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Old 09-28-2017, 09:39 AM   #1
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Hydronic heat

There has been a number of questions lately about hydronic heat. Here is a diagram of my system. It uses an Espar hydronic 10 for the heat source. The unit is 32,000 btu and keeps the water temp between 154 and 185 degrees. There are 3 separate water systems that work together to produce heat depending on the circumstances.
  • Engine cooling system, ethylene glycol, poison
  • Heating system,propylene glycol,not poison
  • Domestic water, hopefully not poison

The water pumps are controlled by thermostats. With engine running heat is picked up through the heat exchangers both in the water heater and for bus heat. When the Espar boiler is running it heats the bus as well as the water heater and the engine. The water heater also has a 120VAC element for hot water when plugged into shore power.



This is the Espar boiler, gray tank is reservoir, white tank is overflow. I wouldn't have needed this to be so big.Gray box is marine water heater.



Detail of zone water pumps, relays and manifolds.



Pex layout under floor.



What a mess



Whew, what a relief, finally.



I can't say anything about anyone else's system. This system works. Keeps me comfy at below zero temps and has been trouble free for three winters. I can't say anything about fuel consumption, I just don't know or care, it draws fuel from the fuel tank.I do know that on a trip approx 400 miles in roughly a week of pretty constant use sitting in one place fuel mileage went from about 7 to about 5.
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Old 09-28-2017, 02:30 PM   #2
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A VERY impressive system/build! Well done!

Could you please come install one in my coach please?!?!
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Old 09-29-2017, 04:54 PM   #3
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Thumbs up Holy Heaters, batman !

You are a wild man.

Thanks for sharing all the details of what looks like to be the coziest system. Package all those parts-up in a kit and sell. Looks like $3K in components.

Very nicely done.
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Old 12-08-2017, 04:17 PM   #4
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Hey, your thread is fantastic and this is one of the most interesting heating methods I've seen for on road and sitting combined. Would you mind going into detail on the heater and how it is designed? I'm a complete noob and don't understand all of the components. It's a marine water heater hooked up to a boiler?

Thanks
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Old 12-08-2017, 06:05 PM   #5
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In the diagram the Espar Hydronic 10 is the boiler and makes the water hot in the mail loop. (big red line). It is used when I am sitting still. When the boiler is running the marine water heater picks up heat from the mail loop making domestic hot water for shower and sinks. A bonus is that it also heats the water in the engine cooling system.

When driving the main loop is heated by the heat exchanger in the engine cooling system. Again making domestic hot water and supplying hot water to the loop for cabin heat. There are four loops for cabin heat. Each cabin heat loop has a water pump controlled by a thermostat. The boiler has a water pump in it to circulate water in the main loop, I installed a switch to turn that pump on when the engine is running and I need cabin heat.

The water heater also has a 120VAC heating element to supply domestic hot water in the summer time when the engine or boiler isn't running. In theory it would make cabin heat but the heating element isn't near big enough for that.

Hope that explains it.
Dick
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Old 12-09-2017, 03:04 PM   #6
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Thanks for the info. Did you buy everything new? What's the estimate on the cost, if you don't mind?

Are you happy you did it this way? Happy with the results?

I assume you put it all together yourself. What is your difficulty rating 0-10?
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Old 12-09-2017, 03:31 PM   #7
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That is impressive. It sounds simple enough when you describe it, but honestly I no comprende. I'm stuck with cold feet.
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Old 12-09-2017, 04:35 PM   #8
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Excellent design and build Dick. Drawing tells the whole story. Thanks for sharing, I may go hydronic down the road.
Well done sir!

John
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Old 10-05-2018, 04:07 PM   #9
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I know this is an old thread, but I was wondering if you could share what type of pumps your using for each of the zones?
Thanks
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Old 10-05-2018, 06:16 PM   #10
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Originally Posted by jay85 View Post
I know this is an old thread, but I was wondering if you could share what type of pumps your using for each of the zones?
Thanks
The pumps are Bosch. They are the same ones that the Espar boiler uses. Mine are 24VDC but are available in 12VDC. Do a search for Espar Hydronic 10 water pump.

