND* the reservoir temperature is above the min-limit.