2013 R-27 Running the Water Heater off Battery/Alternator?

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Bpwicks

Active member
Joined
Dec 24, 2018
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31
Fluid Motion Model
C-302 C
Hull Identification Number
1228065
Vessel Name
B-Pod
When I recently had the water heater replaced, I was informed that the water heater is electrically connected to all the heater to be powered by the house batteries/alternator. The repair guys said I should NOT do this at the current draw from the heater would put too much strain on the alternator and might burn it out.

Is this accurate advice?
Thanks,
Brian
 
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We never run our water heater unless connected to shore power. Our inverter is rated for 2500 watts so might be able to handle the load, but it's too close to risk it. Any other load would put it over 2500. I think some boats have lower rated inverters which would be even worse.
 
Agreed, we leave the water heater switch off unless on shore power (and also on board). OTOH electricity is not required for hot water. It will also heat up from cooling exchange when either the engine or diesel heater are running. And it stays warm for quite a while.

So in practice, if the engine and/or heater run daily, then we have always had enough hot water (note: that is with the 11ga tank on C30, and we don't use the shower).
 
Hello Brian,

Unless the previous owner changed the wiring, that's not how it would have been built by us. Underway your engine will heat up the hot water anyways so there is no need to have the breaker on. The coolant flows from the engine to the hot water tank, cabin heater, then back to the engine. The breaker is intended for shore power use only.

Thanks,
-Kenny
 
Kenny, are you saying that the inverter will not power the water heater? If so, I am surprised but that is good to know! (and makes me wonder what else is 120v but not on the inverter?)
 
The size of the inverter will depend if it can handle the load. However, don't do it for the reasons stated by the mechanic. On my 2011 R-27 all 120v is able to run on the inverter. Not the best setup since you could accidentally overload. We are very cautious not to have any high draw items on. You can isolate what you want to run on the inverter, but I have been too lazy to separate the panel.
 
Agreed! Water heater could kill batteries quickly.

Just to clarify: I read Kenny's post as saying that the water heater is not connected to the inverter at all, since he said to the OP that they didn't wire in the way that was asked. I suspect that was a wording issue and is not the case, and that it really is connected. But in case I read correctly, I wanted to understand more; I had assumed that everyone the 110v circuits were on the inverter (if turned on).
 
For reference, from the factory our 2017 R25SC is wired so that neither the water heater nor the electric part of the alcohol/electric cooktop will work off the inverter. Both units impose too high a load.
 
That is good to know -- and good wiring choice 🙂 Thanks!
 
SJI Sailor":2zjxq7e3 said:
Agreed! Water heater could kill batteries quickly.

Just to clarify: I read Kenny's post as saying that the water heater is not connected to the inverter at all, since he said to the OP that they didn't wire in the way that was asked. I suspect that was a wording issue and is not the case, and that it really is connected. But in case I read correctly, I wanted to understand more; I had assumed that everyone the 110v circuits were on the inverter (if turned on).
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A little more clarification. It all depends on what year and model that you have so I suggest that you make sure what is wired on the inverter and what is not. The newer models seem to have been changed to not include the high draw items on the inverter. Then again the newer outboards do seem to have the ability to run things while under weigh.
 
I'll have to go back and watch the episode of "As The Prop Turns" (many thanks to the RT folks that take the time to put those together!!!) that deals with power management... but if memory serves, Andrew (who has an R23 like ourselves) mentioned that he likes to run his inverter while underway (as long as it's higher rpm's) to heat the water heater, as our OB's don't have the benefit of using the cooling system to heat the water heater. I believe he mentioned that he only does this if he knows that night will be on the hook, and he'll want hot water.

We did this on our last trip, and it worked perfect. Once we hit planing speed, I turned on AutoPilot and went back to turn on the inverter, then the water heater. Before we throttled down, I remembered to turn the heater off and switch the inverter off.

The OB's alternator seemed to keep up with the demand just fine, and there was no appreciable drain on the batts.

I'm hoping I did this right... I'd hate to think I overloaded the inverter and/or batts! :cry:
 
Bpwicks":27ssdaqh said:
When I recently had the water heater replaced, I was informed that the water heater is electrically connected to all the heater to be powered by the house batteries/alternator. The repair guys said I should NOT do this at the current draw from the heater would put too much strain on the alternator and might burn it out.

Is this accurate advice?
Thanks,
Brian
Click to expand...

Brian, as others have stated it depends on the model year of the boat. In our case we have a 2014 R27 that has only a single bank of breakers for 120AC all of which are available to be powered by the inverter when the rotary switch is set to inverter. We have a 1500W inverter and a 1500W water heater. In short, it is possible, but risky, on our boat to heat the hot water with the inverter.

First, the only scenario where it makes sense is if you are docked or anchored with no shore power for multiple days. As Kenny states, the engine will heat the hot water if you drive any significant distance and it will stay warm for at least overnight. Running the engine in neutral without a load however does not create enough engine heat to heat the hot water for a long time. Here is how I do it when and if I’m in this rare situation.

First, I close the coolant lines in the engine bay that run to the helm cabin heater and the hot water tank. The reason is the engine is cold. If you start the engine with the coolant lines open you will first immediately cool the remaining heat in the water heater. Not what you want.

Second, start the engine. This is necessary to not draw the house battery bank down. At 1500W the heater can draw as much as 125 amps! I have a Volvo D3-200 that puts out 180 charging amps running the battery down is not a problem if the engine is running. The battery even gets some positive charge while heating the water!

Third, turn off ALL AC breakers. If the inverter is run with anything other than the water heater it will blow the internal fuses or potentially damage the inverter. Once all are off, start the inverter and once voltage is available on the AC panel the turn on only the water heater. Monitor the inverter meter to make sure it is doing OK. If all OK the water heater should heat up fairly quickly. If the water was even a little warm it should be hot within about 15 minutes. With the heavy alternator load the engine will also warm up more quickly. Once the engine temp is above 130 degrees or so the coolant valves can be opened to allow the engine to provide additional heat. The water should be piping hot very quickly after this if not already.

Of course I take no responsibility for any ill effects from this process. I can only say it works for me on our boat. Worst case scenario, I change the inverter internal fuses or buy a new (bigger) inverter. I can’t see how this would harm the alternator.

Curt
 
KennyMarrs":sz364rlo said:
Hello Brian,

Unless the previous owner changed the wiring, that's not how it would have been built by us. Underway your engine will heat up the hot water anyways so there is no need to have the breaker on. The coolant flows from the engine to the hot water tank, cabin heater, then back to the engine. The breaker is intended for shore power use only.

Thanks,
-Kenny
Click to expand...

Thanks for the help, Kenny. I will stick to engine-heater hot water only, to be on the safe side.
Brian
 
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