SSU Required for furnace?

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sfav8r

Senior Member
I always install an SSU when wiring for a furnace. I did my first one that way, and I admit I have just always done them that way without really thinking if it was required.

Today, I went to look at a home that had correction notices. One of those notices stated "Replace the unapproved furnace wiring with an electrical installation suitable for the conditions of use." When I read this I expected to see a furnace running on an extension cord. Instead I found a dedicated 20a circuit (romex) feeding a j-box mounted to the ceiling joist. There was a disconnect switch in the j-box and the furnace was feed by a drop in 1/2 flex. The room had a light and a plug within about 5'. The only thing I could think of was NO SSU. If it is required, I'm not sure what the code is.

As a side note, has anyone else noticed that HVAC guys often come and install a 20a fuse in an SSU? Seems pointless to have the SSU to me since it's on a 20a breaker.

Thanks.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
IMO one of those is only required if the unit stated that it needed fuse protection.
 

mdshunk

Senior Member
Location
Right here.
Perhaps the inspector considers that flex to be exposed to physical damage, and wants to see something more like EMT? Some model mechanical codes require that the furnace disco or SSU be operable by the technician while the flame is being observed, which would mean right smack on the side of the furnace, many times. If it was me, I'd just phone the inspector right quick and ask him what he had in mind. I'd put money on him wanting EMT in place of the flex.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
mdshunk said:
Perhaps the inspector considers that flex to be exposed to physical damage, and wants to see something more like EMT? EMT in place of the flex.

Marc, no blower on these things?
 

mdshunk

Senior Member
Location
Right here.
chris kennedy said:
Marc, no blower on these things?
Hey, I'm just throwing some stuff out there. Who knows what the inspector's thinking. The red tag language is rather vague. Perhaps the 20amp circuit itself was objectionable, if the unit calls for 15a? Just guessing at some stuff. Perhaps that flex drop was improperly supported and secured?
 
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sfav8r

Senior Member
stickboy1375, I must say I think your signature is hilarious. I have used that quote a couple of times when talking to my guys. I hope it isn't trademarked :)

Back on topic, I left the inspector a message earlier. Hopefully she will remember.
 

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
Was the flex longer then 6' ? If you were in San Fransisco they are real sricklers on where you can run flex. They pretty much only want to see it on the final end of the run connecting it to the furnace. I also thought ssu's had a limit of #14 wire on them keeping them under 15 amp. The last furnace I connected in SFO was EMT to an SSU then MC whip to the furnace about 2' of it. and I had no trouble with that.
 

M. D.

Senior Member
I have wired a least 100 hot air furnaces I have never been asked to use one of those things , I hope he can remember.
 
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