Baseboard heat or other radiant heat with no fan using espar for heat source.

[javajoe79]

How about two loops? One to insert heat into the calorifier, and another to extract it.

Well from what I see, a calorifier is just a hot water heater. So it's stores hot fresh water, not hot coolant. The loop inside doesn't have much volume. So unless people are running fresh water in a loop through their heating circuit I am missing something.

 

[javajoe79]

Not a problem - they come with thermostats - not sure why you see an issue?

My adding a 5 gal tank to my system was just to increase the volume of the hot water to allow a long (quiet) time between the webasto coming on. The tank & manifold & most of the plumbing are in/under cabinets that are connected in such a way that air flows in one end & out through the radiator/fan. So there is no wasted heat - it's all contained within the camper envelope (except the webasto & inlet/outlet hose). The bed is above the tank...The point is there can be a number of ways to enhance the passive, unpowered or low powered extraction of heat from the system - which was the central question of your first post. Moe

Maybe I am over thinking it. I know you can control one thermostatically but that could mean short cycling in a small camper like mine.

So with your 5 gallon tank, you run a separate pump that circulates the hot coolant to your radiator and floor heat circuit correct? I think that is the part I was missing. The internal pump on the espar normally does that job while the espar is running. I suppose I could switch on just the pump inside the espar to avoid having two pumps. Do the webasto units have an internal pump?

 

[dwh]

Well from what I see, a calorifier is just a hot water heater. So it's stores hot fresh water, not hot coolant. The loop inside doesn't have much volume. So unless people are running fresh water in a loop through their heating circuit I am missing something.

Circulate hot coolant in a loop through the hot water tank. Water absorbs heat. Hydronic shuts off.

Circulate coolant through a second loop in the hot water tank to extract heat. Eventually, water temp drops and hydronic comes on to bring water temp back up.

Two things prevent short cycling - the mass of the water takes time to heat, and the water can be heated to a very high temp, which also takes time.

 

[dwh]

In other words, you can accumulate heat in a big jug of coolant, or a big jug of water. Same effect either way.

 

[loonwheeler]

DWH is correct. By adding the calorifier in the loop, it acts as a energy (thermal) storage device that can absorb and store the heat produced by the hydronic heater. A side effect is prolonged run times which prevents the hydronic heater from starting up and only running for a very short period before shutting down. The same thing will happen in an improperly bled system when the circulation pump catches a pocket of air and the flow of coolant is interrupted.

Here is a simple example of a single series circuit that might work. By using the calorifier with the addition of a circulation pump connected to a thermostat, it can allow you to slowly take energy (thermal) from the calorifier and dissipate it by way of the active or passive radiator(s) in your system. When turned on, the hydronic heater is constantly checking to make sure the coolant is maintained above the set point (~85 degrees C) and restarts the combustion chanber when needed - dumping additional energy into both the calorifier and the radiator(s). Some hydronic heaters might be able to be programmed to run the on board circulation pump (if so equipped) to do the above (YMMV).

A more complex series/parallel or parallel circuit could add more user control to the system if desired.

 

[javajoe79]

I was just looking at calorifiers and noticed the twin coil styles. Now I know what the second coil is for. Makes sense now. My whale unit doesn't have the 2nd coil so I may do the extra tank of coolant instead. On second thought, I am going to be a bit short on space inside the camper so now the twin coil style calorifier makes sense. That or I just have a way to run the pump inside the espar unit, even when it is switched off or just use a second external pump.

 

[loonwheeler]

This is one way you can use a twin coil calorifier. From what I understand a more common use is to separate the hydronic heater coolant circuit from the engine coolant circuit.

 

[fluffyprinceton]

"So with your 5 gallon tank, you run a separate pump that circulates the hot coolant to your radiator and floor heat circuit correct? I think that is the part I was missing. The internal pump on the espar normally does that job while the espar is running. I suppose I could switch on just the pump inside the espar to avoid having two pumps. Do the webasto units have an internal pump?"

