Low or High Pressure Steam or Water. Highly Efficient Three-Pass Design. Fully Waterbacked Primary Heating Surfaces. Wetback Design Allows Easy Front and Rear Access for Ease of Maintenance. Made in the USA. Gross Output is 40 HP. 1339 MBH. MSH Input is 1674. 200 SQ. FT. Fireside Heat Surface. 15 P.S.I. Steam. Min. Safeety Valve Cap is 1600 LBS/HR.