NEC code question on disconects

**HVAC/Stud** · 10-20-2005, 01:55 PM

If the main breaker panel is outside on wall (not locked)and in sight of a/c unit, can it be used as disconect. Inspector turned down install for no disconect, the main elect panel was on exterior wall next to unit.

If so, what is the NEC reference?

Thanks,
STUD

**troyorr** · 10-20-2005, 02:57 PM

As the AHJ. That is Agency Having Jurisdiction. The inspector at your location is the one you have to satisfy. Inspectors interpret the disconnect code differently at different locations.

**pecmsg** · 10-20-2005, 03:05 PM

I believe the code states “6' line of sight” but many municipality’s do not consider the breaker as a disconnect. Make him happy and throw in a disconnect.

**curry** · 10-20-2005, 04:17 PM

I think next to the unit is best.

Besides, breakers dont respond to overload condtions as well as fueses.

**mark beiser** · 10-20-2005, 04:48 PM

Originally posted by curry
Besides, breakers dont respond to overload condtions as well as fueses.

True, but we still don't install fused disconnects on residential equipment, unless the breaker in the panel is to large for the new unit and it is an expensive breaker to replace.
Probably 90%+ of the blown fuses I have found on HVAC equipment had nothing to do with the equipment. Almost always a bad connection within the disconnect, frequently within the fuse holders, lol.

**bornriding** · 10-20-2005, 04:58 PM

In sight of & accessible is the NEC lanquage. 6' is not mentioned. However, local codes have precidence. I would have asked the inspector to reference me to the section he is referring to. Of course, the inspectors here know that I will question any situation to learn the proper way - not to argue. But I will not hesitate to have them produce evidence of their requirements. I always maintain a business-like approach so as not to antagonize them.

Hope this helps,
Richard

**curry** · 10-20-2005, 04:59 PM

Originally posted by mark beiser

Originally posted by curry
Besides, breakers dont respond to overload condtions as well as fueses.

True, but we still don't install fused disconnects on residential equipment, unless the breaker in the panel is to large for the new unit and it is an expensive breaker to replace.
Probably 90%+ of the blown fuses I have found on HVAC equipment had nothing to do with the equipment. Almost always a bad connection within the disconnect, frequently within the fuse holders, lol.

Here we try to match the breaker to the electrical requirements of the ac.

But we only use it as a means to kill power to the FUSED disconnect we install on every job.

What made me a believer was when my own ac popped the breaker in the main panel and the HVACR rated otside breaker didn't even get warm.

That was my first year in busines.

I have read several posts on how electrical flows work depending on trans former ect. I'm not an electician but I bow my head in deference to those here who do know.

Ihave picked up so much good stuff here it s unbelieveable.

**trane** · 10-20-2005, 05:05 PM

So your the one still putting all those fused disconnects in.

**bornriding** · 10-20-2005, 05:39 PM

Originally posted by curry

Besides, breakers dont respond to overload condtions as well as fueses. [/B]

Not sure that I agree here - to put fuses on a motor requires that the one-time fuse be rated @ appr. 300% - time-delay fuses act just like breakers - with an inverse time characteristic. The fuse might trip slightly ahead of the breaker on a small overload condition, but only slightly, if anything. Either breaker or fuse will provide adequate protection - if sized properly.

Respectfully,
Richard

**mark beiser** · 10-20-2005, 06:14 PM

Originally posted by bornriding

Originally posted by curry

Besides, breakers dont respond to overload condtions as well as fueses.

Not sure that I agree here - to put fuses on a motor requires that the one-time fuse be rated @ appr. 300% - time-delay fuses act just like breakers - with an inverse time characteristic. The fuse might trip slightly ahead of the breaker on a small overload condition, but only slightly, if anything. Either breaker or fuse will provide adequate protection - if sized properly.

Respectfully,
Richard [/B]

It doesn't happen much 230v equipment, but on higher voltage stuff the contacts of the breaker can actually fuse together before they get a chance to separate under extreme overload conditions.
I got convinced to use fused disconnects on 460v equipment when I accedently shut down a large printing company for a couple of hours.

No cooling call, had no power to the unit, but didn't find anythig shorted to ground. Turned unfused disconnect off, went down and reset the breaker.
Went back on the roof and turned the disconnect on. The electrical conduit to the unit started humming, then I heared a loud BANG from inside the building, followed shortly by the entire building going silent because a protective device shut off the power to the building.

Turned out that the windings in one of the 20 ton compressors were shunted together, but not grounded. When I flipped the disconnect back on, the contacts in the breaker fused, then the breaker exploded in the panel, blowing the door off the breaker panel. At that point a monitoring system for the power supply to the building cut the power to the building.

We found pieces of that breaker imbeded in a sheet rock wall 20' away, fortunatly nobody was in the room when the breaker did its grenade impersination.

They didn't blame me after it was determined exactly what happened, but from then on I have sold fused disconnects for every piece of equipment I have sold, or had to replace the disconnect on, that was >230v. Fuses don't have contacts that can get fused together.

**Midwest** · 10-20-2005, 07:48 PM

Don't have my NEC handy, but it's all in Article 440. Pretty short section. Your area may be under the Int. Residential Code, that may be found somewhere in IRC sections E33 through 42. I am not familiar with the IRC so that's the best I can do for you.

**suemarkp** · 10-20-2005, 10:41 PM

Originally posted by HVAC/Stud
If the main breaker panel is outside on wall (not locked)and in sight of a/c unit, can it be used as disconect. Inspector turned down install for no disconect, the main elect panel was on exterior wall next to unit.

If so, what is the NEC reference?

The NEC location requirements are this:

440.14 Location. Disconnecting means shall be located within sight from and readily accessible from the air-conditioning or refrigerating equipment. The disconnecting means shall be permitted to be installed on or within the air-conditioning or refrigerating equipment.
The disconnecting means shall not be located on panels that are designed to allow access to the air-conditioning or refrigeration equipment.

In NEC usage, "within sight" means you can actually see it from the AC unit and it is no more than 50 feet away. "readily Accessible" means you can get to it without requiring keys, ladders, or moving stuff out of the way.

If you only have a main breaker in this panel (e.g. a 100A or 200A one), I don't think they'll go for that although technically it performs the required function. If the branch circuit breaker for the AC is in that panel, I don't see why he turned you down.

**rsmith46** · 10-20-2005, 10:46 PM

Artical 440.14 Location. Disconnecting means shall be located within sight and readily accessible from the air conditioning or refridgeration equipment.
Beat to the post, but you should be ok if A/C is on its own breaker and clearly marked.

[Edited by rsmith46 on 10-20-2005 at 10:49 PM]

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