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old guy :)
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Discussion Starter #1
Ahoy

OK - what I need is an "Inverters for Dummies" reply here. I understand AC and DC. I can do wiring. I have two deep cycle batteries and a Yanmar 2QM20H with "probably" a 50 amp alternator. (Manual is on board so can't look it up)

After reading some posts on hot water heaters, I would like to wire in a 1500 watt inverter and be able to turn it on for about the last hour of motoring so that the water is hot (rather than just warm). The Yanmar does not run hot - but it does run really good - so I do not want to mess with the engine.

The raw water cooling of the engine warms the water in the tank but a bit hotter would be nice.

I am also not in the market for a $2k pure sine wave inverter. I will not be running hospital equipment nor an oscilloscope with it.

Thanks in advance, and yes - I am ready for the 20 different opinions I will probably see.

:)
 

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Telstar 28
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If your water heater takes 1500 watts—at 12 VDC it will require 125 Amps to run it. If you have a 50 amp alternator, you'd still be shy of power needed by the inverter by about 75 amps. That means you'd draw down your batteries 75 amp-hours in the last hour of running the engine, just to heat the hot water. This is a significant portion of your battery bank capacity, since you only have two deep cycle batteries, and I'm guessing they're not 8Ds. :)

IMHO, you'd be far better off to turn on the inverter as soon as you start motoring, since, as the water heats up, the hot water heater will require less power, and more power will go to charging the batteries after a certain point. This would probably leave your batteries in a better, higher state of charge than doing what you initially planned, especially if you shut down the electrical side of the hot water heater for the last hour of motoring or so... :)

That said, I am quite surprised that the hot water heater isn't getting hot enough off the engine cooling system, via the heat exchanger coil inside the hot water heater. The engine should be running at at least 135-140˚ F at a minimum. If it isn't, then it is likely not running hot enough to be running efficiently. Domestic hot water temps are usually about 100-105˚ F, and the engine, even with conversion losses, should be able to get the contents of the hot water tank up that high. Since it can't, you probably should investigate why it can't. It could be as simple as scale build up in the heat exchanger coils in the hot water heater. Fixing this would make far more sense than killing your batteries, which is what running the electrical side will most likely do.
 

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WRT to the assessment that the engine not providing hot water...I too am surprised. After even just an hour of engine runtime, the waters hot enough to scald in my hot water tank.
 

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old guy :)
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Discussion Starter #4
On our last boat we had a Yanmar 2GM20F (fresh water cooled) and it ran the temperature I thought it should have.

On this one the Yanmar is much older, is raw water cooled and does not seem to run very hot. Going swimming last week - the water was not overly hot coming out of the exhaust hole.

The hot water tank is brand new.
 

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I had an electrician install mine, as I didn't have time to do it. He recommended wiring the inverter so it would not feed the water heater. He was about the third electrician that gave me that advice. I guess the prevailing opinion is you will toast your batteries really fast if you turn it on by mistake, or forget to shut it off.

The water heater should get hot enough on the engine. The water flowing out of your exhaust is constant flow and does not warm up as high as the coolant in the system.
 

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1500 Watts will kill your battery in a short period of time; the battery voltage will go down faster than a prom dress. If the battery bank is 6' from the water heater, you would need 1/0 power cables, which is 0.640" in outside diameter (bigger than the battery cables to the starter).

Inverters are spectacularly inefficient, and one that big will cost about $100, if you don't care what the sine wave looks like (you don't).

A much better plan would be to buy a 2000 W gen set for $200 and run it to heat the water. It means you have to have gasoline on board, but it is much more reasonable than the inverter idea. The bonus is you can charge your batteries in a pinch, and you are all set to add refrigeration and air-conditioning!

Best Regards,

e


.::.
 

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old guy :)
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Discussion Starter #8
Do you have a temp gauge on the engine.
Just the little red lights. :)

I have purchased an infrared thermometer but it is a few miles away from here. I will pick it up in two weeks, then I can do some serious checking.

So - I guess I will not waste my money on the inverter (the little $30.00 one charges the commodore's Mac).

Thanks all of you - I will explore the engine temperature some more.
 

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A much better plan would be to buy a 2000 W gen set for $200 and run it to heat the water.
.::.
Where on earth are you seeing 2000 W generators from a reputable brand for $200?!!

Cheapest I've seen was the Honeywell 2000W Honda lookalike on clearance at Home Depot for $299.
 

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Just the little red lights. :)

I have purchased an infrared thermometer but it is a few miles away from here. I will pick it up in two weeks, then I can do some serious checking.

So - I guess I will not waste my money on the inverter (the little $30.00 one charges the commodore's Mac).

Thanks all of you - I will explore the engine temperature some more.
If it were me, you have 2 good indicators the engine is running cold. (temp of hot water and temp of exhaust water.) I would pick up a thermostat and just go ahead and change it out. You did say it was a older engine. By the time you get done messing around checking the running temp of the engine you could have the thermostat changed out. Just consider it normal maintenance.
 

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old guy :)
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Discussion Starter #11
If it were me, you have 2 good indicators the engine is running cold. (temp of hot water and temp of exhaust water.)
Three - there is a white vapour with the exhaust.

:)

And guess what, I have a thermostat in my spare parts box. That should not be too hard a job.

Thanks all - I do like this group.

Now - if you could just send me some warm weather and take away the rain.

Cheers, all
 

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Where on earth are you seeing 2000 W generators from a reputable brand for $200?!!

Cheapest I've seen was the Honeywell 2000W Honda lookalike on clearance at Home Depot for $299.
Actually, Home Depot. They had an internet-only one for sale in April That I bought to run the polisher when the boat was on the hard and far away from the bureaucratically dominated sources of electricity. It runs great! Made in China (who'd a thunk it?)

Best Regards,

e

.::.
 

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Guys, it seems this old model Yanmar doesn't have closed water circuit, no heat exchanger, likewise the old 1GM10. It's cooled by raw water intake directly through the cilinders. These engines doesn heat at all, they barely warm a bit the exausted water, and many sailors have some trouble geting hot fresh water out of it. SD is correct balancing the energy you need for hot water, my point is using water a bit warmer from raw water out, plus a regular 700W heater (the most common 120V type) in a good water heater tank, might be an option to you. But it will require you to run engine for a couple of hours and pry to tank hold the temp until you need it. I think best solution would be a small gas genset (many people disaprove it due to lethal carbon monoxide emissions). In this case, go for the most powerfull heater you can to reduce engine hours. But I'd go for honda's or yamaha's only ...
 

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In this case, go for the most powerfull heater you can to reduce engine hours. But I'd go for honda's or yamaha's only ...

He's just heating water. If you are a generator snob and need the Honda name to make you feel better, paint "HONDA" on the side of the $200 Chinese generator and pocket the $1,000. In the unlikely event the generator fails, throw it away and buy another one.

Best Regards,


e

.::.
 

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He's just heating water. If you are a generator snob and need the Honda name to make you feel better, paint "HONDA" on the side of the $200 Chinese generator and pocket the $1,000. In the unlikely event the generator fails, throw it away and buy another one.

Best Regards,


e

.::.
My point was that even the cheapest chinese POS (which Honeywell is...they've sold their brandname) is more than $200 for a 2000 W

Please share with everyone if there are deals out there!!
 

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Please share with everyone if there are deals out there!!
He did in post #12

Actually, Home Depot. They had an internet-only one for sale in April That I bought to run the polisher when the boat was on the hard and far away from the bureaucratically dominated sources of electricity. It runs great! Made in China (who'd a thunk it?)
 

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He's just heating water. If you are a generator snob and need the Honda name to make you feel better, paint "HONDA" on the side of the $200 Chinese generator and pocket the $1,000. In the unlikely event the generator fails, throw it away and buy another one.
.::.
I understand your point of cheap replacement, but first, I doubt it will be used for hot water only, 2KW is a tempting amount of energy, and like me, will be soon on diverse applications, second it shouldn't fail on my 5,600 miles trip from US, third only Honda has local presence here with replacement parts.

It's funny Honda considered a snob appliance ... never heard that before :) :)
 

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I understand your point of cheap replacement, but first, I doubt it will be used for hot water only, 2KW is a tempting amount of energy, and like me, will be soon on diverse applications, second it shouldn't fail on my 5,600 miles trip from US, third only Honda has local presence here with replacement parts.

It's funny Honda considered a snob appliance ... never heard that before :) :)

Hey, whatever works for you. A Honda or Kawayamasaki will cost about $1,000 more than mine - so if it will last longer than 5 of my Chinese generators, it's probably a good deaL :D

Best Regards,

e
.::.
 
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