Generator Loads

[Chris989]

Being a Puget Sounder, we don't use the A/C all that often except occasionally on heat mode and as a dehumidifier. However, I discovered that our Westerbeke 4.5 BCGB will not carry the load of the Cruisaire unit. when the A/C comes on, the genny lugs down then the Cruisaire kicks offline, presumabley due to low voltage, and the generator picks back up to normal rpm. I know the startup of the A/C probably has a pretty high current draw, but should the little 4.5 be able to carry this? I have made sure that everything else if off so the only load on the genny is the A/C. This isn't a critical issue, but it is bugging me. Just looking or some random thoughts on if I have a problem or within expected norms.

Thanks!!

 

[370Dancer]

What size is the Cruisair 12Kbtu, 16, 6?

4.5 should be able to keep up with any of those. I run 2 12Ks and a bunch of other stuff on a 7.0BCG, although I'm careful not to try and cold start them together.

You may have a compressor or starting cap issue, potentially from non/low use.

 

[fwebster]

Sea Ray usually does a good job of matching generators to the equipment on the boat. You need to run a generator fully loaded, so more generator capacity is going to cause you to run unloaded which will cause more problems with fouled plugs frequent tune ups etc.

If your generator lugs down then you may have a dying compressor in the A/C unit drawing excess current on start-up which overloads the generator. That would cause low voltage which would shut down the compressor motor.

Your ammeter on the main panel should peg momentarily when the compressor kicks on, any longer than about 1 sec and you are drawing too much current.

 

[Alex D]

Sea Ray usually does a good job of matching generators to the equipment on the boat. You need to run a generator fully loaded, so more generator capacity is going to cause you to run unloaded which will cause more problems with fouled plugs frequent tune ups etc.

If your generator lugs down then you may have a dying compressor in the A/C unit drawing excess current on start-up which overloads the generator. That would cause low voltage which would shut down the compressor motor.

Your ammeter on the main panel should peg momentarily when the compressor kicks on, any longer than about 1 sec and you are drawing too much current.

GReat info ... I seem to also have more start up draw on the a/c when she's in heating mode than on cooling mode.

 

[never monday]

GReat info ... I seem to also have more start up draw on the a/c when she's in heating mode than on cooling mode.

Alex,
That's normal, it requires more to run the heat side. A 4.5 will easily handle a 16k and a 5k at the same time. Westerbeke's carbs are only adequate. When the fuel pressure starts droping from cloged filter or a weak pump, they'll start carrying less load.

Pat

 

[Alex D]

GReat info ... I seem to also have more start up draw on the a/c when she's in heating mode than on cooling mode.

Alex,
That's normal, it requires more to run the heat side. A 4.5 will easily handle a 16k and a 5k at the same time. Westerbeke's carbs are only adequate. When the fuel pressure starts droping from cloged filter or a weak pump, they'll start carrying less load.

Pat

Good to know!! I will anyway go through the fule system of the carb and change filters. I also have a heavy dose of Gumout Regane in the tanks right now. This is one of the best and strongest fuel system cleaners (a godd dose of polyether amine, not just solvent naphta) available and relatively cheap ($5.40 at wally mart).

 

[Chris989]

Man I'm glad you made it over here, Frank. Anyway, I've always been careful to always start the gen. let it run jus for a minute or so then give it a load. Never really run it without a load for the reasons you mention. run the genny with a load. The previous owner NEVER used the AC at all. Will watch the current draw and then call the marine electrician.

Thanks again,

CP

 

[thunderbird1]

I've also had load problems with my Westerbeke 5KW Low CO model. Sea Ray reported to me " The 7K BTU AC amp draw with 25% overage system safety factor is 12 amps. This includes the AC raw water pump." I've never had the AC system quit, but my genset has shut down with an "overspeed" error several times with the AC/heat running. My local Westerbeke Distributor is investigating.

 

[thunderbird1]

Not intending to hijack the thread, but I have two nagging related (possibly goofy) questions.

1. What is the normal voltage range one should expect to get from a generator? The meter in my cabin often reads 100-105 volts with AC, bat charger, and frig running.

2. My generator is started using the same two batteries which start the boat engine. The boat engine and generator both have alternators, although it's not clear to me whether my genset alternator is connected to the two batteries. Is it acceptable/safe to run both alternators at the same time? How about the genset alternator and battery charger at the same time?

 

[Chris989]

Hi-jack away T-bird. Those are both good questions. First and foremost, I solved the problem with the generator cutting out. The SMX II control has a voltage calibration function. Mine was mis-calibrated so that it was 'seeing' 125 volts (no load) when it was actually only getting 120 volts. So when the compressor would start, the slight voltage drop was enough out of tolerance that the low voltage cut-out would kill the AC unit. (You learn a lot from reading the manuals!!).

For T-Bird - 1) I am seeing 118-120 volts, tested with a Fluke meter this afternoon. This is under light and heavy loads. The voltmeter on the electrical panel is only good for a guess as it was reading about 5 volts low.

2) I believe I have the same set up. The generator alternator does charge the battery(ies). Since there is no 'shut off' for the alternators, I've never worried about running the mains with the generator as assumed that the charging circuitry of the alternators recognizes a fully charged battery anyway. Same for the charger, which also acts as a 12-volt power supply if it is the Charles Industries 2000 or 5000 series that have typically come with many Sea Rays.