Hydronic Heat, Hot water, and Engine Pre-heating

TDIVan

New member
Hey Folks,
I'm starting a thread on a hydronic-based build I'm working on for my Vanagon Syncro camper. The schematic shows the general function of the system. There are a few new concepts here but, in general, this is a normal build found in most yachts, river long boats, and commercial boats. It is also more common in RV Vehicles across the pond. The primary companies that outfit this type of system are Webasto and Eberspacher (Espar), more commonly used in the US/Canada for Air-based heaters. The primary reason you don't find hydronic as much in this hemisphere is that it has been targeted towards diesel-powered vehicles common in the rest of the world but rarer here. The most common use of this diesel furnace is for pre-heating commercial diesel trucks.

I thought I'd show the parts as I start building it out as a working model before laying it out in the van. The heart of the system is an Eberspacher D5WS diesel furnace. There are smaller and larger furnaces but for the small Vanagon camper, I think this is just right. You do not need to have a diesel engine to use a diesel-based furnace for cabin heating and hot water. In fact there are models for regular petrol too. You can also install a small diesel tank for the furnace in your gas-powered vehicle. My goal for the van is international overland and so I'm focusing the rest of my vehicle on readily available parts throughout the world and only one source of fuel, the most common throughout the world, and the one that does not let off flammable gasses; diesel. My Vanagon Syncro has been fitted with a 2003 VW 1.9L TDI. Everything in the van uses either Diesel, 120/240 VAC, Solar, Wind, or Hydro-kinetic power. The van is set up to last a long-time off-grid in any weather. The first picture shows the schematic with the components of the system and integration points (without electrical connections for now).
hydronic-2.png
The next photos show the individual components to build the system, some pieces are still in shipping and I'm still deciding on the exact plumbing. Wiring will be all attached to my cabin batteries system which is isolated from the starting system,

IMG_4502.JPG
The digital "Panel" on left is a touch screen backed by a Raspberry Pi micro-computer (all the computer parts under $150). The idea is to use a simple program on the micro computer for controlling three valves, three pumps, reading two temperatures (air & water), reading whether I have 120VAC connected, and cycling on the hot water heater as needed, I will be able to control everything from the touchscreen (or the same app on my phone). The scenarios work for both On or Off-grid, Van running or resting, and which of the three functions I want, when I want them; Hot water, Cabin heat, and/or Diesel-engine pre-heating. To reduce chances of stranded-class failure of any of the sub-systems, all three fluid systems; Engine anti-freeze, Glycol, and Fresh water are all isolated with heat-exchangers. Any of the switches and valves can be operated manually with a quick change-out. It is possible to do all of this without the computer and I will demonstrate that first.

Some interesting scenarios to include:
1. Its cold outside and the van is connected to the grid. Use the 120V system (calorifier/water heater) to heat the engine and cabin remotely from my phone
2. I'm off-grid and I want to keep the van interior at 70 degrees between 6pm and 10pm, then reduce to 60 degrees until 7am, then back up to 70 degrees or until I "pause" it.
3. I'm off-grid or on-grid and I want warm water for dishes and showers for an hour with a single click
4. I'm filling up the kiddie pool with 50 gallons of warm water from the river, saving my stored water, filtered too.
5. I'm snowboarding at 6,000 feet. I want to come back to the van at 6pm with 75 degrees inside and a tank full of hot water.

I'll follow up as I progress and look forward to feedback from those that can give it. thanks!
 
Last edited:

llamalander

Active member
Looking forward to this build, especially the Raspberry Pi elements.
Climbing back into my truck with snow packed in every fold of my ski clothes, I noticed how much water i bring into the vehicle in winter. You might consider a dedicated blower to dry wet equipment if you plan to spend much time in the van snowboarding. A boot/glove dryer and (or in) a heated compartment could mean your trips could last longer than your supply of dry clothes.
 

