In Floor heating

[mark]

Originally Posted by 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.

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

[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....
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 , 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