New York's Cooperative and Condominium Community

Habitat Magazine Insider Guide




Keeping Your Building's Heat Healthy in Winter

New York City

Managing Heat in the Cold
Feb. 26, 2015


A common resident complaint about radiators is the loud banging. The noise is caused by steam coming in contact with cooler water (condensate), creating a rapid expansion of the condensate water in the pipes. In prewar buildings, radiators typically have just one pipe shared by both the steam and condensate. Single-pipe systems rely on the pipe's downward slope to return water back to the boiler for heating it back into steam, but, in aging pipes, the condensate can get trapped in elbows and sags. When steam hits this trapped condensate, the hammering sound is created. The pipe may have to be repositioned or replaced to eliminate the banging. One-pipe systems have air valves on one end of the radiator that should get checked periodically. 

In a two-pipe system, one pipe is used for steam supply and another for condensate return. A steam trap at the bottom of the radiator expands when steam comes in contact with it, blocking the steam from exiting the return pipe. Operating like a diaphragm, steam traps expand and release thousands of times in a heating season, so the element will eventually fail. When a radiator remains cold even as steam is flowing to it, it could mean the steam trap is no longer working and needs replacement. Two-pipe systems don't typically have air valves. 

Cooling Towers

Buildings with central chillers, heat pumps, or fan-coil units use rooftop cooling towers to reduce the temperature of the condenser water circulating through the system. Many properties shut down their cooling systems around October 15, at which time New York City buildings are required by law to provide heat. Supply valves are closed off and drain valves opened to remove any leftover water in pipes to prevent freezing.

Some heating and cooling systems, however, operate year round. For those systems, the water in the cooling tower must be kept from freezing either by adding a glycol-based fluid (antifreeze) to the water or using immersion coils that heat the water. Wood tanks used only as a fire standpipe supply (with no domestic water) also need immersion coils to keep the water from freezing. The building's maintenance staff or a mechanical contractor can provide these checks.

Brick Vents

These vents on the façade of the building bring in fresh air from the outside for fan-coil units used to cool apartments in summer. During the winter, when the fan-coil units are being used for heating, drafts can enter if the dampers to the vents are not shut or sealed. The dampers, however, can be tricky to access: the cover may have to be removed, and a hard-to-reach lever pushed or pulled. For dampers that are stuck or do not close all the way, removable foam insulation can be inserted around the edges of the unit as a temporary measure.

Outdoor Piping

Cold water pipes running to and from a rooftop water tank or cooling tower are often heated using an electric coil, known as heat tracing, wrapped around the pipe to keep the water inside from freezing and the pipe from bursting. A layer of insulation is wrapped around the heat tracing, which is plugged into a ground-fault circuit-interrupter on the roof. A routine roof check should include making sure the heat tracing is plugged in and none of it is exposed by insulation that is worn away or missing.

Your board may also want to call on trained professionals to provide an overall look at your building on an annual or semi-annual basis and identify any potential trouble spots, especially ones that can become more vulnerable during a harsh winter season. 


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