By Marc Burrell, Project Engineer, NGVi
Welcome back to our five part series where we discuss what you need to understand about upgrading your vehicle maintenance and repair facility for natural gas-powered vehicles. The purpose of this series is to touch on each of the major components of a vehicle maintenance and repair facility and explore how it relates to the multiple codes to which the building must comply after being retrofit. Since each facility is unique, it is important to seek an evaluation by a knowledgeable and experienced professional who is familiar with the codes and industry best practices to ensure recommendations are custom tailored to your facility.
In Part 1 we discussed the building envelope and some of the challenges that accompany applying the codes to this part of the facility. If you missed this article, please feel free to view it here. In today’s article, we will explore the heating system.
Heating systems are potential sources of ignition in the unlikely event of a natural gas leak within a vehicle maintenance and repair facility. NFPA 30A, one of several codes that apply to NGV repair facilities, states “Where major repairs are conducted on CNG-fueled vehicles or LNG-fueled vehicles, open flame heaters or heating equipment with exposed surfaces having a temperature in excess of 750°F shall not be permitted in areas subject to ignitable concentrations of gas.”
Therefore, inside the NGV maintenance facility, where there could be an ignitable concentration of gas, codes prohibit:
Open flame heaters of any kind.
Any other type of heating equipment with heating surfaces having a skin temperature greater than 750°F.
Any type of heating system that draws intake combustion air from inside the maintenance facility.
Although it is easy to identify visually whether an existing heater has an open flame or not, determining its surface temperature requires the use of an Infra-Red or Digital Touch thermometer during the facility evaluation and while each piece of heating equipment is operating. These devices read the surface temperature of the existing equipment and will determine definitively whether they meet NGV codes from a temperature standpoint.
In our experience, most existing diesel or gasoline maintenance facilities use heaters that are not NGV code compliant. When this is the case, the existing heating system must be replaced. For facilities with non-central heating systems, existing heaters must be replaced with any type of sealed combustion tube heaters with a skin temperature less than 750°F. Examples include infrared tube heaters made by companies like Roberts Gordon. These types of units meet all the code requirements of NFPA 30A: they use no open flames, draw combustion air from outside, exhaust products of combustion to the outside and have skin temperatures less than 750°F.
In the case of an existing central heating system (which is much less commonly found in vehicle maintenance facilities), it is possible the system can be replaced with a similar heating system located outside the facility. This usually requires more HVAC engineering and can be a more costly solution.
During a professional vehicle maintenance facility evaluation, the entire heating system (which may be composed of multiple units of the same type of system and/or multiple units of multiple types of systems) must be observed and recorded. A determination of their code compliance must be made, and a plan to provide adequate heat for workers using code-compliant heating systems should be devised.
When it comes to heating systems in NGV maintenance facilities and code compliance, the codes are very clear and options are usually straightforward. In next month’s series, we’ll discuss a perhaps more complex issue—lighting and electrical systems.