TDIVan

New member
Hydronic heating has it's merits, Many folks like to use passive radiators so there is no moving air, just heat. This method doesn't dry out the cabin like typical air heaters but less than ideal for removing moisture. It would be cool to be able to fabricate a box with a tumbler inside driven by a 12vdc motor and leverage a hydronic radiator to heat it, then have an exterior vent for the humid exhaust air. Basically a small clothes dryer that could dry a couple articles of clothing but not take up much room. Probably a sound investment for winter sports and remove it during summer...
 

Recommended books for Overlanding

Americas Overland - The Driving Handbook
by Donald Greene
From $20
We Will Be Free: Overlanding In Africa and Around South A...
by Mr Graeme Robert Bell
From $17.87
Drive Nacho Drive: A Journey from the American Dream to t...
by Brad Van Orden, Sheena Van Orden
From $15.95

Alloy

Well-known member
Comments:
- The HW tank is a heat exchanger. What does the preheater do?
- Why circulate through the expansion tank?
- Overflow isn't needed if the expansion tank is sized correctly.
- A domestic water loop and a heating loop each controlled by a separate circulation pump is another possible layout.
- Why the mixing valve on the sink?
- Filtering water coming out of the tanks will become an issue as the filter(s) plug up.
- How will the filters be winterized?
- How many watts will the system draw with the engine off?
- Will FW tank heating be needed?
 

TDIVan

New member
Hi Alloy
thanks for the questions! I'll provide some answers from my research, planned use, and reasoning. It's good to reason through things before I get too far through the process...

- The HW tank is a heat exchanger. What does the preheater do?
----The pre-heater is a more efficient transfer agent than the hot water heater when using glycol as the heating agent. When you are running off-grid (using hydronic coils only, it should provide more efficient overall heat transfer to the water and therefor support a higher volume of flow (better shower) and the process should take less time to reach temperature. I'll simplify if this isn't the case.

- Why circulate through the expansion tank?
---- The expansion tank serves three purposes; first - heat expansion, second - keeps system air-free once bled, third - it increases the volume of glycol in the system by almost double, allowing the glycol to cool sufficiently before cycling back through the furnace. If the glycol temperature is too close to the output heat temperature of the furnace, it can trip the furnace shutdown. This is especially important when the summer loop is running and only the hot water is being heated.

- Overflow isn't needed if the expansion tank is sized correctly.
---- You are correct. The expansion tank needs to vent. I'm using the overflow tank to maximize the volume of glycol in my small expansion tank (1.5 litre) and in the small van, I don't have room for an expansion tank outside my camper and I really don't want to smell the expansion gas which will be vented outside where the tiny overflow lives. As I tune the system, I expect some things to change a bit...

- A domestic water loop and a heating loop each controlled by a separate circulation pump is another possible layout.
---- Not sure I understand. Diagram has separate pumps for water circulation, glycol circulation, and anti-freeze circulation. Do you mean combining the glycol and water loops and just run water?

- Why the mixing valve on the sink?
---- The glycol coming out of the furnace can heat the water in the water heater up to 80°C (176°F) at steady state. The mixing valve will ensure any water coming out of either the sink or the shower is below 120°F

- Filtering water coming out of the tanks will become an issue as the filter(s) plug up.
---- There is an external sediment filter (cleanable) preventing any water in the system having particles over 10 microns. This significantly helps the other filter's lifespan. The other filters handle smaller particles, carbon, and metals. I also have an optional ultraviolet filter for microbes for use in foreign countries. The system was built to ensure purified water from the shower or sink. I built the van for a Patagonia trip and water will be an issue in many of the countries, even when showering as I will be filling my tanks sometimes from rivers and lakes.

- How will the filters be winterized?
----- the filters detach and the water system can be drained for winter. Additionally, the entire water system and filters are in the heated cabin space for winter camping.

- How many watts will the system draw with the engine off?
---- Furnace at 37 watts high (should only run a short time at this speed) and 12 watts on low. Each pump is 16 watts and the fans connected to the cabin heaters run 1.8 watts each. I have 200 watts of solar and 300 aH of house batteries to get me through...

