Water Heater on Inverter

[richard5933]

I dunno.  It wouldn't work for me.  I'm with Tom C on this one (and most of the time).

Geoff

We've sure got a bunch of naysayers on here nowadays...

Not sure what the problem is with having multiple methods to make hot water. Generally speaking, I have much more battery capacity than we need for the time we're dry camping, and if doing this once in a while allows a hot shower without the noise and vibration from the generator it's all good. Like I said, I wouldn't count on this as a full-time solution, but there are so many days with either solar or traveling that this would allow for quiet showers I'm not sure what the down side is.

If you have propane, you could use one of the tiny water heaters to assist heating the electric model. It doesn't  have much output, but could run a few hours to keep the temp up. They have an automatic shut off on some models. Home Depot, Lowes, and Camping World sell versions.

Even the tiny ones require venting somewhere, and that's where I run into a problem. Not keen on cutting more holes in my bus for venting, especially through the doors since they are pantograph.

[buswarrior]

Side benefit of this experiment, you get a demonstration of the losses of your inverter at that level of work.

150 amps at 12 volt in, 12.4 amps at 120 volt out.

For a given output wanted, you need 21 percent more battery than the simple calculation of shifting the decimal point.

That's really important info to know for a given system.

In this case, a hidden consumer of 1/5 more power than simple calculations...

This is exactly how those without battery monitors kill their batteries... discharging significantly more than their "calculations"...

Experiments with good measurements are the path to enlightenment?

Happy coaching!
Buswarrior

[bobofthenorth]

150 amps at 12 volt in, 12.4 amps at 120 volt out

About 83% efficient which fits nicely with the 15% loss that we often see referenced.  And I wholeheartedly endorse the notion that battery monitors are essential.

[chessie4905]

Maybe you can make use of the battery ventilation system already installed. Since they don't  need typical venting or the bathroom venting.

[Jim Blackwood]

So I have a question. Considering that gas furnaces have many decades ago reached into the upper 90% efficiency bracket to the point that about 30 years back they started using a small pcv pipe for an exhaust vent (as well as a pcv inlet vent), why are RV water heaters still back in the stone age?

Jim

[buswarrior]

Same reason anything "RV" is back in the stone age?

The better comparison would be the current performance of gas water heaters, residential and recreational?

Not sure the same compromises that gave us efficient air heaters will work when trying to get water warmed up with a certain time line involved?

Don't try warming your house from stone cold with an "efficient" furnace... going to take a loooong time...

Happy coaching!
Buswarrior

[Fred Mc]

So I'm following this discussion with great interest.
I converted my bus over 30 years ago before inverters, monitors etc were the norm. Put in a Paloma on demand hot water heater. Takes up little room and cut a 4" hole in the door with a corresinding grill on outside. Hard to even tell it is there. Also had a noisy generator. Recently we decided to go solar and discarded the generator. Changed all the lighting to led and put in a catalytic heater for chilly mornings and evenings. No power needed. We also have a suburban forced  air furnace that is a real power hog. We have 300 watts of solar and 2 x12 v batteries. Works fine as long as we have sun but it's easily expandable with more batteries and solar if needed. Also added a 1500 w inverter for tv, toaster, etc. System is dead simple. Either plug into the pole or the inverter. Only problem is there is no remote switch for inverter but that is doable quite easily.
It took me a while to figure out the hot water heater. It works on water pressure so things like water saving shower heads confuse it. But like someone said you can have hot water until you run out of water.
Simple, effective and cost effective.

[bevans6]

I think it's a great way to avoid running the generator at 6:30 in the morning when people are still sleeping yet you want to take your shower...  I put a 15% efficiency factor in my initial calculation that ended up with around 140 amps out of the battery.  Amps out of the battery is always a fudge factor in any calculation because it depends on the variability of the load, and the voltage drop under load.  Perfectly healthy batteries will dip below 12 volts under a decent load - my old F250 would drop to 11 volts for 30 seconds or more while the glow plugs were doing their thing.   Any resistive heating element (like the ones in a water heater) will draw more power when cold than when hot, their resistance gets greater (less power) after they heat up.  I put an RV propane/electric 10 gallon water heater in, cut a great bloody hole in the side of the bus, I would do it differently now.

