Hydronics System Questions

[aernan]

I would like to get a diesel hydronic furnace and use it to pre-heat my engine as well as heat my domestic hot water and cabin. People have suggested that all boxes and enclosed space should have some heating in them so you can dry them out and avoid molds. When putting in a hydronic floor should I could cover the entire area in a system but then I was wondering how I secure my furniture down (to the floor).

Can anyone advise how your hydronic system operates and what individual circuits you have?

 

[Trestle]

I do not have this, but did some investigating for a different build where it did not pan out. The easiest way to do this is to create a sub floor, and run the hydronic tubes under the entire floor area.

-Pick the sub-floor material that you want for your interior space. I will use 3/4" ply as an example because you will be bolting stuff to it so it is a sheer plate so to speak (I am sure some engineer is about to flame me, but let's face it I am a layperson here so don't get your panties in a wad). Cut/configure the ply sheets so that they cover the entirety of your floor, and lay them inside. Use blue tape or other on top to determine where your fixed furniture/walls/etc. will go. Deliberate, and modify until you are happy. Use T-nuts (the triple/quad spiked ones for use with wood) to provide anchor points for everything above the sub-floor. 1/4-20 are readily available, and cheap. Use a lot of them as it is nice to have options, and your actual floor material will cover up any that you don't use. One strategy to tie sheets of plywood sub-floor together is to have your mounts above the floor span the sheets so that an above the floor mount bolts to two or more sheets of plywood. I like to run the ply latitudinally, so that my mostly longitudinal furniture mounts above will hold them all level. Since you are modifying a LMTV/FMTV latitudinally will likely make sense vs. the waste generated for narrower vehicles.

-Separately, you will need a way to securely fasten the sub-floor to the actual floor/frame of the enclosure. I'll leave that to your situation, but you will want at least 4 points for each sheet of ply. If using 3/4" ply, you can counter sink the bolt heads and fender washers into the ply to keep the sub-floor level. You will need some spacers that are the same thickness of your furring strips to keep things nice and flat. You will want to think about the strength of the actual floor to determine what/where to bolt things to. The fewer points you use, the thicker the bolts should probably be.

-Now you will need a network of furring strips to space the sub-floor away from the actual floor it is attached to. Say you run it longitudinally as an example. You will have to run some latitudinal gaps staggered so that no part of the sub-floor is unsupported, but hydronic tubing can move between the longitudinal strips at various points.

-From bottom to top: Floor, insulation sheet (say 1/4 or 1/2"), hydronic tubing (probably the orange PEX), sub floor, above sub floor anchored items (depending upon the type of actual floor surface you may want to sandwich it between the sub floor and anchored items).

-You may also decide to put sprayfoam above the foam sheet and below the sub-floor, co-located with the hydronic tubing. this would add expense, but there are benefits. One, it would provide additional floor insulation. More importantly it would encapsulate the hydronic tubing such that any moments of inertia are less likely to re-configure or damage the tubing due to vibration/heavy impact/etc. Think of how much weight all of this tubing will contain when filled with fluid. If you route it well, the sprayfoam will encapsulate it preventing it shifting/kinking/splitting etc. The goal would be to have the hydronic tubing sit up against the non-insulated sub floor for better heat transfer. All of this furring/insulation/sub-floor will affect the inside height, so this may or may not be an issue for your build.

-Questions to consider would be if you need to coat the underside of the ply sub-floor with anything as a preventive measure.

-Also you will want to plan around any floor penetrations for utilities along the way.

 

[aernan]

When I started initially thinking about this I assumed I would put in a hydronic circuit to cover the entire box floor but then I realized attaching my cabinets down would not work well and that's why this came up.

My box will be hat profile beams with an aluminum skin on the interior. From there I need to build the actual flooring I will walk on and any special flooring for inside the boxes/cabinets.

After talking with my co-worker who has hydronics in his house I think I will only lay it on the walkable areas. For the compartments I will run a pair of hoses with passive radiators to warm each box. This makes it possible to position the radiator element wherever it works best for space and access. I would like to have some ducted hot air so I can warm the seating and bed area so I will do a hydronic to ducted air conversion near there.

For the flooring materials I'm told that stone products are ideal for on top of hydronics. Also the spacing of the hoses are significant because too tight and the floor will be to warm and too far apart you get cold spots. Hopefully with tuning I can get the walkable areas to be nice on my feet.

I was able to find some special floor underlayment that's a foam frame with islands. You con lay the hose into it and it controls max bend angle and spacing. You then poor grout on top of that and level then tile. I have no idea how heavy that would be or tall.
http://www.polyform.com/hydrofoam-en

 

[aernan]

ok I just did a quick look. I see there are companies selling plywood that has channels pre-cut in them and people are using pex to fill that. The floor above is also wood. That gives me lot of flexibility.

 

[Anton2k3]

Not sure if it is any help for your situation, but this is how we did ours:


The black frame is the bench seat foundation. The loops at the left are in the correct position to go under the kitchen cabinets, but not in way of where the units will be fastened to the floor. The right hand loop in the foreground goes partially under the shower tray. The loops at the far end are under unobstructed floor space,. Where the pipes run down the van is the walkway.

