I am getting ready to pour a 16'x50' concrete slab. I have some questions. Does any know how to or where i can get a lay out of the pex circuits? Also how many zones should i run? I have read to keep the runs between 250' and 300'. I found a website that i put in my dimensions and it said i need 1200ft of tubing and space it 8" apart. And one more thing, if my boiler is betwee. 160 and 180, how do i cool it off enough to be able to run through the floor with out damaging the concrete. I think the temp of the water going through the floor should be around 75 to 85 degrees. I think anyways. Thanks for the help.
Floor heat
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maple1
Minister of Fire
You use a mixing valve to get the temp down. It mixes in cool return floor water to the floor supply, down to the right temp. Which doubles up the importance of boiler return temp protection and another mixing valve there. Does your boiler have return temp protection? Same principal at each spot - one is mixing the temp down, the other is mixing the temp up.
No direct experience with infloor here - I always had 1' of pipe per sq.ft of floor space in mind, but not sure where that came from. The most important thing is to get lots of insulation under the slab. Don't think I would do less than 4" of foam board. And around the edges.
No direct experience with infloor here - I always had 1' of pipe per sq.ft of floor space in mind, but not sure where that came from. The most important thing is to get lots of insulation under the slab. Don't think I would do less than 4" of foam board. And around the edges.
hondaracer2oo4
Feeling the Heat
http://www.avenir-online.com/AvenirWeb/LoopCAD/LoopCADHome.aspx
That is Loop CAD. They offer a free trial for 30 days, download that and put in your dimensions and building specifics and it will do a layout for you as well as tell you how many gpm you need to flow etc.
The most important detail of insulation besides the xps under the floor is the xps around the perimeter separating it from the frost wall. If you don't do that the frost wall will act like a cold heat sink and suck the heat right out of the slab. Some people say they would only do 4 inches minimum xps but I'm not really sure what people base that number on, all the reading I did pointed to 2 inches being the standard. I guess if you have an extra $1200 to double the insulation in the floor than no harm no foul. Here is a decent article. http://www.radiantcompany.com/details/methods/grade/
That is Loop CAD. They offer a free trial for 30 days, download that and put in your dimensions and building specifics and it will do a layout for you as well as tell you how many gpm you need to flow etc.
The most important detail of insulation besides the xps under the floor is the xps around the perimeter separating it from the frost wall. If you don't do that the frost wall will act like a cold heat sink and suck the heat right out of the slab. Some people say they would only do 4 inches minimum xps but I'm not really sure what people base that number on, all the reading I did pointed to 2 inches being the standard. I guess if you have an extra $1200 to double the insulation in the floor than no harm no foul. Here is a decent article. http://www.radiantcompany.com/details/methods/grade/
Highbeam
Minister of Fire
I put in 2" of foam on all sides of my slab. 1/2" pex on 12" spacing gets you 1 LF per SF of building. Yes on the 250-300 lf per loop and keep loop lengths within 10% of each other if they are all in the same zone.
Here's mine. 30x60 slab. Still not being used because the actual boiler and other above ground parts are extremely expensive. The insulated slab and building hold heat surprisingly well.
Here's mine. 30x60 slab. Still not being used because the actual boiler and other above ground parts are extremely expensive. The insulated slab and building hold heat surprisingly well.
Attachments
My boiler doesnt have return temp protection. Honestly im not real sure what that is. So i take the return water coming out of the floor and using a mixing valve, mix it with the hot water to get desire tempature. I do have some questions on that. Wont that hurt the flow? Also when i initially start circulating water through the floor, will be too hot at first? The water coming out of the floor will cool enough the bring down the tempature of the boiler water?
I have 2" thick foam board insulation 2 feet down along the foundation and am putting 2" foam board down under slab and also putting 6mil poly plastic down over base gravel as moisture barrier. A few people in my area that i have talked to said to only put 1" foam board under the concrete slab. I would rather over due it on insulation.
hondaracer2oo4
Feeling the Heat
Do not go 1 inch under slab. 2 inch is minimum but I personally think 4 inch is over kill and a waste of money but then again you can never do it twice. Make sure that you place 2 inch foam board between the slab and the frost wall. Extend that foam to the frost depth so frost can't creep under the slab.
maple1
Minister of Fire
I don't have any quick links or pics etc. but there should be lots of info out there on mixing setups. It's a fairly basic & important component of slab heating, and is needed to control slab temp. Won't do a thing to flow. (You have to make sure the mixer & circulator are orientated properly with respect to each other so flows flow they way they should). Floor flow will be cool at first since it will send cool water back through your slab before hot boiler water even gets to it.
You are really going to need boiler return temp protection. Going without it with slab heating is setting yourself up for some seriously bad creosote condensation in your firebox. Boiler return temps should be (need to be) 140 or above, which you might be able to maintain without protection using ordinary baseboard with hot supply temps. But a slab will be returning water back to the boiler maybe in the 70 area - not good for your boiler, at all.
Highbeam
Minister of Fire
They put these mixing valves on domestic hot water heaters for scald protection. The hot water will never reach your slab, it will all be mixed down from the mixing valve. We're not talking about a lot of flow here. The water moves slowly so that it has time to give up the heat in your slab.
There are different ways to make sure that your boiler stays at a safe and hot temperature while your floor steals heat from it. You just don't want your boiler to be running at slab temps. It needs to get hot and stay hot while providing heat to the slab.
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