Hot Water Heater Options

[sledhead]

you could use a system like this with a loop off your system now . your  Webasto should start and stop as needed and if you are on the poll you could use the elect . side


http://www.defender.com/product.jsp?path=-1&id=2092718

dave

[buswarrior]

Buswarrior: Interesting idea that shouldn't really need that much to get going.

If I understand correctly, I would add a loop pumping water from the hot side of my current water heater, through the plate exchanger, and back into the cold side of the water heater. I imagine I could use another Bosch electric water pump to move the water similar to the one I'm using now to move the Webasto heat through a loop going to pre-heat the bus engine.

Do I need to add a water temp sensor to shut off the Webasto once the water heater reaches proper temp? Otherwise wouldn't it just keep going till the overtemp shut down kicked in? I'm thinking that I could use a DPDT switch to re-route the thermostat in the coach to the water temp sensor for use in warm weather. I could get a NC sensor with a preset open temp around 130-150 degrees, which should cycle the burner as needed to keep hot water hot.

You're correct - it should not be difficult to add a few jumpers to keep the Webasto burning in warm weather, but I'll also probably need to add a manual fan shut off switch to keep it from blowing into the coach.

What size heat exchanger do you think would be needed?

Richard

If it were me... you are verging on too many parts now, only need to add the exchanger and a pump for the domestic hot water circulation, an anti-scald valve for safety, and a 3-way valve for coolant return efficiency.

In the wiring, step back and re-think the whole system, adding and adding more switches to half bake an existing system isn't good design...

Control the Webasto, control the water heater, control the coach heat. Don't intertwine the controlling of them. 

The Webasto should regulate itself by design at 160 degrees, or it has been monkeyed with...

So, when turned on, the Webasto will make a supply of hot coolant somewhere at 160 degrees, and maintain that. Nothing else happens, it cycles as needed to maintain that. Insulate all of this piping and tankage for more efficient operation.

Then, as commanded by you, the coach heat may be engaged, and it's thermostats take care of fan on and off to regulate the temp.

And, in the warm weather, the domestic hot water needs are not an ongoing run, you turn it and the Webasto on, get the hot water tank up to temp and shut it all off.

A three-way valve in the return from the plate heat exchanger lets you use the same loop/hoses/pump as the engine pre-heat. The 3-way short cuts the return back to the Webasto supply for efficient operation (no need to heat the engine block), or directs the flow the long way thru the engine block. Depending on how this loop is set, you will be able to get hot engine coolant to give you free heat into this entire system, while driving down the road.

WARNING!!! in using these higher temp sources, a busnut MUST install an anti-scalding valve in all good conscience and safety for all who touch the coach. Engine temp domestic hot water, which will be up at 180 degrees, will BURN and disfigure.

So, in conclusion, a busnut has to keep the parts count down... and the mind blowing thought processes complicated...

happy coaching!
buswarrior

[chessie4905]

Keep making these systems more elaborate and in a couple of years, when you start having issues, you better know how to diagnose and repair many yourself or the enjoyment of a conversion can quickly wane. Add engine electronics, inverter, battery, solar, and generator systems,and can be overwhelming when two or more systems take a crap at the same time out in middle of nowhere, esp in very hot or very cold temps. KISS didn't come out of nowhere. Just food for thought.

[PP]

Will - Can you describe how you vented an LP water heater from the middle of the bus to the outside? Maybe I just haven't found the correct unit yet, but the ones I've seen seem to indicate that the preferred way to install is against an outside wall.

Richard

There is a screened opening in the floor directly below the front of the heater so it can draw fresh air up into the burn chamber and then a tunnel made of galvanized sheet metal lined with some kind of material that might be asbestos leading over the opening and down. It was part of the original Marathon conversion. I use the space in front of the tunnel for storing tire chains. When I open that bay door, you can see the front of the water heater if the tire chains weren't piled up in front of it. Of course, when the old heater began leaking, I wouldn't have noticed it if not for the huge icicle growing in the middle of the bus underneath.
It seems using a second exchanger for your Webasto makes more sense though than losing valuable storage space for venting when you have almost everything already there. I'd go with BusWarrior's suggestion. Will

[Scott & Heather]

I second BusWarriors wanting on scald protection. We have little ones now so I installed just such a device on the hot output of our water heater. That 150°F water is cooled to 118°F water before it even hits my hot lines throughout the coach. Definitely a solid $85 investment to protect everyone.


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[richard5933]

It's been some time since this thread was active, but I'm once again trying to figure a way to make hot water without plugging in to the pole or running the generator.

As most know already, the 4106 this conversation started with is no longer with us. The current situation is a 4108 with a really nice 6-gallon water heater that runs on 120v only. This bus has no Webasto and no plumbing to bring engine heat anywhere near the hot water heater.

There is, however, LP plumbing just on the other side of the bulkhead from where the hot water heater is located. So, I'm once again exploring options for making hot water using LP and/or 120v.

