Run the water heater from the inverter?

[Simi 60]

If you think you can make hot water even with low wattage heater element from your batteries, for days, you are wrong.

Mate, I have been running a 180 litre 240v hws every day for 4 years without using genset.
Don't tell me it can't be done.

There is this big thing in the sky called the sun.
Perhaps you've heard of it? (-;

 

[catalinajack]

Simi 60, no need to be so snarky. I'm hazarding a guess that OldDan43's opinion was based on boats that do not have solar or enough solar to do it as you do. Based on my observations only 20% of boats, at most, have solar panels. Could you have said "It can be done with sufficient solar capacity. Here is what I have that works". Bottom line is, without a big solar array, it cannot be done.

Mate, I have been running a 180 litre 240v hws every day for 4 years without using genset.
Don't tell me it can't be done.

There is this big thing in the sky called the sun.
Perhaps you've heard of it? (-;

 

[OldDan1943]

I was not offended by Simi's comment. He was bragging. LOL
I have 2 130watt solar panels also
When I find necessary, I am not afraid to run the generator.
Even underway, sometimes the AC runs and makes the entiror very comfortable in FL

 

[catalinajack]

If you were not offended then I apologize to Simi. The written word sometimes does not impart the meaning that was truly intended. I have been misinterpreted on occasion. I once responded to a posting on the Great Loop website about Lake Champlain that I thought was misleading. Still do. The poster publicly excoriated me in the worst way, that I should be ashamed of myself when, in fact, I was just trying to offer a different view. I let it pass. Simi 60, will you forgive me?

I was not offended by Simi's comment. He was bragging. LOL
I have 2 130watt solar panels also
When I find necessary, I am not afraid to run the generator.
Even underway, sometimes the AC runs and makes the entiror very comfortable in FL

 

[OldDan1943]

If you were not offended then I apologize to Simi. The written word sometimes does not impart the meaning that was truly intended. I have been misinterpreted on occasion. I once responded to a posting on the Great Loop website about Lake Champlain that I thought was misleading. Still do. The poster publicly excoriated me in the worst way, that I should be ashamed of myself when, in fact, I was just trying to offer a different view. I let it pass. Simi 60, will you forgive me?

These days people seem to be easily offended resulting in a growing number of shootings.

LOL He better forgive you.

I am not easily offended and when it happens, I just stab'em

:lol:

 

[Ski in NC]

When traveling in the Caribbean area, we barely ran the water heater. It and the water tank are in the engine room and showers were pretty warm from engine heat. Might run the gennie for 15min, it's good for it to run anyway.

I too do not want the water heater hooked to main engine coolant. Our single engine is sacred and I have seen numerous engine failures due to the heater loop leaking or getting air bound. Just not worth it to me.

And pulling a big load on a main engine alt to make hot water is full of risk. Burn out that alt and that is a big problem compared to a 30min gennie run.

 

[BrianSmith]

I want to know why this wasn't answered buddy?

I think you're joking, but if not... I didn't answer it because it didn't seem to be a reasonable response. I have a generator that can make hot water, and there's no problem doing that. No reason whatsoever to take cold showers for a week.

 

[BrianSmith]

Just my take, doing long offshore passages i always try to shower just before sleeping on my first off watch at night. Having a good shower ( hot and of moderate length) really helps me sleep better and gives me something to look forward to. Running the genset for a hour to make some hot water and run the water maker is good for all the systems and uses very little fuel. I never understand a power boater that worries about a little fuel use by the genset. Your going to burn around 600 gallons of fuel for the trip.. whats 15 more?.
Great boat by the way, Have a friend that used to have the Kristin
trawler" Aruna". have a great trip.

HOLLYWOOD

That's a good way to think of it. We're not looking forward to this trip AT ALL, but it'll be necessary if the Bahamas doesn't open their waters in the next month - which seems unlikely. We'll have 1 or 2 crew onboard (probably a friend/friends, but possibly hired), and if everyone can have a nice hot shower every day or two, and there's no water rationing because we're making water for an hour a day... that will make it more pleasant for all onboard.

In the long term, however, there have been some really good ideas from this discussion:
1. A smaller hot water tank that takes less power to heat all the water, and less power to keep it hot.
2. A lower-wattage water heater, that will be much easier to power from the inverter (whether the batteries are being powered by the main engine alternator, or by the sun).

In the long run, however, what we REALLY need is more battery capacity, and the answer to that riddle keeps coming up "Lithium batteries".

 

[BrianSmith]

1. you have gas cooking?
2. your fridge and freezer, 12 volt?

IMO, your voyage is a good reason to have a 12 vt water maker. When I had my WM installed, I opted for a 12 volt system.

