Frequently Asked Questions

Payback calculations can be performed by evaluating the savings associated with a boiler system upgrade (incorporating the thermal efficiency gains, radiant heat loss decreasing, and electrical consumption decreasing). A payback calculation can show how long new equipment will take to pay for itself, meaning the money that would have been used to operate an old system would be used toward the cost of purchasing a new system. Simple payback is calculated as the cost of installation / yearly savings.

Any boiler where the products of combustion flow on the inside of a tube with the heat transfer media (ex. water, steam, or hot oil) on the outside. The tubes can be orientated vertically (ex. Fulton VMP), horizontally (ex. Fulton FBS) or pitched at an angle (ex. Vantage).

Any boiler where the products of combustion flow on the outside of a tube with the heat transfer media on the inside (ex. Fulton Reliance).

Pulse combustion is a form of combustion occurring in a heat exchanger specifically designed to form a Helmholtz resonator. Pulse combustion is self-aspirating, requiring no draft assist fan to provide combustion air. This form of combustion produces more energy than a conventional power burner combustion, allowing for smaller heat exchangers (less materials) and smaller vent pipe sizes to be utilized. Pulse combustion requires no moving parts and is a self sustaining process, requiring minimal electricity.

A hybrid boiler system is a vague term, and can mean a number of things. An example is incorporating boilers with a variety of fuel sources into a common system such as a wood fired boiler with an oil fired boiler - if the cost of oil dramatically increases, the customer has an option to avoid using oil altogether. Another example is installing condensing boilers with non-condensing boilers into the same hydronic system that may experience a wide range of loop temperatures. This allows the initial cost of purchasing boilers to be lower (boilers designed to have high thermal efficiencies as a result of flue gas condensation are more expensive than boilers that cannot withstand flue gas condensation). Depending on the system temperatures required during operation, the condensing or the non-condensing boilers can be utilized. A specifically designed control system is critical in any hybrid boiler system, as the various types of boilers should only be able to operate when conditions are appropriate for that particular boiler.

Turndown is the ratio of a boiler’s minimum fuel input as compared to its maximum fuel input. For example, a boiler with a maximum fuel input of 2,000,000 Btu/hr and a minimum fuel input of 400,000 Btu/hr would have turndown ratio of 5:1 (2,000,000 divided by 400,000 is 5).

Modulation is the ability of a boiler to adjust its firing rate based off of the temperature setpoint the boiler is trying to achieve. Fulton boilers can be built in a number of electrical configurations to accomplish modulation by operating off the controls on the boiler itself or receiving a signal from a control system or building management system. For example, a Fulton Pulse boiler with a maximum fuel input of 2,000,000 Btu/hr, would be set up to operate and any input between 400,000 Btu/hr and 2,000,000 Btu/hr.

A thermal fluid system is a closed loop using mineral or synthetic oil as the heat transfer fluid. These systems operate at elevated temperatures while maintaining low system pressures.  Fluid is circulated within the heater tubes and flue gases heat the fluid.

The choice between a steam system or a thermal fluid system is governed by the process requirements. The range or process temperature is a deciding factor.  If the system’s required temperature is above the freezing point of water (32°F) and below approximately 350°F, the choice is usually steam. However, if the required temperature is below 32°F or above 350°F, thermal fluid may be a better solution. Thermal fluid heater systems can be designed with maximum operating temperatures to 750°F.

The requirement for a stationary engineer is dependent on the jurisdiction. Most jurisdictions have not required stationary engineers for thermal fluid heaters.

Steam carries about 1000btu/lb useful energy. Hot water and thermal fluid carry much less energy (1-100Btu/lb). Steam does not require a pump to transfer the energy. Generally, if the heating temperatures required are <200°F, then hot water can be used and if temperatures >400°F are needed then thermal fluid might be a better choice. For process temperatures between 200°F and 400°F steam is considered a viable option.

The pressure of the steam is directly related to its temperature. So process temperature will require steam used to be at a specified pressure. For example, a process requirement that needs temperatures at 300°F will require steam delivered at 55 psig or higher.

Boilers with low water volumes require a minimum flow requirement to prevent localized boiling and subsequent heat exchanger damage in a low to zero water flow situation. Minimum flow requirement varies by boiler design. Regardless if a boiler itself has a minimum flow requirement, every hydronic heating system needs to be designed to carry the energy being created away from the boiler to avoid high temperature shut down.

Because Pulse combustion requires so little electricity, it is an ideal boiler for projects with alternative energy sources, such as wind or solar. When running, a Fulton Pulse boiler requires about 0.75 Amps of electricity, so that electrical requirement can be easily configured to draw power off of a single solar panel. There is not another design of commercial hydronic boiler on the market that consumes as little electricity as a Fulton Pulse Boiler.

Any boiler can produce condensed flue gases, but not all boilers are designed and built to withstand the by products associated with flue gas condensation. Only boilers that have heat exchangers designed and constructed to withstand the acidic qualities of flue gas condensate should be put into systems designed with water temperatures that would cause condensing to occur. Any system with return water temperatures less than 140°F should have full condensing boilers designed into it, otherwise the boilers are subject to heat exchanger failure from flue gas corrosion. Examples of materials that cannot withstand flue gas condensate are copper and cast iron.

