[Neweller]

Q
237 1/24/2001 3:47:09 PM 1/24/2001 TechTalk Staff TechTalk@newellcoach.com roof AC from eng. & inverter? Through the years, we have equipped a handful of new coaches to operate a 120 volt air conditioner from a large inverter powered by a high capacity alternator. However, we are not enthusiastic about this approach. While the system can be designed within the theoretical capacities of the individual electrical components, the alternator and inverter are being pushed very hard under these circumstances. In addition, the large amount of DC current flowing between the alternator and inverter to produce the approximately 1500 watts to run an a/c can result in a simple fault (i.e., loose connection) having a serious result (i.e., fire). Further, there is a temptation to push this approach even further, running an a/c from the batteries, a situation we feel is far too aggressive. We suggest using the on board generator to operate the a/c and avoiding the considerable extra expense and risk of attempting to use the inverter for this job. By the way, using the alternator to supply the inverter with current for air conditioning loads is not "free power." The alternator under this type of load will consume an extra 15 hp or so from the main engine. This is power that is not available for climbing hills, etc., and fuel mileage is affected. Operating the generator supplies independent power for the a/cs, and the fuel used is, to some extent, an offset from the decreased mileage of putting this load on the main engine. Others may differ, but this is our opinion.