In Floor heating

[Slick Fork]

Hi there,

I'm hoping someone out there can help me out... On our acreage, I have a detached shop/garage. The building is split in two with a workshop side and a garage side. Currently each side has a hanging forced air propane heater that are ridiculously expensive to run.

Now, the previous owners (we've been here 3 years) had installed the beginning of an in-floor heating system on the workshop side by laying the pex pipe down and pouring a concrete slab on top. So my question is, I'd like to finish the work on the in-floor system... from what I can see I'll need an expansion tank, manifold, heat source and circulation pump.

Now, drawing on my plumbing experience from the tank, I'm not worried about installing the manifold or the expansion/pressure tank. My question is on sizing the heat source and circulation pump.

So, given the portion to be heated is roughly 600 Sqft, with a very tall ceiling what can I use for a heat source? I was hoping for the sake of simplicity to put an electric hot water tank in.

What sort of flow and what can I use for a circulation pump?

And finally, Is this stuff I can get at Home Depot, Rona, Totem etc.?

Thanks

[lastlight]

Why not feed your tank water through it? Free chiller!

I'm SURE that won't work but it'd be pretty cool.

[sphelps]

I'd find a company that installs these kinds of systems and ask them, but I would assume if you have a general idea of what's needed to go bigger rather than smaller for the heating source. Heating systems work on a thermostat so if the heat source is a little big for the job it shouldn't really matter. The circulation pump will be a little more critical but if you can find out the recommended flow rate for the size piping you're using you should be able to simply multiply that by the number of pipes you're using.

[mike31154]

A little bit off on a tangent perhaps, but since you have an acreage, you might want to investigate a full blown geothermal system not only for the outbuildings but also for your home. They may be able to include the already installed pipe in the system. Fairly hefty investment and the pay back takes many years, but you're a little ahead of the game with an acreage. When I looked into it for my place I found out to install the geothermal loops, the contractors would have to drill deep vertical holes since my property is too small for horizontal loops. Horizontal tends to be less costly since it's less work to dig.

I'm in the process of renovating much of the flooring in my house and have installed a small run of electrical in floor heating under ceramic tile I laid at my living room bay window. Very small area and uses under 200 watts of power but does a decent job of keeping the tile cozy. The most expensive item was the damned programmable thermostat. I plan on doing the same when I tile the kitchen and bathroom. This will supplement the forced air gas furnace.

A number of years ago I rented a house in Germany that had hot water piping heating the tile floor in the bathroom. Many homes in central Europe use boilers to circulate hot water through radiators placed at the window in each room. This in floor system was tied into the main boiler that also supplied the radiators in the other rooms. That convinced me to make plans for in floor heating when I finally settled down in my own home. Reportedly more efficient than forced air systems by far since the warmth rises slowly. Forced air systems tend to send heat to the ceiling too quickly, so only tall folks benefit....

Best of luck with your project, should be a great way to go.

[MitchM]

I just built an 1800 sq ft. workshop with infloor heating. I use a NG boiler supplemented with 60 vacuum solar tubes. I really like the dustless infloor heat.:smile:

Use this heat loss calculator

http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

It will give you a good idea of what size heating unit you will be looking at.

What size/type pex pipe do you have?
Make sure that you get a compatible glycol.

Mitch

[MitchM]

A few other points:

my system runs at about 15 psi
the pumps are: http://www.bellgossett.com/productPages/Parts-NRF-22.asp
the pumps run about 5 gpm, take 92 watts of power each
system temp is 120F

HTH,
Mitch

[MitchM]

One more thing...:lol:

If a pressure test has not been done on the pipes....do one.
If I remember correctly, we did 60 psi for 24 hours.

Mitch

[hillegom]

+1 on the pressure test.
You have to ask yourself, the previous owner went to the expense of laying the pipe, why did he install a different type of heating?

[russp]

I built a 1400 sq ft house with attached garage, for the main heat I installed a forced air furnace but I also ran in floor heat in the basement & garage. I used a standard 33 gal gas hot water heater & it works fantastic. It is a closed system and I run a max pressure of 10lbs hot. If you hire a plumber to install it they will tell you that it is not allowed but if you do it yourself it is a great way to go. I could easily maintain a 20dg temp all winter & the square footage of the heated area was about 1000 ft in the house & 500 in the garage. The main items you will need are a water heater , circ pump & expansion tank. but as previously mentioned the first step is to pressure test the pipe layout.

[intarsiabox]

A friend of mine just did in floor heating in his new garage. He was going to use a hot water tank but found that it is a code violation. He found a hell of a deal at Bartle & Gibson on a boiler, pump, manifold, plumbing, etc for only a couple hundred bucks more than a high effeciency hot water tank alone. The catch is he rebuilds classic cars and so did the salesman so he ended up with a better deal than most would, but even before this B&G was way cheaper than anywhere else.

[Slick Fork]

Some great responses so far guys thanks,

I'll definately pressure test, any suggestions on equipment needed for that that's easily rentable? I think the previous owners installed the reznor units first and then decided to look into in-floor as the new slab with the pipe is quite a bit higher than the side that doesn't have it.

Mike: How do you feel about the return on your investment with the electric in-floor heat? I've considered it for places like bathrooms, kitchens, etc. as retrofitting the house for hot-water heat is way too big a project for us right now. Same goes with Geo-Thermal although I would absolutely love to do something like that.

Carpentersreef: Thanks for the link and info, I'd love to add solar but am doing this project on the cheap.

Russ: What are you using for a circulation pump and Temperature controller?

