Two years ago, a five-story townhouse in the historic district of Manhattan’s East Side suffered a fire on its upper floors. Built in 1917, the building’s reported original architect was Cass Gilbert, who also designed the New York City Public Library and the United States Custom House in lower Manhattan. Its owner wanted to put the heating system back into operation and arranged for an inspection.

Despite fire and smoke damage on the top three floors and water damage throughout, the building could be rehabilitated and put back to use. The building’s original design was intact, supplemented by an addition to the rear. The style of radiators used on the addition dates the addition project to sometime in the 1950s.

Given these facts and the present booming economy, the building was bound to find an eventual buyer. However, the subsequent inspection of the building’s heating system revealed many problems that had nothing to do with the 1998 fire.

A Law-Breaking Burner

The heating system was a one-pipe steam system, and it seems that the boiler was originally fired with hard coal. The original radiators and piping were still intact from top to bottom, except where the radiators had been disconnected in the process of structural repairs. Several radiators were missing.

The rear addition had necessitated changes in the heating system to provide warmth to the new space. However, it became clear that these changes were not made in a way to provide proper system operation, and the lack of understanding regarding one-pipe steam systems led to more problems.

A new boiler appeared to have been installed during the addition process; it had a steel shell with fiber glass insulation, and the latter was not generally used to insulate boilers until the 1950s. The new unit was an H.B. Smith boiler, Series 25, with a firing rate of no more than 6.45 gal/hr of Number 2 fuel oil. However, the burner was a Carlin 950 FRD-1 burner that is rated to fire between 7 and 13 gal/hr of the same oil. As one might imagine, H.B. Smith has since come out with a new series of boilers, but the boiler in this particular building was designed to be hand-fired or stoker-fired with hard coal.

Another problem arose when I examined the Air Resources permit from the New York City Department of Environmental Protection (DEP). All fuel oil-burning equipment over a gross input of 350,000 Btuh must have a permit to operate within the city limits of the City of New York. The permit was for a Carlin 301 CRD burner. Thus, the burner on the boiler did not match the permit and was illegal.

The building owner wanted to replace the boiler. Experience, however, suggested that the cast iron boilers from this manufacturer were reliable and could last for decades without replacement. So what the plumber did, which he was not supposed to do, was to open up the doors on the front of the boiler. When we looked inside, we found a considerable amount of soot as the boiler had not been cleaned in several years. We did not see any internal water leaks, so I pronounced the boiler in generally good condition.

When the doors were put back on the boiler, the plumber did not have any furnace cement or roping to properly seal them. Thus, when the boiler was turned back on, smoke came out the front of the boiler and proceeded to the third floor.

The boiler was quickly shut off. I told the owner that the burner needed replacement, since the present burner was not only illegal, but also had not been manufactured by Carlin for at least 25 years. I quickly called the Carlin representative and received the new model type. Calling a representative at DEP determined that such a burner would not require a new permit. The owner subsequently replaced the burner with a legal model.

Additional work along with burner replacement included sealing the doors, cleaning the boiler, and putting the barometric draft back into proper operation. I told the owner to purge the oil lines and clean the fuel oil tank of any sludge, and recommended a chimney cleaning.

Figure 1. A simple schematic of the Manhattan townhouse's existing boiler setup. Part of the problem surrounding the right takeoff was how the design had condensate and steam flowing in opposite directions. One result was a fluctuating water line in the boiler.

Fluctuations and Complications

My initial survey of the building included a listing of every radiator, its location, and its size, so I could go back to tables to compute the total sq ft of Equivalent Direct Radiation (EDR). The first calculation revealed a major discrepancy between the total exposed radiation in the building and the boiler net output.

It turned out that the source of the smoke on the third floor was hot-air ducting that ran from the basement to the third floor. There were cast iron radiators in the basement’s ductwork, and those radiators heated air that supplied the third floor. I told the owner that the ductwork needed to be cleaned out, since there was what looked like 80 years of dirt in the system, and this dirt was a potential indoor air quality problem. (When the boiler was installed, the fin-tubed steam coil did not exist, or else it wasn’t widely used. Cast iron radiators do have the advantage of being fairly easy to clean in the ductwork; a simple brushing off is sufficient, and the fancy high-pressure water needed to clean today’s fin tube coils is not necessary.)

Unfortunately, the steam piping was installed incorrectly when the new boiler was installed in the 1950s. The steam piping above the boiler and in the boiler room must be considered part of the boiler itself. It is here that any condensate or liquid water which is mixed up with the steam is separated from the steam and returned to the boiler. Energy waste results when the steam sent into the steam lines has more than 2% condensate or liquid water in it.

It is imperative that the steam and condensate flow in the same direction in a steam line. The piping above the boiler (Figure 1) shows two takeoffs from the boiler into the header. Note that in the right takeoff, the condensate was flowing against the direction of the steam flow. That is bad, because it creates a fluctuating water line in the boiler. This phenomenon is visible when the water in the sight glass bounces up and down. Other factors can also cause this bouncing to happen, including dirty water in the boiler.

The fact that the header was only 20 in. above the water line also presented a problem. For low-pressure steam systems, the main header should be positioned at least 24 in. above the boiler water line. Next, the equalizer line forming the main steam header back to the boiler was undersized; it was only 1 in. in diameter, and there was a steam trap on it! Given the building’s one-pipe steam system and a boiler firing at 3.5 gal/hr of Number 2 fuel oil, the equalizer should be 2.5 in. in diameter.

Figure 2. The proper boiler configuration. With the lines to the steam mains positioned to the right of the righthand boiler takeoff, the flow problem (and consequent fluctuation) is eliminated.

Strange and Expensive

Figure 2 shows the proper piping for this boiler. Note that the lines going to the steam mains are to the right of the right boiler takeoff. Steam cannot flow against condensate. The equalizer in the figure is sized properly for the boiler.

Back in the existing scenario, large sections of the condensate return lines had been removed from the system. Also, every condensate line return had a steam trap on it, even though the system had one-pipe steam radiators. By removing portions of the condensate return lines, what was once a wet- return system was changed into a system with a dry return. When this happens in conjunction with changing the water line in the boiler, it can upset system operation rather dramatically.

To get condensate back to the boiler, a condensate receiver and condensate pump were installed on the system, totally unnecessarily. The condensate receiver and condensate pump were removed during the renovations, and the steam traps were taken out as well. Elsewhere, a steam trap was found on a line on an upper floor, draining condensate out through a pipe piercing the wall. To do this, a steam trap was put on this “relief” pipe. This trap has since been removed from the system.

Some very strange things had been done to the system in this building. It is taking tens of thousands of dollars to rectify the mistakes. One final tip: when dealing with a one-pipe steam system, try operating it with 0.5 lbs of steam pressure. Almost every one-pipe steam system that has ever been built can operate on just that pressure. Crank the pressuretrol way down, and you will find that the system operates much more quietly. ES