Central AC disconnect

scottysDecember 28, 2009

I am installing central ac for the first time and I am running the line myself. Do I need a fusible or non-fusible ac disconnect switch for my outdoor condenser

unit? The 220v unit will be fed by #10 wire protected by a double 30amp breaker located in the main panel.

Does the fusible switch offer a measure of "extra" protection? or would i be better off with the more compact and cheaper non-fusible disconnect?

Thanks.

Thank you for reporting this comment. Undo
terribletom

The local disconnect is simply that -- a disconnect. It does not need to be fused and there is no compelling advantage to buying a fused disconnect. A cheapie should be fine here.

[BTW, have you checked the manufacturer's specific recommendation on the breaker size? The reason I ask is that AC units are sometimes fused at the max amps rating to accommodate the starting surge of the compressor whereas the wire is sized according to the minimum circuit. This may be a case where you can use #10 wire on a 40A breaker, so doublecheck that rec' before buying the breaker.]

    Bookmark   December 28, 2009 at 2:55PM
Thank you for reporting this comment. Undo
saltcedar

"It does not need to be fused and there is no compelling advantage to buying a fused disconnect. "

In some jurisdictions it won't pass code enforcement without one!

    Bookmark   December 29, 2009 at 3:56PM
Thank you for reporting this comment. Undo
terribletom

Just so I'll know for future reference, where, exactly, are a few of these jurisdictions located? Is this a commonplace local code modification in some region or another? Does it apply to residential applications?

Alternatively, if the "code enforcement" is based on the NEC, what's the code cite used to disapprove an unfused disconnect? (Notwithstanding the obvious case where additional overcurrent protection is needed at the point of a disconnect fed from an oversized circuit.)

Has anyone else run into this problem?

    Bookmark   December 29, 2009 at 4:44PM
Thank you for reporting this comment. Undo
maryland_irisman

I've never run into the requirement for a fusible disconnect in addition to a protected circuit. One of the counties here in Maryland (Anne Arundal County)has some of the most stringent local requirements in addition to NEC, in the country and the only requirement for a disconnect is, a lockable disconnect at the condensing unit.

    Bookmark   December 29, 2009 at 6:09PM
Thank you for reporting this comment. Undo
pharkus

... There are some units whose manufacturers specify FUSE. This is the case when a fused disconnect will be required.

ie, your A/C unit states "30A Fuse or circuit breaker" = no fused disconnect required. However, if it states "30A FUSE", one IS required.

    Bookmark   December 29, 2009 at 6:18PM
Thank you for reporting this comment. Undo
terribletom

"However, if it states "30A FUSE", one IS required."

Yep, that makes sense to me, Mike. If a manufacturer specifically calls for a fuse then I reckon you'd have to follow that instruction. What complicates matters, I suppose, is that the term "fused disconnect" is also commonly used to include disconnects with breakers. Similarly, a topical heading like "Fusing" often refers to overcurrent protection in general, whether by breaker or fuse.

(BTW, I wasn't aware of manufacturers who specifically require fuses for small residential A/C units these days. But if they're out there, I agree with you.)

    Bookmark   December 29, 2009 at 7:58PM
Sign Up to comment
More Discussions
Inspection Report
Had a gorgeous 1909 house inspected yesterday and don't...
cmae17
Wiring in a 1 1/2" thick wall cavity
I need to run 12/2 wire thru an existing thin wall....
baker1mich
Testing a fluorescent bulb
I've got a light box that isn't lighting up when I...
kudzu9
Garage florescent light flickering - bulb or fixture problem?
I replaced the GE F40 RES garage lights with a GE F40...
bibbus 7b
Code changes
In outlining the electrical layout for our new home,...
mtvhike
© 2015 Houzz Inc. Houzz® The new way to design your home™