Baseboard Hydronic Plumbing

Chris_78

I am replaceing my fin type baseboard radiators with cast iron baseboard radiators. Cast iron radiators have two inlet/outlets on each end. Does it matter which way you plumb them? Should the water enter the radiator in the lower inlet and exit through the top outlet in order to fill the entire radiator or can any combination be used?

Brad White_9

Connections

I suppose in the big picture it does not matter too much within the following scenarios:

1. Many times the connections on the bottom are used with the top connections plugged and they work fine. Internal convection makes it's way to the top. Best if used on long runs, not on short runs where the water might short circuit across the bottom. Not my first choice.

2. The notion of supplying the top and returning the bottom to promote natural convection and so that the leaving air sees the hottest water has some merit. Plus the top-in/bottom-out pattern makes for even flow across all passages. Reverse-return essentially. This is my second choice almost a toss up to my first, which is:

3. Bottom supply and top return is favored for even flow but also that it scoots the air to the vent (high on the return side) best of all. That would be my first choice.


I am sure others have preferences (and better reasoning) than I. This is just my personal take.

WaterHeaterGuy

If we're taking a poll.. I'd choose #3 as well. Of course with the specific detail of bottom left to upper right (or vice versa) never bottom to upper left (or vice versa) which would short circuit the radiator.

ScottMP

more importanlty

Is that the cast iron baseboard should be piped differently than the copper fin tube. Most fin tube is piped as one long loop. If you do this with cast iron you'll have too high a temp drop and the last units on the run, won't heat well. We ussually do cast iron with a monoflow system or two pipe to get even temperature.

Scott

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Chris_78

Thanks

Thanks so much for your responses. I agree with #3 as well. I installed two 4 ft radiators in tandem. The first, water enters at the top and leaves through the bottom. The second enters the bottom and leaves through the top. Both have automatic vents installed. When I tested yesterday the first radiator was hot near the inlet but was not hot near the outlet, however, the second radiator was consistantly hot throughout. I'm going to try adding a manual air vent in the top outlet of the first radiator to purge the air. Again, thanks very much for your time and smarts.

Brad White_9

Hey, Milne...

Get back to work!



"Constantin"


BTW: I agree with your notion not to run too much CI BB in series, or any radiation for that matter. Two-Pipe Rules. Monoflow is a close second.

ScottMP

you engineers

think you know everything, you should try getting out in the field.

Scott P.E.

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Brad White_9

As a matter of fact, I AM

out standing in my field....

And in truth am leaving shortly to a job site. I spend about 25% of my time on job sites, unlike some semi-retired P&H guys on the North Shore (Excuse me, Nahth Shah), that I can think of...

Weezbo

thanks...