function calcSize()
{
   var surface = window.document.sizing.area.value;
   var atemp = window.document.sizing.air.value;
   var wtemp = window.document.sizing.water.value;
   var templimit = waRange(wtemp);
   var diff = airTemp(wtemp,atemp);
   var btu_per_sf = 10;
   if (!diff || !templimit) {
   var text = "ERROR: Please change your entries.";
   var seeanswer = document.getElementById("answer");
   seeanswer.firstChild.nodeValue = text;
   return false;
   }
   btu_per_sf = appType(btu_per_sf);
   var btu = btu_per_sf * surface * diff;
   var kw = Math.round(btu/3413);
   var text = "This application requires at least " + kw + " kW.";
   var seeanswer = document.getElementById("answer");
   seeanswer.firstChild.nodeValue = text;
   
}



function waRange(temp)
{
  if (temp < 70 || temp > 104){
   var text = "Water temperature must be between 70 deg and 104 deg.";
   var watercaution = document.getElementById("watercaution");
   watercaution.firstChild.nodeValue = text;   
   return false;
   }  else {
   var text = "";
   var watercaution = document.getElementById("watercaution");
   watercaution.firstChild.nodeValue = text; 	
   return true;
  }
}

function airTemp(w,a)
{
  var tempdiff = w - a;
  if (tempdiff < 10){
    var airtext = "It is recommended to use at least a 10 deg differential when sizing.";
    var aircaution = document.getElementById("aircaution");
    aircaution.firstChild.nodeValue = airtext;
    return false;
  } else {
    var airtext = "";
    var aircaution = document.getElementById("aircaution");
    aircaution.firstChild.nodeValue = airtext;
    return tempdiff;
    }
}

function appType(btu_sf) {
   var location = window.document.sizing.indoor;
   
   if ( location.checked == true) {
	btu_sf = 8;
   	
   }
   return btu_sf;
}