A second loop placed in the garage and under the fresh water tank:



Third loop is for the battery box. The material we routed the pipes into is marmox board, which has excellent compressive properties. 20mm board, 12mm pex-al-pex pipes.

Pipe pushed into the routed channels with foil tape behind it, then the whole floor taped over to spread the heat a little:





Finally, sub floor laid back down (12mm ply), and the pipe location traced on to it so that we can ensure no screws hit the pipes:



As for the plumbing, going with the standard house solution using a 12v pump, fed by hydronic loop:


Thanks,

Anthony

 

[Trestle]

I would caution against any stone/cement products. The reason they suggest them is that the stone is heated and creates additional thermal mass. That is great for a non-dynamic situation. In a rig that will see movement/vibrations/flexing, it will not hold up, and it will add a lot of unnecessary weight. If you want to split the difference, you can go with a small ceramic tile for the flooring over your sub-floor. It will weigh more than rubber, wood, or other choices, but they make a flexible grout that will work with it. I have used in to do a shower wall in an RV, and it survived without any issues over 1.5 years continuous use. It was laid on the floor, walls, and ceiling of the shower, so all possible surfaces. I say smaller ceramic tiles so that you can get more grout in there. The special grout is actually a silicone base, so it is flexible and not heavy like normal grout. We happened to do 1" penny tiles. So about 60% tile, 40% grout. This gives you significant thermal mass (60%), but does save a lot of weight too. The 2nd reason to look at small tiles is that no matter how strong you build your structure, there will be some flex. Larger tiles are more likely to break than smaller ones since they span a larger surface area.

Here is the company that makes the adhesive and filler grout: http://flextile.com/ No affiliation, just a customer that had positive results.

The second comment is about passive radiators vs. full floor coverage. It would be easier/cheaper to go with a full floor system vs. having additional components to manage such as passive radiators. The point of the sheer plate type sub floor is that you can run full floor and yet have the anchor points of the sub floor to tie into from above. The only obstructions for the tubing would be any penetrations for utilities, and the 4x (or more) puck type spacers that tie the sub-floor to the actual body floor. Each of those should not take up more than a 2" diameter circle, which can easily be worked around. If you want to use sheet foam instead of spray foam, then to route channels into the sheet foam to lay the pex into (as shown in the above post), that would likely be a better option. Really elegant and well thought out. The pics help greatly too. If you go with a sheer plate type sub floor, than that precludes the use of thinner ply as you are asking the sub-floor to become part of the structure. If you have any critical items that need real HD anchoring, say a seat with a restraint belt, those would have to be planned in so that they can penetrate through all floors and be bolted thru the structure floor...and possibly into the vehicle frame.

 

[aernan]

Anthony. Thanks. The pictures and diagram are exactly what I was looking for. This really helps me understand how the system operates. Also understanding how many circuits and what you used them for is a giant help as well.

 

[aernan]

How are you securing the hydraulic layer to the next layer down?

Are you putting in the cabinets directly on this layer or floor then cabinets?

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[Anton2k3]

Hi Aernan,

The insulation the pipes are set in to 'floats', but is a tight fit. The marine ply floor then sits on top of it and is fastened down using the OEM floor fastenings, clamping it all in to place. All of the cabinets and furniture will be attached directly to the ply floor, then the finising floor (8mm waterproof laminate) will be fitted around everything. I prefer to do it this way as it allows changing of the final floor if it ever gets damaged.

 

[aernan]

Thank you so very much for explaining this to me. That saves me a bunch of guess work.

To get the "floats" in the marine plywood are you using a router? Are you glueing the marine sub floor in place or just screwing it down?

 

[Anton2k3]

I think there is some confusion here. The insulation layer is a floating floor in that is is not glued or fixed down. The heating pipes are laid in to the insulation (the channels for the pipe are routed in using a 12mm round nose router bit, set to a depth of 12mm), and the plywood just placed over the top. The ply is fastened down with the OEM fixings, which essentially clamps the insulation (with the pipes in), stopping any movement. You can see the original fixings in the last photo, the black cups. There will be a finishing floor installed once the build is complete, again not glued down (might want to change it). Let me know if that makes sense.

 

[aernan]

ok that makes more sense. So the stack is:

- cabinets or actual top floor material
- marine grade plywood (to fasten things into)
- foil tape layer
- insulating layer with pex hydronics
- factory floor

I will be be building my box from scratch so I have no OEM of factory fasteners. Can you make a recommendation of what type of fasteners and through which layers I would drive them?

 

[Anton2k3]

What will your box be made from? Could always glue some batons, which are the same thickness as the insulation which you lay the pipes in to, to the box floor around the perimeter. Then just screw the marine ply floor down at the edges where the batons are.

 

[aernan]

My box will be:
- outer skin - aluminum + CARC paint
- aluminum beams
- insulation will be XPS in the beams and sprayed closed cell foam
- inner skin - aluminum

From there I am looking for suggestions. I assume 1/4" vernier or some lath strips to hang other wall materials on.

To reduce thermal bridging from the beams I might put a layer of wood or aerogel between the beam and inner skin.