I suggest that you size whatever boiler that you get @ 100000 BTU per gallon of flow rate that your equipment puts out. 5 gpm machine 500,000 BTU burner. This sizing of the burner should get you at least a 100 degree temperature rise.
Also suggest that you install a temperature gauge and a pressure gauge.
Dave Olson
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Tidy Powerwash Service, Inc. P.O. Box 781, Catlin, Illinois 61817 Phone 217-427-5557, Fax 217-427-2632 We are a commercial cleaning contractor serving East-Central Illinois and West Central Indiana since 1984.
http://www.tps-inc.com