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Joined:  Apr 2008 
Posts: 11  
 
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 am in the process of having 30 furnaces changed out in some rental units and am in a bit of a disagreement with the HVAC guys about the disconnects.  While we both agree that one is required, they want to remove the existing SSU's and just install a switch.  I would like to leave the SSU's intact, but see the point that an accessible switch serves the purpose.  So, I figured I would pose this question to you guys and see what your opinions and/or facts are.
  Thanks in advance
  
 
  
"We can do it, you can't help"  said my son to the HD guy
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Joined:  Oct 2006 
Posts: 745  
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Please forgive me, but what do you mean by the acronym "SSU"? 
 
  
---Ed---
  "But the guy at Home Depot said it would work."
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Joined:  Feb 2003 
Posts: 369  
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Service/safety/switched shut-off unit? 
  I wonder if that is another name for disconnect? 
 
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Joined:  Apr 2008 
Posts: 11  
 
OP
 
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SSU/SSY....the terminology escapes me at the moment, but it is the switch used as a disconnect that also incorporates a fuse block. 
 
  
"We can do it, you can't help"  said my son to the HD guy
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Joined:  Oct 2006 
Posts: 745  
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Are these gas/oil units or electric?  If gas/oil, then a standard switch will suffice.  The existing disconnects can be reused, but I'd spend the extra couple of bucks and replace it with a new one.  If it it an electric/heat pump unit, then that depends upon the manufacturer's name plate ratings as to whether a fused disconnect is required or not. 
 
  
---Ed---
  "But the guy at Home Depot said it would work."
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Joined:  Mar 2005 
Posts: 399  
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SSU is a switch and Edison base fuse holder on a handy box cover, manufactured by Bussman. A switch only would work for the furnace.   The advantage of the SSU is that a T rated, time delay fuse with a setting close to the rating of the motor can be used to aford better protection than the branch circuit over current device.  I used one on my water well, going from a 20 amp circuit breaker to a time delay 8 amp fuse at the pump. It has been in service this way for over 25 years. The fuses cost about $ 3.oo each now but that is still a lot cheaper than a new pump motor. 
 
  
Alan-- If it was easy, anyone could do it.  
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Joined:  Apr 2002 
Posts: 7,413 Likes: 9  
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OK, now that Alan explained that one; I have not seen one of those in 20 years. Didn't know that Bussmann still made them!
  Alan: Is it a true Edison base fuse, or a Fusestat?
 
  
 
  
John
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Posts:  70
Joined: January 2002
  
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