Using a dryer circuit for an EVSE

[QueenBee]

This topic is pretty close to what I need, so...

I had thought that my garage had no 240 volt capability, but I recently found that there are two buried 10-3 cables running to it, and I can get 238 volts from two opposite fuse holes. That's right, it's a fuse box, but a fairly modern 60 amp, 6 circuit (3 in use) unit, with good romex-type cable running to it through conduit. So here is my plan: I'm going to get a Clipper Creek PCS-25, use two opposite fuses with 25A mini-breakers or slow-blow fuses in them, and since having just one fuse blow is dangerous, I'm going to run the cable to a nearby (either near the box or the EVSE) fusible quick disconnect, a Square-D 30 amp unit, down-rated with two 25 amp regular fuses. Then I'll run cable to a junction box inside the garage, with the CC EVSE mounted on the outside wall and the wiring running into the box through the wall. I will try to use conduit in the garage, but may run exposed cable in the "attic" instead. (The ceiling is kind of cluttered.)

Have I overlooked anything? I can't afford to replace the box (and see no need for it in this case), so please limit opinions to how to make this installation as good and safe as possible.

Is it really a FUSE box? Honestly if it is, I would have it replaced with a box with breakers and use the proper double breaker.

Seriously return that disconnect and spend $8 more on something like this: http://m.homedepot.com/p/GE-PowerMark-Gold-125-AMP-6-Space-12-Circuit-Indoor-Main-Lug-Circuit-Breaker-Panel-TLM612FCUDP/100163880/" onclick="window.open(this.href);return false; and you can probably find some used breakers for it really cheap.

Don't try and save a few dollars by cutting corners.

By 10-3 are you using the industry standard meaning of #10 with 3 wires and a ground? Or just 3 wires total including the ground? If 3 wires total then I think the only way to do this to code is to have two subpanels. One 120 volt panel and one 240 volt panel. This would also give you a bit more power as well as you'll have two circuits to the garage. One 30 amp 120 volt and one 240 volt.

 

[LeftieBiker]

A 240V breaker would be safer than 2 fuses. In the breaker if one side trips the whole circuit is opened.

The idea is that if one fuse blows the EVSE will stop working, or at least throw an error code. I can then use the shutoff to kill *all* power to it, and look into it without worrying about 120 volts lurking in there. This is less elegant than another sub-panel, but it should be effective. I am hoping I find that two breaker panel I removed from an unused citcuit, though. I'm already spending $200 more than an open EVSE would cost to get a three year warranty, so adding a real breaker box is not doable. Again, the fuse box is in excellent shape, as are the two 10-3 romex-type cables feeding it.

 

[wwhitney]

Again, the fuse box is in excellent shape, as are the two 10-3 romex-type cables feeding it.

Why do you have two 10-3 cables feeding the fuse box? The NEC does not allow paralleling conductors smaller than #1/0. If you are feeding the two 10-3 cables with a single 60 amp breaker, that is a hazard.

Cheers, Wayne

 

[LeftieBiker]

Again, the fuse box is in excellent shape, as are the two 10-3 romex-type cables feeding it.

Why do you have two 10-3 cables feeding the fuse box? The NEC does not allow paralleling conductors smaller than #1/0. If you are feeding the two 10-3 cables with a single 60 amp breaker, that is a hazard.

Cheers, Wayne

I checked them, again, and it's one 10-3 and one 14-3. Any idea what's up with that? And I don't know what size pull-out fuse block feeds the garage box from the cellar sub-panel, yet. Probably a 50 amp.

 

[smkettner]

Better post up a few pictures at this point.

 

[LeftieBiker]

I was going to leave the panel open, but I was chastised for that idea by my SO. I'll try to remember to take photos when I do the work. This house had a lot of the wiring done by the employees of an oil business, and I've spent a lot of time doing things like removing '5th branches' that were snaked in under junction box lids, removing 240 volt circuits that tapped into two different, *already in use* circuits, etc. The garage panel looks much more professional, so I'm guessing they did something that was acceptable in that time...

Anyway, the place in the box I'd want to add the 240 circuit is vacant and uncluttered. There are no other high-drain circuits in the garage, except the wall circuit presently being used by the L-1 EVSE, and that will be replaced by the L-2 20 amp unit.

 

[wwhitney]

it's one 10-3 and one 14-3. Any idea what's up with that? And I don't know what size pull-out fuse block feeds the garage box from the cellar sub-panel, yet. Probably a 50 amp.

Please confirm you are using the standard terminology that 10-3 means 3 conductors plus a ground. Where do each of the cables terminate?

The 10-3 needs to be protected no higher than 30 amps. The 14-3 needs to be protected no higher than 15 amps. [There are rare exceptions, such as motor circuits.]

Is the garage attached or detached? If it is detached, it is an NEC violation to have two different branch circuits or feeders running from one structure the other. The one applicable exception would be if the 14-3 is only used for, say, control of exterior garage or house lights from locations in both buildings.

Cheers, Wayne

 

[BrockWI]

Just a guess on the 14-3, do you have a 3 way light switch for some outside or garage lights that are in teh house and the garage? Those are typically run over 14-3.

 

[LeftieBiker]

I understand wire designations, and mean three insulated wires and a bare ground wire. I know the amperage limits for the common cables, although I'm not sure about the actual box limit with this odd setup. The cable for the lights (also a 14-3, I think) is separate from the two conduit-carried cables. As for code, this was done long ago, and outside any municipality. They apparently didn't need no steenking codes around here. I'm now more glad than ever that I went with a 20 amp EVSE.

 

[DaveEV]

Leftie, please do yourself a favor and don't rig it up with the fuses. You've gotten very good advice from the others here.

If it were me and I were doing it on a budget, I'd ditch the fuses, install a proper breaker box in it's place and install another sub-panel in the garage. Parts will be less than $100. It's not worth risking fire to take short-cuts.

 

[LeftieBiker]

What exactly is the fire risk? The risk I see is of only one fuse blowing, and I'm trying to mitigate that. People tend to associate fuses with fires, when the actual risk is almost always from overloaded circuits and damaged appliance cords, which don't have anything directly to do with fuses. Sometimes the risk is from too-old cabling, and these cables are in good shape. The input wiring may have to be corrected a bit, but the box isn't overloaded.

I'll keep checking the topic, but I'm not going to keep reiterating what I stated in the very first post in the thread: I can't replace the garage fusebox. If I can install a sub-sub-panel I'll do that.

 

[kieranmullen]

For those will ful breaker boxes here is some info on what you can do with Tandem Circuit Breakers. (aka cheaters, slimmers etc)

http://www.structuretech1.com/2012/02/tandem-circuit-breakers/" onclick="window.open(this.href);return false;

 

[rogersleaf]

What exactly is the fire risk? The risk I see is of only one fuse blowing, and I'm trying to mitigate that. People tend to associate fuses with fires, when the actual risk is almost always from overloaded circuits and damaged appliance cords, which don't have anything directly to do with fuses. Sometimes the risk is from too-old cabling, and these cables are in good shape. The input wiring may have to be corrected a bit, but the box isn't overloaded.

I'll keep checking the topic, but I'm not going to keep reiterating what I stated in the very first post in the thread: I can't replace the garage fusebox. If I can install a sub-sub-panel I'll do that.

Sounds like the concern is putting a 20 amp continuous load on a 14-3 wire (#14 is for 15 amp, 12 amp continuous load). The fire risk is overheating the wire, melting insulation and igniting the framing of your building. Do yourself a favor, pull a 10-3 which is good for a 20 amp continuous load. Just wired my garage for a 30 amp EVSE, used 8-3 stranded on a 40 amp breaker. Had maybe $200 into the project including a service disconnect, breakers, and an additional 12-2 line for a 20 amp 120v while the garage wall was open. Clipper Creek 30 amp L2 should arrive any day to finish the job.

 

[LeftieBiker]

Read it again. You got it wrong.

 

[smkettner]

I am sure the fuses are fine. If it was mine I would replace the panel to have breakers that is all.
As long as it is not knob and tube you are fine.

 

[LeftieBiker]

I am sure the fuses are fine. If it was mine I would replace the panel to have breakers that is all.
As long as it is not knob and tube you are fine.

I had to replace some of that in the house. Mix of everything ever used, I think, in these walls. I should probably note, if only so I don't have to keep responding, that I'm in poor health and my hands, arms and legs are affected. Installing the EVSE circuit alone will be taxing. I'm also on a tight budget. So I can't do a teardown and rewire myself, and I can't afford to pay someone else to do it. Further, the two remaining fuseboxes for the main house, with their ancient wiring, would be my top priority, not the perfectly good one with modern cabling in the garage. Anyway, the last "Master Electrician" we hired ("Grounded Electric" in the Albany area - avoid) wired our freezer (located in the cellar) to our cellar light circuit. Much fun ensued.

I don't see a second 240 feed at the box, so now my main concern is the one 35A feed being marginally enough. The lights in the garage are all CFL and LED, but I do have an electric bicycle and electric motorcycle. I would have to not use the cycle charger while the Leaf was charging.

 

[wwhitney]

I don't see a second 240 feed at the box, so now my main concern is the one 35A feed being marginally enough.

Your 10/3 feeder to the garage needs to protected at 30 amps or less. While the 75C rating of #10 is 35A, NM cable (and UF cable) is limited to the 60C rating of 30A. Plus small conductors (#10 and below) are limited to the "standard values" as listed in NEC 240.4(D), which is 30 amps for #10.

BTW, the garage feeder should be UF cable, not NM cable, as it runs underground.

Cheers, Wayne

 

[LeftieBiker]

Even if it's in a metal conduit? Anyway, I'm not comfortable with 30A total available, even though it would work. I'm going to run 10-3 UF cable 45' from the main 200 amp service panel, around the front of the house and across the side yard, buried, to the sidewalk. It will be a real PITA with roots to bury it, but at this point it seems the best option. We are also planning to replace the two linked fuseboxes in the cellar, as the wiring in them has degraded even more. The garage fusebox is staying, as there is nothing whatsoever wrong with it as presently configured.

 

[smkettner]

What is wrong with 30a supply for 20a charging?
Run it as is. Check for heating with a one of those point and shot temp guns.
I bet it is all cool as a cucumber as it sits.

Even get a Leviton 16a on a 20a fuse. Still plenty to charge LEAF overnight.

 

[LeftieBiker]

That's 30 amps for the whole garage, not just the EVSE. I wouldn't want a 16A EVSE, and the 20 amp unit is already en route.