Fused Disconnect Versus Subpanel

Old 11-23-17, 01:55 PM
Thread Starter
Join Date: Feb 2015
Posts: 19
Upvotes: 0
Received 0 Upvotes on 0 Posts
Fused Disconnect Versus Subpanel

I'm trying to replace a non-working fused shutoff in a greenhouse behind my mother's house. It contained a burned up rat and looked like maybe it was not functioning for a long time, maybe bypassed? The conduit, junction boxes and outlets are not sealed. The existing setup looks something like this:

1. main shutoff
2. main breaker
3. wiring under house, probably around 40ft of white romex looking wire
4. junction box at corner of house
5. 40ft of conduit
6. broken fused disconnect
7. 6-8 outlets, some controlled by 2 light switches, romex some in and out of conduit, kind of a mess
8. There is an oil fired water heater that uses around 6 amps.
9. A small mini fridge, let's say around 1 AMP.
10. 3 taco water pumps, around 0.7A for 2 and 1A for the 3rd.

So the equipment alone without lights and anything else connected to outlets is using around 9.4amps.

After buying a similar disconnect I realized I want to move it outside the greenhouse but still on the corner of the greenhouse to decrease the moisture exposure and seems like a bad idea to operate a shutoff while standing in water. The current conduit turns out to be trashed, apparently crimped underground right before it comes up to enter the house. So this is looking more like a complete rewiring from the junction box at the corner of the house to the greenhouse so now I'm questioning the whole plan.

Sorry, I don't have the amp-rating of the breaker in the main breaker panel, I think it is either 15A or 20A but I know that is pretty important. Other places in the forum say anything above 20A needs a subpanel for sure.


Can a fused shutoff be used on an outbuilding without a subpanel?
If I could use a fused shutoff would I need to put it yet-another-grounding-rod at the greenhouse?

Otherwise can a subpanel be wiring into a 20A or 30A breaker?

Old 11-23-17, 02:17 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,393
Received 4,046 Upvotes on 3,630 Posts
If your circuit is protected at 15A or 20A at the main panel...... no further protection is needed. You can use a heavy duty 20A light switch as a disconnect.

Old 11-29-17, 03:02 PM
Thread Starter
Join Date: Feb 2015
Posts: 19
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the info on the switch. I confirmed that the breaker is indeed a 20A breaker.

Now I'm having trouble determining the best/better way to bring the conduit to the outer wall of the house.

There is a cable running under the house that is spliced in at a junction box that then the old conduit connects into in a weird way. I'd like the splice box to be on the outside of the wall, with a LB junction box, but the concrete foundation is offset from the wall between 4 and 8 inches. Is there any way to get the conduit to where it needs to be without unnecessary sweeps and/or another pull box hanging in the air? Tried to attach photo.

I could use a sweep out of trench into another sweep across to wall into a LR junction box against wall and then a short run of conduit to the new LB junction box that goes under the house. But that seems like I'm over doing it.
Attached Images  

Last edited by dogowner; 11-29-17 at 03:05 PM. Reason: fixed text in image
Old 11-29-17, 04:10 PM
Join Date: Nov 2015
Posts: 1,580
Received 204 Upvotes on 174 Posts
Unless it is something you turn on/off often, just use non-fused disconnect in place of fused disconnect. Switch works fine, but a disconnect will have more room inside and easier to install. Also very cheap.
Rated up to 60A.
Old 12-01-17, 10:02 AM
Forum Topic Moderator
Join Date: Sep 2005
Location: USA
Posts: 6,124
Received 425 Upvotes on 378 Posts
A couple feet of liquidtight conduit would bridge that gap easily since it's flexible. You can get an adapter to adapt it right onto your underground PVC conduit. PVC conduit would work as well, but would require a few bends. Either way you may want to put a rock or something near it to reduce the possibility of it getting hit with a mower or something.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: