Generator replacement

[markrsimon]

With the original 7.5KW, you could basically run everything (including water heater) - until you get to the stove. When you scale down to the 5.0KW, you loose 33% capacity.

I used 11,000 BTU because it was easier to grab. Again, these are generic reference numbers to give you a sense of what you can power up at the same time. Your mileage may vary, given the make/model of each device you have, and the newness (which typically equals lower power consumption).

The only thing I updated was the first line (in green). The usability results are the same as before (prev post).

7500 watts @120v = 62.5amps [Original 7.5KW Quicksilver]
5000 watts @120v = 41.6amps [New Kohler 5.0KW 5EKD]

Fridge 0.4amps [Norcold DE-0061, 7cu ft]
Ice Maker 2.5amps [Uline 21"]

AC Total 32.6 / 19.7
AC 16,000 BTU 17.6amps / 10.8 [start/run]
AC 11,000 BTU 14amps / 7.9 [start/run]
AC Water Pump 1amp [0.99amps]

Microwave 9-15amps
Stove 10amps / 10amps / 10amps [each burner (3) is 1200w]

BattCharger 4amps* [Pronautic 1240P - 15amp AC breaker]
12volts * 40amps = 480watts / 120v = 4amp*
*unable to find actual specs for AC current draw

WaterHeater 12.5amps [1500watt element]

 

[CaptRonn]

I would think 5kw would work, but just don’t run both AC units at the same time.

Like previously mentioned, the start up of the compressor is where the high amp drain occurs.

 

[ttmott]

Add a couple of Dometic Soft Start kits to the AC compressors and you'll be fine. The resistive loads aren't your problem; it is the inductive loads (motors) that drag generators down.

 

[bobeast]

Thanks for the breakdown. Correction on the Quicksilver it is a 7.5KW and the a/c units are 16,000 and 12,000. How does your calculations breakdown to total watts???

total amp draw * 120 will equal required watts. Conversely available watts / 120 will give you available amps.

so 7.5Kw can output up to 62.5 amps
5KW -> 41.6

So you are looking at about a 20 Amp rated difference.

Just add up your total maximum expected amp draw and see which one fits. You can likely get away with a smaller generator. You just have to be judicious about which appliances you use at the same time. Also take into consideration startup surge on the ACs. Best to do your calculations assuming the max, to give yourself a buffer.

 

[northern]

In rush current on starting big motors can be high. I was told it can be 3+ times as much as running amps. We have 8KW generator and a water maker. To start the water maker I have to have all other power draws off. If I do not when the watermaker starts things will drop off. We have an inverter that is also a 140 AMP battery charger. If I leave it on when I start the watermaker it shuts off then comes back on.

 

[menos22]

Great info, thanks. Guess I would be ok starting the A/C units one at a time. I.E. let one get up and running and then start the other. And watch what else I need to turn on.

 

[CaptRonn]

Great info, thanks. Guess I would be ok starting the A/C units one at a time. I.E. let one get up and running and then start the other. And watch what else I need to turn on.

If you have both AC units running, and the compressors kick off (fan only) until the unit needs to cool again, then let's say both units compressors start at the same time, you will have a problem.

It's the compressor start up that demands the high amp load. AC cycles the compressor to meet the demand.

ttmott made a great suggestion:

Add a couple of Dometic Soft Start kits to the AC compressors and you'll be fine. The resistive loads aren't your problem; it is the inductive loads (motors) that drag generators down.

 

[menos22]

I messed up on the A/C units, they are 12,000 and 7,000 units, not 16k and 12k. So with that in mind I have a chance to pick up this 5kw Kohler with sound shield and wire harness for 4,500.00. It only has about 6 hours and was never installed because the boat was trashed before that had a chance to install it. Its been sitting in the garage. Think this can work. A/C aft. 15Amp start 11.8 run. A/C fwd. 12Amp start 9.3 run.
A/C water pump 1A. Microwave 12A. Stove 2 burner 10a per burner. Ice maker 2.5A. Fridge 0.4A. Not using water heater and will not use microwave and both burners on stove at same time. What do you think? Will it work? With everything running except for stove and water heater, I come up with about 37Amps. Genny puts out 41.6Amps. What do you guys think. Should I go for it, $4500 sounds like a sweet deal for an almost new Kohler. The start up figures on the A/C units is a guess, might be a little high. Defer to the experts. Thanks

 

[CaptRonn]

Make sure it starts and runs. If you buy, replace the raw water impeller before use. Also oil and filter.

