Cast iron baseboard for steam

Cast Iron Steam Baseboard Information

Piping steam cast iron baseboard into a steam system can be a bit tricky. Copper tubing is not recommended for steam applications due to high heat loss through the tubing and thermal expansion noise. Maximum recommended length for steam applications should be limited to 10 lineal feet. Use of PTFE (Teflon) tape or paste containing PTFE is not recommended as over tightening is possible, causing cracking of the Base Ray tapping's. It is not recommended that cast iron baseboard be used in a One-Pipe Steam System. Two-Pipe Steam or Vapor Systems are steam systems in which each cast iron baseboard assembly is provided with two piping connections, and where steam and condensate flow in separate mains and branches.

The vapor system differs from the low-pressure system only in the type of air valve used. The trick here is to convert the baseboard to a two-pipe application even if the system is one pipe. This can be done a few different ways as shown in the drawings below.

The baseboard will need to be pitched toward return tapping. The pitch for a 10' piece of baseboard would be about 1-1/2" low side being the return piping end.
The key is to keep the live steam from entering the return, be it wet or dry returns, see the comments below.

2 Pipe to Dry Return w/Steam Trap

If the installation will require piping the baseboard to a dry return you could use a steam trap on the end of the radiation. The trap will allow air to pass through but when steam gets into the trap the trap will close. When enough condensate accumulates in the trap it will cool approximately 10f. The trap will re-open to allow the condensate to exit the trap and close again. When the live steam enters the trap the process starts over again. An air vent on the radiation would not be required.

2 Pipe to Dry Return with Pipe Trap w/Air Vent

If you do not want to use a mechanical trap on the return side of the baseboard and you have the room you could create a water seal between the baseboard and the dry return with a piped trap. Steam will not get into the return as it cannot get through the water seal. Pipe the return side below the dry return and back up to create the required water seal. The water seal must drop 30" per pound of steam pressure below the return connection point. It is imperative no live steam enters the return pipe. It will create heating problems in many radiators.
This application would require an air vent on the return side of the radiation.

2 Pipe Trap return condensate to Supply Main w/Air Vent

This is the same as above, but the wet seal is returning back to the steam main not the system return. I prefer this drawing less than the above drawing as much more water ends up in the steam main possibly causing water hammer noises in the system. If you apply this application it is important to have good main pipe insulation to assist in reducing the chance of water hammer.
This application would require an air vent on the return side of the radiation.

2 Pipe to wet return Below Water Line w/Air Vent

In this last drawing you would be piping the return side of the cast iron baseboard into a wet return. Verify the connection will always be below the water level of the steam system to create the wet seal. Since water will seek its own level, the water in the system piping will be equal to the water level in the boiler.
This application would require an air vent on the return side of the radiation.

2 Pipe to wet return Below Water Line w/Alternate Air Vent Location

This could be applied to any of the above piping when the vent is required after the baseboard.

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