- Will FW tank heating be needed?
---- Mine will be in the main heated cabin so I just need to ensure that the interior does not freeze. I'm a bit concerned about my diesel fuel in really low temperatures so I pack some anti-gel supplements
 

Joe917

Explorer
Interesting comment about Patagonia. You will never need to fill from rivers or lakes. Fresh clean water is readily available.
 

javajoe79

Fabricator
That all looks good. To me the added heat exchangers and extra pump for engine coolant seem excessive. I understand your reasoning though. I just like to keep things simple. Same reason why I am doing manual valves in my system and in general, minimal computer control of anything.
Having the expansion tank in line makes sense to me too. Similar to a swirl pot setup on some race cars I've built but since the espar flows much less than an engine water pump I don't see why you wouldn't just put the expansion tank in line with the flow instead of as an offshoot.
I would also like an overflow on my system because like you mentioned the expansion tank traps any air which rises to the top and then purges out through the cap once the system pressurizes. Plus you can have on overflow that allows visible confirmation of the fluid level. If you see that it's low, you might have a leak somewhere.
What pressure cap would you run on the expansion tank? Seeing as how a higher pressure isn't needed to raise boiling point and eliminate hot spots in the system like in an engine cooling system, I wonder what pressure would work best. I've probably read that in official documents somewhere but I don't remember.
 

TDIVan

New member
Interesting comment about Patagonia. You will never need to fill from rivers or lakes. Fresh clean water is readily available.
Thanks Joe, I'm sure you are a much better authority than I am on South America ;) I have a few primitive properties on the Olympic peninsula (WA) where we stay for a week or more with only river water so I built the solution to prevent Giardiasis, which I contracted in Mexico and in Colombia on vacations (though not from river water) . I assumed better safe than sorry driving through central america...
 

TDIVan

New member
That all looks good. To me the added heat exchangers and extra pump for engine coolant seem excessive. I understand your reasoning though. I just like to keep things simple. Same reason why I am doing manual valves in my system and in general, minimal computer control of anything.
Having the expansion tank in line makes sense to me too. Similar to a swirl pot setup on some race cars I've built but since the espar flows much less than an engine water pump I don't see why you wouldn't just put the expansion tank in line with the flow instead of as an offshoot.
I would also like an overflow on my system because like you mentioned the expansion tank traps any air which rises to the top and then purges out through the cap once the system pressurizes. Plus you can have on overflow that allows visible confirmation of the fluid level. If you see that it's low, you might have a leak somewhere.
What pressure cap would you run on the expansion tank? Seeing as how a higher pressure isn't needed to raise boiling point and eliminate hot spots in the system like in an engine cooling system, I wonder what pressure would work best. I've probably read that in official documents somewhere but I don't remember.
Hi JavaJoe,

It is a bit complicated. Eventually I'll publish some other components of my rig and you will see more of this trend... During the actual build-out and debugging of the system, things tend to get simpler.

I have a 0.8L overflow that shows fluid level. It will be mounted externally somewhere, not sure where yet. My expansion tank is stainless 1.5L and uses, currently a 1.1 bar (roughly 15psi) pressure cap. It came with the tank so it will need to be validated. I'll also have inline temperature and pressure measures, at least during the bench-testing phase at various points in the system. I'm waiting for the electric valves and check valves to arrive next week.
 

MattScott

Approved Vendor
I have a Webasto in my 80 series (1HDT) and love it for engine pre-heating. We'll use it to heat the interior once the pop top is installed.
 

luthj

Engineer In Residence
The plate heat exchanger allows for on-demand style hot water. For example you haven't run the hydronic unit in several days, and you don't want to wait 20 minutes for the tank to heat. Some hot water tanks have marginal hydronic coils, so the plate unit allows for that (assuming the hydronic unit is running).

