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Old 01-31-2014, 11:16 PM   #1
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Hydronic Radiant Heating in a Bus

As a building Contractor, I've had the opportunity to install heating and cooling systems of all sorts. Most get the job done, but far less than perfect. Only one system covers all bases, is fully modular, and virtually limitless.

In the pages to follow, I will post pics, Tech, and ongoing research into how to install this all into a bus. Then in the spring I will install the system into the Haul All.

Some history.

The fist Hydronic Heating system I installed was in a small 416 square foot cabin. It's a realy small space, so I used a 40 gal propane hot water tank rated at 38 000 Btu output, but only 58% efficient. Two loops of 300 feet each run under the floor spaced every 6", laying in aluminum heat plates, under a layer of 3/8th OSB, fallowed by a layer of glue strip vinyl plank flooring. For redundancy, I used two Grundfos UPS15-58FRC 3-Speed Circulatory Pumps. System is a closed loop, run at 30PSI, filled with glycol.

Cabin has R60 in the floor and ceiling, R20 in the north and south walls, R12 in the east and west walls. All walls are wrapped with 1.5" rigid Styrofoam board decoupling the framing from the cold / heat of the outdoors.

Even with that realy low efficiency hot water tank, the Cabin uses less than $50 a month to heat. Potable hot water is done by a 12 gallon electric so the heating tank can be shut down in the summer.

Now it's the warmest / most efficient building on the farm. After that one install I was hooked. So was the guy who owns the land I live on. He has 2 more rentals, and his own house. All now to be converted to Hydronic Radiant Heating. At this time, a combination of propane and electric run the Hydronic Radiant Heating systems here. But in time they will all be converted to pulling heat from a massive, centrally located coal boiler. After that, this farm will finally start to make a sizable profit, rather than simply breaking even.

Nat

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Old 01-31-2014, 11:40 PM   #2
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Re: Hydronic Radiant Heating in a Bus

This Is my Revised system layout. My first layout used only one pump, but would have caused the tankless heater to short cycle under small loads. Also research indicates tankless heaters have internal restriction that must be overcome by a mid to large size circulation pump that use up to 2 amps at 120 volts. Trying to keep this system off grid, I added a smaller pump on the floor heating loop, and a custom buffer tank.

Click on the pic to view the whole picture.


This system uses a custom made stainless steel 60 gal Buffer tank that contains a 20 gal fresh potable water tank inside. Heated glycol from the tankless heater completely surrounds the fresh water tank. At the bottom of the outer tank are 6, 1" NPT pipe thread openings to accept common electric hot water heating elements, as well as low voltage water heating elements to utilize electricity from Solar and Wind. With this many heating element positions, I can use a 120 volt, 1500 watt, a 12 volt, a 48 volt, and three 240 volt heaters for when 50 amp shore power is available.

The configuration of the components allow for the tankless water heater to finish heating the loop if the alternative energy sources have failed to keep up to demand for heat. Main loop circulatory pump is activated by a temp switch located in the buffer tank's outer tank.

For high demand application, fresh water is directed through a flat plate heat exchanger before entering the buffer tanks inner tank. This way once the first 20 gal of heated fresh water is gone, the flat plate heat exchanger will have started heating as soon as the buffer tank lost heat. Hot fresh water flow should never run cold.

I also incorporated a flat plate heat exchanger and circulatory pump to heat engine coolant for preheating the engine. At the 199 000 BTU from the water heater, it shouldn't take longer than 20 min to bring the engine block up to near operating temperature. This would require manual activation of the Main, and the engine circulatory pumps.

I also added extra connections from the buffer tank for future heating loops. I could heat a fuel tank, or my tool trailer, or a fellow skoolie if they had a connection to their hydronic heating system.

Engine heat exchanger can also be used while driving to heat the main system. Both the main loop pump and the engine loop pump would need to be activated manually. Due to the engine coolant only reaching a set safe temp, there is no risk of overheating anything.

Extra heat loops can be connected to things like the wood stove using a different type of heat exchanger. However, this requires safety systems to avoid dangerous steam pressure build up. This I will cover separately in another post.

Nat
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Old 02-01-2014, 06:29 AM   #3
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Re: Hydronic Radiant Heating in a Bus

Nat,

Thanks much for posting this. I've been brainstorming a hydronic system myself.

In a previous post, you (at least I thought it was you) warned about taking care using care about possible leaks between glycol and potable water, as glycol is poisonous in even tiny quantities. I believe the recommendation you gave(WAS it someone else?) was to avoid cooking with the resultant hot water.

Playing devil's advocate, however, I'd expect that it's almost certainly going to happen someday. If not you, then a buddy who's a either few beers in and making ramen or a little foggy while making coffee one morning will likely say 'screw it' at some point. Murphy's law and all.

Wouldn't having the fresh hot water tank inside of the other greatly increase the danger of such a leak? Additionally, wouldn't you incur significant expense building the concentric tank?

Why not just use a single heat exchanger in a loop between a small hot water tank and a hot coolant tank, separate from each other? I'd think if your heat exchanger had enough exchange surface area, you could even get away without using a hot potable water tank at all. That would mean a single tank to hold all of your heat. This would only work if you planned on keeping your glycol tank significantly hotter than you you wanted your hot water. A 60 gallon glycol tank at 180* would store enough heat to raise 60 gallons of hot water from 40* to 110*, with a sufficiently large heat exchanger-- and if you had solar, engine coolant, propane, and/or a wood stove heating the glycol, too, it would be near limitless.

Just some food for thought. I'm pretty stoked to see your finalized system.

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Old 02-01-2014, 06:40 AM   #4
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Re: Hydronic Radiant Heating in a Bus

Nat,

Here's one such heat exchanger I found with a cursory Google search:

http://www.pexsupply.com/Bell-Gosset...FYYF4godSRsAsQ

It's even rated for Domestic Water Heating:
Boiler Side: Water 180 Degree F Supply, 130 Degree F Return, Flow: 2.5 GPM, Pressure Drop: 1.6 PSI
Domestic Water Side: Water 50 Degree F Supply, 140 Degree F Return, Flow: 1.3 GPM, Pressure Drop: 0.3 PSI

What do you think?

JDecker
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Old 02-01-2014, 10:47 AM   #5
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Re: Hydronic Radiant Heating in a Bus

Thx JDecker

To avoid the possible contamination of toxic Glycol in the potable water, the system uses off set pressure differences between the fluids.

Most toxic is the Engine Coolant. This system is run at the lowest pressure of all. It is limited to the pressure held by the radiator cap, around 14 PSI.

Next is the Main Tankless heater loop filled with Glycol. This system is closed loop, and will be run around 25 psi.

Last is the potable fresh water Loop. It will be run at the highest pressure of all the systems, around 35PSI.

In the event of a leak in the custom buffer tank, or one of the flat plate heat exchangers, the lower pressure system will take the fluid transfer. With the potable water being the highest pressure, extra potable water would end up in the glycol loop. Upon inspection, it would be detected as a spike in the glycol loop pressure.

We can also use Double Wall Series flat plate heat exchangers. They have a air buffer between the systems, that is diverted to the outside of the unit so the leak can be visually detected.

Now we can also get non toxic Corn Glycol. At one time all I could get from our suppliers was the toxic industrial glycol. Now for $10 more a pail, I have the non toxic option.

Nat
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Old 02-01-2014, 10:50 AM   #6
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Re: Hydronic Radiant Heating in a Bus

Quote:
Originally Posted by JDecker
Nat,

Here's one such heat exchanger I found with a cursory Google search:

http://www.pexsupply.com/Bell-Gosset...FYYF4godSRsAsQ

It's even rated for Domestic Water Heating:
Boiler Side: Water 180 Degree F Supply, 130 Degree F Return, Flow: 2.5 GPM, Pressure Drop: 1.6 PSI
Domestic Water Side: Water 50 Degree F Supply, 140 Degree F Return, Flow: 1.3 GPM, Pressure Drop: 0.3 PSI

What do you think?

JDecker
Those are the heat exchangers I plan on using. If one is not enough, more can be added into the loop in series.

I like that site. Lots of good info, prices, ect.