When the vapors produced from combustion in a boiler change phase from a gas to a liquid, that liquid is referred to as condensate. This phase change occurs at the dew point of the vapor, which is approximately 135°F. The temperature of the water coming into a boiler will determine whether or not the vapors of combustion will be at temperatures that are subject to condensing.

Condensing of flue gases is a natural process. The dew point of the flue gas (approximately 135°F for natural gas, varies for other fuels) determines at what temperature flue gases will begin to condense. When the vapors produced from combustion fall below that dew point temperature, a phase change occurs and the vapor becomes a liquid.

The vapors produced from the combustion process in a boiler contain energy. Flue gas condensate contains approximately 1,000 Btu’s of energy per pound (latent heat of vaporization). Instead of that energy remaining in the flue gas vapor phase and going up the stack, it is recaptured as sensible heat in the liquid phase. For one hour, every pound of condensate collected adds 1000 Btu to the output capability of a boiler. For example, a 2,000,000 Btu/hr input boiler operating at an efficiency of 88% would have an output of 1,760,000. The boiler is operated for an hour at this condition and 80 pounds of condensate is collected. The overall thermal efficiency of this boiler is actually 92%.

1,760,000 + (80 x 1000) = 1,840,000.
1,840,000 / 2,000,000 = 0.92 = 92%

If a boiler has not been specifically designed to operate in the temperature ranges associated with condensing operation, the flue gas condensate will corrode the heat exchanger. Examples of materials that cannot withstand flue gas condensate are copper and cast iron.

A minimum flow rate is required in order to maintain the appropriate velocities through the heater (typically 10-12 ft/sec). If the velocity is too low the film temperature could increase, potentially destroying the fluid.

A typical system includes the heater, circulation pump, expansion tank and the user. Depending on the temperature requirements and the system design control valves may also be utilized.

The required operating temperature along with the physical properties (specific heat, maximum operating temperature, vapor pressure, specific gravity and coefficient of thermal expansion) of the fluid should be evaluated when choosing a thermal fluid. It is important to choose a fluid specifically designed for heat transfer as opposed to a multi-purpose of turbine oil.

Mixing different fluids and subjecting them to high temperatures can have unpredictable results. In addition, once fluids have been mixed, the baseline analysis of the fluid is no longer applicable making it difficult to perform an annual analysis of the fluid for degradation.

All thermal fluids expand as they are heated. The amount of expansion is based on the operating temperature, system volume and the coefficient of thermal expansion of the fluid. An expansion tank must be provided to accommodate the increased system volume at operating temperature. NOTE: All fluids expand at a different rate?

Typically, thermal fluid systems should use either carbon or stainless steel components. Brass, bronze, cast iron and aluminum are incompatible with thermal fluid. Piping should be schedule 40 seamless SA 106 material. Valves should be cast steel or ductile iron with steel or stainless steel trim. Gaskets should be rated for the temperature and pressure of the system. NOTE: Threaded connections larger than 1” should not be used in the flow circuit.

When an expansion tank is pressurized with nitrogen (to eliminate the possibility of exposure of the fluid to oxygen), it is said to have a nitrogen blanket.

A nitrogen blanket is required under the following conditions:

• Systems not equipped with a cold-seal tank (allowing the expansion tank to be under 200°F)
• Systems where the expansion tank is located outdoors
• Systems where the inlet to the tank is not the highest point in the piping system.
• Systems where the operating temperature exceeds the atmospheric boiling point of the fluid.

Typical thermal fluid systems are designed to operate above the fluid’s flash point and fire point but not above its auto ignition temperature.

Typically, thermal fluid will last between 5 and 8 years. Annual testing of the fluid is recommended.

The insulation should be a cellular foam glass non-absorbent insulation; Pittsburgh Corning Foamglass or equal.

Within the turndown ratio of the heater, +/- 5°F can be achieved. By designing the system with primary/secondary loops, +/-2°F can be achieved.

The heater will be built and stamped to either ASME Code Section I or ASME Code Section VIII Div. 1 depending on the local state requirements.

The gas pressure requirement will vary with the type of heater and burner chosen. In general, the "A" model heaters require 7"wc (max inlet pressure of 14" wc), FT-0080C thru FT-0400C require "14"wc (higher gas pressures are available upon request), FT-0600C thru FT-0800C require 40"wc (5 psig max) and FT-1000C thru FT-1400C require 120"wc (10 psig max). For low emissions burners, please consult the factory.

Low emissions gas burners are available upon request. The NOx levels range from 30 ppm to 15 ppm depending on the heater size. Please consult the factory for specific emissions requirements.

Most thermal fluid heater systems are provided with NEMA 1 unclassified controls. The requirement for the Class I Div I or Class I Div 2 controls is typically driven by process requirements, location and insurance requirements.