I have an older Dayton model 3E473A wall furnace that has a bad gas valve. Grainger no longer sells replacement parts for this furnace. I went on line and using the part no. of the existing bad gas valve (Robert Shaw 7000 AERB-5-S7C), I found a cross referenced replacement gas valve (GSV720402). My concern is that my furnace is rated at 40,000 input BTu's and the specs for the replacement gas valve says up to 150,000 BTU furnace. Does the burner control the amount of btu's or does the gas valve control the amount of gas to meet what the furnace is supposed to put out in heat?