So far, I've only found two options. The first is a traditional RV water heater which uses either LP or 120v. Downside appears to be that I would have to mount this against an outside wall AND cut a hole in the bay door to accommodate the large venting hatch for the water heater. Second option is a tankless water heater which vents through the floor. Downside here is the high price (over $1K, just for the water heater) and the fact that tankless water heaters can actually waste water when showering since every time the shower head is turned off & on you've got to wait till the thing heats up again to make hot water.

So now I'm back to trying to get an tank style LP hot water heater that can be remote vented through either the floor or an outside wall (without having to cut a hole large enough for the access hatch.)

Will had mentioned he had one that was reconfigured like this, but I was hoping that somewhere out there some one knew of a unit designed for the type of installation I need.

Any help would be appreciated.

[buswarrior]

Tom's model will be cheapest?

Use an inverter to make hot water power while driving, make hot water with generator while making morning coffee/charging batteries etc.

Wrap the 6 gal. tank in more insulation, to make heat retention even longer.

How much hot water do you need?

Happy coaching!
Buswarrior

[windtrader]

With a 10 gallon tank, heating options are electric, engine, and Webasto. If on the pole, no brainer, just run on electric. Most of the time we boondock, so like busnut says, we run the genny in the morning, bulk charging the house batteries drawn down from the previous night, making coffee, and running the hot water heater. Even 30 minutes gets the water plenty hot for a shower or dishes; 60 minutes burns your skin. It is well insulated as it will stay hot all day.

The only operational kink is manually flipping the fuse in the sub panel. Working on ideas to have an automated way to engage the water heater when on the pole or running the generator. Do not want to heat the water when on batteries alone.

[richard5933]

I'm aiming for the ability to go through a weekend without having to run the generator. I know that it might seem silly, but we really want to ability to run quiet for 2-3 days, and our 1974 Kohler generator with the Perkins diesel is anything but quite. It's not about being stealthy or anything like that, it's just about wanting to get away for a few days and not hear all the usual machinery and noises associated with life in the city.

We'll have approximately 800aH in our batteries and will be running minimal 12v loads while dry camping. The only creature comfort on our list that we won't be able to accomplish on batteries alone is the hot water tank. That's the reason I'm searching for a way to heat the hot water with LP, something that if possible would result in a quiet hot shower in the morning. Cooking and heat will be done with LP.

In this coach we have no Webasto. We also don't have a large enough inverter to run the water heater (nor do I want to run the bus engine to heat the water using a heat exhange). The only viable quiet option I know about is an LP hot water heater, hence the search for an LP water heater that can be vented differently than most RVs.

I'd be willing to consider doing something like Will has, but my concern is about the safety of trying to do this without having anyway to verify that I've done it properly. Venting an LP hot water heater and not getting it right can be deadly.

[Geoff]

You need a water heater like I have.  It works off electric, propane, engine heat exchanger, and radiant heat from the engine compartment.  In your situation, you need a propane/ electric RV water heater.  Just vent it outside for propane use, you don't have any other solution except to build a unit using firewood a few feet away.

[richard5933]

You need a water heater like I have.  It works off electric, propane, engine heat exchanger, and radiant heat from the engine compartment.  In your situation, you need a propane/ electric RV water heater.  Just vent it outside for propane use, you don't have any other solution except to build a unit using firewood a few feet away.

Which brings us back to the original question - how to vent it? Do you have yours vented through one of the bay doors or is your upstairs in a cabinet or something? Right now ours is in the bay with the fresh water tank, and there is no easy way to vent through the bay door due to the way they open/close.

[Geoff]

You are going to have to cut a hole in the floor of the bay.  Propane exhaust is not deadly air, but I would add a slip-on exhaust pipe to take the fumes from under the bus to the outside.

[PP]

Richard, even though ours vents through the floor of the bay, I never feel comfortable when we have to use it on gas. I've checked it during use and the plastic cover over the circuit board on the front of the unit is almost hot enough to melt. If I had to use it all the time on LP I would put a vent of some type in the bay door with ducting to make sure the heat gets outside since there isn't any way to move the unit closer to the bay door without a lot of work. When i replaced the unit last summer I would have if it had been an easy project. This was originally a professional install by Marathon, but that doesn't mean it's safe. I use AC 99% of the time.
HTH
Will

[richard5933]

You are going to have to cut a hole in the floor of the bay.  Propane exhaust is not deadly air, but I would add a slip-on exhaust pipe to take the fumes from under the bus to the outside.

Not sure how this would work - the RV units sold all vent through the side, and there doesn't appear to be an easy way to add a remote vent to this. They also don't have any type of forced exhaust that I can see, which means we're asking hot exhaust to vent down instead of up which would be its nature.

Unless of course you have another type of tank hot water heater which is intended to vent through the floor, which is what I'm searching for.

Will - those are the exact type of issues which would keep an OCD person like myself from every wanting to run the thing on LP.

[luvrbus]

I saw a Truma water heater in a high dollar RV that was vented through the floor,doesn't seem like it would be that hard to vent any brand out the bottom of a bay with a little sheet metal work.
People told me I had to have a propane fridge on outside wall with the ugly vent that didn't happen no way was I going to cut a hole in the side of the bus for a vent, that fridge is still in the middle of the bus and always worked too