AC Startup Power with Generator
- Thread starter SqPeg
- Start date
Which Webasto unit are you looking at? The numbers just don't look right. Is the 57 amps at 12v? or at 120v?
SqPeg, your numbers seem in line with the 16,000 btu Dometic unit that I'm using. It has a starting current of 62 amps and a running current at max cooling of 10.4 amps and 13.6 amps for maximum heating. All these figures are 120 volt AC. It easily runs on a 3.5 kw generator.
Yes, the starting requirements for an A/C unit is around 4-5 times the running current. I concur with Ted that a 3.5 kw generator would provide very adequate performance.
Yes, you fuel and operate on the swim platform (LOVE that swim platform), but the location does not stay dry when operating the boat. Which means you need a separate stowage location, and that needs to accommodate the hazardous gasoline fuel - you don’t want that stuff in your bilges. Everything needs to be secured, don’t want a 60lb loose cannon.
To me it’s no different then carrying fuel for your dingy. But you are right that you need to make safety number one. We use a Predator 2000 on our boat and it works very good for handling our power supply. We have two compartments on the stern that has no drains in them. We store our sealed gas can in one of those lockers.
Absolutely! I am always astonished when anyone implies a distinction between the hazards of portable generator gas storage on a boat when an outboard dinghy motor is almost ubiquitous.
General rule of thumb for planning a motor control circuit is to assume locked rotor current at 6 times full load amps. That is in line with a 10.4 amp motor drawing 62 amps at start up. Often, actual start up current is less with certain loads, but a compressor load (AC unit) usually has one of the higher start up currents.
Generators frequently have two ratings, a running rating & a surge rating. The surge capacity needs to be enough to handle the inrush current of the compressor starting. Lower end traditional generators have surge ratings that are about 10-20% above normal run ratings. More expensive ones, with better windings, sometimes have much higher surge ratings. Inverter generators (like the Honda briefcase types) often have some of the lowest surge ratings.
3500w/120v= about 30 amps. In the case of a 3.5kw generator that puts out 220vac, the amp number would be half of that. I would not expect a 3.5kw generator to handle a 60-amp starting load. You might want to take some measurements to see what current you are actually drawing when that thing starts & you might want to find out what the surge rating on your generator is. A 3.5kw generator trying to run a 60 amp start up, sounds like a recipe for a brown out & the subsequent repair bills that follow.
Gasoline, propane, alcohol, natural gas and diesel fuel are all combustible and their fumes are all explosive in high concentrations if unable to escape an enclosed space. There is no better protection than knowing the characteristics and dangers of each fuel. We know gasoline expands and contracts with changes in temperature, we know the usual gas cans can only hold a limited amount of pressure before leaking fumes out into the open. We have kept gasoline for years in cockpit lockers; we keep nothing larger than 3 1/2 gallon containers and choose those with tight fitting lids. We may carry 5 gallon cans attached to a board at the stanchions but prefer the smaller cans. We keep them at stable temperatures as well as possible and if it gets too hot will vent them in the open deck before returning them to a locker. The newer no vent tanks are a poor compromise btween regulations and manufacturing so we use old ones we have tested and trust. We are vigilant about removing any possible source of sparks from the locker. The nose makes for an excellent sniffer, gasoline fumes have a strong odor. No cooking or open flames near the locker. Quit smoking many years ago so don't have to worry about that other than occasional invitee. We used to run a copper line from a propane tank on deck to a stove inside the cabin and we are still here we knew the dangers and used to perform all the functions that today's fancy switches and sensors perform in a propane system. Always keep the tank valve closed when the stove is not in use, always stand in front of the stove to watch for flare ups or flame outs. Keep a clear path to the tank valve and periodically use your nose to sniff for gas leaks. We did have a pressure gauge so that we could test for leaks. Is good to have all the new technology but it is better when combined with the knowledge of each fuel. I grew up at a time when we did not get many second chances from mistakes so we paid attention to those that came before us and fervently applied the teachings.
