In-floor heating advice

[davisdesigns]

This post is primarily about the flooring aspect, insulation and tubing and heated media i.e water, oil, Fukushima water... I know nothing about in floor heating.

My initial thought was to use PEX but I think aluminum or copper tubing would have better heat transfer.

I was thinking on laying 1-2" foam board on the sheet metal deck and inlaying the metal tubing maybe 3/8" the full length of the bus at specific widths so as to not accidentally puncture it later on.

Covering it with 1/2" or 5/8" ply [i don't like mushy floors and prefer concrete but even the lightest stuff would be way to heavy.] Topped off by bamboo engineered flooring w/ real bamboo not the picture board stuff.

My biggest concern is a leak down the road and having to tear the flooring up which i plan to do in some sort of herringbone pattern.

 

[RC000E]

Dont really try to reinvent the wheel here. PEX is affordable, durable, not subject to corrosion, and plenty efficient for radiant flooring...it's what everyone uses. Why change the system that's proven, not to mention add cost and complexity when it comes to piping and making leak free joints, etc.

I'm considering the same thing myself and I'll be using PEX personally...

 

[Timelord-SKO]

I plan on PEX with oxygen barrier and using the proper heat spreader for it. No need to reinvent the wheel on this one.

 

[somewhereinusa]

Pex works, I did basically what you are suggesting. Plenty of pictures on my build post and my website.

 

[superdave-SKO]

make sure you use the right stuff.
https://www.teksupply.com/contractor/supplies/prod1;ts_tekcoil_radiant_coil_8;pg109149.html
they sell a lightweight concrete product made for shaping shower stalls
Shop MAPEI Gray and Silver Indoor and Outdoor Leveler at Lowes.com
foor heat needs mass to work properly, remember a bus that holds 40 kids would add 6000 pounds to the bus. good luck

 

[cadillackid]

PEX for the heat supply.. but id be leery of putting anything concrete and ceramic in a bus thats goign to flex alot.. unless this is a drive once, park and live in for years kind of project... people CAN and DO heat vinyl and Fake wood flooring succesfully...

-Christopher

 

[Jolly Roger-SKO]

I have done a lot of heated flooring mainly for dog kennels but anyway buy one solid length/roll of piping.( Pex is a name brand but the type is what is needed) the solid roll is to eliminate any joint/connections under the flooring then the only other thing I would do is lay a thin layer of foam or flooring underpayment to keep the tubing from rubbing on the metal and get the spacers sold for the tubing you get.
No joints,no rubbing equals no leaks.
Or you could put down your 2" foam and carve out the tubing channels in the 2" foam to eliminate the spacers and the thin layer underneath and use that thin layer over the top.
Most of what I have done has been in concrete but it still needed to be within an 1" or less of the top of floor so sink it in the foam board just enough for the 1/8-1/4" underpayment will cover it.
I also used the engineered bamboo flooring with a teak mix and a little Brazilian cherry. but mine was given to me for helping a flooring company with some plumbing they needed help with.

A piece of a broken porta band blade or hacksaw blade taped to a stick (horseshoe style) the width of the piping diameter you are using will help a lot just mark the lines with a razor knife first and set the depth on your stick when you tape the blade on.
If you choose the carving option?
Good luck.

 

[somewhereinusa]

I used a router to cut the channels in the foam, goes really fast.

 

[superdave-SKO]

without the tubing encased in a product that would absorb the heat the efficiency would be so low its not worth doing. use a product that will flex.

 

[family wagon]

As much fun as the foam snow maker (router) sounds, I want to see somebody build a hot wire cutter! A router running a ball end, bowl, or core router bit makes more sense from the "just get it over with" perspective though.

Continuous loop(s) with no fittings make sense for leak avoidance. If you're worried about developing a leak through puncture, chafing, etc then you could go to the other extreme. Short sections with the joints concealed above floor level somehow would enable easy abandonment of any section that became damaged in the future. It could be hard to expel the air out of a system so arranged, though.

 

[superdave-SKO]

this is what you want, might work well with a small on demand water heater and pump.
Warmboard-R is a radiant panel designed specifically for retrofit applications | Warmboard, Inc.

 

[somewhereinusa]

this is what you want, might work well with a small on demand water heater and pump.
Warmboard-R is a radiant panel designed specifically for retrofit applications | Warmboard, Inc.

I looked at that stuff, it's a bit pricy but, the spacing on the tubing is 12" I don't think you could get enough tubes in the space available. Mine are about 4" apart. That's the tightest bend radius I thought I could get by with. That's tighter than recommended but so far I have gotten by with it. Still ok after 2 winters.

Dick

 

[Eden-SKO]

Also I'm not sure personally if we have this eighty, but it seems like we had to abandon a bundle of pex sections because the connectors or the tool to connect them or something was too unexpectedly expensive for our small budget.

