Heat build up on power pack.

[Anonymous]

I have a 7' x 8' Nscale layout. It is the donut style. I have two TECH - II 2400 power packs. I notice that after I have been running trains for a while (45-60 minutes), the packs are hot to the touch. This doesn't seem right to me. After all, I can run a good engine for hours and it never gets hot. Is this normal? Does it mean that I need more power? Maybe I should run them until they fail and replace them with new TECH 4 units. I don't usually run more than one engine per train. Sometimes I'll run two engines per train. The 2400s aren't as powerful as my old Locomotion 2500s. I've liked this because you get to use more of the 320 degrees on the throttle knobs. Do some power packs have adjustable ending voltages? I think I read somewhere that some of the TECH 4 units have this feature. Thanks for any insight or information you can give me.

[Anonymous]

Heat build up is a normal occurence, The heat comes from the chaging of AC to DC. My tech 2 does it, but my tech doesn't do it as often becuase, I use it to power my DCC booster. they're fine if they run warm, or alittle hot. They should be just fine

[Leon Silverman]

Most power packs control engine speed through a potentiometer which introduces a variable resistance to control the train speed. There is no resistance involved when the power pack is running at full speed. The typical N-guage locomotive is operated at a maximum voltage of 8 to 9 volts. This means that the current going thru the power has go through a resistance to drop from 12 to 9 volts. This results in a heat generation proportional to the square of the current (i-squared r losses).
When running at full speed, the locomotive may get hot because it is using a relatively large current. At less than full speed, the locomotive runs cooler because it is using less current. In the power pack, however, that current sees at lot more resistance than it would when the power pack is operating at full voltage. This is what generates the heat.
I used at Tech II power pack to operate an Athearn DD40 two motor locomotive and noticed the power pack heating up when tha engine was operated at less than full speed. MRC used to advertise how many locomotives their power packs could operate at once, but they never told you at what power setting and for how long before the circuit breaker would cut out.
Certain Power pack designs can vary the voltage electronically without introducing resistance into the circuit to operate at less than 12 volts , but this is why you see recommendations to buy the better powerpacks. What you could do after 45 minutes of running is to run your trains very slowly for a few minutes to allow the power pack to cool off. This lower speed introduces more resistance to the circuit but it reduces the current demand. In addition, the current flowing thru the power pack is now goiong through a larger physical mass (more resistance) which makes it easier to absorb and disappate the heat generated.

[Don Gibson]

HOW HOT IS HOT?

Forget 'how many locomotives can run' Ads. On the back of your Power Pak is a rating in 'VA' - Volt Amperes. Divide by 12 to get an Amp rating (@ 12 volts).

ATHEARN motors pulled 0,5A amp - !,0 amps each , depending on the age of the unit.,so your DD-40 with 2 mutors is using somewhere around 1 - 2 amps, You could be exceeding the capacity of your tech II 2400

An external meter ($16) will give you accurate readings,

[CP5415]

What gauge wire are you using from your power pack to the track?
I've run 2 Athearn BB locomotives for an hour & my power pack barely got warm.
I'm using 16 gauge wire from the power packs right now, but I'm going to be using 14 gauge for the bus wire & 18 gauge to the track from there.

Gordon