# Panel switch/ circuit breaker recommendations

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#### 8davebarker

##### Well-Known Member
Does any have a recommendation for a combination panel toggle switch/ circuit breaker similar to those used in house wiring breaker panels.? Something small and compact suitable for a small crowed aircraft panel

#### Rhino

##### Well-Known Member
I don't know them well enough to recommend them, but toggle switch breakers are few and far between for aircraft. Klixon is a well known brand.

#### Rhino

##### Well-Known Member
The entire series is here:

#### rv7charlie

##### Well-Known Member
Are you open to other solutions?

#### wsimpso1

##### Super Moderator
Staff member
The Klixon is terrible expensive ($180!). If that were my only option, I would just connect a switch and conventional breaker in series and place them next to each other on the panel. The TYCO/ Potter and Brumfield W31-X2M1G- series is more reasonable ($30-\$50 depending upon trip amperage) for the same task:

Available from Steinair, Digikey, Mouser, Jameco, etc.

#### Dana

##### Super Moderator
Staff member
The P&B switches are tempting... I only have two fused circuits (toggle switches and tubular fuses) in my Hatz at the moment, but I need to add two more for the lights and strobe I want to add. Four of these could use the existing four holes (2 switches plus 2 fuses) in the panel.

#### rv7charlie

##### Well-Known Member
The ones Van uses have the contacts on the back side, but they definitely use automotive blade fuses. A lot of us RV-x guys are using the Bussman holders. They're available with up to 20 positions, and you can put them almost anywhere out of sight. (Yes, that is legal, if you do it right.) I've modified one to allow two buses in one fuse block.

Hey Dana,
Friends don't let friends use glass fuses.... ;-)

#### wsimpso1

##### Super Moderator
Staff member
The fuse blocks are great. The shown fuses are plain. If we are using them in the cockpit and have wired the airplane where we need to access them in flight, you might want either the fuses that are lit when they have blown or the ones that that are actually circuit breakers. Both types are available to go in these fuse holders.

A better way to work things is wire so that any one blown fuse means little. Engage the backup and motor on. Then you can just use fuses, and put the fuse box under the seat or next to the battery. Debug the circuit problems on the ground later.

Billski

#### Pops

##### Well-Known Member
On the JMR , I have no electrical system but have a 12v x 9 amp battery for the handheld radio and electrical oil temp gauge and electric elevator trim servo and also my tablet. In the pictures you will see 2 fuse boxes that has 4 fuses each on the inside of the firewall. Right of the battery. Also have LED strobes and LED position lights if I want to use them.

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#### dtnelson

##### Well-Known Member
FWIW, I've had two of the Potter & Brumfield switch circuit breakers fail in my airplane. One, interestingly enough, failed resistively - i.e., it made a very resistive contact (which dropped the voltage to my com to the point that it became "lights on but nobody's home"... hard to diagnose!).

Not sure, but I no longer believe they are intended for the kind of daily use a regular, quality, switch is made for.

Dave

#### wsimpso1

##### Super Moderator
Staff member
The only purpose I have for a switch-breaker is ground power, which is really infrequent. I may just go with a SPST and a conventional CB for that.

#### rv7charlie

##### Well-Known Member
A better way to work things is wire so that any one blown fuse means little. Engage the backup and motor on.
This has been the Aeroelectric book's philosophy for a long time. IMO, putting the circuit protection (for most devices) out of sight/reach makes a safer a/c. If a pair of airline pilots and their flight engineer can fly an airliner into the ground troubleshooting tripped breakers, I gotta figure it's not a good idea for me to troubleshoot in flight. Being able to buy all my circuit protection and all my switches for the entire plane for about the price of *one* of those breaker-switches is a nice side benefit. ;-)

#### wsimpso1

##### Super Moderator
Staff member
This has been the Aeroelectric book's philosophy for a long time. IMO, putting the circuit protection (for most devices) out of sight/reach makes a safer a/c. If a pair of airline pilots and their flight engineer can fly an airliner into the ground troubleshooting tripped breakers, I gotta figure it's not a good idea for me to troubleshoot in flight. Being able to buy all my circuit protection and all my switches for the entire plane for about the price of *one* of those breaker-switches is a nice side benefit. ;-)
AeroElectric Connection Book is where I saw the light. LOTS of great design philosophy from lots of painful history. Words to live:

Nuckolls' Laws of Airplane System Design:
Nuckolls' First Law: Things break.​
Nuckolls' Second Law: Systems shall be designed so that when things break, no immediate hazard is created.​
Nuckolls' Third Law: Things needed for comfortable termination of flight require backup or special consideration to ensure operation and availability.​
Nuckolls' Fourth Law: Upgrading the quality, reliability, longevity, or capability of a part shall be because you are tired of replacing it or you want some new feature, NOT because it damned near got you killed.​

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#### Dana

##### Super Moderator
Staff member
FWIW, I've had two of the Potter & Brumfield switch circuit breakers fail in my airplane. One, interestingly enough, failed resistively - i.e., it made a very resistive contact (which dropped the voltage to my com to the point that it became "lights on but nobody's home"... hard to diagnose!).

Not sure, but I no longer believe they are intended for the kind of daily use a regular, quality, switch is made for.

According to the B&B catalog they're supposed to be good for "more than 6,000 cycles at 100% of rating, or 10,000 mechanical cycles."

#### FinnFlyer

##### Well-Known Member
I, too, had a P&B fail. No idea how long it had been in service (cycles). However, it has a design flaw. No support of the braided wire, means it puts stress where the wire is spot-welded to contact. We all know that non-solid wires need support where the wire is soft so that no back-and-forth movement occurs where wire goes from flexible to solid (whether soldered, welded or crimped).

This 10 amp switch/breaker supplied an engine monitor, drawing much less than one amp. So failure was definitely mechanical fatigue and not current-related.

Very good type

#### Dan Thomas

##### Well-Known Member
I wanted all my fuses or breakers accessible from the pilot's seat. Losing the lights or radios at night is no fun at all.

Now, why would they demand that for the average puddle-jumper FAR 23 airplane like a 150 or 172? Because, sooner or later, some pilot is going to have to make a night approach, maybe to IFR minima, to an airport surrounded by mountainous terrain, and that ILS had better be alive. If the radio breaker pops, shut off something you don't need, maybe the second Com, and reset the breaker. For the same reasons, fuses were replaced by breakers in FAR 23 airplane production a long time ago.

I taught some IFR when I was instructing. We often made night approaches at rural airports that used ARCAL lighting, and you'd better have that Com alive to turn the runway lights on. I was also the director of maintenance at the school, and any complaint of a breaker popping got me looking close to see what might be haywire. I didn't want anyone in my airplanes to suffer an outage in actual IMC. Mostly it was old breakers that would pop early due to contact heating of oxidized contacts in the breaker.

#### Marc Zeitlin

##### Exalted Grand Poobah
I wanted all my fuses or breakers accessible from the pilot's seat. Losing the lights or radios at night is no fun at all.
So the first sentence does not follow from the second sentence. We may have discussed this before, but this is an architecture problem, not a "can I reach the CB" problem. All resetting a CB does is give the wire another chance to set itself on fire. If you're using unreliable CB's that "pop early", as you state later on, then you shouldn't be using them - use something that doesn't have that absurd failure mode (like automotive ATO fuses, which never pop unless overloaded).

Now, why would they demand that for the average puddle-jumper FAR 23 airplane like a 150 or 172? Because, sooner or later, some pilot is going to have to make a night approach, maybe to IFR minima, to an airport surrounded by mountainous terrain, and that ILS had better be alive.
So your argument is that you want to give the airplane a 2nd chance to catch on fire because you have no redundancy for IMC flight? I don't think the problem in this case is whether or not the CB is resettable - it's far deeper, in the architecture of the electrical system.

For VFR flight, the ONLY electrical items that MUST work are those that keep the engine running, if any. For IFR flight, redundancy as needed to get on the ground safely. If the circuit protection devices are less reliable than the wires and components that they're protecting, then they should be replaced with something more reliable, or redundancy of wiring/avionics should be provided. The answer is not to give the airplane another shot at burning up.

If the radio breaker pops, shut off something you don't need, maybe the second Com, and reset the breaker. For the same reasons, fuses were replaced by breakers in FAR 23 airplane production a long time ago.

Rather than do the right thing, which would have been to redesign the electrical system so that a single circuit failure, due to current overload, doesn't cause a safety issue.

Also note that E-AB aircraft (or ANY Experimental aircraft, for that matter) aren't subject to Part 23, and if something better than Part 23 is available, then using that is perfectly acceptable. And in any case, you've quoted the old, obsolete version of Part 23 - the new version's paragraph of interest is 14 CFR Part 23.2525, which basically states what I've indicated above:

The power generation, storage, and distribution for any system must be designed and installed to -​
(a) Supply the power required for operation of connected loads during all intended operating conditions;​
(b) Ensure no single failure or malfunction of any one power supply, distribution system, or other utilization system will prevent the system from supplying the essential loads required for continued safe flight and landing; and​
(c) Have enough capacity, if the primary source fails, to supply essential loads, including non-continuous essential loads for the time needed to complete the function required for continued safe flight and landing.​

(b) is the relevant sub-paragraph. While a resettable CB MIGHT be a solution to this requirement, it also allows for unsafe system behavior - i.e., a fire starting.

... I didn't want anyone in my airplanes to suffer an outage in actual IMC. Mostly it was old breakers that would pop early due to contact heating of oxidized contacts in the breaker.
And with TC'd aircraft, you don't have the freedom to "do something better" than what the FAR's required, or what the folks who designed the aircraft implemented.

But we do. And should.

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#### Dan Thomas

##### Well-Known Member
And with TC'd aircraft, you don't have the freedom to "do something better" than what the FAR's required, or what the folks who designed the aircraft implemented.
Resetting a CB once is unlikely to start the fire. The wire is sized to take considerably more current than the CB allows, and it will pop again if necessary. If it pops again, it's left off. There something in FAA/Transport Canada stuff somewhere that speaks to that.

And in Canada there is the option to change a TC'd system that needs changing. The 172L had a 250-watt landing light on a 20-amp breaker. That 250 watts is based on a 14-volt system. That meant that the breaker was carrying almost 19 amps as a constant load, far too close to its limit, and that breaker would get warm and start oxidizing its contacts, adding resistance so it would pop all the time. The breaker would get so hot that the crimp terminals were discolored and oxidizing. The landing light switch would sometime melt. The whole affair was Cessna's engineering mistake. Cessna eventually specified 4-year replacement intervals for those switches, but they never addressed the undersized breaker.

The Canadian Aviation Regulations Standards have an Appendix to determine what is and what is not a minor modification. It's a series of questions to which, if the answer is Yes, it's a major mod and needs an STC or Service Bulletin or some other form of approval. If the answer is No, it's a minor mod that can be done using acceptable data such as AC43.13. For the electrical system, we read this from the Appendix:

Standard 571 Appendix A-Criteria for the Classification of Modifications and Repairs

• (e) Other Qualities Affecting Airworthiness
• Does the modification or repair:
• (7) alter an electrical generation device, or the electrical distribution system between the generating source and either its primary distribution bus, or any other bus designated as an essential bus?

The landing light system is not between the generating source and its primary distribution bus, so the answer is No.

The solution was to increase the wire size to 12 gauge and the breaker to 25 amps.