Diesel hot water systems

whatcharterboat

Supporting Sponsor, Overland Certified OC0018
Continued from "More design ideas / questions"

Dontpanic42 said
I am really enjoying this exchange and am learning a lot. I have been interested in retro fitting my camper with a diesel hot water system and cooker. I really want to lose the propane syetem. Here in the lower 48 and particularly the Republic of TEXAS, they act as you are out of your mind for suggesting such a thing. Can you point me towards some websites, vendors, or reference materials so that I can learn more about the systems and availability.
Bruce, Sorry for sounding dumb but what does the “lower 48” mean?

I’ll just throw you some info on diesel heating systems now and maybe this will help. Also I must emphasize that any installation that differs from the manufacturers recommendations should be checked with them before going ahead blindly. And that this post will refer only to Webasto’s products that we have used and may not specifically apply to others or other brands.

I really want to lose the propane syetem ……….they act as you are out of your mind for suggesting such a thing
LOL. Same here and our propane (LPG) systems in Australia are nowhere near as advanced as in the States. Not the stoves and hot water systems but the propane storage itself . In Aus we don’t have tanks > just bottles. So storage is more limited. LPG is still the norm here for camping but we stopped installing it in our motorhomes about 3 years ago and haven’t looked back.. We also use alcohol yacht stoves/ovens as an alternative to the diesel cooktops depending on the clients’ preference but I’ll concentrate on the hot water systems for now.

Terms I’ll use:
diesel furnace : heats coolant and normally has a pump attached or built in
calorifier : a storage tank with 1 or 2 coolant / heat exchange circuits passing through it
dual top: one unit that combines a furnace , watertank and fan and does NOT heat coolant
space heater: a radiator/fan combo similar to a normal under dash unit.

A typical “diesel furnace” based hotwater system comprises of a furnace that draws diesel prefererably straight from the vehicles fuel tank. (BTW best practice is to install a separate pick up in the main tank as opposed to a “T” into the main fuel line.). However there is nothing wrong from running a separate tank for the furnace supply if you need to set it up this way to allow for removal of the camper or if we are talking about a camper trailer/caravan.

Typically the furnace heats coolant in a circuit, which can run through a calorifier and the trucks cooling system. As an example in an FG this circuit can simply be “T”ed in parallel with the factory cabin heater. Also a space heater can easily be plumbed in parallel with the calorifier (BTW if you do this put an isolation “Gate” valve in series with the space heater so that it can be shut off in summer OR so the coolant can be fine tuned to flow more or less through the heater or calorifier).

So what we now have is an engine, furnace and a calorifier/space heater in a circuit. When the engine runs the coolant heats the calorifier and the furnace remains off. When the furnace runs it heats the calorifier AND the engine so you have your pre heat for cold climates/sub zero starting. The tricky bit is isolating the engine from the circuit, so that when you don’t need the engine pre heat you aren’t losing coolant heat through the engine block when you are camped up but still retain the engine coolant heating when you are traveling.

2 or more ways to do this. Firstly you can isolate the truck with manual valves but this is a bit off a hassle to do all the time or alternatively you can use solenoid valves. More than a couple of hundred bucks each here and you need 2 of them. (BTW make sure you get the “normally closed” or “normally open” bit right so that the valves are energized only when the ignition is “on” and not drawing power when your camped up. So when you are driving the engine is IN the circuit and when you are camped the engine is OUT of the circuit.

If engine pre heat is not a priority, another option is to use a dual circuit calorifier. This gives you an engine coolant heating through one circuit of the calorifier and the furnace runs through the other circuit. The down side here, although minor, is that you have to have a separate coolant header tank for this circuit. With the first option, of course, the engines’ radiator is in effect the header tank and point of fill.

The calorifiers come in a big range sizes from 10 litres up and we have even used a straight heat exchanger (about the size of a brick) with no storage tank at all and this was still successful.

While this next option may not be the most efficient, it is probably the one we do most of and particularly suits short stays and fairly constant travel rather than periods camped up. That is to simply have a calorifier “T”ed in parallel with the engine. If you pull up in the afternoon clients tell me that they still have hot water for a shower the next morning and if it’s necessary you can run the engine for 20 minutes to give you enough heat for a shower. Sure that’s a lot of fuel just for a shower but do the math. You’re charging batteries at the same time and saving the cash outlay of the furnace. Not the way I’d go but simple all the same. I’d prefer to camp up for long periods.

