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| 12/21/2005 9:01 AM |
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How do you select the design Data, Outdoor temp and Windspeed ? Do you design for worst case. Our current design is at a temperature that is not the lowest we see in the area. We have extended periods that are below the temp selected. Should I be concerned ?
Also, the max tube spacing that can be used without feeling the heat is not even in the floor ( hot stripes) . Will 12 inch spacing in a 4 inch slab have even temp throughout the slab.
Single story, 4 inch slab, 9 foot ceilings and some 12 foot ceilings
Many Tks
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| 12/22/2005 9:25 AM |
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Design should be done by Pros! Most of the questions cannot be answered from the info provided . If you doubt your design -- pay & get it checked. You need to describe the building envelope carefully for heat loss calculations -including what you propose below the slab & at edges. If the system has a substantial reservoir of heat as in Legalett you will have a worst case that is a little less demanding as even without supplying heat you can coast for several days with little internal drop. The Legalett system has been developed with design included in price . It can be installed with little special skills as they are now using plastic pipe. I have the old pipe system . You can identify pipe locations only at bare concrete.
Check out http://www.legalett.ca/Index.htm
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Posts:2321
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| 12/24/2005 8:08 AM |
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The system is being designed by a heating contractor. They are using software from Wirsbo. They have not selected worst case design data, instead they are using a skyray table ( or something that sounds like that)
My questions is are these tables practical, some say they don't believe in them.
2nd questions, I have been told not to allow spacing of more than 9 inches for the tubing if you are going to have a tile floor, as you will notice warm spots if 12 inch or more spacing.
The house is ICF construction, 3000 sq ft, 9 and 12 foot ceilings, any comments
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| 12/24/2005 10:29 AM |
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If you don't have confidence in your contractor now -- what will it be like later? Ask them to provide references where they have used the tables you speak of & check them out .
I heat with propane which is now more expensive than electricity -- So I have the radiant system set to a low "base" temperature & heat more quickly with supplementary electric heaters on an as required basis. If your contractor screws up you can still supplement although not the nicest arrangement. I also have an ICF lower level - great way to go.
PS -- See that you get the final calcs & input factors for the sizing so if you have problems you have them by the short & curlys!
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| 01/03/2006 1:35 PM |
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Outdoor temps and wind speeds are provided by your county building department. They'll tell you what you need to meet code. Your envelope R and U values will provide you with more guidance when doing heat load calculations.
Heat striping is partly a matter of heat load, not just line spacing, slab depth, or depth of hydronic lines in the slab. Lines 12oc are going to be half as long as lines 6oc. In a poorly insulated home and high or quick heat demand, you may need to max out the heat in 12" lines and you'll feel the striping. In a very well insulated house with smaller fluctuations, you may never notice that the lines are 12oc. Also, 6 or 9oc may be nice for walking/sitting areas where striping can be detected and 12oc fine for other areas. So, no easy answer.
If somebody has run software calcs for your system, get a copy. Shouldn't be too difficult to have somebody else give you a second opinion of the results. Finding out that the calcs are wrong does little good after the concrete is poured. It's your house and you should know the basics of why it's being built the way it is.
Mark Fleming
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