A Modern-Day One Pipe?

Original inquiry: Looking at a complete, down-to-the-studs remodel of my 1915 condo in San Francisco. I have about 1,800 square feet and the prior owner had a cobbled-together forced-air gas system installed. My wife and I both like steam heat and were wondering if you guys could opine on what a “modern day” one-pipe system would look like? My design help looked at me like I was crazy to consider such an idea. The good news is that top-notch weatherproofing will be in order and we never get below freezing. So it seems that a nice, steady heat source would be ideal. So fire away! Am I crazy? SteamCoffee

Replies:Your idea is good, but maybe a two-pipe vapor with orifices would be even better for the mild winters you have. You will have to look at the radiators you intend to use, and see if the outlet side can be opened. A tekmar controller with an outdoor sensor would be a good method of control. nicholas bonham-carter

Not crazy at all! I just wouldn’t want one pipe; with a two-pipe system, you don’t have the vents and noise from them to deal with. There are several good reads in the library here on people installing a “dead man’s system.” I would just make sure to find someone local that is actually up to the task. It’s one thing to maintain an old system that was installed by a pro of that era vs. doing all the calculations to run the correct dimensions and slopes of pipes to ensure all your steam gets to where it needs to be, and all the makeup water comes back to the boiler. Moneypitfeeder

Sounds like what you may be looking for is the comfort of steam radiators. While I believe that a steam system existing in a house can be an excellent delivery system for comfort, I do not necessarily think that if you are doing a down-to-the-studs renovation that steam would be your best bet. Have you considered a modern, highly efficient hot water system? You could still use your old fashioned radiators, which would give you the look and feel of steam, but you would have a much more efficient system that would use modulating water temperature. In your case, that may be a better choice. Greg Maxwell

Two-pipe steam with supply orifices would be best with a modulating boiler and full reset of supply pressure to give modulating output to the system. The efficiency of this system would likely meet that of a modulating hot water system as noted above. However, with your moderate climate, I would expect the payback of a more complex system to be very long.  Sticking with a simple system probably makes the most sense, with steam able to provide both the comfort advantage of radiant heat (if using radiators) and quick response to get the chill off in shoulder seasons.

What about a minitube system, such as the one Gerry Gill installed?  Though it would be a two-pipe system. That was some beautiful work.  I loved watching his videos on YouTube. ChrisJ

The “down to the studs” part of the equation may be out of the question. My architect  said that if I open the walls, I open myself up to the new California Title 24 energy “green” codes. The good news is it refers mostly to nonsteam systems! Part of the original steam pipe remains in the walls (as does massive amounts of gas pipe for the original gas lighting system).

The unit is on the second floor and has plenty of access to run pipe, install a boiler, etc. As for the specifics, two pipe is ideal, especially for modulating each room. I thought simplicity favored the one-pipe system. I know the payback period is longer, but nothing beats the steam system to fight off the chill of fog and constant sea breeze. The remodel would have to replace the cobbled forced-air heat anyway; no air conditioning necessary here! So getting the right system makes sense. I have some studying to do! SteamCoffee

Return Of Off The Wall

Dan Holohan’s website, www.heatinghelp.com, includes a message board called “The Wall.” Regular participants include some of the brightest and most dedicated practitioners of hydronic and radiant heating in North America. As a result, the useful information found here rivals that found on any online forum in the industry.

With Dan’s return to Plumbing & Mechanical, Supply House Times and PM Engineer, we are again sharing with readers, with Dan’s permission, some of the posts (edited by PM staff for style and grammar) that pertain to technical problems in the field or other items of interest.