Actually I spoke to the guys at Watts2c (See thread “Simple electrical system for expedition vehicles) regarding development of a new water-cooled DC Genset and the possibility of plumbing a calorifier into its’ coolant circuit. This would be another way to possibly eliminate the furnace say if the genset was to run for ½ an hour a day.

The last common option is to run a Dual Top. We haven’t used one yet but I’m sure they have a place. They don’t run coolant at all and heat the water directly. Also they have 2 hot air outlets that can be ducted into the vehicle for space heating. So a bit of co-generation going on there. Very compact and have a tank built in.

Some other points to make here are that the calorifiers all have an electrical heating element built in so that if you pull into a vanpark or a mates’ place you can run off electricity for awhile and the other point for now is that if you are going to run a calorifier especially plumbed into the engine then fit a thermastically controlled temperature kit to it as a safeguard. These are an adjustable valve that goes on the hotwater outlet of the calorifier and mixes with coldwater to give set output temperature..Very simple to set up but well worth it. If the engine has provided the heat the temps can get very hot and vary so its’ not as simple as dialing down the thermostat on the furnace.

If you could follow all that you’ve done well cause I went to sleep about 3 paragraphs ago. Open for questions but like I said I’m sure there are guys a lot smarter than me around here but this stuff works really well in our climate here and I know all the clients are happy not having to worry about gas.

Hope this helps Bruce. Guess Texas climate would be similar to here too.
Regards John.
 

DontPanic42

Adventurer
John,
Thanks for the info. I appreciate you taking the time to put it together.
"Lower 48" refers to all the States in the US south of Alaska and Canada. Guess I picked it up from friends and relatives in Eastern Canada.
I must admit it took me a bit to catch on to what "Oz" is.
Thanks again. Don't be surprised if I ask some very basic questions in the near future.
Bruce
 

FusoFG

Adventurer
John,

Nice summary of diesel options.

I have an Espar furnace, an Indel single heat exchanger circuit calorifier and 2 space heaters connected to the engine as you suggested.

Some additional points:

I use a "Ball" valve instead of a "gate" valve to isolate the engine from the furnace. You can tell whether the valve is open or closed just by looking and you won't break something by trying to turn the handle the wrong way thinking the valve is jammed.

I think you only need a valve in one of the coolant lines between the engine and furnace to stop the coolant flow. Think cab heater control.

A calorifier with 2 heat exchanger circuits not only needs a coolant header tank in the furnace circuit, it also might need 12v pumps to move coolant in the circuit that's not "hot".

I insulate any long coolant hoses between the engine, furnace and space heaters that are exposed to outside temperatures to save diesel when heating the camper in cold weather.

I use both the espar timer and a battery operated room thermostat to control the furnace.

I use the timer when I want engine preheat at a certain time of day or if I want to run the furnace for 15 - 20 minutes to heat shower water after sitting for a day or so.

I use the thermostat to keep the camper comfortable when camped incold weather. It's programmable to a cooler setting at night and a warmer setting in the morning.

The space heater fans can be controlled by the furnace control (that's how I did mine) or they can be controlled by an "aquastat" that doesn't turn the fans on until the coolant reaches a certain temperature. Prevents the space heater from blowing cold air waiting for the furnace to get hot.

You are absolutely right about the requirement for a mechanical thermostat valve on the calorifier. When heating water with the engine it can reach over 212 F (100C). Even the diesel furnaces can reach 180F. This may cause severe burns.

Calorifiers for use on boats are designed to be heated by engine coolant and often come with a thermostatic mixing valve from the factory (at least in the US).

Maybe it should be a separate thread, but if you're going to use a diesel furnace to avoid propane (lpg) you also need to change the propane cooktop.

You mentioned marine alcohol cooktop / oven. People like alcohol on a boat because the fire can be extinquished with water.

But alcohol requires carrying another fuel and an alcohol flame is almost invisible so a fire can start unoticed pretty easily. I had a friend that burnt his boat to the waterline because a fire spread from his cooktop before he saw the flames.

