Bus wire size

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NickB

Wannabe Engineer
Ok everyone quick question. I'm running HO, and I know Allan Gartner recommends 12 for his bus but says 16 is ok. What is everyone's opinion?? I see no problem in 16, I was planning to do some quick connects from my bus up to some feeders and I found quick connects that accommodate wire size 16-22 which is perfect since I was going to run 22 for my feeder. I feel 16 would be fine just do to everything I have learned as an electrical engineer, but I have one more question what is everyones experience with these quick connects?? I guess I'm just being a little unsure of myself and my wife is constantly telling me not to.
 
16 works fine and soldering is best. Quick connectors are ok but they are subject to moisture and humidity causing corrosion and it is possible down the road you wont be a happy camper.

Good Luck
 

RexHea

RAIL BENDER
Nick, considering the size of your layout, I agree with the others on 16 gauge being fine. As you know, the longer the runs the more resistance, but your runs aren't that long. If you had to run 30 or more series feet, then I would recommend no smaller than 14 and better at 12. I also agree that soldering is the best way to go (even though it's a pain in the butt:eek: :D .)

ADDED NOTE: Remember that we are not concerned about current capacity, as any of the sizes are more than sufficient. We are looking at voltage drop because of the wire resistance. I run 12 on my large layout and do not have any significant drop at the far end.
 
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Larry

Long Winded Old Fart
I run 14 the entire length & width of my layout (18X36ft) & use 20 ga. for drops & I always solder at the buss & the track. I've never had a drop in current & I run 3 engines on all my main lines.
Layouts in the past I ran 16 & 18 for a buss on a smaller layout (12X21ft) & used quick disconnects & always had problems. I had terminal connecters under the layout to connect all my plus or minus wires to & had problems w/those too. So, now, solder, solder & solder. Practice makes perfect.

Larry
 

NickB

Wannabe Engineer
Alright thanks fellas, just needed that extra re-assurance. Time to go get the wire and start in on it today.
 

Joe Daddy

C & SF, my obsession
Nick,
Just HOW big is your layout? I never saw where you said. Especially how long will the longest piece of wire be from the DCC power output to the track? Sixteen is probably just fine but if you have wire lengths over 50-60 feet 14 might be better. Ampacity is the issue.

When you get your layout wired, I recommend you use the quarter test to ensure that your connections are of sufficient quality to allow your overload protection to kick out.

Joe
 

RexHea

RAIL BENDER
Joe:
Nick has a DCC one room home layout with short runs for his bus wires.

As to ampacity, my above post is directly in reference to the ampacity rating of the size wire as per the NEC. As stated above, all the sizes mentioned (16, 14,12) have the capability to handle (bus) the currents used in (HO) Model Railroading, but the smaller the size wire, the more resistive the wire is to this current. Thus, the more resistance, the more voltage drop caused by that wire.
The ideal is to use the largest wire possible to prevent voltage drop even though a smaller wire can handle the current load, e.g. we want a peninsula using 6 amps of current to have as much of the main supply voltage as possible.;)

To add to the thread:
Instead of only one main bus throughout the layout, you can also have a main bus with a large size wire and then feed off of it with several parallel bus of the same size or even smaller wire. This will divide the wire currents and keep the branch currents low and only the main bus will have the full load. In a sense, this is done when you install track feeders with the smaller wire.
 

Joe Daddy

C & SF, my obsession
Rex,

My one room home layout has a bus currently 20 feet in length (16 gauge). It will soon be in excess of 60' and that is using a splilt T format. Until one knows the length of the bus, selecting the appropriate sized wire is not possible.

We disagree that one should use the largest wire possible. The point is to use the appropriate sized wire according to the size of the layout. Workmanship issues are always the #1 problem with reliable layout wiring. The difficulty to connect small (20-24) gauge wire to wire larger increases with wire size. Meaning it is much easier to get quality bonds with 16 gauge than 14, 12 or 10. Especially when soldering and mechanical skills are unknown or not well developed.

Calculating ampacity without knowing the length of the wire is impossible.

Joe
 

NickB

Wannabe Engineer
Using 14 with 22 feeders and I'm soldering them. Works very well as since my previous job was assembly and testing where did smt soldering for 2 years.
 

Joe Daddy

C & SF, my obsession
Using 14 with 22 feeders and I'm soldering them. Works very well as since my previous job was assembly and testing where did smt soldering for 2 years.

Are you keeping the 14 gauge parallel and close together (under 1") apart? No need to twist, but running the wires some distance apart does have issues.

Glad you know how to solder! You know must know the problems cold solder joints cause.

Good luck!
Joe (PS, I grew up in Norman, OK)
 

NickB

Wannabe Engineer
Yea I'm keeping them close together, yea actually J-standard certified in soldering. Thanks I pretty much have it almost done and been testing it and it's getting better. Norman huh don't know if I can be talking to someone from Sooner land :D I got my bachelors in electrical engineering technology from OSU. Seeing where your at now is sure some strange coincidence, I have relatives in Montrose.
 

RexHea

RAIL BENDER
Joe,
I'm sorry that you missed Nick's earlier threads on his new layout. If you had seen the posts, you would know that this layout is a temporary one and total space available is very limited, i.e. future expansion with this one is not likely.

Your point of not knowing a proper size needed for the bus because of future expansion is exactly why you want to go with a larger wire in the beginning. Most cannot understand the relationships between wire size, distance, and the total current that the wire will handle. That is why most recommendations are made in general rather than specifics. It is better to be too large than too little.:) My layout has grown from a half-garage to a full garage size, but fortunately I began using 12awg for my bus system with many parallel branches. I don't have a booster and I don't experience any significant voltage loss and the "coin test" works fine.

I'm not sure I understand what you are saying about your layout bus size. If you are saying it is OK as is, I agree that there is nothing wrong with you using 16 gauge for 60 feet, but better if you divide the busing into parallel branches of short lengths. You are only looking at 4.26 ohms of resistance per 1000 feet for 16awg or 2.68 ohms/1000 for 14awg.

Your point of soldering/connection difficulties is well taken. When splicing bus wires of a large gauge, it is electrically correct to use twist connectors (top hats) or even split-bolt couplers to connect to each other.

However, when soldering smaller parallel track feeders to the bus, I simply pull back the insulation of the bus, clean, wrap wire and solder. I prefer a solid bus wire (12awg) simply because it is easier to form and also to solder to, but this is a personal preference.

I am curious as to what you meant about the wire separation issues. The DCC signal is so relatively slow, a need for wire twist (e.g. spec. Cat 5) or parallel runs for prevention of signal concellation/crosstalk has not been a problem that I am aware of. More of concern would be avoiding noise sources.
 
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