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  1. #1

    Accutherm Therma-Fusers any Field Experience Good or Bad?

    I am looking at Therma-Fuser installations that serve conference room (s). It does not work well and many occupant/user complaints. The Conference rooms are relatively small and have about four to six individual Therma-fusers installed. The Static air pressure from the AHU is high enough that the Therma fusers are installed with an "air gap" ring (an Accutherm product?)between the Therma-Fuser and the connecting flex duct. An air gap?!. The excess air simply dumps into the plenum space and then off course drops out the return grill into the space. Sub cooling it. The owners are being scolded by the PE for not controlling the plenum pressure to a negative so the air does not drop out. Of course the PE designed the system with 100% OA. Which of course pressurizes the plenum and the slight negative air pressure needed in the plenum cannot be maintained by the exhaust fans accurately or with existing controls specified. What to do?

    This seems like another PE design being tried by someone who does not understand the nature of the control problems involved. Incidently the controls are not adequate to even do what is needed. It all sounds good so has anyone seen another one of these "efficient" systems? Any where? How did the Therma-Fusers become the little darlings of the Leeds/green movement?

  2. #2
    Join Date
    Sep 2004
    Location
    SoCal
    Posts
    446
    Thermafusers work well as long as your supply static pressure is .25" or less. Anything above that and they won't close down sufficiently. We've had good luck with the LON based units and when coupled with a VFD - you can do a pretty good job of zone control and no wall mounted thermostats to deal with! Plus, with the networked LON Tfusers, you can monitor CFM , supply air temp, and terminal load as well as adjust setpoints. On DX systems we use supply air low limit strategies to prevent coil ice-ups. Placement of the diffusers in the room is also important in order to ensure that the space sensor located in the face of the diffuser gets proper air induction and reads an accurate space temp.

    I also like the auto changeover feature that detects supply air temperature and switches heat/cool modes.

    Their support has always been good too.

    Good luck!
    lb
    A hundred million nodes - it's a LON story.

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