I think a diesel cooktop is the way to go.

There are 2 types - an open flame burner similar to a alcohol or propane cooktop and the sealed burner typed manufactured by Wallas and sold by either Wallas or Webasto.

The open flame type has a distinct diesel smell and requires alcohol to preheat the burner.

The sealed version doesn't smell and has an outside exhaust to reduce condensation from water vapor created by combustion.

The newest version has a switch to allow high altitude operation, a complaint lodged against older versions.

I've never had any trouble with my older version unless battery voltage was too low for the built in glow plug or the camper was parked so wind blew in the exhaust pipe. The newest model can exhaust through the floor which would eliminate the wind problem.

Tom
 

Recommended books for Overlanding

Dreaming of Jupiter
by Ted Simon
From $16.43
Long Way Round: Chasing Shadows Across the World
by Ewan McGregor, Charley Boorman
From $14.59
Drive Nacho Drive: A Journey from the American Dream to t...
by Brad Van Orden, Sheena Van Orden
From $15.95
Crossing the Congo: Over Land and Water in a Hard Place
by Mike Martin, Chloe Baker, Charlie Hatch-Barnwell
From $32.5
4WD Driving Skills: A Manual for On- and Off-Road Travel
by Vic Widman
From $17.27

Mickldo

Adventurer
My first introduction to Webasto products was when I worked on this GU Patrol camper. It had diesel stove fitted. In the top photo you can see the back of the stove on the top shelf and the separate diesel tank/bottle on the bottom shelf. You can also see the exhaust pipe/stainless skin fitting at the bottom left.



 

whatcharterboat

Supporting Sponsor, Overland Certified OC0018
FUsoFG

"Lower 48" refers to all the States
Bruce. Of course. But now I do feel dumb.

Tom, Glad you replied cause it will clear a few things up.

I use a "Ball" valve instead of a "gate" valve to isolate the engine from the furnace.
I should have said that we do too. Of course in any "on/off" or isolation only type situation a ball valve is the correct type for all the reasons that you stated. In the situation I refered to (in space heater circuit parallel to the calorifier ) where you may need some adjustment (albeit a little crude), IMO a gate valve is more suitable.

I think you only need a valve in one of the coolant lines between the engine and furnace to stop the coolant flow. Think cab heater control.
I could never picture this happening. Remember I live in the sub-tropics so I am the last person to claim to be an expert in "engine pre-heat" but when we have been doing a typical system it has been with a “normally closed” solenoid valve before the one of the “T”s in the engine heater line and a “normally open” solenoid valve between the 2 lines heading to the “T”s in the heater line. I'm sure a diagram would explain this better. Let me know if it's not clear as mud. So anyway this gives you flow from the engine heater line through the “normally closed “ valve, through the furnace and calorifier and back to the other engine heater hose when the engine is running and the solenoid valves are energized.

When you are camped up the first valve closes the circuit from the engine heater (eliminating coolant flow through the motor but still maintaining coolant level through the other engine heater line). Then the second valve opens and allows a bypass loop so the furnace can pump in closed circuit. As this is wired, it doesn't allow for pre heat but could easily be reconfigured (electrically) that way if required.

Tom. Do you want a diagram? Very keen to learn from your experience on this one.

A calorifier with 2 heat exchanger circuits not only needs a coolant header tank in the furnace circuit, it also might need 12v pumps to move coolant in the circuit that's not "hot".
Webasto furnaces have a pump either built in or attached to the out side case. They are also "freeflowing" . Not the correct terminology but let's just say that the engine heater coolant can easily pass through the Webasto pump when the pump is "off".

I insulate any long coolant hoses between the engine, furnace and space heaters that are exposed to outside temperatures to save diesel when heating the camper in cold weather.
Absolutely, but the G O is to have the hose runs as short as possible. We use the same hose insulation as we use on the air con pipes. A good tip to make it easy to slide over your heater hoses is to use plenty of talcum powder.

I use the timer when I want engine preheat at a certain time of day or if I want to run the furnace for 15 - 20 minutes to heat shower water after sitting for a day or so.

I use the thermostat to keep the camper comfortable when camped incold weather. It's programmable to a cooler setting at night and a warmer setting in the morning.

