Dc or dcc connector strips 3a, 6a, 15a, 30a

[huw_capper]

Hi all, sorry if this has already been covered or if I'm being completely stupid, but I can't seem to find the answer.

 

Connector /terminal strips? I notice in places like screwfix and toolstation you can buy plastic connector strips if joining cables together, link below

 

https://www.screwfix.com/p/3a-terminal-strips-pack-of-10/25545?tc=AB8&ds_rl=1248181&ds_rl=1245250&ds_rl=1249481&gclid=Cj0KCQiA38jRBRCQARIsACEqIev4AeFM3-Nr4OJHOmRi6H08ui3zQw5Ht6YtJNzI8pQdXSB8orRqaZUaAm7-EALw_wcB&gclsrc=aw.ds&dclid=CIrOydHNidgCFeYS0wod9Z4AXQ

 

 

What is the difference between the amps as they go all the way up to 30amps???

 

Im running a basic bus wire around the layout, what amp rated connectors should I use?

 

Thanks

 

Huw

[66C]

Hi Huw

 

Very simple - what is the maximum output (in amps) from your controller?

Buy the next value up screw connector block.

 

Regards.

Edited December 14, 2017 by 66C

[RFS]

But the amperage of these connectors is based on 240 volts, whereas your controller output is only going to the 12-16 so you won't need the heavy duty ones.  Just pick one that is appropriate to your wire size.

Edited December 14, 2017 by RFS

[Enterprisingwestern]

As RFS says, unless you're going to get technical and invoike RMS, V over IR etc etc!

 

Mike.

[cpman46]

Currently helping to wire a DC / DCC layout in '0' gauge. We are using the 3A rated screw terminal blocks throughout which are more than adequate.

 

Mike C

[RFS]

If you want to get technical, then power is expressed in watts by the simple equation "amps x volts = watts".

 

So with a 3a, 240v connector 3 x 240 = 720 watts.  Typical DCC will usually be no more than 5a x 16v = 80 watts. Hence 3a connectors will suffice for all model railway needs. 

[Brian]

Size of the terminal blocks tube hole is the main criteria you need to worry about.  That will depend on the number and size of the wires going into any one connector.

Generally 5 or 6 Amp versions are adequate for most layout uses.  3 Amp may be suitable too if only thin wires or a low number of wires are in one connector.

Edited December 14, 2017 by Brian

[John ks]

66C’s reply is the on I would most agree with followed closely by Brian’s

 

RFS said “Just pick one that is appropriate to your wire size” would also be acceptable

 

But comparing a 3A connector at 16V & 240V I believe is a flawed argument

 

A device connected via a connector consuming 3A at 240V would consume 720W but the connector  would not, if it did then it would start to glow red in a short time .

 

If you argue that the connector rated at 3V,240V can supply a device rated at 720W, then logically that connector

 must also be capable of supplying a 16V*45A=720W device & this is the flawed argument.

Try running 45A through the 3 A connector & it will heat up

 

The power consumed by a connector is determined by the current flowing through it & its resistance i.e. I²*R. The resistance is determined by the type & amount of material that the connector is made of.

 

If the terminal has a resistance of 0.01 ohms then at 3 amps the power lost in that terminal strip will be

3*3*0.01 or 0.09Watts where as if the current is 45A then the power loss will be 20.25W

Most of that 20.25W will be converted to heat, how hot does a 20W filament bulb get? (Remember that in a bulb most of the energy is converted to light)

 

The voltage rating for a connector is related to its insulation qualities.

 

A connector rated at 12V that was connected to 240V would fail due to the insulation breaking down.

 

​John

[AndyID]

Don't worry about the current rating. If you can stuff the wires into the holes any resistance in the connector is going to be insignificant compared to the resistance of the wire. The voltage rating is irrelevant at the voltages you are concerned with.

 

It's more important to know if the connections are going to remain "gas tight" over a long time. That means that the screw has to maintain pressure on the wire(s). If the wire is not able to resist the pressure exerted by the screw indefinitely, or the screw loosens due to vibration, the connection will eventually become unreliable.

[huw_capper]

Thanks all, it's good to know that if you're stuck with something there is a friendly community out there willing to help, hopefully in years to come I may be helping out newbies too as at the moment I'm a relative newcomer

[DCB]

Generally the smaller the connector the better, the limiting factor is the screw gripping the wire and the more nearly the wire fits the hole the better the retention will be.

If it is a permanent join twisting the wires together and soldering before heat shrinking a cover instead of using a connector strip  is much better.   I find 90% of wiring faults are wires necking off in screwed connectors.

If you have a Bus wire it sounds like you are going DCC so make sure your wiring will take the full load of the locos and stock using the layout, its easy to get a couple of amps worth and that will really sort out duff fishplates and point blades.   I would never use a single bus, divide it into power zones or sections with switches or your hobby will be amateur electrical sleuth as you try to find where the fault is without removing every single loco and lighted coach from the layout and then testing every point with a multi tester. Even with power zones faults can be challenging but an intermittent fault and DCC without power zones is the stuff of nightmares

Edited December 17, 2017 by DavidCBroad

[Crosland]

It has nothing at all to do with voltage in the circuit (e.g. 240 or 12 V). Unless you have a serious problem there will be very little voltage across the terminal block, and little power dissipation.