 

[RBB]

I messed up on the A/C units, they are 12,000 and 7,000 units, not 16k and 12k. So with that in mind I have a chance to pick up this 5kw Kohler with sound shield and wire harness for 4,500.00. It only has about 6 hours and was never installed because the boat was trashed before that had a chance to install it. Its been sitting in the garage. Think this can work. A/C aft. 15Amp start 11.8 run. A/C fwd. 12Amp start 9.3 run.
A/C water pump 1A. Microwave 12A. Stove 2 burner 10a per burner. Ice maker 2.5A. Fridge 0.4A. Not using water heater and will not use microwave and both burners on stove at same time. What do you think? Will it work? With everything running except for stove and water heater, I come up with about 37Amps. Genny puts out 41.6Amps. What do you guys think. Should I go for it, $4500 sounds like a sweet deal for an almost new Kohler. The start up figures on the A/C units is a guess, might be a little high. Defer to the experts. Thanks

If it runs and you buy it I would take it by a electrical shop that repairs generators and have it tested unless u have the know how or your buddy. if any repair needed it will be cheaper than once its on the boat.

 

[menos22]

New impeller is being install and oil/filter change. Owner has run it to make sure it still works. think he said it has 6hrs on it.

 

[CaptRonn]

You’ve scored on this one. Gas generators are only going to get more expensive and harder to buy new.

 

[390x]

I guess I'm the only naysayer who can't figure out for the life of me why you'd ever downsize a generator.

 

[RBB]

New impeller is being install and oil/filter change. Owner has run it to make sure it still works. think he said it has 6hrs on it.

I would still run it and take it by a shop. your call sir

 

[CaptRonn]

I guess I'm the only naysayer who can't figure out for the life of me why you'd ever downsize a generator.

Gas generators are now down to one manufacture (Westerbeke) and are only getting more expensive.

The next choice is an overhauled unit from a reputable vendor, if they have what your looking for.

Last choice is a used one that may work 1,000 hours or blow up on hour one.

OP found a unicorn. Hope it works out for him.

On my boat, my gas westerbeke 9.5 burnt out, and I couldn’t separate the armature from the shaft to get it overhauled. I replaced it with a 7.5 Phasor diesel unit. And even dropping from 9.5 to 7.5 I haven’t noticed any changes.

Gas generators are going to get harder to find. Those that rebuild them are going to have an improving market for sure.

 

[menos22]

As previously noted, gas Gennies are hard to find. Kohler is out of the gas business. My Antiquated Quicksilver 7.5kw belongs in a museum or boat anchor. I can make the downsize work, one 12k and one 7k A/C units running and be mindful of what else I turn on, I do not use the water heater, it gets heated by the stbd eng. Only other big amp. draws are the microwave, small unit only 700w and 2 burner stove, would not be running at same time. Plus as Capt. Ron stated it is a sweet deal and will add to re-sale value. Think people would be turned off by a non working generator. Think Im going to go for it. Will let you know how it works out. Now I have to worry about removing the Quicksilver and installing the Kohler. Thanks for all your input, it was very helpful in making my decision.

 

[CaptRonn]

The swap out is not difficult as far as wiring. Get the wiring diagram for the boat and the diagram for the genset.

What is difficult is lifting out the old unit and dropping in the new one. I used a crane on back of a truck.

 

[menos22]

I got the 5kw kohler. Removed the 7.5kw Quicksliver and installed the Kohler. used existing wiring from the AC panel to new Kohler, installed new remote start switch with oil pressure and temp guage. Genny runs fine under load. Will be doing some load testing on it this week. Fits nicely in engine room with sound shield installed. Thanks for all your advise and suggestions, finally got it installed and running.