/*
**	Functions to calculate gas heater sizings for swimming pools and spas.
*/
function toDecimalPoints(num, dec) {
	var result = num.toFixed(dec);
	return result;
}
	var	mj_percentage = 0.0175;
	var	heater_size_percentage = 0.33;
	var	spa_heater_size_percentage = 0.0052;
	var	spa_volume = 2000;
	var	spa_temp_rise = 24;
	var	pool_surface_area = 40;
	var	pool_temp_rise = 20;
	function prepopulateForm()
	{
	var poolform = document.getElementById('poolform');
	var spaform = document.getElementById('spaform');
	poolform.surface_area.value = pool_surface_area;
	poolform.temp_rise.value = pool_temp_rise;
	spaform.spa_volume.value = spa_volume;
	spaform.temp_rise.value = spa_temp_rise;
	poolGasHeaterSizing(poolform);
	spaGasHeaterSizing(spaform);
}
function poolGasHeaterSizing (poolform)
	{
	poolform.heater_size_needed.value = toDecimalPoints(poolform.surface_area.value * poolform.temp_rise.value * heater_size_percentage,2);
	poolform.total_mj.value = toDecimalPoints(poolform.heater_size_needed.value * 24,2);
	gas_cost = poolform.total_mj.value * mj_percentage;	
	poolform.gas_cost.value  = '$' + toDecimalPoints(gas_cost,2)	
	poolform.master_temp_200_hour.value = toDecimalPoints(poolform.total_mj.value / 200,2);
	poolform.master_temp_300_hour.value = toDecimalPoints(poolform.total_mj.value / 300,2);
	poolform.master_temp_400_hour.value = toDecimalPoints(poolform.total_mj.value / 400,2);
}
function spaGasHeaterSizing (spaform)
	{
	spaform.heater_size_needed.value = toDecimalPoints(spaform.spa_volume.value * spaform.temp_rise.value * spa_heater_size_percentage,2);
	spaform.total_mj.value = toDecimalPoints(spaform.heater_size_needed.value * 1,2);
	gas_cost = spaform.total_mj.value * mj_percentage;
	spaform.gas_cost.value  = '$' + toDecimalPoints(gas_cost,2)	
	spaform.master_temp_200_min.value = toDecimalPoints((spaform.total_mj.value / 200)*60,2);
	spaform.master_temp_300_min.value = toDecimalPoints((spaform.total_mj.value / 300)*60,2);
	spaform.master_temp_400_min.value = toDecimalPoints((spaform.total_mj.value / 400)*60,2);
}