[mike31154]

ROI on the electric infloor heating? It's going to take a while to figure that out since I've only installed the small 183 watt loop recently by the bay window, approx 20 sq ft. My living room faces north, I think the bay was an add on by a previous owner and that area of the room has always been a little cool in the dead of winter. So the ROI was not a prime consideration when installing this, I'm just glad that this area is now a little warmer without having to rely on the forced air furnace. Heck, I use 3 times that amount of power to light up my fish tank! Not sure what the cost of the system was anymore since I purchased it a while back. As I mentioned, the electronic, digital thermostat with built in GFI (a requirement apparently) cost quite a bit. I think almost $280, that almost made me flip out and reconsider. I think they may have a less costly mechanical thermostat available, not sure. I just set up the heating cycles last week. Similar to most modern digital thermostats with different programming options etc. The features are way overkill for what I'm using it for at the moment. An On Off switch would probably do the trick just as well. The heating loop itself was less than $200 I think. It's made by True Comfort Systems and I got it at the local HD.

You need dedicated circuits from your breaker panel for any electric heating and the larger runs for more power/square footage are wired for 240 volt, same idea as your electric dryer or range. Even though I only have a 183 watt run at the moment, I've used 12 guage wire so it won't be a problem to tap into that run when I get around to doing the kitchen & bathroom floors. Should be able to do all of them on one 15 amp circuit, my house is not large by today's standards.

[mike31154]

At the risk of hijacking your thread, here are a couple of photos of the electric infloor heating install before I laid the tile over top.

http://s1rq4w.blu.livefilestore.com/y1pS3wu_Cg98Wsd-mfZEpaURrX9GlXZHRTz8ae2CSx-a7h8JfXeU_tsuKx0NRSKnV0BCh38Are1DtNvf-42J1WUzXFXDLSjPjSG/DCP_0005.jpg

You should be able to see the soft copper tubing I used to house the thermostat sensor in the second photo. This is so I can remove or replace it should it become faulty. It's an option and the system manufacturer's normal instructions call for simply embedding the sensor in the mortar. And yes, the sensor is a bit too close to the one wire, it should be centered between any two of the wires.

http://s1rq4w.blu.livefilestore.com/y1p7EO7j0dEFmOQWaxZqwFfl-stW5z0iCcN6HZxJ9JgQQ4Io3Gjrv79DNOM6-sIbb0OgCkVVSGhFPw0ggTPSKc00JNvGYr3sugA/DCP_0009.jpg

[mark]

A friend of mine just did in floor heating in his new garage. He was going to use a hot water tank but found that it is a code violation.

Well not totally true. You can't mix your domestic hot water supply with a radiant heating system, but they do make hot water tanks that can be used in radiant floor applications. Can be cheaper than the cost of a boiler based system.


CMHC radiant link (http://www.cmhc-schl.gc.ca/en/co/renoho/refash/refash_010.cfm)

[BMW Rider]

I have radiant infloor heat in my garage and set it up using a hot water tank. It has been working quite well for the past ten years. I do want to upgrade to a proper boiler at some point since it is a more energy efficient method. I have a plan to add a bit more shop space on in a few years and will look at that upgrade then.

The hot water tank is cheaper to buy, but holds a lot more volume. If you choose to run antifreeze rather than plain water, that adds some cost back in. I don't recall the size of pump off hand, but its not overly large. I have three loops of piping in the floor fed off a manifold from a single pump. The thermostat cycles the pump on and off to modulate the temperature. i keep the tank set at a medium temperature setting. I also have a small expansion tank and an air bleed valve on the system, so it is a fully closed system.

One thing to look at with the piping that was laid in the floor is what type did they use. The proper stuff has an oxygen barrier to prevent corrosion in the system due to O2 transfer through the piping. I used OxyPEX, which is like regular PEX with the addition of the O2 barrier on the outside. it is red in colour.

The second question is, how long is the run(s) of tubing they laid. It is important to not use too long of runs as there will be excessive flow reduction due to friction loss and thus excessive heat loss in the run. Usually 200 -250 feet is the maximum length. This is why I have three loops and the manifold setup.

[Slick Fork]

Ok, so it looks like what they put in the floor is just regular 1/2" pex tubing. There look to be 3 loops of unknown length.

[MitchM]

I know you're trying to set this up on the cheap, but because the building is separate, I would still run a glycol mix through the system.
Even though you have a separate heat source, if the electricity goes out in below freezing temps....:surprise:
The unknown is what effect the glycol will have on PEX made for domestic water supply.
Also, I wasn't promoting solar in my previous post :wink:, the link was for you to enter the values of the building and come up with a BTU loss number.
There are other calculators if you google for "heat loss calculator" or "BTU loss calculator".

Also, the crimping tools (rent or purchase) and hardware for a pressure test are all available at HD.

Mitch

[BMW Rider]

I don't thing the glycol shouldn't have any adverse afffect on the PEX tubing, the OxyPEX is the same material inside. The only issue is that you will get some O2 absorption which may increase the rate of corrosion. I couldn't say how big an issue that will be though.

[MitchM]

I found this information from the DOW website:

Quote-
Plastic Piping
There has been a steady increase in the use of plastic tubing over the last 20 years. Polyethylene (PE) or cross-linked polyethylene (PEX) represent the most popular choices in terms of reliability and cost. Other materials such as chlorinated polyvinyl chloride (CPVC) or polyvinyl chloride (PVC) may also be used depending on operating temperatures. Several TES systems using either ethylene glycol- or propylene glycol based heat transfer fluids have operated successfully for years with no detrimental effect on their PVC piping.

However, some PVC/CPVC suppliers recommend that propylene glycol-based fluids only be used in solutions no greater than 25%. In every case, regardless of the plastic being considered or the concentration of glycol desired, it is recommended that you consult the plastics supplier to verify compatibility with ethylene or propylene glycol fluids before installation.
-end quote


Here's the site: http://www.dow.com/heattrans/fsa/system.htm

Mitch