Nat
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Old 02-01-2014, 10:55 AM   #7
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Re: Hydronic Radiant Heating in a Bus

Quote:
Originally Posted by JDecker
Nat,
Why not just use a single heat exchanger in a loop between a small hot water tank and a hot coolant tank, separate from each other? I'd think if your heat exchanger had enough exchange surface area, you could even get away without using a hot potable water tank at all. That would mean a single tank to hold all of your heat. This would only work if you planned on keeping your glycol tank significantly hotter than you you wanted your hot water. A 60 gallon glycol tank at 180* would store enough heat to raise 60 gallons of hot water from 40* to 110*, with a sufficiently large heat exchanger-- and if you had solar, engine coolant, propane, and/or a wood stove heating the glycol, too, it would be near limitless.
JDecker
The cost of the custom buffer tank will be around $1500 to have it fabricated. This is a special need in my system only for the use of Alternative energy. It also makes the system more efficient not having to use a pump to force the water across the heat source. This is realy important when all circulation pumps will be running off solar.

I will make drawings of more simple, less costly systems for others.

Here is one to start. This one is set up the way you mentioned. Hardest part to overcome, is the lack of ports on a electric water heater.
Using the store bought Electric water tank with only one element Limits you a bit. You have to decide if you want to be able to use it on 120, or 240 volt when running on shore power. Using it as a 1500 watt 120 volt, 5 000 BTU, water would take a long time to heat, but the propane could finish heating it. Using a 3000 watt, 240 volt, 10 000 BTU element, you could use the heat for space heating and potable water heating. Last using a 4500 watt, 240 volt, 15 200 BTU element, should be able to heat your bus, and potable water with no help from the propane tankless heater.

Click on the pic to view the whole picture.


Nat
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Old 02-01-2014, 11:00 AM   #8
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Re: Hydronic Radiant Heating in a Bus

Neat system. I'd also be looking at contamination issues with the dechilled cold water going back into the potable water tank. All the commercial hydronic systems I've seen have backflow preventers to keep system water from mixing with domestic cold water.

No idea whether this would work, but would RV antifreeze work in the heating loop? No poisoning issues with that.
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Old 02-01-2014, 11:17 AM   #9
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Re: Hydronic Radiant Heating in a Bus

Thx guys.

Quote:
Originally Posted by roach711
No idea whether this would work, but would RV antifreeze work in the heating loop? No poisoning issues with that.
Only approved glycol should be used with hydronic circulation pumps / systems. This is due to the mix of stabilizers, lubricants, and water tension additives that help the product do its job.

Other forms of antifreeze may contain dry alcohols (Methanol, Ethanol) that will destroy the system in a short time. Being RV antifreeze is food grade, I suspect the anti freezing agent to be a food safe Ethanol.

Quote:
Originally Posted by roach711
All the commercial hydronic systems I've seen have backflow preventers to keep system water from mixing with domestic cold water.
The commercial systems are preventing water that has been exposed to possible Bactria from water sitting at a neutral temperature. Food grade water (potable) needs to be treated like anything food grade. Storage needs to be hot, or cold to prevent the growth of harmful Bactria.

The loop I added to "Dechill" the water would only be used in cold environments, where having all that cold mass under my bed is a PITA. It would also work well to give the tankless water heater a good workout once in a while to burn the crud out of the system. Doing this prevents fouled burners that won't light due to constant low burn from small, on going loads.

Pasted from the site below.
"The FlatPlate DW Series Brazed Plate Heat Exchanger is a double-wall vented heat exchanger for isolating potable water in the safest possible manner. It is designed to meet local, state and provincial codes for double separation of potable water from boiler water, other non-potable fluids or refrigerants"

From this same site.


The down side is they cost twice as much.

Nat
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Old 02-02-2014, 08:07 AM   #10
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Re: Hydronic Radiant Heating in a Bus

sounds like a lot weight lots of pipes and things to go wrong just to heat a bus
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Old 02-02-2014, 09:39 AM   #11
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Re: Hydronic Radiant Heating in a Bus

Quote:
Originally Posted by gbstewart
sounds like a lot weight lots of pipes and things to go wrong just to heat a bus
gbstewart

Agreed...far to complex and costly for just a bus...or a house for that matter. But what do I know, I live in MT.
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Old 02-02-2014, 02:13 PM   #12
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Re: Hydronic Radiant Heating in a Bus

Quote:
Originally Posted by opus
Quote:
Originally Posted by gbstewart
sounds like a lot weight lots of pipes and things to go wrong just to heat a bus
gbstewart

Agreed...far to complex and costly for just a bus...or a house for that matter. But what do I know, I live in MT.
It's not nearly as complicated as it looks.

