 |
|
Page: 
|
|
Once we got the air out we walked down to the boiler room because we couldn’t think of anything better to do. To our delight, the relief valve was popping and splashing hot water across the floor. We looked at each other and smiled. We had found the “compression tank.” Actually, we had found a lot of compression tanks. The Dead Man had used the top portion of each cast-iron radiator as a little compression tank. He saved himself some money. Pretty clever, eh?
With a bottom-to-bottom connection, the radiator always heated. It might not heat all the way to the top, but it would heat. The Dead Men didn’t have circulators; they ran all of these old systems on gravity. The hot water would rise out of the boiler because it was lighter than the cold water up in the radiators. The cold water would fall from the radiators and shove more hot water up. Before long, they had this neat Ferris wheel of convective currents going, and the whole house was beautifully warm. Hot water will rise inside the freestanding radiator the same way it does inside the system piping. The colder water falls from the top of the radiator and leaves through that bottom connection. It’s beautifully simple.
You can solve this problem by using the supply valve at each radiator to throttle the flow through the radiator (assuming those supply valves are still working). By slowing the flow as it enters the radiator, you’ll promote gravity circulation within the radiator and increase its output. That may not make sense at first, but it works.
|
So I started digging in my old book collection (I should have done that sooner), and I learned why the Dead Men liked to connect their freestanding, cast-iron radiators across the bottom, even when they planned to use an actual expansion or compression tank. When you pipe bottom-to-bottom, a cast-iron radiator will never air-bind. Had they used a top connection for either the supply or return line, trapped air could stop all circulation to the radiator and create problems for them.
But when you add a circulator to one of these old gravity systems, wacky things can happen. If you use the wrong circulator - one that’s too powerful - the water will zip right through the radiator’s lower nipples, significantly slowing the natural gravity circulation within the radiator. Get it? The cold water that’s trying to fall out of the top of the radiator will be stopped by the hot water that’s zipping through the bottom outlet connection. You wind up with a radiator that heats only across the lower nipples; the rest of the radiator will eventually heat but it takes a long time.| Dan Holohan - [Intro] | [Email] | [Website] |
| The views expressed in this article are those of the individual author and do not necessarily reflect the views of the management or staff of MasterPlumbers.com |
