## Electrical specs for soldering irons

### Electrical specs for soldering irons

Question:
Does anyone know how many amps are required for a 100 watt soldering iron?
Alternatively, how many 100 watt irons (running at full heat) will a 20 amp
circuit support?  I teach a beginner's class, and it seems that my student's
irons cannot heat up enough when we solder steel.

Thanks,

Tim Sundell
Minneapolis, MN

### Electrical specs for soldering irons

Quote:

> Question:
> Does anyone know how many amps are required for a 100 watt soldering iron?

Just under 1 amp.

Quote:
> Alternatively, how many 100 watt irons (running at full heat) will a 20 amp
> circuit support?

24 max... that'd be pushing a breaker trip.  I had a 20 amp breaker
trip at 18 amps before.

Quote:
>  I teach a beginner's class, and it seems that my student's
> irons cannot heat up enough when we solder steel.

You say "running at full heat."  If you're running them through
some sort of amperage controller, why not plug them directly into the
wall when you need max heat?  Even when the controller is set at 100%
you are most likely still getting some voltage drop.

Quote:

> Thanks,

> Tim Sundell
> Minneapolis, MN

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### Electrical specs for soldering irons

writes:

Quote:
>Does anyone know how many amps are required for a 100 watt soldering iron?
>Alternatively, how many 100 watt irons (running at full heat) will a 20 amp
>circuit support?  I teach a beginner's class, and it seems that my student's
>irons cannot heat up enough when we solder steel.

Assuming your wiring is not dropping the voltage too much, then you probably
have about 115 volts available.  20 amps times 115 volts is 2300 watts, so
theoretically you could have 23 irons running on the circuit.  However, if you
have them plugged into a series of extension cords or power strips, the latter
in particular having 16 gauge wire that is only rated for 15 amps (in short
cords), you may be pulling down the voltage (and heating up the wire) if
several extensions feed into one.  If the main wiring is 12 gauge, but 14 gauge
was used on the table outlets, that will also drop the voltage somewhat.

On the other hand, what kind of steel are you soldering?  I would expect any
reasonable chunk of steel (say 1/8" x 1/2" angle or bigger) to be beyond the
range of a 100 watt iron.  If you are doing thin sheet, it might be reasonable.
Do you have success soldering the same steel when you use an iron working
alone with no other irons on?

Mike Firth, Hot Bits furnace glassblowing newsletter

### Electrical specs for soldering irons

Tim, if it is a true 20 amp circuit, the outlet should have a one of the
holes T shaped as well as the 20 breaker and correct wire size. Breakers
should not be run above 80% of their capacity. If it is an old breaker and
has had a few trips in its life it may not even carry 80%.  You could have a
dual set of outlets available, one for full power to get rapid heatup and
the other thru the usual controller. A large enough controller can service
several irons for students but gives up individual adjustment. Typically for
a resistive load like irons you can use the volts times amps for watts and
so forth.
Using a "quad" outlet box, you can have 2 outlets and a dimmer on a
convenient cord. Sometimes I stick a night light in one to show that it is
on. Will send an Epicture if you want.
Doug

### Electrical specs for soldering irons

writes:

Quote:
> Tim, if it is a true 20 amp circuit, the outlet should have a one of the
>holes T shaped as well as the 20 breaker and correct wire size.

Beg to disagree, somewhat. (Sayeth he who passed the City of Dallas test to
rewire his own house including the service entrance and then did it.)

A 20 amp outlet is only required when an appliance or tool is to be plugged
in that needs more than 15 amps (and less than 20.)  The appliance must have
one prong perpendicular to the other.  A 20 amp outlet may have either the same
arrangement of slots (or much more commonly) one t shaped slot to permit 15 amp
parallel prong plugs to go in.
The purpose of the breaker is to protect the wiring (and the house) so every
inch of wiring attached (in the walls or desks, etc.) must be 12 gauge rather
than the 14 gauge used with 15 amp wiring.
The outlet(s) at the end may be the 15 amp arrangement or 20.  Most houses
today have 20 amp breakers, 12 gauge wiring, and several (max is 6 I recall) 15
amp outlets, on the circuit.   The durability of a 15 amp outlet and plug, if
someone forces it to pull 19-20 amps, is another matter.  Notice that a 20 amp
breaker would, in theory, allow the 15 amp rated cord leading to an appliance
to slowly burn up, without tripping, if it were pulling 18-19 amps, but
usually, this does not happen because things are somewhat overrated and
appliances do not normally partly fail.  However, sometimes people use under
rated extension cords and then run them under carpets, etc., and then we hear
about a fire on the news.

Mike Firth, Hot Bits furnace glassblowing newsletter