Not just a 1-pipe dream

I LOVE CHALLENGES. I love old systems. This call had both. My customer informed me that a school building was about to undergo a big renovation. The son of the owner of the local major league baseball team had donated lots of money to get this project started. Located in a struggling, near-downtown neighborhood, it sounded like a great idea for a good cause. I was glad to help. The catch and there

I LOVE CHALLENGES. I love old systems. This call had both. My customer informed me that a school building was about to undergo a big renovation. The son of the owner of the local major league baseball team had donated lots of money to get this project started.

Located in a struggling, near-downtown neighborhood, it sounded like a great idea for a good cause. I was glad to help.

The catch — and there is always a catch — was that a new YMCA building would be added onto the existing school building.

My customer was working with a construction manager to see what needed to be done to the steam system. We met him on-site to develop a plan.

The building is a grand old place, built in the early 1900s, with the names of famous authors and historical figures carved in stone on its sides. It was about to be reborn as a college prep charter school, along with the new YMCA.

Currently, there is a one-pipe steam system, with huge cast iron radiators. The new YMCA would get a modern HVAC system, while the school would stay on steam.

The steam system was in decent shape, despite years of neglect and poor maintenance. It also had a few oddities, such as radiator air vents installed as main vents. Obviously, that had to be changed. The system would also require significant re-piping.

The team wanted my advice on which pipes should stay and which should go.

These issues were just some of the challenges. The benefactor seemed to have deep pockets, however, so I could dream big.

The troubleshoot

The team wanted my advice on which pipes should stay and which should go.

I found the end of the seven steam mains that needed to be re-piped in a basement room where a giant system was going to be re-piped — the kind you can walk into and then get lost.

On a one-pipe steam system, the steam main carries the steam, the air present at start-up, and all the condensate from the radiation and piping.

The air in the risers and radiation go out the radiator air vent. The air in the main — and there can be plenty of it — goes out a main air vent(s) on a gravity return system and through a steam trap on a pumped return system.

Because a new boiler feed unit was part of the renovation, seven traps would need to be installed.

We used float and thermostatic traps with Y-strainers to keep out the crud at the end of heating mains because they do a great job of passing both condensate and air. The outlets of these traps were then combined into a header to start a return pipe pitched down to the new boiler feed tank.

The idea is that the condensate slides into the tank, while the air flows out through the open vent pipe on the tank.

In order to size the traps, we had to determine the amount of radiation connected to that main. Unbelievably, the construction manager found a copy of the original heating plan.

From that, I calculated the load of each of the seven mains. I just added up the square foot rating of every radiator supplied by that main (traps are rated in pounds of condensate per hour).

To convert, I divided the square foot total by four. After applying a safety factor of 50%, I was ready to pick a trap based on condensate load.

But what about the air load? The trap has to pass the air present in the main at start-up, or the system won't heat evenly.

This point became more important when boilers went from coal fire (slow to steam, plenty of time for the air to get out) to automatic fire (fast to steam, a lot less time for the air to get out).

The vent rate for the F&T traps I selected is more than 20 cu.ft./min., which is much more than a typical main air vent.

Knowing the pipe size and length of the mains from the plan (and using pg. 85 from my "Field Guide to Steam Heating"), I determined that the traps could easily vent the large volume of air present at startup from the existing 6 in. and 8 in. mains.

The follow-up

With the re-piping plan complete, attention was now directed to dreaming up improvements.

The first item for any steam system this big is a boiler cycle rate control. By varying the boiler run cycle length in relation to the outdoor temperature, we were able to achieve significant energy savings.

The next items for improvement were thermostatically controlled radiator vent valves, which vary the radiator's vent rate in relation to the room temperature.

The teachers can now control the heat in their own rooms. Also, the thermostats can be turned down when the room is not in use, thus saving even more on energy costs.

After adding the seven traps, the cycle rate control and the thermostatically controlled radiator vents, the system performs flawlessly. The deep pockets of the benefactor were able to pay for all of it.

The results: Teachers and students love the comfort. Administrators love the low energy bills. My customer and the construction manager love the fact that it works. I loved being able to see my dream rise to glory.

Patrick Linhardt is the sales manager at Aramac Supply in Cincinnati. His book is "Linhardt's Field Guide to Steam Heating." To order, visit steamupairoutwaterback.com or call 513/703-5347.

TAGS: Plumbing