Dedicated Heating / Hydronics / Diesel heating thread

Geo.Lander

Active member
Hi all!
Part of the planning I have been putting off is the heating system, hence my previous preference to just go with the Truma Combi 6D solution to knock that question into submission without much thought (I still think that is a great system).

However, I am planning to install a fairly large (Eberspacher M10 or similar Webasto) furnace in the truck's engine bay to pre-heat the engine and driver's cabin and I know its probably the sane thing to hook into that loop and use a calorifier boiler for the hot water and heating (I am still thinking about underfloor heating, if not that then a heat exchanger blower with one or 2 radiators).

Question there..
  1. What are the control systems like for when I just want hot water and don't need to pre-heat the engine or provide heat to the box's heating loop?
  2. How good are the thermostats / remotes for these systems? are they designed to heat engines and camper boxes with one unit?
I am a bit put off by all the plumbing, holes needed to be drilled between the engine and box, etc and wanted everyone's input here. I didn't find a dedicated heating thread, of course plenty of stuff on you tube for vans but not much for trucks. I did see a nice video from a Krug expedition truck with a very large system but I am not really comfortable using so much space for plumbing, I am much more at home with electrical stuff :D

For the water pressure loops I am however decided on a 350L fresh water tank, 24v Aqua Jet pump, composite manifolds and PEX piping from Uponor Q&E system.. Getting there..

Screengrab from that video i mentioned
Screenshot 2021-10-07 at 21.54.26.png
 

Joe917

Explorer
First "fairly large". Bigger is not better in heating. A unit that is too big will cycle too often.
You will get many differing opinions here, this is what I have got out of 8 years living with a truck with a 28 year old Webasto system.
The original Thermotop C was replaced 6 years ago.
Our engine coolant is directly connected to the coolant loop in the habitat.
Heat comes from 3 passive radiators, no blowing air no interior fan noise.
Radiators can be turned off individually with mechanical valves as needed.
A mechanical valve can disconnect the engine loop to allow heating the habitat when parked.
We control the Webasto with a 12 volt Heatmiser T stat. I discovered this through the boating world. The Heatmiser has flexible set points and is fully compatible with the Webasto.
A simple set up like this can easily be configured to do anything you want, just heat the bathroom towel bar(highly recommended) or only heat the water in the hot water tank (Isotherm Spa) or only engine pre heat. All by opening and closing a few valves.

Underfloor heating sounds great, the problem is keeping the floor from getting too hot. The Webasto puts out coolant at 70C the engine runs at 80C and can run hotter.
 

Sitec

Adventurer
For fear of making our system too complicated, I went the other way in the hopes of keeping it simple... I have two seperate systems. For hot water we have a Truma Aqua Go. Gas fired hot water on demand, as we have plenty of gas storage on board. For heating the Hab Box, I have gone for the Russian Autoterm 4D diesel air heater. I have insulated the floor between the rails on our build (50mm to 100mm where possible), and think this will be more than plenty. Time will tell... :)
 

Iain_U1250

Explorer
I have a Webasto 90ST, and like most, run that through the engine cooling system to warm up the block, also acts as a nice heat soak to ensure the cycle times are long. I have two Kalori Silencio 2 radiators, ( 5KW each) with fans, one set of almost silent computer fans, just a vague hum, and then the standard fans from the unit which go from noisy to very noisy mode. I have a passive radiator in the boot, to keep the tanks warm, and also the batteries ( since the Lithium ones must not freeze. ) I run the engine cooling system all the ay to the back of the truck into a manifold, which I can manually control what get the water, in hot climates, only the 25l hot water tank does, when it is cold outside, then I open the other valves to provide heat to camper. It is great when doing a long run when it is cold to get into a toasty warm camper. The Websto give out 9kW when starting and settles down to 5-7kW. It takes about 5 minutes to warm the heater circuit. The silent fans run off a thermostat, so only come on when the truck cools down.

