Roger Long
Senior Member
I would like some real world experienced ground truthing of theory. Most of us know that running a diesel generator at light or no load is bad for it. I used to do generator load analysis (a quarter century ago) to properly size gen sets. However, things always look different in the real world.
We put a new Westebeke 7.5 kw unit in our trawler last year. As a result of my load analysis experience, I would have preferred to put in a much smaller one and done load management but we knew that we would only own the boat for a few years and took the advice that selling it would be difficult if it didn’t have one of the size expected on boats of comparable size. One of our AC / Heat units is inoperative and we haven’t replaced it yet because we don’t need it much on our cruising schedule. We were just barely able to get the unit up to the minimum recommended load for break in by doing things like running a portable heater in the stateroom with the AC on and letting the hot fresh water run slowly.
I monitor the output frequently and almost always find the amp meters (split buss for service and AC) at zero. The water is hot, the reefer and fridge are cold, and the AC or heat thermostat has tripped off. I shut down and restart a lot but this often results in the ice cream getting soft and the fridge not being cold enough to make it through the night with power off. Most of the running time, this 7.5 KW unit is putting out only about 10 amps, 15% load. A lot of the time, it is just free wheeling. I still find myself starting up the portable heater in the stateroom with the AC going.
I’m sure from this experience that lots of trawlers are running their generators very, very lightly. So, my real world questions: Are any of you seeing the bogy men I was told about back when I was doing load analysis, wet stacking, maintenance problems due to blow by from light piston ring loading, etc.? Are we likely to see problems with this unit or are we just shortening its life by some indeterminist amount way down the road after we are doing our cruising in Barco loungers in front of the nursing home TV?
I know there are solutions to this issue such as a golf cart battery bank with an inverter for the fridge but we are cruising on a frayed shoestring and I’m trying to get a handle on the issue to prioritize with other needed upgrades.
We put a new Westebeke 7.5 kw unit in our trawler last year. As a result of my load analysis experience, I would have preferred to put in a much smaller one and done load management but we knew that we would only own the boat for a few years and took the advice that selling it would be difficult if it didn’t have one of the size expected on boats of comparable size. One of our AC / Heat units is inoperative and we haven’t replaced it yet because we don’t need it much on our cruising schedule. We were just barely able to get the unit up to the minimum recommended load for break in by doing things like running a portable heater in the stateroom with the AC on and letting the hot fresh water run slowly.
I monitor the output frequently and almost always find the amp meters (split buss for service and AC) at zero. The water is hot, the reefer and fridge are cold, and the AC or heat thermostat has tripped off. I shut down and restart a lot but this often results in the ice cream getting soft and the fridge not being cold enough to make it through the night with power off. Most of the running time, this 7.5 KW unit is putting out only about 10 amps, 15% load. A lot of the time, it is just free wheeling. I still find myself starting up the portable heater in the stateroom with the AC going.
I’m sure from this experience that lots of trawlers are running their generators very, very lightly. So, my real world questions: Are any of you seeing the bogy men I was told about back when I was doing load analysis, wet stacking, maintenance problems due to blow by from light piston ring loading, etc.? Are we likely to see problems with this unit or are we just shortening its life by some indeterminist amount way down the road after we are doing our cruising in Barco loungers in front of the nursing home TV?
I know there are solutions to this issue such as a golf cart battery bank with an inverter for the fridge but we are cruising on a frayed shoestring and I’m trying to get a handle on the issue to prioritize with other needed upgrades.