First thing I would do when back is to replace that HW heater with one with engine coolant coils. In the process of replacing the HW heater, put a couple of valves on the water line to and from the engine cooling system.
IF for some reason the tank coil fails (highly unlikely) you can isolate the HW heater from the engine coolant system.
I know my N46's JD had a coil on the engine and I just ran the hoses to and from the engine cooling system and put isolation valves in line.

Personally, I would be more concerned about burning up the engine alternator. Yes, I have for a spare alternator but, after running for a few hours, that engine and engine room will be way too hot to work in ER while bobbing around in the ocean.

Push come to shove, I vote for running the generator while running the water maker at least. We have a generator for a purpose so why not use the generator. I doubt the generator uses a gallon of fuel per hour. Sounds like, in a manner of speaking, you want to go camping again.

If you are worried about fuel, a couple of small fuel bladders will resolve that problem.

Are you transiting during the hurricane season? If so, this presents even more problems.

God's speed and have a safe voyage.

1. Propane cooking - yes.
2. Fridge / freezer is AC/DC, automatic switching.

The compartment for the water heater is a LONG WAY from the engine - the hoses to reach it would be at least 25 feet. And the engine is keel cooled, which may or may not pose additional issues (we don't need to discuss that here). As much as I like the idea of free hot water, I think I can get that from the main engine and the solar panels with a smaller water heater (smaller tank size and lower wattage).

Not worried about fuel. We'll have 1,000 gallons when we leave St. Thomas, and the whole trip shouldn't use more than about 700, even if we run the gennie a couple hours a day.

Not traveling during hurricane season. This is the trip to get us out of the Caribbean BEFORE hurricane season - sometime in May.

 

[BrianSmith]

If you've gotten this far, Dear Reader, I think we've covered this topic in sufficient detail. Thank you all very much. As always, I learn a LOT when I ask a question on TF!

 

[dieck]

We often run the boat for 4-5 hours at a time, and it's not unusual to run it for 8 or more. But in the next 30 days or so, we may be looking at running it non-stop for about 140 hours, to cover the distance from the USVI to FL. (If the Bahamas don't loosen their restrictions, we have to go around them.)

I don't want to run the generator more than I have to, and everything that we'll need for a long passage like that is either DC, or runs off the inverter. Except the watermaker and the water heater. I expect to run the generator and watermaker for about an hour every other day, which will heat up some water, but in between, with the main engine running and charging the house bank, what about running the water heater from the inverter?

I would turn it on only once the house bank is fully charged, but then just leave it on all the time, so as it draws power from the house bank, the alternator will keep the house bank topped up.

Inverter: Magnum 3000 watt model.
Water heater: Seaward S1900E - 1500 watts, 120 volts.
ME alternator: Balmar 205 amp
House bank - 760 amp hours (8 GC batteries, not yet 3 years old)

The amp calculators I find online refer to something called the Power Factor that's necessary to calculate amps, and from what I can tell, a resistive load like a water heater is 1.0, or very close to it. Assuming 0.9 for the Power Factor, the water heater will draw about 14A AC, or 140A DC.

Thanks for any input. (Except for any input like "just go through the Bahamas - they'll never know!". Not doing that.)

I fail to see the problem. A generator on board should be operational and if its operational there should be no restrictions in using it. To heat up water from your house bank via the inverter makes no sense at all. Your batteries are your safety in case you develop a problem with power generation on board. That happens often enough. Dont sacrifice that because you are afraid of running the generator. If you have a generator problem, just have it fixed. Good luck.

 

[dutch-barge]

Ok I wil throw in my 2 Euro cents

we have 2 hot water heaters the original , which is electric and engine cooling
the other is diesel continuous hot water
Both are. run from the batteries, and having a victron inverter, I have it programmed to automatically turn on the generator when the SOC of the batteries falls below 70%

Now how much energy do you need to heat up your 20 gallon
1 gallon is 8.3 Lbs
you want it at 120F. so lets say the cold water is 55F, so the delta is 65
the heat capacity f water is 1BTU/1F
the heat needed. is 20 * 8.3 *(120-55) *1. = 10,790 btu

which translates into 3.2 Kwh
add some losses ..so to heat the whole tank you need about 4KWH

so about 2 1/2 hrs to fully get it warm @ 1500 watt =
@12 V = 125 amps. (333 amp hr)
and @24V 63 amps. (160 amp hrs)

so now you can see it is not that difficult...

always look to the numbers.
you have a 200 amp alternator so I don't see any issue...

 

[Iggy]

Nope. It used to be, but somewhere along the line, a PO replaced the water heater with one that's electric-only.

