Bertram31.com General Bulletin Board

Re: Thoughts on gens and A/C

Posted By: Sean Burlingham
Date: Friday, 16 September 2005, at 4:03 a.m.

In Response To: Re: Thoughts on gens and A/C (Capt. Dave Kosh)

Brain,

Add up your Amp usage for everything you think you want to run at the same time, and see what size you need. Here is the math I did when I replaced the genset on my B33:

Fresh water pump: 15A
Convertor (battery charger): 10A
Microwave: 12A
Fridge: 1.5 A
Air Conditioning Condenser: 14A
Big A/C Blower: 3.8A
Small A/C Blower: 2 A
A/C raw water pump: 2 A
Total = 60.3 Amps

If the spec sheet on a particular genset doesn't give output in Amps, the formula is Volts x Amps = Watts, so

8kW gives you 8,000 Watts/120 Volts = 66.7 Amps
6kW gives you 6,000 Watts/120 Volts = 50.0 Amps
5kW gives you 5,000 Watts/120 Volts = 41.7 Amps

I've also heard of guys that change the main breakers in 5kW units to get more output, and the sets give them what they ask from them, but I bet their burning out their generator windings over time and also experiencing voltage drops during times of heavy load. Voltage drops are okay for some things, but will burn many things up in time.

It is bare minimum, at least for me, to be able to microwave something while sink is running and A/C is on. I went with an 8kW set, which is what originally came with my boat too. The 8kW Kohler I ended up getting puts out 66.7 Amps total so I have some capacity to spare for future ice maker & water maker, but I'll probably have to do some load management when running those (if/when I get them).

The start-up load on your A/C shouldn't be a problem, because that's probably the first thing you'll turn on after starting the genny and will be the only thing drawing power when it is starting up.

I don't know if an 8 KW is an option on a B31 though, might be too big. I understand the Westerbeke's are really low profile and are meant to fit into tight spots.

Messages In This Thread

Thoughts on gens and A/C
brianb -- Tuesday, 13 September 2005, at 8:19 a.m.

Re: Thoughts on gens and A/C
John D -- Tuesday, 13 September 2005, at 9:40 a.m.

Re: Thoughts on gens and A/C *NM* *LINK*
John D -- Tuesday, 13 September 2005, at 9:46 a.m.

Re: Thoughts on gens and A/C
Capt Patrick McCrary -- Tuesday, 13 September 2005, at 10:28 a.m.

Re: Thoughts on gens and A/C
brianb -- Tuesday, 13 September 2005, at 10:48 a.m.

Re: Thoughts on gens and A/C
brianb -- Tuesday, 13 September 2005, at 10:51 a.m.

Re: Thoughts on gens and A/C
Capt. Dave Kosh -- Wednesday, 14 September 2005, at 10:22 a.m.

Re: Thoughts on gens and A/C
Sean Burlingham -- Friday, 16 September 2005, at 4:03 a.m.