Cast Iron Baseboard for Steam

Roadking

Does anyone have any experience replacing radiators with cast iron baseboard on a one pipe system? I looked at a steam job today where someone removed 4 radiators and replaced them with cast iron baseboard. The baseboards are pitched to drain back toward the valves, but the inlet risers and valves are only 3/4" coming off a 1-1/2" main (about 15'-20' long) coming off the main header. Steam and condensate flow are counter and the 1-1/2" main is pitched back toward the header with a 1" drip at the lowest point where it branches off the main header. The CI baseboards are about 8' long (4 sections) each and are pitched about 1/2" at the far end to drain condensate back to the inlets. As you can imagine the system bangs like hell. Most of the hammer is in the baseboard units themselves. I was asked to help by the owner. I thought of re-pitching the main and relocating the drip to make the steam and condensate flow the same direction but I've never seen cast iron baseboard used for one pipe steam before. Most of the water hammer seems to be in the baseboards. I'm really not confident that the system can be made to work properly with this type of radiation.

jpf321

certainly ...

certainly that 3/4 inlet is a bit small for steam and condensate to coexist...you can try pitching away from inlet and adding a drip at the far end of the CI boards .. i think there are quite a few 2-pipe convectors which may use 3/4", but don't hold me to that. if you get the condensate flowing paralell to the steam, you may be better off. it would seem that he installed Hot Water baseboards .. this link to Burnham baseray rads shows 1" or 1 1/4" for steam and 1/2 or 3/4 for HW. http://www.burnham.com/pdf/baseray_spec.pdf



of course, the smartest idea is to replace the radiators that he removed .. it takes 10ft of baseboard to supply the EDR equivalent of a modest sized radiator. did he perform proper EDR equivalent rating when the baseboards were installed?

jim_72

CI Baseboard

Roadking CI baseboard should be piped 1" at the least for steam. Lengths longer then 6' should be two piped.They have narrow passages that restrict flow in a counter flow system.

Roadking

Another Knucklehead

Thanks for the help guys. JPF, you and Burnham have provided confirmation of my suspicions that these are hot water baseray knock offs. Even if I repitch the main and create a parallel flow system the radiation is still wrong and will most likely continue to be a problem. The job is located in an upscale bar/restaurant and the room was refinished in mahogany woodwork including custom covers for the offending baseboards. Replacing the radiators is no longer an option. The good news is that the knucklehead couldn't fix the mess he created and the customer stopped payment on his check. I have decided to rip out the faulty steam piping on this portion of the system and run a separate hot water zone to heat the room using the existing baserays. (What they were designed for.) The boiler has an unused tankless heater of sufficient capacity so rather than run a vacuum loop I'll probably set up a pressurized system using the heating coil to serve the new dining room.

Steamhead

Sure

they'll provide enough heat on hot-water?

Roadking

EDR

The baserays will produce about 25% less radiation on hot water than on steam. The room is well insulated and the building has been weatherized so the existing radiation was oversized, even after he converted it. I expect that the system will run a little longer cycle but do not anticipate any problems with sizing. If necessary there is room to add 1 more rad to the system to make up the 25%, but I don't expect that it will be needed for this application. The room is not used every day and with a hot water zone it's easy to control heat to the area when it's not being used. I love steam as much as anybody, but sometimes a different solution makes the most sense for the customer.

Andy14

Plumber

In my experience using cast iron baseboard with steam, whenever I installed more than 6', I always installed a return and never had a problem.