I have a 5 gal Isotherm hot water heater. It only uses 750 watts and takes about 25 to 30 minutes to heat up. That water stays warm for almost a day and you can heat the water off the engine. It may be worth getting.

Personally, I would not heat the water off the inverter. At 1500 watts for 1 hour thats about 65 amps being sucked out. Now add in the 8 to 10% inverter loss and anything else you have on. Lights, VHF, GPS, AIS, .......

You need to do the math between Alt output, total D.C. power being used and the size of your batteries in amp hours. Remember too, of your Alt is rated at 110 amps, the engine will need to be running about 2500 RPMs to get that. Every engine is different so you may need to check with your dealer on that too.

Use the genset! Save your batteries!!!

 

[Birdman]

Just run the generator for 30 minutes or so and you'll have plenty of hot water for 12 to 24 hours minimum for several showers. My hot water heater (only a 5 gallon unit or so) stays hot/warm for 2 or 3 days after heating up.

 

[Tingum]

If it was plumbed to heat with engine water why not just replumb it?

 

[motion30]

I have a 20 gal water heater. 30 min barely warms the water

 

[motion30]

Hi think I am going with the iso therm 4 gal heater. 67 amp draw tru the inverter and warm water in 20 min

 

[AdkChris]

Have not seen anybody mention the idea of running the genset while and for a bit after you shower. That is when the water heater will be 'on steady' the rest of the time it will only be running intermittently to keep the water up to temp.

Shouldn't a 205 amp alternator be able to supply 140 amps with a fairly low duty cycle.
Or you could shut of water heater then before you shower start generator make and heat water. take shower turn of water heater and maker when water tank topped off,

 

[AnnapolisJoy]

Bahamas open for transit.

We often run the boat for 4-5 hours at a time, and it's not unusual to run it for 8 or more. But in the next 30 days or so, we may be looking at running it non-stop for about 140 hours, to cover the distance from the USVI to FL. (If the Bahamas don't loosen their restrictions, we have to go around them.)

I don't want to run the generator more than I have to, and everything that we'll need for a long passage like that is either DC, or runs off the inverter. Except the watermaker and the water heater. I expect to run the generator and watermaker for about an hour every other day, which will heat up some water, but in between, with the main engine running and charging the house bank, what about running the water heater from the inverter?

I would turn it on only once the house bank is fully charged, but then just leave it on all the time, so as it draws power from the house bank, the alternator will keep the house bank topped up.

Inverter: Magnum 3000 watt model.
Water heater: Seaward S1900E - 1500 watts, 120 volts.
ME alternator: Balmar 205 amp
House bank - 760 amp hours (8 GC batteries, not yet 3 years old)

The amp calculators I find online refer to something called the Power Factor that's necessary to calculate amps, and from what I can tell, a resistive load like a water heater is 1.0, or very close to it. Assuming 0.9 for the Power Factor, the water heater will draw about 14A AC, or 140A DC.

Thanks for any input. (Except for any input like "just go through the Bahamas - they'll never know!". Not doing that.)

This morning the Bahamas opened for transit. No stopping. Check on line.

 

[Kiwi.]

It's worth knowing your generator overhead. By "overhead" I mean the amount of fuel your generator uses to run without putting out any electricity. Why? Because that is the only difference between using you main motor mounted alternators and using your generator. Your main motor uses the same amount of fuel per watt generated except for the overhead. My 22kva Onan generator uses 1.5 litres per hour "overhead" plus 0.25 litres per hour per Kilowatt. (0.4 of a US gallon per hour "overhead" plus 0.066 US gallon per hour per kilowatt.) So I never start the generator unless it's got a serious job to do. Mainly watermaker and waterheater!

 

[mvweebles]

I think it will be just fine, especially for an occasional long run like this.

Once heated, it will turn off, so won’t be running all the time.

Just keep an eye on the alternator temperature, and the battery charge state. If either starts getting into trouble, turn off the water heater for a while.

Ditto - surprised this school of thought was more or less solo on this thread. Heck, OP just needs to get through a week or two, not exactly planning an assault on Omaha Beach here. Balmar with three stage regulator should handle this without too much sweat, especially in a warm climate with high ambient Temps. Worst case is he could toggle water heater on/off. I'm sure he has a long list of prep. Besides, there's half a chance he'll hit some headseas and spray and need to shut windows and turn on AC/generator anyway.

There are still a few folks left who don't like running generators so I'm with OP. Always been fascinating to see east coast boats with tons of generator hours.

Also ditto on idea for lower wattage heating element. I recently purchased a Quick Nautique water heater that allowed three different wattages. I forget exactly, but I think I went with 600w. My thinking was warm weather boating doesn't need the bigger element.

