DIY Hydronic heating on the cheap!

[Technomad]

Been exploring doing a hydronic heating system but was having trouble sourcing a heating element— these are made for the RV and Marine industries, but didn’t seem to be available at retail.

The trick to this system is that all the other components are readily available— as they are made for building liquid cooling PCs.

A system consists of:
- fuel fired instant hot water heater
- coolant
- A reservoir
- A pump
- Heat exchangers

The PC industry has nice little radiators for their systems built just the size to use PC fans (I’m in the room with two such radiators right now, and despite being sensitive to noise they don’t bother me- the fans are 120mm and run rather cool, the radiators are very efficient)

You can also use regular heat sinks as a form of radiator if you want a completely radiative system— just run the coolant thru aluminum pipe and attach the heat sinks. But sticking to off the shelf, use the PC radiators where you want your heater vents to be.

The reservoir is good for keeping the fluid air free, and for adding fluid to the system, many of these have pumps built in.

And now for the missing piece— to heat the water we need a fuel powered instant hot water heater, and I just stumbled upon that:

Camp Chef HWD5 Triton Water Heater https://www.amazon.com/dp/B001J4AU2E/ref=cm_sw_r_cp_api_eD9DAbR3SFDFF

Would need some support items like adapters and hosing and maybe a motor controller for your pump, etc, but nothing too bad.

The system could be built off the shelf using amazon parts right now for well under $500. Probably under $250 if you wait for sales or buy used stuff.

I’ve covered a lot of ground here, and like I said, some experimentation is necessary— I think you will want to make sure you drop the temperature of the water returning to the system enough so things don’t get too hot.

Fortunately the heater is adjustable and rather than thermostatically controller this would be a case of finding a good equilibrium between heat output and fuel usage and turning it in and off yourself, but a programmable thermostat with a relay could be rigged up to do it.


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[Technomad]

Here’s an example radiator:

Tiptiper Water Cooling Cooler Heat Radiator Aluminum 18 Pipe Heat Exchanger CPU Heat Sink for Computer 360mm https://www.amazon.com/dp/B077MFPLG7/ref=cm_sw_r_cp_api_UP9DAbF3YPJXS

While this is an all in one system not really useful for our needs it’s pictures show what a hooked up radiator looks like (in case people have trouble visualizing what I’m talking about)

Corsair CW-9060025-WW Hydro Series, H100i v2, 240mm Radiator, Dual 120mm PWM fans, Advanced RGB Lighting and Fan control with software, Liquid CPU Cooler https://www.amazon.com/dp/B019EXSSBG/ref=cm_sw_r_cp_api_uQ9DAbN9VCACZ

Here’s an example of a heat sink— it’s purpose is literally to radiate heat into the atmosphere:
URBESTBlack Aluminum Heat Sink Heatsink for Three Phase Solid State Relay https://www.amazon.com/dp/B01A9VUFGS/ref=cm_sw_r_cp_api_PR9DAbFHMHXCG


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[Trebor English]

https://www.amazon.com/gp/aw/d/B01CJPU6JI/  
Search Amazon for propane camping tankless water heater.  

This may work with coolant.  Since this is intended to heat, coolant may be counter productive.  You want heatant.  : )

 

[Technomad]

SMH


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[John61CT]

Smaller units need to slow down the flow rate to get high temps.

The thermostat control system should just stop the flow when the return heatant is no longer cool, restart flow when the first radiator gets cool, ANDed with air temp so the space doesn't get too hot.

All the piping in between should also radiate into the space, some guy was using his platform struts made of 8020, but I think that center hole was too small.

Webasto / Espar coolant heater would be more robust, take less space but yes lots more expensive.

Interesting idea using PC cooling parts if you need air blowing

but I think for just maintaing temps, plain rectangular tubing embedded into the top of the floor insulation just inside the cabinetry would be simple to do and out of the way, and some thermal mass will help increase the interval between heating cycles.

 

[Technomad]

Yep that was me. Only problem with using the structural 8020 is that it would require plumbing at the points of structural connection and make that more complicated.