[chessie4905]

How many drain/charge cycles do the batteries have?

https://www.campingworld.com/eccotemp-l5-portable-tankless--water-heater-37786.html?gclid=EAIaIQobChMIlaet5PPD4gIVAaeGCh0T3AMPEAQYAyABEgIT8PD_BwE

This maybe a feasible idea to plumb into existing water heater. IF you have propane.

[richard5933]

How many drain/charge cycles do the batteries have?

https://www.campingworld.com/eccotemp-l5-portable-tankless--water-heater-37786.html?gclid=EAIaIQobChMIlaet5PPD4gIVAaeGCh0T3AMPEAQYAyABEgIT8PD_BwE

This maybe a feasible idea to plumb into existing water heater. IF you have propane.

I looked into using something like that. Read through the manual and you'll see that it requires a flow rate of 2L/min to activate the burner. When we use the water at a very slow flow odds are it won't ignite. We try to make our 80 gallons of fresh water last a week (for two of us) so we sip water very slowly for dishes and such. Even the low flow shower head may not move enough water for this thing.

Also, it is intended for use outdoors. Not sure what kind of safety hazard I'd be creating by installing it in a bay, and I have no desire to set up an outdoor water heater and run plumbing to/fro each time.

[chessie4905]

That was an example. The flow issue can be dealt with a small pump or one that doesnt need the flow you have. It may be too complicated for you to make it work. Best to just stick with your battery idea. Don't want to burn the coach to the ground or die from carbon monoxide.

[buswarrior]

All sorts of things can be solved with bypass circuits back to the fresh water tank, built-in and/or manually activated as required.

Bigger flow, without consuming lots of water, instant heat without running the water down the drain, freeze protection of fresh water tank.

With a little trickery, a busnut could have a "better" water system in the coach, than they have in their dirt house.

Happy coaching!
Buswarrior

[Geoff]

Well, Richard did not design his bus.  If he had, he might have a generator that is quiet enough to run without bothering him.  I do.

As far as water heaters go,  I have an Attwood that has five ways to heat 11 gallons of water:
(1) propane
(2) electric
(3) loop from engine coolant
(4) loop from Webasto
(5) Radiant heat from engine compartment

After driving for a couple of hours, the fresh water stays hot all night parked for two people to take showers in the morning.  Otherwise, I can heat it up using one or two of the other methods.  Fastest heating is running electric with propane at the same time.

[Oonrahnjay]

Well, Richard did not design his bus.  If he had, he might have a generator that is quiet enough to run without bothering him.  I do.

As far as water heaters go,  I have an Attwood that has five ways to heat 11 gallons of water:
(1) propane
(2) electric
(3) loop from engine coolant
(4) loop from Webasto
(5) Radiant heat from engine compartment

After driving for a couple of hours, the fresh water stays hot all night parked for two people to take showers in the morning.  Otherwise, I can heat it up using one or two of the other methods.  Fastest heating is running electric with propane at the same time. 

     Very similar to my setup.  Someone earlier said something like "the loops don't work because they're too small".  Not in my experience.  Within a short period of running down the road, I have 10 gallons that's at about 180º.  A great feature is that there is a "tempering valve" in these Attwood heaters -- the water out of the valve is always at 106º or 110º (whatever it's set for); if the water in the tank is very hot, you get many gallons of "mixed" hot water, if the water has cooled some but is still reasonably hot, that water will be drawn out at service temp with less cooler water mixed in.  But even hours later - the next morning in Geoff's example -it's still "hot water" in the dish sink or shower.
     Certainly, no one would want to be stuck with that being the only source of hot water -- it would be terribly inconvenient, and highly expensive, to have to fire up the engine and run on the road (just idling wouldn't do it), but it's a feature - FREE hot water - for the days you're actually traveling, and for many hours afterwards.