 

There will be some finite resistance in the joint between the wires and the screws etc., which could lead to very small voltage drop. The larger rated terminal blocks allow larger cables and have larger screws to allow a greater contact area.

[Crosland]

So with a 3a, 240v connector 3 x 240 = 720 watts.  Typical DCC will usually be no more than 5a x 16v = 80 watts. Hence 3a connectors will suffice for all model railway needs. 

 

This is like a well known DCC retailer who used to multiply the insulation breakdown voltage of their cable by the current rating and came to a power rating of kW.

 

If your typical DCC system is rated at 5A then your connectors need to be rated at 5A, end of.

[Junctionmad]

Generally the smaller the connector the better, the limiting factor is the screw gripping the wire and the more nearly the wire fits the hole the better the retention will be.

If it is a permanent join twisting the wires together and soldering before heat shrinking a cover is much better. I find 90% of wiring faults are wires necking off in screwed connectors.

If you have a Bus wire it sounds like you are going DCC so make sure your wiring will take the full load of the locos and stock using the layout, its easy to get a couple of amps worth and that will really sort out duff fishplates and point blades. I would never use a single bus, divide it into power zones or sections with switches or your hobby will be amateur electrical sleuth as you try to find where the fault is without removing every single loco and lighted coach from the layout and then testing every point with a multi tester. Even with power zones faults can be challenging but an intermittent fault and DCC without power zones is the stuff of nightmares

Please do not solder the ends of wires that are to be used in these " chocolate block " connectors , as they are known . The solder creates a hard point at the interface between it and the wire and it fails there in time. Equally under the screw pressure the solder " flows " and as a result the wire loosens. Use a bootlace ferrule instead and do it right.

 

Overall these connectors are cheap and that's about the only positive thing you can say about them.

Edited December 15, 2017 by Junctionmad

[PaulCheffus]

Please do not solder the ends of wires that are to be used in these " chocolate block " connectors , as they are known . The solder creates a hard point at the interface between it and the wire and it fails there in time. Equally under the screw pressure the solder " flows " and as a result the wire loosens. Use a bootlace ferrule instead and do it right.

 

Overall these connectors are cheap and that's about the only positive thing you can say about them.

Hi

 

Out of interest how long does this take as my wires have been soldered then screwed into the connectors for the last 15 years without any ill effects.

 

Cheers

 

Paul

[AndyID]

Hi

 

Out of interest how long does this take as my wires have been soldered then screwed into the connectors for the last 15 years without any ill effects.

 

Cheers

 

Paul

 

Hi Paul,

 

It depends

 

If your layout is subjected to a lot of movement/vibration or extreme changes in temperature, a problem might show up in hours, but if it's static in a fairly constant environment you might never see a problem.

 

Andy

[cliff park]

Hi

 

Out of interest how long does this take as my wires have been soldered then screwed into the connectors for the last 15 years without any ill effects.

 

Cheers

 

Paul

If the wires are never moved they will be ok. But if they are often moved or flexed they will quickly break. And I have to say that Crosland is right (it had to happen eventually),  the voltages involved have absolutely no relevance to the current rating of devices. A 1 amp fuse is a 1 amp fuse and will blow at 2 amps (approx) regardless of the voltage supplying that current. 

[PaulCheffus]

If the wires are never moved they will be ok. But if they are often moved or flexed they will quickly break. And I have to say that Crosland is right (it had to happen eventually),  the voltages involved have absolutely no relevance to the current rating of devices. A 1 amp fuse is a 1 amp fuse and will blow at 2 amps (approx) regardless of the voltage supplying that current.

 

Hi

 

Ah my layout is fixed so I should be ok.

 

Cheers

 

Paul

[Crosland]

And I have to say that Crosland is right (it had to happen eventually),  

 

What's that supposed to mean?

[cliff park]

Sorry Crosland, don't take it to heart. I think I hit the festive spirit too early. Merry Christma

[DCB]

Diverging slightly off topic

 

This is what I have been using connector strips for for well over 20 years.  Route setting. This one is for a 6 road storage siding module.

 

1 amp Diodes are strung between the connector blocks direct the DC current from the 6 road selector switches to various combinations of the 10 point motor solenoids. Up to 4 diodes are clamped under each connector screw and the 6 wires from the switch are 10 amp car wiring loom wires clamped into the 3 amp connectors.   Max amperage has to be around 5 amps supplied by a 22 000 uf Capacitor strung across the 12 volt DC H&M transformer output, however 1 amp diodes have been working for 20 plus years.

 

I had issues with a sticking motor mis diagnosed as a failed diode which led to the whole module being hauled out and repaired Christmas day afternoon and this evening.  I know its ugly, the strips are too close but 30 years ago diodes were more expensive and recovered ones came with shorter leads.   Starting from scratch I would space them further apart.

 

Connector strips are cheap.  Diodes were about £ 2.99 for 100 from Ebay  The UK supplier delivered in 3 days, and although this one has a 6 position rotary switch with a push button to energise my others have electric pencil, or a dead Bic biro with a wire down it and just ordinary screws in plywood with wires soldered on.  I changed the capacitor for a new one (from Hardings in Cheltenham High Street) 22 000 uf for  £2.50ts.