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Thread: solid tube disconnect?
11-08-2012, 09:47 PM #1
solid tube disconnect?
Sorry - I have a picture but I can't seem to upload it. A while back there was a thread concerning the type of disconnect that looks like it can accomodate fuses but instead just has two brass or copper tubes. The one in the thread had failed, burnt, melted or whatever.
I came across last one last week whose contacts were corroded. I cleaned them up, popped it back in, amped the unit and all was well until I was called back today. Electric furnace service disconnect, panel breaker ahead and unit breaker after. As soon as I entered the condo I knew what happened, unmistakeable smell of burnt wiring. Thick. Disconnect was toasted.
Two questions (ok three): Is there something about this type of disconnect that lends itself to failure? Do they heat up and become loose or something? Why would they - looks like a regular nonfused disconnect? I called another tech after the first visit and he felt the set up was fine.
Why didn't the breakers before or after the disconnect trip?
How close did I come to burning down a luxury condo complex and ending my very short HVAC career?
11-08-2012, 10:02 PM #2
I'm not sure what disconnect your talking about but as for not tripping the breaker look at it this way. You get a service call that the out door unit isn't running ,you get there and you have power to the unit but it isn't running ,you look in the control box and find the contactor fried. because of a bad connection it over heated and burnt up but didn't short to ground and cause the breaker to trip. I would think you may have had a bad connection and it just slowly started burning up.
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11-08-2012, 10:19 PM #3
11-08-2012, 10:53 PM #4
I had just polished the entire thing less than a week ago. You can see by the lower right side contact how shiny the entire unit was. Now only days later you can see dark corroded areas bad enough to completely destroy the entire disconnect and create a lot of heat in an indoor closet space.
I feel extremely lucky, humbled and troubled. Seriously - I know to thoroughly inspect an outdoor disconnect and have installed a new one on installs when it wasn't on the worksheet but I didn't like the looks of it more than a few times.
Other than the corrosion on the contacts, the entire disconnect was in great condition and had been for 8 years or so. Once cleaned the unit amped fine, no voltage drop across the contacts, wires (6 gauge) in great shape.
I've seen what an outdoor disconnect can do when it's bad - happened right around the corner from my Mom's condo after a brand new install. Burn marks half way up the side of the house and melted siding, fire department called. Reputable, good contractor. Thank God the H/O were present and competent.
This truly frightens me and I don't mind saying it. This disconnect was inside a dwelling and potentially deadly.
11-09-2012, 10:02 AM #5Professional Member*
- Join Date
- Aug 2009
Is this a joke? It looks like a fuse holder rendered useless by somebody replacing the fuses with two pieces of copper. They probably either couldn't solve the problem of blowing fuses, or had no fuses on their truck so they did this instead. They endangered the homeowner and his family (possibly causing fire or electrocution).
11-09-2012, 10:08 AM #6Local 597 Service Fitter
Metal Trade Journeyman
PAY ME NOW OR PAY ME LATER
It was working when I left...
11-09-2012, 10:24 AM #7
This was wrong on so many levels.
..Do not attempt vast projects with
half vast experience and ideas.
11-09-2012, 08:53 PM #8Professional Member
- Join Date
- May 2011
Wait, I'm surely reading this wrong. You fixed the disconnect by polishing the copper pipe stuck in the fuse holder?! You're lucky you didn't kill someone or get sued. Please, go to your parts house and get an assortment of fuses for your truck!
11-09-2012, 09:09 PM #9
There are breakers before and after this service disconnect on this electric furnace. It is no different than a non-fused disconnect at an electric furnace in an attic, far away from the breaker panel or an outside disconnect. In theory. It passed local inspection about eight years ago and I just cleaned up (brass) what was already there ( something I'll never do again, mind you).
Apparently this is/was an acceptable practice...but I'm still wondering if this type of breaker is prone to problems. Specifically - do they become hot and loosen, making a bad connection, where a fuse would blow?
The disconnect I replaced it with is a standard non-fused pull type like we always use when we put in electrics. Again, with breakers before at the panel and after at the unit.
I thought the same as many of you, when I first saw the other thread 2sac included.
11-10-2012, 08:06 AM #10Professional Member
- Join Date
- Aug 2012
- Gainesville, FL
If you have a breaker AFTER this disconnect then you don't need the disconnect. The whole reason for a disconnect is to provide the technician with a safe way to verify that power has been turned off. A breaker at the unit can serve as the disconnect
11-10-2012, 08:14 AM #11
11-10-2012, 11:18 AM #12
Pete - yes, I suppose. We often include them in attic locations, however. I never thought to ask why. Because the breaker panel is so far away and what happens if the unit breaker has an issue?
2sac - yes, that was the very thread I thought of the moment I pulled the disconnect - and thanks for going to get it. The question is did they use that in lieu of a fused d/c? In my example they didn't as they didn't have to - but I'm still questioning the integrity of this type of d/c. I'll never let one stand again without the client swearing in blood that we are not liable.
All - Seems I could use a quick lesson on what type and in what situations of d/c's are needed according to NEC and most local codes. I know they should be in eyesight of the equipment - but fused, non fused, whatever the manufacturer mandates?
I'm kind of backwards as I'm newer in the trade and 90% service. I am beginning to see how that is a disadvantage at times...
11-10-2012, 12:06 PM #13Professional Member
- Join Date
- Sep 2010