 

[Ambition ll]

I would install a stand alone heat exchanger. They are not expensive. And your problem solved.

 

[AdkChris]

This would not work in warmer climates but I have been wondering for colder climates why not use an engine operated heat exchanger to bring the entire water tank up to say 100 degrees F. It would be a nice warm addition to a cold boat and not burn any extra fuel. The only technical reason I have thought of is it might speed up the reproduction cycle of any life forms in the water. The electrical duty cycle of the water heater would then be minimal.

 

[Firestorm]

Solar showers are cheap and work great!

Why not just buy a 5 gallon solar shower for $25? Or if you need more than five gallons of water, buy two or three solar showers. Then replace your Seaward water heater to a hybrid version when you get back to Florida.

We often run the boat for 4-5 hours at a time, and it's not unusual to run it for 8 or more. But in the next 30 days or so, we may be looking at running it non-stop for about 140 hours, to cover the distance from the USVI to FL. (If the Bahamas don't loosen their restrictions, we have to go around them.)

I don't want to run the generator more than I have to, and everything that we'll need for a long passage like that is either DC, or runs off the inverter. Except the watermaker and the water heater. I expect to run the generator and watermaker for about an hour every other day, which will heat up some water, but in between, with the main engine running and charging the house bank, what about running the water heater from the inverter?

I would turn it on only once the house bank is fully charged, but then just leave it on all the time, so as it draws power from the house bank, the alternator will keep the house bank topped up.

Inverter: Magnum 3000 watt model.
Water heater: Seaward S1900E - 1500 watts, 120 volts.
ME alternator: Balmar 205 amp
House bank - 760 amp hours (8 GC batteries, not yet 3 years old)

The amp calculators I find online refer to something called the Power Factor that's necessary to calculate amps, and from what I can tell, a resistive load like a water heater is 1.0, or very close to it. Assuming 0.9 for the Power Factor, the water heater will draw about 14A AC, or 140A DC.

Thanks for any input. (Except for any input like "just go through the Bahamas - they'll never know!". Not doing that.)

 

[OldDan1943]

Hey we can buy a couple of black plastic "solar showers" and go camping?

 

[rsn48]

During refit of my gas powered boat, I decided to add additional heating other than just my Dickinson Newport Propane Fireplaces P9000. I have lived a couple of years on and off in RV's, trailers and motorhome. While living in these units in the winter, I often got nervous about the propane supply and I didn't want to use up propane heating the boat when it is also used for BBQ and stove.

So I decided to add an Espar heater that could run off of diesel or kerosene, I favour kerosene. While I was discussing this with my refitter, he suggested a hot water tank that could run off the Espar, I've gone with this set up. He assures me 3 gallons of diesel/kerosene will run the Espar for quite some time.

My boat is too small for a generator and I don't like them anyway from my RV days. I do bring a Ryobi propane generator along (peak 900 and run 700 watts) just for emergency back up. But I have Efoy and solar to boost my house battery bank.

 

[Birdman]

Along the lines of some of these suggestions that obviously didn't understand the actual question, here is mine: Buy a new boat!

 

[mvweebles]

OP has a 52 boat with 1500 nm range. He's sitting in Panama - I have to assume he's a savvy owner who is well past solar showers.

Underway, he is likely consuming around 40A @12v on average with refrigeration and electronics being the biggest draws. He has charging capacity of 200a via a balmar. Using a roughly--right number of 80% peak on the Balmar for efficiency,, he has an effective charging of around 160a per hour. Subtract the standard load of 40a for electronics and refrigeration and you're left with 120a. 1500w water heater converts to 125a @12v if it were to run nonstop. Given the ambient temp of Panama to Florida, let's say it runs a generous 20% of the time, or an average of around 25ah. So the alternator is running at around 70a on average, less than 40% load.

I just don't see a problem with what the OP asked about. Certainly not for for a week's run. The inverter is plenty big enough. Batteries will buffer any spikes.

Thoughts?

Peter

 

[twistedtree]

Exactly. Just remember, the OP is looking for a solution for a single extended run, not for a refit.

Just go. If the batteries get low or the alternator gets too hot, then turn it off. Worst case you run the gen for an hour or two here and there.

Just go.

 

[OldDan1943]

I had an aunt, you give her something to wear and her comments was always, "I'll save it for good." Well she did, she had many thing she never wore before she died. You know the drill, saving them for a special occasion etc.
So you just go right ahead, save your generator for good and the next owner may run it every day maybe 24hrs a day thanking you for the generator with very few hours on it.

You need to puts some hours on it so when you need it, you know you can depend on it.