The coldest we have been us only -5C, and we turned the heater off before we went to sleep and 8 hours later it was still 18C inside, and we keep the roof hatches slightly open and have fans drawing air into the truck from a vent in the hot water compartment. Ten minutes with the heater on and it was back up to 25C inside. Key thing is blocking off the cab, as we don't have decent screen on the windows and would lose a lot of heat out the cab.

The hot water tank stays hot for about two days at least. I have a thermostatic valve on the hot water outlet, but the first little bit of hot water is still very very hot. Temps in the tank are the engine temp - around 85C.

I used 19mm stainless steel braided teflon hoses to run from the engine ( where the 90St is) to the back, as they are the highest risk of leaks, in theory these should last many years, given they are mean for hot oil running much higher temperatures than the cooling system. I run silicone hose everywhere else, and all the hot water hoses are insulated . I have bleed vales at the high points to get rid of the air locks, only when filling up the system, then close the valve and put a plug in the end.

Our floor is well insulated, and seldom feels cold. If it does, we put our bath mat down, the one we stand on after we shower inside, nice shaggy pile cotton mat. :)
 

joeblack5

Active member
Geo.lander. we have floor heating in our bus . 2" foam , Alu omega shape heat spreader and 7/16 plywood floor.. webasto TSL17. 1/2 pex o2.

We used three parallel equal length loops. This will give less temperature difference between the in and outlet.. also fold the loops inside each other so that you get a more uniform temperature...
Making parallel loops helps with matching the pump curve better to the load...
Slightly less noise and electricity. Each loop can be isolated with ball valves for redundancy and purging.

Good luck,
Johan
 

Peter_n_Margaret

Adventurer
We used a Webasto Thermotop C and a 30L calorifier with 2 heat exchange circuits to separate the engine from the house.
Surejust > 30 litre horizontal twin coil Surecal calorifier
It also has a 240V immersion element that can be powered from solar via the inverter.
Of course one heat source can be transferred to the other circuit via the calorifier.
A couple of small radiators with fans, a booster pump on each circuit and some 3 way valves make a pretty simple system.
We are able to heat the bathroom without heating the rest of the house so we can dry the laundry.
The Thermotop C has more capacity than we usually need so sometimes we will heat the engine, just to dump some heat and reduce cycling of the Webasto.
20 minutes either driving or running the Webasto provides water in excess of showering temperature. 45 minutes of Webasto to pre heat the engine.
Great system.
Cheers,
Peter
OKA196 motorhome
 

Geo.Lander

Active member
A mechanical valve can disconnect the engine loop to allow heating the habitat when parked.
As i thought 😭 , so if I need a manifold with manual values that feed into the box heating loops and also one for the engine loop.. Either that or solenoid values or similar.. This is the added complexity I was fearing..

For hot water we have a Truma Aqua Go. Gas fired hot water on demand, as we have plenty of gas storage on board
Yea, the Aqua go seems really nice, but we wont have Gas at all so its out of the equation. I think independant systems are a good thing in some aspects too!

The coldest we have been us only -5C, and we turned the heater off before we went to sleep and 8 hours later it was still 18C inside, and we keep the roof hatches slightly open and have fans drawing air into the truck from a vent in the hot water compartment. Ten minutes with the heater on and it was back up to 25C inside. Key thing is blocking off the cab, as we don't have decent screen on the windows and would lose a lot of heat out the cab.
We are looking at sustained winter temps of -20C and below, day and night. I know the 62mm Box will provide a hell of a lot of insulation but I really want a capable and not so noisy heating system that can keep the temps topped off automatically :)

We used three parallel equal length loops. This will give less temperature difference between the in and outlet.. also fold the loops inside each other so that you get a more uniform temperature...
Great insights into the underfloor loops, thanks! I was thinking of using the low profile (LoFlo) boards with 10mm pipework, should be easy enough to hook up to the coolant circuit but my thoughts revolve around pumps and regulation (thermostats), the control boards and pumps are all 230V and I assume the control board is using the pump as means of temp regulation. So do i even need a pump or will the furnace/engine provide enough pressure? Then I suppose I need the furnace to regulate heat in one go (hot water and heating). Not exactly finite control thou is it.. I think I need a design session with Eberspacher as the Webasto guys here in Norway had never done anything like this before..
 

joeblack5

Active member
Geo.lander. the TSL17 has it own 12 v or 24 v pump.. the reason for the floor heat was less energy use in fans and less noise.