I still think I will use some separate 8020 bars for heating, run coolant thru them and attach heat sinks.... but keep it separate from the structure. I’ll do this to give radiant heat along the floorboards.

Then use the PC radiators where I want to blow hot air.

Good point about varying the volume of flow. Trying to KISS and not go down the path of writing a bunch of software, though. Will definitely need some experimentation.

Nice thing about PC liquid cooling components is they deal with much higher temperatures... so they should be pretty safe and efficient at dissipating the heat.


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[Technomad]

I actually would still prefer an eberspacher if I can find one for sale— will have a control system integrated and easy thermostat accessories etc. The money is worth the time savings... but also I’m more comfortable with a propane tank in a side (exterior) box than plumbing into the vehicles fuel line.


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[Technomad]

Are you planning on using multiples of the CPU coolers or heat sinks? What is the size of the tubing on the CPU cooler? Why not use a automotive heater core and an efficient fan? Needing a minimum 35PSI to use the water heater will cost energy. Where will you mount the W heater, somewhere inside where it will require ventilation of the living space?

Guy

Water heater will be mounted outside, near the propane tank. The box truck will have a bunch of truck boxes mounted under the box at the outer edges, hard to describe unless you’ve seen this kind of truck.

What’s important is to extract as much heat from the coolant as possible during its time inside the living quarters before returning it to the heater.

Do you have reason to believe a heater core would be more efficient or cost effective? One nice thing about PC fans is they are efficient and quiet, I suspect a car heater assemble doesn’t need to be either, but I’m open to it.

Yes I will need to spend energy to drive the pump, and the fans and all that, but likely less energy than a forced air furnace would and much quieter (though I will have to experiment).



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[John61CT]

> What’s important is to extract as much heat from the coolant as possible during its time inside the living quarters before returning it to the heater

Why?

I would think fuel efficiency per BTU input would be most important.

Just insulate any outside pipes well.

Also, I think those instant HWS styles need to me mounted vertically, and exhaust vented out the top.

So wall mounted near the ceiling inside may be better.

 

[SchortBus]

The trick to this system is that all the other components are readily available— as they are made for <s>building liquid cooling PCs.</s> heating.

A system consists of:
- fuel fired instant <s>hot water</s> heater
- <s>coolant </s>
- <s> A reservoir</s>
- <s>A pump</s>
- <s>Heat exchangers</s>

FTFY  

 

[Technomad]

FTFY  

You will never find one of those in any vehicle I own.


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[SchortBus]

You will never find one of those in any vehicle I own.


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That's odd, because the on-demand water heater you have proposed in your hypothetical hydronic heating sytem (HHHS), is pretty much just a Mr. Heater Buddy with a radiator, and a flow switch, to heat the water. 

I can understand reinventing the wheel as well as anyone though, it can be a fun mental exercise.

 

[John61CT]

No, radiation style and air blower heaters are a completely different category from hydronics.

And the biggest issue is unvented combustion within the living space, as opposed to a vented combustion chamber using heat exchangers.

 

[SchortBus]

No, radiation style and air blower heaters are a completely different category from hydronics.

 

[Technomad]

And the biggest issue is unvented combustion within the living space, as opposed to a vented combustion chamber using heat exchangers.

Yes, that’s the biggest safety issue. I don’t want any combustion in the living space at all. Even suburban brand furnaces are borderline for me, and they have a long safety record.

Another thing is that hydronic heating can heat the space more uniformly.

The hot air from a furnace can do something like drying out the air that is suboptimal for me.

All I know is I’ve experienced both and hydronic heating is a lot more comfortable.


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[SchortBus]

The hot air from a furnace can do something like drying out the air that is suboptimal for me.

Mr. Heater Buddy, and I understand this is counterintuitive, does anything but dry out the air. In fact, burning propane in a semi-isolated (read cracked windows) environment will increase humidity 10 fold. Magnesium Chloride will become your friend in such situations.

Byproducts of Propane Combustion ¥

https://sciencing.com/burning-propane-water-6635338.html