Find some brief answers below to frequently asked questions about Fulton products and heat transfer equipment. Should you have any further questions, please Contact Us.
General Application Questions
- Q: How do I calculate payback?
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.
- Q: What is a fire tube boiler?
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 (i.e. Fulton VMP, J Series), horizontally (i.e. Fulton FBS, RBC).
- Q: What is a water tube boiler?
Any boiler where the products of combustion flow on the outside of a tube with the heat transfer media on the inside (i.e. Fulton FT-C).
- Q: What is the turndown of a 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 585 kW/hr and a minimum fuel input of 117 kW/hr would have turndown ratio of 5:1 (585 divided by 117 is 5).
- Q: What is modulation?
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 boiler with a maximum fuel input of 585 kW/hr, would be set up to operate and any input between 117 kW/hr and 585 kW/hr.
- Q: What is a thermal fluid system?
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.
- Q: When should I use a thermal fluid system?
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 (0°C) and below approximately 180°C, the choice is usually steam. However, if the required temperature is below 0°C or above 180°C, thermal fluid may be a better solution. Thermal fluid heater systems can be designed with maximum operating temperatures to 360°C.
Steam Systems
- Q: When should I use high-pressure versus low-pressure steam?
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 150°C will require steam delivered at 3.8 barg or higher.
Hot Water Systems
- Q: Why do boilers have a minimum flow requirement?
Boilers with low water volumes require a minimum flow requirement to prevent localised 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.
- Q: What is a condensing 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 60°C 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.
- Q: What is flue gas condensate?
When the vapours 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 57°C. The temperature of the water coming into a boiler will determine whether or not the vapours of combustion will be at temperatures that are subject to condensing.
- Q: When does condensing occur?
Condensing of flue gases is a natural process. The dew point of the flue gas (approximately 57°C for natural gas, varies for other fuels) determines at what temperature flue gases will begin to condense. When the vapours produced from combustion fall below that dew point temperature, a phase change occurs and the vapour becomes a liquid.
- Q: Why are condensing boilers more efficient?
The vapours produced from the combustion process in a boiler contain energy. Flue gas condensate contains approximately 0.645 kW/hr of energy per kg (latent heat of vaporisation). 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 kilogram of condensate collected adds 0.645 kW/hr to the output capability of a boiler. For example, a 585 kW/hr input boiler operating at an efficiency of 88% would have an output of 515 kW/hr. The boiler is operated for an hour at this condition and 36.4 kg of condensate is collected. The overall thermal efficiency of this boiler is actually 92%.
515 + (0.645 x 36.4) = 538.
538 / 585 = 0.92 = 92% - Q: When would condensing be discouraged?
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.