Temporary Boilers: An Overview and Their Applications

Boilers are among the main heat sources used in buildings, and they play a fundamental role in making indoor spaces suitable for humans. However, boilers are vulnerable to component failure like any piece of mechanical equipment, and disconnection may be required during building renovations or heating system upgrades. Temporary boilers can meet the heating needs of buildings under these circumstance. Note that the NYC Department of Housing Preservation & Development requires space heating availability from October 1 to May 31, and hot water availability during the entire year.

There are many possible scenarios where a building may be left without a boiler temporarily, and the following are some examples:

• Heating system fuel conversions, for example from #4 heating oil to natural gas. These projects can take from 6 to 12 months to complete.
• Boiler reparations and component replacements.
• Building damage due to extreme weather.
• Chimney reparation, replacement or new liner installation.
• Asbestos abatement in a boiler room, requiring all equipment to be shut down.

There may also be temporary situations where heating demand is higher than normal, for example very cold winters. There are also healthcare applications where the hot water supply is critical and must not be interrupted under any circumstances, requiring a backup system.

Renting a temporary boiler is an effective solution when heating output is needed urgently, and the existing boiler is unavailable or falling short in capacity. The cost of a temporary boiler is normally in the range of $5000 per month, but the building can continue normal operation while its heating system is brought back online or upgraded.

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Installing a temporary boiler is much faster than installing a permanent unit, but project planning is still important. Depending on your location, there may be a significant transit time given the weight and size of the unit, and then it must be connected to your building. Operator training may be necessary, and also keep in mind that availability of temporary boilers may be reduced during emergencies like winter storms.

Temporary Boilers and Code Compliance

Code compliance is a key challenge when deploying temporary boilers. Considering their important role in buildings and the risks associated with combustion, they are subject to stringent requirements despite being temporary. Code compliance can be planned for in advance in a normal project, but the time available is normally short when dealing with temporary boilers.

In 2012, Hurricane Sandy revealed how vulnerable NYC buildings are to extreme weather events, leaving many properties without electricity and heating. The NYC Department of Buildings and NYC Department of Environmental protection recognized the need to simplify their approval procedure for temporary boilers in emergency situations. The NYC DOB changed its rules to allow installation prior to approval, subject to the following conditions:

The procedure above also applies for temporary fuel oil storage, if needed for a certain application. The approval process can be accelerated by using the NYC Dept. of Buildings electronic filing system.

When filing the Emergency Work Notice, the installer must include the following information:

• Project address.
• Description of the emergency situation requiring a temporary boiler and/or fuel storage.
• Licensed contractor information: Name, license number, and telephone/fax or email.
• Registration number of the existing boiler.
• Statement of LAA1 filing within 5 days and complete filing/approval within 60 days.

The NYC Dept. of Environmental Protection must also be notified, and the information required is the following:

• Project address.
• Make and model numbers for the boiler and burner.
• Boiler input or firing rate in BTU/hour.
• Fuel type, only #2 heating oil and natural gas are allowed.
• Licensed contractor information: Name, address and phone number.

After the notification has been submitted, the NYC DEP assigns an installation number and provides a temporary work permit. This permit expires in 30 days, and a complete work permit application must have been filed by then.

Temporary Boiler: Unit Features and Configurations

A temporary boiler has many features that make stand-alone operation possible, summarized below. Note that some features are optional, used to enhance performance or in special applications.

• Feedwater make-up system: A water supply is fundamental for boiler operation, since water is the heat transport medium. A temporary boiler becomes much simpler to install if equipped with a feedwater tank.

• Fuel burner

• Steam pressure reducing valve (PRV): In buildings that use steam heating, this device allows steam pressure adjustment as needed by the distribution system.

• Gas pressure regulator: Reduces the pressure of compressed gas if needed by the boiler, since the utility gas supply pressure varies by location.

• Chemical treatment device: Removes solids and gases dissolved in the water supply, increasing boiler efficiency and heat transfer.

• Expansion tank: Provides pressure relief.

• Pre-wired boiler control unit.

• Pre-piped relief valves.

• Water pumps: Primary and standby, dual feed.

• Chemical pumps: For injection of chemical additives, if required by the application.

• Variable speed drives: Modulates the speed of blower or pump motors, achieving significant energy savings.

• Fuel storage

• Heat exchanger: Allows water heating at two different temperatures for space heating (hydronic) and domestic hot water.

• Exhaust stack and combustion air intake

• Space heater: When the outdoor temperature is very low, the boiler enclosure may require space heating to protect components from freezing.

• Emergency shutoff: Manual stop in case of emergency.

The most common temporary boiler configurations are the following:

Advantages and Disadvantages of Temporary Boilers

Temporary boilers have advantages and disadvantages compared with permanent units. In general, they are intended for emergency situations and periods when there is an unexpected increase in heating demand.

Concluding Remarks

Temporary boilers are effective when buildings suffer a boiler breakdown, when heating systems are being upgraded, or when facing unexpected heating demand that exceeds installed capacity. However, they are not a long-term solution due to their increased operating cost, noise and public exposure.