We did use a large oversized radiator with computer fan in series with the floor heat. That helps with heating up from start.
There is a fphe with the engine loop. To run the engine directly thru the pex is dangerous because of the high temps and pressures. The bus has a separate engine coolant circulation pump. The floor heat also uses the non toxic glycol...the shower heat exchanger is parallel to the floor heat. Manual ball valves for isolation.

Good luck,

Johan
 

Alloy

Well-known member
Comments about cycling from too many BTU/Kw are correct. A heat calc is easy to do. There's lots of heat calcs online


Also want to run the system at the lowest possible temp. No need to heat glycol to 180F when 140F is enough. Hotter also means dealing with more expansion in the PEX.

Infloor should not be the same temperature as the radiators and hot water tank.

When using the expander tool on Upunor PEX it's important keep rotating the tool. Good chance the connections will leak if you don't.

Balancing can be done with valves or in a reverse return method but this require more piping.




A small plate heat exchanger can be used to separate the engine from the box.

Standard solenoid valve ope/close too quickly. Hydronic solenoid (zone) valves open/close slowly.

I ducted (wish we had hydronic but it would have taken weeks retrofit) the forced air system so the bathroom can be heated separately. Temps right now are 1C to 3C. For the last week the bathroom is the only area being heated. When temps drop to -4C tommorow the furnace will be needed to keep things from freezing.

Snow is coming down the mountain.
20211008_074201.jpg
 
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Geo.Lander

Active member
Comments about cycling from too many BTU/Kw are correct. A heat calc is easy to do. There's lots of heat calcs online
I'm just going with the cloud 9 advice as reff to the larger M10 furnace... I think Neil's build site has provided my only knowledge to this heating area. Such an excellent resource!

Back in the UK we sent our requirements to their head office in Hampshire and one of their chief engineers ( Jon Jennings ) examined our requirements and made all his calculations and came to the conclusion that the 10 KW was the right choice.
10 kw of heating is a huge amount and could easily heat a small house let alone a 5 meter well insulated cabin.

The reasons given where :-
1. When up to temperature the M10 can tick over at 1500 watts making its running more economical than the D5 which has a low setting of 2400 watts.

2. The D5 is not suitable for high altitude and requires a further kit to enable it to be used to up to 4000 meters. ( the extra altitude kit is nearly as expensive as the heater ) Whereas, the M10 is already suitable for altitudes of 4000 metres ( tested ) and needs no additional kit or modification.

3. When at high altitude both heaters can run at as little as 30% power and in theses circumstances the 5 kw would not be sufficient to pre heat the engine.
 

Alloy

Well-known member
I'm just going with the cloud 9 advice as reff to the larger M10 furnace... I think Neil's build site has provided my only knowledge to this heating area. Such an excellent resource!

Back in the UK we sent our requirements to their head office in Hampshire and one of their chief engineers ( Jon Jennings ) examined our requirements and made all his calculations and came to the conclusion that the 10 KW was the right choice.
10 kw of heating is a huge amount and could easily heat a small house let alone a 5 meter well insulated cabin.

The reasons given where :-
1. When up to temperature the M10 can tick over at 1500 watts making its running more economical than the D5 which has a low setting of 2400 watts.

2. The D5 is not suitable for high altitude and requires a further kit to enable it to be used to up to 4000 meters. ( the extra altitude kit is nearly as expensive as the heater ) Whereas, the M10 is already suitable for altitudes of 4000 metres ( tested ) and needs no additional kit or modification.

3. When at high altitude both heaters can run at as little as 30% power and in theses circumstances the 5 kw would not be sufficient to pre heat the engine.
The M12 modulates down to 1200w.
 

Peter_n_Margaret

Adventurer
Comment on your layout.
The calorifier needs to be as close as possible to the shower to save water wastage and temperature variations.
Cheers,
Peter
OKA196 motorhome
 
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