Really, any water pump,that can take the heat, will do. It's a circulation pump not a pressure pump.
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Old 11-23-2018, 09:12 PM   #11
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Figured it would be better to revive this thread than create another. I'm currently experimenting with propane water heaters using engine coolant loops and would like to share my experience thusfar.

The OP has floor heat it looks like, I just have a coolant loop and three-speed blowers. I was looking at diesel-based heating solutions and the top wattage I was seeing was around 30kw. Looking over at the portable LPs (typically used for showers), from the ratings at least they easily match or beat that.

I've spent some time tinkering with a really low-end (Eccotemp L5) insta-shower heater and I got it hooked up to the coolant loop. Full disclosure- This is not what this equipment is meant for, its a hack.

First, I separated my hydronic loop from the engine loop. This is probably temporary, I'll likely join them via a water-water heat exchanger.

From:
Reservoir -> Pump -> Engine -> Radiator -> Booster Pump -> Heater Blowers -> Reservoir

To:
Reservoir -> Pump -> Engine -> Radiator -> Engine Reservoir

Reservior2 -> Pump2 -> Heater Blowers -> Reservoir2

Next, my first idea was to simply put the water heater inline with the loop. However the heater is mechanically dependent on water pressure to open the gas valves, and coolant pumps move volume rather than push pressure. This didn't seem like it was going to work.

Then I had an idea, two loops with a common reservoir.

Reservior2 -> Pump2 -> Heater Blowers -> Reservoir2
Reservior2 -> Pump3 -> Water Heater -> Reservoir2

I still think I'm going to have to find a unit that I can start without pressure, but this is what I finished with today. Since Pump2 turns the water over very quickly, the heater water from pump3's loop is distributed quite quickly and evenly.

I was able to get the heater running and heating the loop up, but it was late and bitter cold out, so I called it a day. Tomorrow I'm going to see what kind of a dent I can actually make in the cabin temperature.

This unit claims "37,500 BTU" (11kW?). I have a vented unit on the way with an output rating of 37kW for a more pemanent installation if it works out (if not, I'll just use it for freshwater heat). The numbers suggest it will. Engineering problems at play:

-Using a diaphragm pump meant to create 50, 60PSI of pressure and a 30% duty cycle. I think a hard requirement going forward is a finding a way to run this using a centrifugal pump meant for coolant loops.

-I'm going to attempt to keep the coolant around 90F-110F to see if that is effective out of consideration of the pump, I anticipate I'll need to go higher, so again.

-Automating a burner process using a microcontroller. Pumps first, followed by the heater, followed by blowers as water temp rises. I may need to use temp sensors to make good decisions around burner activation, and rest the pump at intervals.

-Consider whether this really is a good idea, which is why I'm here. Assuming safety is properly addressed, I don't see why this would be a particularly bad- Maybe it will work, maybe it wont. My current testing seems to indicate it will.

Let me know what you guys think, maybe I'll post some pictures tomorrow.
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Old 12-08-2018, 12:57 PM   #12
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Kaz,

All interesting thoughts. Forgive me if i'm new here but i've been doing research for quite a while for my own skoolie power/heating systems.

What is your primary drive for using propane? Diesel has 139k btu per gallon vs propane having 91k btu per gallon. I feel like you would go through a whole bunch of propane to heat if you considered a propane fired hydronic system or a forced air propane furnace for that matter. Lets say for a nice round number your instant hot water is 30k btu/h and you run it 3 hrs a day. That's 90k btu per day, or 1 gallon of propane per day. If you keep 10 gallons on board, you'd need propane in 10 days. I know that is a crude estimate and there are a lot of other things that would go into that, but it's something to think about.

I've been wanting to use diesel wherever possible with my build i'm planning, simply for the fact of how easy it is to get. If you have an on-board propane tank you will need to find a place to fill it, or call a truck which can be expensive. Diesel you can just stop at the pump and fill up.