There really isn't any need for a pressure cap at all, a simple vent to the atmosphere is totally acceptable.
 

dreadlocks

Well-known member
for reliability sake id suggest you look at an alternative to the RPI, check out oDroid w/MMC card.. Ive got alot of experience with lil arm boxes and the Pi has rather poor power regulation on em and it causes em to eatup SD cards at the most inconvenient time... for a while I kept thinking it was cheap/counterfeit flash even though I had always verified em and tested em, then I talked to a buddy who is package maintainer for arch linux arm official repos (he has like every arm board on market) and he told me how and why (all his eat up cards real fast with the load he put on em since software building/testing is high read/write).. under his suggestion I started moving to BeagleBones and now oDroids, I've got some Beagles that have been in operation for nearly a decade now w/out ever giving me grief..

Pi's are great for the community support and libraries that abstract all the IO for you, but if your already pretty technically savvy then its really just linux and what board it runs on dont matter much.
 

TDIVan

New member
for reliability sake id suggest you look at an alternative to the RPI, check out oDroid w/MMC card.. Ive got alot of experience with lil arm boxes and the Pi has rather poor power regulation on em and it causes em to eatup SD cards at the most inconvenient time... for a while I kept thinking it was cheap/counterfeit flash even though I had always verified em and tested em, then I talked to a buddy who is package maintainer for arch linux arm official repos (he has like every arm board on market) and he told me how and why (all his eat up cards real fast with the load he put on em since software building/testing is high read/write).. under his suggestion I started moving to BeagleBones and now oDroids, I've got some Beagles that have been in operation for nearly a decade now w/out ever giving me grief..

Pi's are great for the community support and libraries that abstract all the IO for you, but if your already pretty technically savvy then its really just linux and what board it runs on dont matter much.
Hey, You are probably correct on this, however, I am a long time Microsoft developer and run Windows 10 on my Pi. Old dogs, new tricks, etc. I have a spare Pi and spare programmed Sd cards. I have a nice event-driven framework that allows me to monitor everything in near real-time and respond to what's up on the van. It even alerts me on my phone if the freezer dips above 28 degrees, fridge above 40 degrees or any of the batteries drops below 12.4 volts. I can then decide what to do. I can monitor all the critical van components even as trivial as an unexpected battery drain or whether the van dips below 35 degrees, I can turn interior or exterior cameras on to see what's up and eventually record video from motion sensors. Eventually I'll configure a "clapper" to turn the interior lights on... half-kidding. It's really limitless what I've been able to do pretty simply. I'm working on a "Night-night" feature that with a single click, intelligently puts the van to sleep. Alexa integration seems a step too far... I have my standards ;) I retired from Microsoft 12 years ago so my ability to retrain myself is limited...
 

Recommended books for Overlanding

Long Way Round: Chasing Shadows Across the World
by Ewan McGregor, Charley Boorman
From $16.69
Don't Go There. It's Not Safe. You'll Die.: And other mor...
by Jared McCaffree, Jessica Mans, Kobus Mans
From $19.99
Deep Survival: Who Lives, Who Dies, and Why
by Laurence Gonzales
From $9.99

TDIVan

New member
Hey, You are probably correct on this, however, I am a long time Microsoft developer and run Windows 10 on my Pi. Old dogs, new tricks, etc. I have a spare Pi and spare programmed Sd cards. I have a nice event-driven framework that allows me to monitor everything in near real-time and respond to what's up on the van. It even alerts me on my phone if the freezer dips above 28 degrees, fridge above 40 degrees or any of the batteries drops below 12.4 volts. I can then decide what to do. I can monitor all the critical van components even as trivial as an unexpected battery drain or whether the van dips below 35 degrees, I can turn interior or exterior cameras on to see what's up and eventually record video from motion sensors. Eventually I'll configure a "clapper" to turn the interior lights on... half-kidding. It's really limitless what I've been able to do pretty simply. I'm working on a "Night-night" feature that with a single click, intelligently puts the van to sleep. Alexa integration seems a step too far... I have my standards ;) I retired from Microsoft 12 years ago so my ability to retrain myself is limited...
Another thing I need to remember... I want my phone to remind me when my 150w portable solar panel needs to be moved back into the sun. Often I forget to move it about when i'm in the middle of nowhere and the sun moves. I like to park the van in the shade which makes the top mounted panels pretty inefficient.
 
Top