NFPA 110, 1999 edition, chapter 3-1.1 as well as NFPA 70, 1999 edition, chapter 700-12 (b) (3) require the generator notbe solely dependent on a public utility gas supply for their fuel source. (Later editions include the same requirements)
NFPA 70 also disallows cooling systems that rely on off-site sources like the public water system.
Some jurisdictions have accepted a letter from the utility stating that the fuel source will not be, or is unlikely to be, interrupted. This is entirely your surveyor�s call. While some jurisdictions may accept this affirmation from a utility, others may not.
Dual fuel systems, natural gas and LPG, have been available from the manufacturers for a long time. They should be ordered with the system since it is an expensive and awkward field modification. The biggest problem comes from timing. NG and LPG require an ignition timing change because of the difference in heat value of these two fuels. With some of the newer systems this is possible while some of the older systems cannot effect the timing change.
Natural gas with diesel as an alternate fuel is not a likely option because of the great difference in compression ratio between a spark ignited engine and a compression ignited engine.
Generators and automatic transfer switches as well as their appurtenant devices employ high voltages that can hurt you. Do not attempt to work with this equipment unless you are qualified. Observe all rules and cautions found in the manufacturer�s manuals as well as NFPA 70E, Standard for Electrical Safety in the Workplace.
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