So we're looking to buy a continuous pipe instead for costs sake, I think it is somehow cheaper than connecting the ones we had for free.

As much fun as the foam snow maker (router) sounds, I want to see somebody build a hot wire cutter! A router running a ball end, bowl, or core router bit makes more sense from the "just get it over with" perspective though.

Continuous loop(s) with no fittings make sense for leak avoidance. If you're worried about developing a leak through puncture, chafing, etc then you could go to the other extreme. Short sections with the joints concealed above floor level somehow would enable easy abandonment of any section that became damaged in the future. It could be hard to expel the air out of a system so arranged, though.

 

[joeblack5]

Dick, just looked over your floor heat built on your site. Do you think in retrospect that it was useful to have so many different zones in a relative small space as a bus?
Also , if I look at your 4 pump picture and your diagram then it appears that the espar provides the hot water to the pumps and from there thru the floors.
Then from there it goes thru the domestic heat exchanger.

my questions..
-The domestic water is partially depending on the return temp of the floor heat, why did you not put the domestic heat exchanger in series with the output of the boiler. What temp setting are you using for the boiler?
-How do you regulate the floor heat temperature when you are using the engine for heat, i did not see a tempering valve.

For Dory I like to use floor heat. In our house I added pex under the wooden floor. That worked good but it was a pain to get the air out. In Dory I would like to run the lines in the length of the bus and make a header in the front and in the rear as to reduce the line length and get a more uniform floor heat.

What are your temps at the begin and end of your longest floor heat loop?
Thank you,
later J

 

[o1marc]

Is it basically just laying the pex and hooking it to a water heater/pump/thermostat? I'd like to add that to my build. I figure all that needed is to lay it down the middle 3' of the bus. I picture my floor as 1/2" or 1" foam board, loop the ex with 1/2" foam between the loops and then hardwood laminate right over that.

I had a thought and it was verified here to instead go back to my 1' or 2" foam board and using a router to cut the channel for the Pex. I would use one loop that goes up and back 3 times (6 runs) in the middle 36-42" width of the middle of the floor. Can anybody post some links for kits with the thermostat/pump/heater?

Would a single loop lose too much heat and would 3 runs with a manifold be obviously more efficient?

 

[somewhereinusa]

Do you think in retrospect that it was useful to have so many different zones in a relative small space as a bus?
Also , if I look at your 4 pump picture and your diagram then it appears that the Espar provides the hot water to the pumps and from there thru the floors.
Then from there it goes through the domestic heat exchanger.

While the four zones wouldn't be strictly necessary I do seem to keep the rooms at different temps. The picture is basic it's how it is, but not quite. The two heat exchangers are in series with the Espar unit which has an internal pump. In reality the domestic water heater is first then the engine heat exchanger then the manifold for the floor loops. I did put a valve in the main (3/4) loop that would force hot water to go out to the heat loops before returning to boiler but, I have never closed it. That loop is 3/4 pex.

The domestic water is partially depending on the return temp of the floor heat, why did you not put the domestic heat exchanger in series with the output of the boiler.

It is see above.

What temp setting are you using for the boiler?

Between 154 and 185 degrees, not adjustable set by Espar.

How do you regulate the floor heat temperature when you are using the engine for heat, i did not see a tempering valve.

The engine simply adds heat to the main loop, temperature is still controlled by the thermostats and pumps. When using engine heat I turn on the Espar internal pump to circulate water in the main loop.

I would like to run the lines in the length of the bus and make a header in the front and in the rear as to reduce the line length and get a more uniform floor heat.

Not sure what that means, you need to have a loop so that the water returns back to it's heat source. If you mean that you would run a bunch of parallel lines I would think that would be uneven since water would flow through which ever path had the least resistance.

What are your temps at the begin and end of your longest floor heat loop?

I measured it once but don't remember the numbers. Seems like there was less than 10 degrees difference and that all loops were about the same. I remember being surprised at how little the difference was.

The only thing I would change would be to put more bleeder screws at the far ends. The biggest problem I had was getting the air out.

 

[cadillackid]

getting the air out is always an issue.. home systems will have an expansion tank which helps greatly in getting rid of the air.. the air tends to travel to the expansion tank over time. with no tank, the air just moves around until it eventually finds a high point and never moves..
-Christopher

 

[Robin97396]

I thought there would be enough water pressure to push any bubbles out of the lines. It must be a slower moving system than I thought.

 

[somewhereinusa]

The only pressure is what the water heating up makes. Mine is built like an automotive system with a 15 lb radiator cap. Since it's a loop, pumps provide flow. Air tends to collect in high places.

 

[o1marc]

The only pressure is what the water heating up makes. Mine is built like an automotive system with a 15 lb radiator cap. Since it's a loop, pumps provide flow. Air tends to collect in high places.

You still have a pump that creates the pressure up to 15lbs.