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Can you replace a 20-yr old Unico system with a Spacepak

My 20-yr old Unico high velocity system needs to be replaced. I was able to get two quotes for replacing the system with a new high-velocity system. The first contractor said that I had to replace with a Unico. The second contractor said it was no problem to replace with Spacepak, and they prefer that system. Also, I had good experience with a Spacepak installation in my previous house, and I have little experience with Unico.

So is it possible to replace the system (reusing the ducts), or was the first contractor right?


  • Jamie Hall
    Jamie Hall Member Posts: 23,635
    If the duct sizing, velocities and pressure drop requirements are very similar, I myself don't see why it wouldn't work. But you would be replacing pretty much everything except the ductwork, and the airflows would have to be close.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • clammy
    clammy Member Posts: 3,113
    It all depends both are high velocity air handlers and either may be used in that type of system but depend on the material used for your duct system and weather it is tight and not leaking air . 20 years ago even w hi velocity system guys where really not sealing system all that great . Now a days all joints are and should be sealed w a gasket tape or mastic . I personally prefer to do high velocity systems using spiral round duct work ,proper gauge metal , no length long snap seam and non adjustable 90 and tees so much if not any air leakage . Also I would image that your duct insulation isn’t up stuff . I usually use a r 8 foil faced wrap 20 years ago we where using r 4 big difference . On small note 20 years ago the the accepted route was 6 registers per ton now a days it’s a mim of 8 per ton . So from my experiences replacing a 20 years unico or spacepak isn t just a swap like all things in life it will require a little bit more work then slip it in also note that your going from r 22 to 410 I would suggest a new line set which will be the cheapest thing to do on the whole job . Personally I install unico it just always seems as I rarely see a great high velocity installs done by the book but I see more crappy hacked in space pak jobs then I ever see hacked unico ,I think it’s basically the supply house that sell them and the type of contractors that frequent them .both are expensive but either one installed corrrectly should be as quite as a standard system when installed correctly and installation details are followed . Beware not all sheep’s are sheep’s and make sure that it not gonna just be a quick swap out and if registers need be added they are added not after there’s issues . And if using a ecm motor on indoor unit install a surge protector it cheap insurance Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating