Switchable breaker for DC fridge and freezer units.

[JDCAVE]

I'm looking for options for a switchable circuit breaker, surface mount, for my DC fridge and freezer. I like the idea of the Blue Seas Bussmann 185 or 285 series circuit breakers but they don't go down to 20 amps, which is what I need for the fridge and freezer units. I want to b able to shut the units off and open the doors without the interior lights coming on.

The fridge and freezer units were formerly Sub Zero AC units, with breakers on the AC panel. The PO switched to Novacool DC units. But he didn't put circuit protection in, as near as I can tell, unless it's on the units themselves. I'd like to install switchable breakers on the DC distribution panel in the engine room, right of the labeled vertical bus bar. Rerouting cable to the DC breaker panel in the saloon would be a pain. Any ideas or will I have to use a fuse block instead?

 

[O C Diver]

Did you trace the wires from the unit to the power distribution to ensure there isn't a fuse or breaker? While I don't expect the unit has a fuse, did you check the owners manual? Wouldn't it be more convenient to put a fuse block at the distribution panel and install a switch next to the unit.

Ted

 

[Larry M]

We went through the same thing although we only needed 2-15 circuits for the fridge and freezer . We added a Blue Sea 3 breaker panel and used the extra breaker for the electric fuel pump we added. You could ask Blue Sea if they would substitute the 15 amp breakers for their 20 amp breakers or you could do the change.

https://www.bluesea.com/products/8025/Traditional_Metal_DC_Panel_-_3_Positions

The pic show where we mounted the panel. It's above the voltage regulator in the lower left.

 

[av8r]

The small rectangular objects that are connected between the bus bar and the freezer and refrigerator wires may be automotive self-resetting circuit breakers.
The Blue Sea 7135 series 187 surface mount breaker is rated at 25A, check your wire size to see if that provides adequate protection.

 

[C lectric]

A typical threaded shaft nose OR twin screw mounted breaker would work. Just need a bracket made that would hold them. Lexan would be a good material as it is tough, bendable with heat, can be worked relatively easily.

Magnetic Single Pole Circuit Breakers | Ancor

Some Plastic fabricators I think would make the bracket or do you have a capable friend.

 

[JDCAVE]

Thanks guys...

Did you trace the wires from the unit to the power distribution to ensure there isn't a fuse or breaker? While I don't expect the unit has a fuse, did you check the owners manual? Wouldn't it be more convenient to put a fuse block at the distribution panel and install a switch next to the unit.

Ted

I looked around some time ago but couldn't see one. The PO said it was fused somewhere but wasn't specific. It really would be easiest for me to switch it off from the engine room, as the only other "easy" install would be behind the units, accessed under the Pilothouse watch berth, but that's worse for access than the engine room.

Larry: I don't think I've got room for even a small panel, although I will check and see. I've filled up the AC side with several devices. All full at the inn!

The small rectangular objects that are connected between the bus bar and the freezer and refrigerator wires may be automotive self-resetting circuit breakers.
The Blue Sea 7135 series 187 surface mount breaker is rated at 25A, check your wire size to see if that provides adequate protection.

The manufacturer recommends a 20 amp breaker, though I think the wire size would indicate a larger fuse. I'm uncertain of the wire size. I will check to see if the "block" is fused. I hadn't thought about that possibility.

Clark: I don't think I've got room for that in the compartment.

Possibilities to ponder.

Thanks, Jim

 

[Bay Pelican]

Blue Sea sells a fuse panel - 12 positions. I have found this to be a useful addition as I separate the various 12 volt items each with its own fuse.

 

[twistedtree]

Jim, I've used a lot of DIN rail mounted breakers, relays, etc. You buy the rail in 3' lengths, cut to the length you need, then the devices snap into it. This stuff is widely used in industrial automation.

Here's a 20A, 60VDC rated breaker S201U-K20 - ABB - CIRCUIT BREAKER, 1 POLE, 20A | Newark element14

Two of these would probably fit in that space - more if you want. That wiring bus bar should probably be inspected to be sure all the attached sires can handle whatever breaker rating is feeding it. It looks really problematic as wired, and a few more breakers might clean it all up.

Once you have figured out how many breakers you want to stack up, get two end lock pieces. They are essentially book-ends that clip on the rail and lock the stack of devices into position on the rail.

 

[JDCAVE]

Thanks Marty, Peter. I need to determine if the fridge and freezer are fused with those inline "blocks", as Av8r suspects.
Peter: this is a photo of the fusing arrangements on the other side of that bus bar. I am concerned with the "parallel" fusing arrangement of the "capstan" (2 Rule winches) on the boat deck. I just need to determine the fuse amperage required.

 

[JDCAVE]

Peter: further to the points you raise: were you concerned about the capacity of the bus bar or the adequacy of the fusing of the loads that come off of it?

 

[JDCAVE]

I've gone to the boat and found that the fridge and freezer are fused individually with a "Shortstop 24VOC R19 20A". The Webasto is fused with a "Shortstop 24VOC R19 30A". These look to be resettable.

"Bussmann 'Short Stop' circuit breakers are Available in type 1 auto reset (12 and 24 volt DC options), type 2 modified reset (12 volt only), and type 3 manual reset (12 or 24 volt dual voltage use)."

These units are 12 volts. How do I know if this fuse is "ok" for 12 or if it is for 24 volt applications only? Are they acceptable for marine applications in the engine room?

 

[C lectric]

Bussmann Automotive Circuit Breakers - Wiring Products


http://www.cooperindustries.com/con...akers/series_12x_shortstopcircuitbreaker.html

Jim,
study the above link. According to this there are three types of C.B. like yours.
#1 - completely auto reset meaning it will cycle on/off as it reacts to overcurrent and the cools off.

#2 - will trip and remain tripped untill the source of current is removed.

#3 - will trip and remain tripped untill a reset button is pressed.

I suspect you have either #2 or #3 type. If that is the case and the amperage rating is good then the breakers are fine.

The voltage rating has to do with the arc extinguishing ability under an overload [ short circuit] situation. Higher voltage overcurrent [shorts] situations are harder to extinguish the higher the voltage is.

If the specs were reversed and a 12VDC were used on a 24VDC system and an overcurrent occurred the breaker MAY not be able to stop it. At least not quickly and not without possibly serious damage to the breaker itself, the wiring or the device.

If yours are 24VDC and it appears they are then they should be just fine on your 12VDC system.

So now how to simply turn things off. Reconnect the C.B.s that are present and simply install a switch any where you please since overcurrent protection is taken care of right at the supply bussbar..

Just be sure that the C.B.s are either type #2 or better #3.

I learned something from this. I was aware of the auto reset C.B.style but not aware of the types 2 & 3. T.Y.

 

[twistedtree]

Peter: further to the points you raise: were you concerned about the capacity of the bus bar or the adequacy of the fusing of the loads that come off of it?

I was concerned about the loads, but see from your later picture that everything is fused. I've never seen stud fuses like you have on the fridge, assuming that's what they are.

Re your capstain breaker that you are concerned about, is that the dual parallel breaker? Yes, that's a bit funky. In theory two parallel breakers will give twice the capacity. But they really should be tied together so if one trips they both trip. A number of manufacturers make panel breakers that work that way. In this case, ideally you would have a single breaker with the correct rating.

 

[JDCAVE]

Thanks Clark and Peter: Clark I'm pretty sure it's "type 3" as there is a little button on the side of the unit. I will put a switches on the fridge/freezer side of the fuse. Peter: I think I will go ahead and replace that parallel set-up. It's been on "the list" for a year now. I just need to determine the acceptable rating for the winches/cables.

Jim

 

[C lectric]

Which windlass do you have?
What is the present wire size? The wire size should be printed on the wire insulation. Should still be visible as the wire looks to be in good condition still.
What is the capacity of the two breakers now, individually?

I'll lay odds that the combined capacity of the two breakers is the needed capacity of a singe larger breaker or very close. Best though to do it properly with the windlass and wire specs.

The question didn't come up before but is your system 12VDC or is it 24VDC? Your boat is bordering the size that 24VDC is often used so the question to be sure.

 

[JDCAVE]

Hi Clark: The boat is all 12 volt except for the bow thruster, which is 24 volt. I got an email back from "Chris" at wiringproducts.com and he confirms the resettable fuses used for the fridge and freezer will work for both 12 and 24 volt systems.

I believe the winches are Rule T33S winches. One raises and lowers the boom and one raises the line to the skiff. The cable to the winches looks to be a bit smaller than the thick 2/0 cable in those photos. 1/0 or 1 AWG? It will be one or the other. One of the parallel breakers is 50 amp and the other is 100 amp. Those Blue Seas breakers are expensive, and I'm guessing that the PO had the other two available so twinned them instead of using a single breaker. Just a guess.

The photo shows the winch cable coming up past the large fuse for the inverter/charger which is cabled with 2/0. The cable size cannot be determined from the text in the photo.



Jim

 

[C lectric]

The marking should be there but it may take some disassembly of connections and twisting the wire to find it.
I looked but cannot find anything on the net for specs. of those winches. I'll venture that some looking around the chandleries and 4x4 shops and trailer boat shops that you might be able to find the info.

Western Marine and Paynes may have access to the specs.

Keep in mind too that the actual wire size might/likely be several guages larger than strictly by the book to allow for Vdrop especially if the circuit is long. The winch motor likely does not truly draw what the wire is capable of BUT the size is needed to prevent an unacceptable voltage loss which will cause at the least, poor winch performance and worst a burnout.

The C.B. would be sized for the actual motor draw, not the wire size in a case like that.
I would guess from here that the winch motor would draw maybe 75A to 100A under load but that literally is guesswork.

Try to find the specs. Have you examined the winch housing itself? If the weather hasn't been to harsh the label may still be readable.