The space heater fans can be controlled by the furnace control (that's how I did mine) or they can be controlled by an "aquastat" that doesn't turn the fans on until the coolant reaches a certain temperature. Prevents the space heater from blowing cold air waiting for the furnace to get hot.
This sounds great. The furnace heat adjustment on the Webastos is excellent but we haven't really played with the space heaters that much.The space heaters we use are really small and only run 1 or 2 computer fans. After reading this I will look at thermostat control for these on the next one for sure.

Maybe it should be a separate thread, but if you're going to use a diesel furnace to avoid propane (lpg) you also need to change the propane cooktop.

You mentioned marine alcohol cooktop / oven. People like alcohol on a boat because the fire can be extinquished with water.

But alcohol requires carrying another fuel and an alcohol flame is almost invisible so a fire can start unoticed pretty easily. I had a friend that burnt his boat to the waterline because a fire spread from his cooktop before he saw the flames.
Yes it requires another fuel but they are still excellent > easy to use and install , self contained (no wiring or plumbing), have an oven (Webasto don't at this point) and relatively safe and virtually nothing to go wrong (so I'm told anyway).

Can relate to the boat story. My brother said he helped put out an alcohol fire on a neighboring boat and while they saved it, they used 3 extinguishers to do it. Imagine if they only had 2. So while I think of alcohol (metho) as dangerous fuel, the newer generation of metho stoves are much safer than the older units. They no longer use a tank but rather use flat cans full of material similar to a fuel cell in a modern race car. Therefore they are non-splillable and the fill opening must be about 2 & 1/2" diameter.

We aren't really biased either way. Diesel or metho. The diesel works out at more money but as you say > only one fuel that can be sucked straight from the main tank. So I suppose less hassle (if it all goes to plan).

There are 2 types - an open flame burner similar to a alcohol or propane cooktop and the sealed burner typed manufactured by Wallas and sold by either Wallas or Webasto.

The open flame type has a distinct diesel smell and requires alcohol to preheat the burner.
The open flame type doesn't sound that great. Never seen one in a motorhome before.

The newest model can exhaust through the floor which would eliminate the wind problem.
The Webasto cooktop have an exhaust for the diesel fumes that runs out through the floor and a larger one that forms a shroud around it and blows air from underneath the cooktop and out around the smaller pipe which also cools the smaller pipe as it passes through the cupboard and then the floor. Webasto also provide extremely detailed installation instructions regarding the running of the exhausts.

The newest version has a switch to allow high altitude operation, a complaint lodged against older versions.
Tom. Any idea how a metho stove would rate against this diesel unit at altitude. Oz is basically flat (and hot) so I can't comment on this either but at what altitude is a diesel or alcohol stove affected? What happens? Performance drops away or just won't work at all??

Last thing. Took a pic for you today. If you end up with a Webasto product, they come with a complete fuel pick up/ filter / supply line kit. They advise that this is better than "t"ing into the main truck fuel line. Most of our campers get a custom fuel tank and we add seperate pick ups for these type of devices. However most Mitsubishi and Isuzu trucks use "Tokyo Radiator" fuel tanks as standard, which have a spare /inspection plate so it's easy to just drill through this plate to fit the Webasto pick up. Just be careful that the down pipe doesn't conflict with the swing of the fuel gauge sender.

Thanks for the reply Tom.
 
Last edited:

spressomon

Expedition Leader
Since everyone here seems to know alot about hydronic heaters and because I'm basically lazy :sombrero: can one of the Espar water heaters be utilized in trailer application for on-demand water heating? How long does it typically take (I know this is a function of water temp...but just a general guide question) take to get hot water (100 degrees F) from the time the Espar is fired up to the heated water?

Can the Espar water heater be utilized in a stand-alone type application such as a little trailer?

Thanks in advance,
Dan
 

Bogo

Adventurer
The Espar Hydronic series of boilers specifically state they are for heating coolant water only, not fresh potable water. There is nothing to stop you from running that cooleant water through a water to water heat exchanger. Just remember to plumb your water to water heat exchanger so it is easy to fully drain the fresh water side when the camper is stored during freezing weather. You'd need a coolant expansion and reservoir tank in the coolant loop. Might as well add air heating heat exchangers too.
 
Last edited:

Bogo

Adventurer
Just thought of this. A small car engine radiator and overflow tank could be used as the expansion tank and water to air heat exchanger. You'd need a fan but that is easy. Often small car ones are electric.

The gas fired Espar units are max 4300W and 5000W output so their instant water heating capacity is limited. Diesel fired boilers are available with much higher outputs. They should be able to heat water on demand for a shower head like used on the sun shower bags. I'd plumb in a temperature limiter valve after the heat exchanger in the fresh water side and set it for the desired shower temperature.

I'm planning on using a gas fired unit in my micro RV for heating and may go with a small calorifier for hot water. IsoTemp has a slim line 5 gallon unit that looks tempting.
 

Bogo

Adventurer
Another thought I had in my notes: The tank for a heater could be a jerry can. I have heard of people doing this and have ran across caps for jerry cans that have fuel pickups and fill volume senders already installed in them. I figured I'd just make my own cap/pickup unit when the time came.
 

Bogo

Adventurer
I'm in the process of designing the Micro RV which is to be built on a '94 Toyota 4x4 mini truck pickup (Hilux). Space is at a real premium so I decided to go and get the sizes of the Hydronic 5 unit and it's accessory parts.

Things I noticed while at the Espar site:
  • The documentation they have online is very good.
  • I saw mention of an Airtonic 4 for petrol.
  • They have a high altitude compensation device, it is for all models, big to small and gas or diesel. They only say it optimizes emissions and just changes the fuel flow of the fuel pump.
  • They say protect the Hydronic units from excessive splashing. I take this to mean it can't get dunked in a stream crossing.:eek: I see the solution being to install it in a diving bell :D and make sure the exhaust and air intakes are water proof and run to above the expected high water line. Hoses can go through the sides via bulkhead fittings while the exhaust and air intake are routed through the open bottom. A side will need to be gasketted and removable for installation and servicing.
 

Seawali

New member
John,

Nice summary of diesel options.

I have an Espar furnace, an Indel single heat exchanger circuit calorifier and 2 space heaters connected to the engine as you suggested.

Some additional points:

I use a "Ball" valve instead of a "gate" valve to isolate the engine from the furnace. You can tell whether the valve is open or closed just by looking and you won't break something by trying to turn the handle the wrong way thinking the valve is jammed.

I think you only need a valve in one of the coolant lines between the engine and furnace to stop the coolant flow. Think cab heater control.

A calorifier with 2 heat exchanger circuits not only needs a coolant header tank in the furnace circuit, it also might need 12v pumps to move coolant in the circuit that's not "hot".

I insulate any long coolant hoses between the engine, furnace and space heaters that are exposed to outside temperatures to save diesel when heating the camper in cold weather.

I use both the espar timer and a battery operated room thermostat to control the furnace.

I use the timer when I want engine preheat at a certain time of day or if I want to run the furnace for 15 - 20 minutes to heat shower water after sitting for a day or so.

I use the thermostat to keep the camper comfortable when camped incold weather. It's programmable to a cooler setting at night and a warmer setting in the morning.

The space heater fans can be controlled by the furnace control (that's how I did mine) or they can be controlled by an "aquastat" that doesn't turn the fans on until the coolant reaches a certain temperature. Prevents the space heater from blowing cold air waiting for the furnace to get hot.

You are absolutely right about the requirement for a mechanical thermostat valve on the calorifier. When heating water with the engine it can reach over 212 F (100C). Even the diesel furnaces can reach 180F. This may cause severe burns.

Calorifiers for use on boats are designed to be heated by engine coolant and often come with a thermostatic mixing valve from the factory (at least in the US).


Tom
Good Day!
Adam from Poland. I am new over here. Good to see you.
Interesting in exp camp. Would like to ... you know what :smiley_drive:

Tom may you tell who made that system you talking about. Is it Webasto?

all the best,
Adam
 

Recommended books for Overlanding

Sailing Alone Around the World: a Personal Account of the...
by Joshua Slocum
From $26
The Essential Guide to Overland Travel in the United Stat...
by TeriAnn Wakeman
From $64.95
Overlanders' Handbook: Worldwide Route & Planning Guide: ...
by Chris Scott
From $19.35
Top