I am using a Digitrax Super Chief 5 amp booster/command station on my layout. I have uaed 14 gauge wire for the power bus and 20 gauge for the feeders. What I am seeing, or rather hearing, is that in sections of the RR the booster doesn’t shut down when a short occurs. Rather I will hear a high pitched whine from the place where the short is occurring and it seems to happen in places furthest away from the booster/command station. i do have the ‘scale switch’ set for HO. Is it time to add another booster? Other than that, everything is running normally.
You may not need a booster. What you may be hearing is the ARC caused by the short circuit. What you should do is divide your layout into several districts with an adjustable circuit breaker like the PSX series with one for each district. There are times when the short circuit will not trip the command stations circuit breaker because the short does not draw enough current to trip it, but the heat generated at the short location will cause some damage. Break up the power buss into two or three seperate districts and set the circuit protection to a lower trip current.
I agree with the previous reply.
How big is your layout?
A 5 amp booster is a lot of power, so it takes quite a bit to require a second booster.
If your current booster isn’t tripping, you need to look closer at the number of feeders. You probably need more feeders.
Do the quarter test along your layout at various points to be certain that the booster is tripping in all cases.
Rich
I could easily set up two districts since where this conditon occurs is inside of a large return loop which was added last year. I will admit I am little bit of a novice so could you offer a little explanation to your comment - or maybe point me in some direction.
Thanks - I am sure this is the solutiion.
Harold, is that “large return loop” a reverse loop?
Rich
Rich,
This occurs inside of the reverse loop section which also contains a small yard. I am running additonal feeders today as I am doing other wiring in a different place in the layout.
I also thought the installation of the AR1 might be a culprit. The unit won’t accept 14 gauge wire. So I ran 22 gauge into it from one bus, ran 22 gauge out to a new 14 gauge bus which powers the loop. I was never happy with that arrangement.
Size of the layout - it’s about 252 square feet.
Yes, it is a reverse loop wired into an AR1. Without measuring, it’s about 25-30 feet long.
Harold, one more preliminary question.
Are the shorts only occurring in the reversing section (loop), or does this short circuit problem without tripping the booster occur in other parts of the layout as well?
I might add that the size (gauge) of your bus and feeder wires is adequate, in my experience.
Rich
Interesting question. I just went down and tried the quarter test. The booster trips everywhere else except in all the track contained in the loop. When I do the test within the loop, the AR1 clicks rapidly as if it is trying to trip and I hear the whine at the point of the test. Maybe I need to adjust the trip current??? Also interesting, I just installed a separate reverse loop closer to the booster than the other one and it does the same thing - AR1 ‘clicking’ and whining.
I can still set up power districts but need a little guidance…[D)]
The first thing that I would do is to adjust the trip current on the TTC screw on each AR1. Each one-quarter turn of the screw increases (or decreases) the amperage sensitivity.
If the quarter test throughout the layout, outside of the reversing section(s) trips the booster, then you need to increase the sensitivity of each AR-1. Trial and error with the turn of the screw will get it right - - - - unless the AR1 is faulty.
Rich
A quick story about power districts.
I have a double main line measuring 162 linear feet around the layout. My DCC had been controlled by an NCE PH-Pro 5 amp booster with 5 AR1’s controlling five different reversing sections.
I decided to divide my layout into 4 power districts by adding a series of four PSX circuit breakers. I ran into all kinds of problems in that the mechanical relays on the AR-1s didn’t act as quickly as the solid state PSX units. I wound up replacing all 5 AR1s with PSX-ARs, a costly undertaking.
Because of the configuration of the PSX/PSX-AR units, I wound up adding a second booster. Ugh.
So, look before you leap.
Rich
Ready?
It’s working fine. The AR1 is “intercepting” the short, which is what an auto-reverse unit does. The booster (or base station) should not trip under these conditions. Only the reverse loop shuts down, because that’s the only part of the layout which sees a short.
You should, however, do something about feeding the AR1 with larger wires. If nothing else, solder a very short length of narrow wire to your standard bus wires so the thin-wire run is minimized.
Thanks guys - will try what you have suggested. Looks like I have a little work today - adding more feeders, adjusting trip currents and fixing the wires going to the AR1. It’s going to be hot today so a good day to spend in the cool basement.
I am not so sure about that. Harold says that he hears the relay on the AR1 clicking repeatedly and he hears a whining sound which tells me that the short is pesisting. The AR1 should click once and only once.
Either the TTC adjustment is insufficient or the relay is sticking. It is not fine.
Rich
The AR1 is a relatively new unit. Once I get back down there i will try adjusting the trip current aling with a couple other ideas from you guys. Believe me when I say I am a novice when it comes to RR electronics so anything to keep it simple is fine with me. As a side note, i do wish i could find a comprehensive book on he topic.
Adjusted properly, the AR-1 should click once when the rails are shorted and if the short persists after the relay clicks, the booster should shut down.
It’s OK to run smaller wire to the AR-1 terminals, but it should be kept short, a few inches to give enough room to connect it to the full-size bus. Voltage drop in the wire is proportional to botht he size of the wire and length, so short lengths of smaller wire will not cause enough drop to be a problem, unless everything else is marginal to begin with. You should be able to fit at least #18 wire in the screw terminals of the AR-1.
–Randy
It would have been nice if you mentioned the reverse loops in your original posting. The AR1 operates by detecting a short circuit condition when a loco enters the reverse loop and it flips the polarity of the loop to correct that condition. Either the AR1’s sensitivity is too low or it is detecting a short in the reverse loop that it cannot correct. Make sure you have all the insulated joiners or gaps in their correct places and try readjusting the trip sensitivity. The PSX AR’s are a better choice but they are a little more costly.
I was an avid user of AR1s for years. But they are, admittedly, out of date technology with the mechanical relay.
I have no regrets with the switchover to the solid state technology of the PSX-AR along with the PSX circuit breakers.
Rich
First of all, thanks guys for your help. I did go down and adjust the trip current on one of the AR1’s and it works perfectly. The one which controls the reverse loop I was referring to is also fine. i am almost ashamed to admit, but when I crawled under the layout to add more feeders I said ‘what was I thinking when I wired this???’ The feeders are way too long, there aren’t nearly enough of them and the bus is way too short which probably accounts for the feeders being too long. SO, tomorrow there is a trip to Lowe’s in my future along with a significant re-wiring project in this one area. Going forward I will also look into the PSX devices as the Digitrax devices are probably updated. Thanks for that tip.
Like I said, there’s never time to do it right, but there’s always time to do it over. (sigh)
Harold, glad to hear that the TTC adjustment worked. As long as it is working properly, there is no need to move to PSX-AR solid state technology at this time. I might suggest that the same applies to adding circuit breakers or a second booster at this time.
Chances are, if you create power districts and use solid state technology for the circuit breakers, you are going to have to replace the AR1s as well. That gets expensive, so hold off until you absolutely need to go in that direction.
But definitely get those bus wires and feeder wires in order.
Rich