I've considered using a combination of a Espar D2 or D4 diesel air heater for a full size skoolie, in combination with electric floor heating for spot heating. The D2 is only 7,500btu on max output, but i've read they work best at high output. I can supplement with zone based electric floor heating that I run through my Magnum inverter. Having a warm floor to put your feet on makes the "percieved" temp much higher than actual temp. For example, for a bathroom or desk area I would consider: https://www.homedepot.com/p/FloorHea...36-3/305388093

This comes in at 100 a/c watts. If I run it 3 hours a day, and consider 80% inverter efficiency, that equals out to 30Ah/Day from my battery bank which is tolerable. I'm also going to max out my roof top solar hopefully 1kw or higher if possible. btw 100 watts times 3 hours = 300 watt/hours 300/12 is 25 DC AH times 1.2 (for 80% inverter efficiency) equals out to 30 Ah from my batteries with 3 hours run time on the floor heating. Remember these floor mats also are thermostat operated so 3 hours should be enough of an estimate I would imagine.

I love the idea of the hydronic floor heating with the Espar diesel heater, I just don't know if I want to have that much complexity in my build, but major props to the OP nonetheless and it looks like a very solid build.

Sorry if I mucked this thread up I just figured it was a fair comparison considering the floor heating discussion and make spark some other ideas.
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Old 11-19-2019, 05:32 PM   #13
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Quote:
Originally Posted by somewhereinusa View Post
There has been a number of questions lately about hydronic heat. Here is a diagram of my system. It uses an Espar hydronic 10 for the heat source. The unit is 32,000 btu and keeps the water temp between 154 and 185 degrees. There are 3 separate water systems that work together to produce heat depending on the circumstances.
  • Engine cooling system, ethylene glycol, poison
  • Heating system,propylene glycol,not poison
  • Domestic water, hopefully not poison

The water pumps are controlled by thermostats. With engine running heat is picked up through the heat exchangers both in the water heater and for bus heat. When the Espar boiler is running it heats the bus as well as the water heater and the engine. The water heater also has a 120VAC element for hot water when plugged into shore power.



This is the Espar boiler, gray tank is reservoir, white tank is overflow. I wouldn't have needed this to be so big.Gray box is marine water heater.



Detail of zone water pumps, relays and manifolds.



Pex layout under floor.



What a mess



Whew, what a relief, finally.



I can't say anything about anyone else's system. This system works. Keeps me comfy at below zero temps and has been trouble free for three winters. I can't say anything about fuel consumption, I just don't know or care, it draws fuel from the fuel tank.I do know that on a trip approx 400 miles in roughly a week of pretty constant use sitting in one place fuel mileage went from about 7 to about 5.
Sorry to revive and old thread here, but I was wondering if you could touch on this picture in a bit of detail:

I understand the shutoff valves on each manifold, but what is the additional valve-looking thing on the manifold not attached to the pumps? Additionally, did you buy those manifolds from pexuniverse, or make your own? I was looking at the stainless steel ones, but their max temp is 158F, which is lower than the operating temperature for the engine and coolant heater, so I'm thinking that won't work well.
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Old 11-19-2019, 05:38 PM   #14
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With about an 8" minimum bend in the PEX, your living room trace is 8' long and the 2 short ones 4' front to rear.
I ran mine front to rear.
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Old 11-19-2019, 05:40 PM   #15
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The extra valves are air bleeds. I bought the manifolds off of eBay. I haven't looked at the valves you mention, not sure why stainless would not work. Wouldn't be too hard to solder one in copper.
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Old 11-19-2019, 10:24 PM   #16
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Originally Posted by somewhereinusa View Post
The extra valves are air bleeds. I bought the manifolds off of eBay. I haven't looked at the valves you mention, not sure why stainless would not work. Wouldn't be too hard to solder one in copper.
That makes sense, thanks!

The only reason the stainless steel wouldn't work is it says its Max temp is 158F, and I expect temperatures to be up to 185F, so it might fry some delicates in the manifold. It might be cheaper to fabricate one from simple brass/copper anyway.
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