Really, it's more simple than most of the forced air systems in homes.

Around here in the north, the heating system is the most important part of a residential dwelling.

And the highest costing component is insulation.

Remember, some of use the bus as our home. No such thing as to expensive.

My system allows me to heat with four fuels, including alternative energy's that cost me nothing . Can any of yours do that?

I knew most of you would be over whelmed by what you don't understand, at one time I was too. So last night I made a few simple, Low cost drawings.

This is the most simple system that can be assembled. Under $1000 with all components. Later I will post pump sizes, and other specs for other who wish to use it. It is also the system currently in use in the cabin I built.


This system has one of the existing bus heater cores plumbed into the system.


This system has all of the above, with the ability to heat potable water for $250 more.


Nat
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Old 02-02-2014, 05:34 PM   #13
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Re: Hydronic Radiant Heating in a Bus

so are planning on putting this system into your bus, and living in it when its -30 to -40?
you may have to burn all 4 fuels at one time to handle our winters, I have had 38 days in a row where the ambient air temp has been -33 to -38c and 16 days where it was below -40 with wind, that's pretty cold to be out in a bus. I think Ill stay with my forced air propane furnace and electric heat pretty simple system works fine, and when it gets real cold ill head south
And yes I do understand how it works and was not'' over whelmed'' I have a good back ground, and others on the site could just as easy surf the net and figured this out
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Old 02-02-2014, 05:44 PM   #14
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Re: Hydronic Radiant Heating in a Bus

I think I am elated with my Webasto on the bus and my wood stove in the house. I too have a very good idea on radiant heating.

To each his own........
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Old 02-02-2014, 07:59 PM   #15
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Re: Hydronic Radiant Heating in a Bus

I have an outdoor wood gasifier powering in-floor radiant systems in my basement, garage and 54x80 farm shop and would change NOTHING about the way I've designed the heating systems in my life. I've got a dual fuel LP/AC boiler in the basement just in case for backup ... when it routinely hits -25F here I am taking NO chances with not having heat. I even have a Honda 5000w genny in the shed to power the circ pumps if the power goes out. No messing around.

On the surface, it does seem like a lot of work to put into a bus BUT like Nat said, where we are heat, and heat retention, are the areas where the most money is spent in any warm structure. I want a method of heating that I trust.

I am very intruiged by the idea of on demand domestic hot water in your bus using the radiant heat system as the source. I've got a heat exchanger in the house and love it !!

Thanks for taking the time to share these plans with us, I'll stay tuned to see where this goes for sure.
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Old 02-03-2014, 08:13 AM   #16
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Re: Hydronic Radiant Heating in a Bus

I think it is important to remember that not all of us have the same goals with our buses. For me, I am moving south in June, and don't plan on full-timing in my bus at any point in the near future, and if I did, I would remain mobile enough that I could just stay where it is warmer in the winter. That being said...some here live in extreme climates and plan to eventually full-time in their buses. While this sort of system looks overly complex, it's just like anything else, start breaking it down and it slowly starts to get simpler and simpler. For someone up here in the great north, this sort of system guarantees that you are always going to have heat, and it is likely to be incredibly efficient. Is it overboard? Probably. Who cares?! It's good tech and you can pick and choose what you want to glean from it. I eventually plan to convert a Prevost H3-45 or comparable. That one, I plan on full-timing in with my wife for extended seasons and want to be able to travel wherever the hell I want, whenever the hell I want. For that reason, I am going to be bookmarking this and going back to it from time to time to make sure I understand it. Even if I don't copy it verbatim, there is good info here. The more I research it, I may even find portions I think should be done differently...big deal, it's still a great starting point to get someone who is interested thinking outside the box.
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Old 02-04-2014, 04:02 PM   #17
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Re: Hydronic Radiant Heating in a Bus

