Iowa State University

Client Need 
The existing steam line serving Lied Rec Center was in need of replacement.  Replacement of this line would be difficult and costly due to the conflicts with several other utilities and Lied Rec was now the only building served by this line.  ISU Utilities choose to abandon the existing steam line serving Lied Rec and provide a new gas-fired heating water plant within the building to meet building heating and domestic water needs.  
Approach 
The existing steam pressure reducing station, steam-to-water heat exchangers and heating water pumps for the building are located in a second floor mechanical room that also contains several air handlers.  Locating the new boiler plant in place of the existing steam infrastructure made sense but two key issues needed to be addressed: maintaining domestic hot-water and building reheat during construction and separating the boilers from the mechanical room that functioned as a return air plenum.  This involved creating a phased construction plan during design, which allowed for 100% availability of domestic hot water, and providing a new Boiler Rm within the existing mechanical room.
Solution 
Four new gas-fired heating water boilers comprise the new heating water plant.  One of the boilers is a condensing style and the other three are non-condensing.  With existing heating devices sized for a higher heating water temperature, it did not make sense to provide all condensing boilers for the building, when the system would only operate in a condensing mode during the summer.  Domestic water heating is provided by plate-and-frame water-to-water heat exchangers that are fed by the new boiler plant.  New correctly sized heating water distribution pumps with VFDs are provided.  A new room was constructed around the new boilers.  New electrical service was extended to the new equipment.  ISU Utilities provided new gas service to the building for the new boilers.