The internal pump on my webasto only runs as part of the on/off cycle - in practice it runs for a while after the burner cuts out - I don't know if it can be run manually. After the webasto pump shuts down, my "passive" system uses the heat in the tank & related gear (which are enclosed in cabinets to control the air path) by using low draw computer fans to pull heated air from my cabinet arrangement in effect scavenging the heat from the shut down system - it's very useful in borderline temps or while sleeping when you just want a little heat. I can adjust the fans to suit the amount of heat I want to suck out. I have separate pumps for the floor circuit & engine preheat circuit. In practice the floor circuit is so efficient at pulling heat out of the system I rarely run it without the webasto running as it would cool down in 20 minutes or so.Moe

 

[javajoe79]

So you don't have a separate pump for the radiator? Only fans?

 

[fluffyprinceton]

So you don't have a separate pump for the radiator? Only fans?

That's right - the webasto pump handles the flow through the radiators - you could run an aux pump for when the webasto is shut down but unless you had a lot more than my approximately 7gal total heated liquid it would suck that heat out quickly & then the webasto would turn on...

As you can see, the design goal is to balance the heat output of the webasto with the physical ability of your installed heat transfer devices to shed that heat. In my system I could use more heat transfer ability - but the ability of my system to slowly (& quietly!) shed that heat is excellent...I don't think your concern about too much heat is valid (thermostats...) but you are on the right track trying to figure out how to maximize the passive/low energy draw heat transfer of your system. Moe

 

[javajoe79]

Thanks for the help guys! Definitely have a better understanding now.

 

[javajoe79]

Floor radiant..... a potential easy way to do this is a false floor with the tubes attached to surface of real floor underneath. Something like a nice looking lattice floor the dirt can fall into and disappear till you get the hankering to tilt up the sections of floor and vacuum it all out.:wings:

I like this idea too. Should prevent hot spots on the floor. My other thought was to use aluminum sheet over the tubes to spread the heat and still have the planned wood floor over that.

 

[javajoe79]

DWH is correct. By adding the calorifier in the loop, it acts as a energy (thermal) storage device that can absorb and store the heat produced by the hydronic heater. A side effect is prolonged run times which prevents the hydronic heater from starting up and only running for a very short period before shutting down. The same thing will happen in an improperly bled system when the circulation pump catches a pocket of air and the flow of coolant is interrupted.

Here is a simple example of a single series circuit that might work. By using the calorifier with the addition of a circulation pump connected to a thermostat, it can allow you to slowly take energy (thermal) from the calorifier and dissipate it by way of the active or passive radiator(s) in your system. When turned on, the hydronic heater is constantly checking to make sure the coolant is maintained above the set point (~85 degrees C) and restarts the combustion chanber when needed - dumping additional energy into both the calorifier and the radiator(s). Some hydronic heaters might be able to be programmed to run the on board circulation pump (if so equipped) to do the above (YMMV).

A more complex series/parallel or parallel circuit could add more user control to the system if desired.

Ok now I am really getting it. I leave the espar unit turned on and allow it to cycle on and off based on water temp but then I control cabin heat by thermostatically switching the radiator fans and auxiliary pump.

 

[javajoe79]

So I think I have a plan for how this will be laid out.

Espar>hot water heater>5 gallon storage tank>radiator and floor circuit>auxiliary pump>back to espar. This way the espar is left alone to cycle on and off based on coolant temp and the thermostat will cycle the fans and pump to regulate cabin temp.

 

[fluffyprinceton]

"I like this idea too. Should prevent hot spots on the floor. My other thought was to use aluminum sheet over the tubes to spread the heat and still have the planned wood floor over that."

The aluminum sheet is an great idea & I wished I'd tried it on my floor. In my floor the tubes are 4" apart & in freezing temps my IF thermometer reads 110F on the tube & 75F in the space between them. That's as high as my floor temp gets but it's heated through a heat exchanger so maybe full webasto heat would require those grates? My floor is a separate circuit using a heat exchanger because I wanted moderate even heat below the 130F tolerance of the epoxy I used to build it. If I used a single floor tube the heat might be gone by the time it reached the end so I have a manifold that feeds 4 separate tube lines giving roughly even heat flow over the entire floor. Don't know if that was necessary but it does work - I just wish I'd either doubled my tubing or added a transfer sheet like you suggest.

"Espar>hot water heater>5 gallon storage tank>radiator and floor circuit>auxiliary pump>back to espar. This way the espar is left alone to cycle on and off based on coolant temp and the thermostat will cycle the fans and pump to regulate cabin temp."

Or just let the webasto supplied thermostat control cabin temp & have a aux switch/s controlling the aux pump & fans for fine tuning.Moe