The best head loss Calculator I have found so far.
http://www.freecalc.com/fricfram.htm

Some good info
http://www.vanguard.ca/guides/Hydronic% ... Manual.pdf

The holey grail of circulating pumps for low power consumption, off grid applications. This pump has a incredible power curve.
http://www.pexuniverse.com/grundfos-alp ... 1-6hp-115v

The most efficient, long lasting, fastest recovery rate tank style water heater. 100% stainless steel, 75 000 to 200 000 BTU
http://www.amazon.com/Polaris-Heater-34 ... m_sbs_hi_2

How the Vertex is made.


Best way to build a wood free, light weight countertop.


As I find better resources, the links here may change.

Nat
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Old 02-12-2014, 01:28 AM   #18
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Re: Hydronic Radiant Heating in a Bus

I agree with JakeC and Bamper. I've still got about 10 more months until I get my own bus, so I'm no expert, but we all have different values. The system described IS complex, and will be expensive up front, but it provides utilities most buses don't. Radiant heat. High efficiency. Multifuel capability. High heat output. High hot water output.

We all tailor our systems to our situation. If you take short showers, live in the forest, and don't mind cutting wood, get a wood stove and a small hot water tank. Get a Webasto if your boss lets you fill up on diesel at work for free. Use primarily electric heat if your local grid is reliable and cheap or your campgrounds almost always have free 50 amp hookups.

Nat's bus is ready for anything. I dig it.

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Old 02-17-2014, 01:15 AM   #19
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Re: Hydronic Radiant Heating in a Bus

After a bunch more research, I have decided to go with a tank style, high efficiency, 100,000 BTU, 34 gallon Polaris 444 Stainless Steel Water Heater as my primary boiler.
http://www.americanwaterheaternews.com/ ... olaris.htm



Pic of the heater's burner.



And my system layout.


I will have a welding shop tig weld a 10 gallon tank with 6, one inch NPT ports in it for my electrical heating needs. Anytime the electrical heat is being used, the circulation pump for that loop will need to be activated. This small additional electrical load would be no problem when using that many watts in heating.

Main reason for not adding the electrical heating elements into the Polaris water heater is changing out elements. This would require draining the 34 gallons of glycol each time a heating element needed service. By using an additional tank, it can be isolated from the main system, rotated to position the elements on the top, and change a element without spilling a drop of glycol.

This system has less than 5 feet of head in any of the heating loops. By using the Grundfos Alpha 15-55F/LC (59896832) brushless Circulatory Pump, I am able to take my circulating pump electrical load from 80 watts to under 20 watts for each pump.

In comparison, the tankless heater would have needed a pump that required 300 watts to operate. When running on solar, that increases the cost, and defeats the efficiency goal.

Nat
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Old 03-31-2014, 07:41 PM   #20
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Re: Hydronic Radiant Heating in a Bus

Carried over from a different thread so we would not clutter it up.

Quote:
Originally Posted by texasrednek
Quote:
Originally Posted by nat_ster
Run two 3/4 pex lines from your gas hot water heater to the place you need heat, ad a circulator pump,

Nat
I know this is off topic some but I figured if it were plausible maybe the OP could use the idea.

Nat, instead of using a circulator pump, could you run a coil up through the roof and back down to the heater in the return line effectively creating a thermal siphon, and eliminate the electric draw on your system for the pump? The coil outside I would recommend copper for its thermal quality's as well as not breaking down under UV's.
Circulator pump I would use in this application is the Grundfos Alpha. For the amount of line in this type of setting, the pump would only need 15 to 75 watts when running. The pump draw is vary small compared to the draw of the fan on the heater core. The fans will take 5 to 10 times that much power.


For a system with radiant heat lines in the floor, there would be no fans, so the thermal siphon idea comes back. However, upon calculating the perimeters for such system, the
thermal siphoning will never move enough water to carry enough heat with the size lines we use. If we use 3\4 lines with a pump, you would need 5 inch lines with the thermal siphoning.

Also with the thermal siphoning, you would have to run Glycol is a dedicated water heater to keep the water from freezing before returning due to low flow.

Nat
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