Soldering iron earthing

[Irilia]

I'm surprised to not have found a topic about that.
I'm looking to earth my solder iron, but I think I need a resistor between the earth from the electrical circuit and the tips of the iron.
So I need to know the value
If there is anything I need to consider please tell me.
Best regards.

[Zero999]

Every mains soldering iron I've used has been earthed.

Are you talking about a battery powered iron?

[Irilia]

T12 soldering iron (the majority are not connected to earth.)

[Ian.M]

Ref: NASA-STD-8739.3, section 6.4.3 (page 30):

6.4 Tool and Equipment Control
...
   3. Power tools used during the soldering process shall comply to the tool requirements herein and have a three-wire grounded power cord. The area making contact with the workpiece shall be grounded. When measured from the workpiece contact point to ground, the resistance shall not exceed 2.0 ohms and the potential difference shall not exceed 2 millivolts root mean squared (RMS) using methods indicated in the supplier's engineering documentation.

Irons with mains voltage elements should *always* have a grounded tip (no series resistor).
 
Low voltage irons are a different matter if you aren't an aerospace contractor.  If the max. potential on the tip due to leakage currents and capacitive coupling to the element is small enough (i.e. no more than a few hundred mV so it cant significantly forward bias a silicon PN junction), a non-grounded tip with provision to dissipate ESD is probably acceptable.

[Xena E]

So as an antistatic precaution?

A 470k resistor to a good PE ground point would suffice. I wouldn't recommend tying to anything else.

X

[Xena E]

The T12 is 24Volts maximum, not mains.

Most stations/handles they use are functionally double insulated.

X

[madires]

Usually the tip / heating element is connected directly to PE / earth, also for 24V irons.

[Karel]

Weller WS81 soldering station grounding:



I use a 1MOhm resistor connected to the earth terminal of the AC outlet.

[wraper]

T12 soldering iron (the majority are not connected to earth.)

Just measure resistance between the iron and the earth terminal on mains plug. In the past I worked at mobile phone repair shop where a few technicians ran a wire from iron of Weller soldering station to earth because someone told them it should be earthed. I was like - WTF dude, it's already earthed from factory.

[CaptDon]

It seems all safety standards point to the tip being tied to P.E. with very low resistance. I still often use the old Ungar 'wood burner' style with the ceramic heater and the screw-in tips. Those are not bonded to P.E. in any way since they have a two wire cord. They actually show a few microamps of mains leakage probably due to capacitive coupling in the element. Tips bonded to ground is sort of a double edged sword. I would never be holding the metallic part of a hot iron so I am not concerned about the shock hazard and it wouldn't bother me to have maybe 100K ohms between P.E. and the tip. My uncontrolled ceramic heater irons float, my temperature controlled workstation irons are earthed. I am o.k. with either but use common sense thinking about possible gate damage when repairing equipment containing MOSFET's like SMPS's or MOSFET power amplifiers.

[Xena E]

... but use common sense thinking about possible gate damage when repairing equipment containing MOSFET's like SMPS's or MOSFET power amplifiers.

 

This

A tip with a few hundred kilohms to earth is best for leaking away static charges that are built up when soldering sensitive components, where a low impedance ground connection can cause damage with an instant discharge... I  think that this is what the TS was eluding to.

A double insulated station, or soldering gun should not cause personal danger if it doesn't have an equipotential grounded tip, though personally I wouldn't want to use a floating tip on a cheap mains firestick iron. (Unless I was doing live soldering )

[Irilia]

The fact is your will generally inject some statics electricity if you aren't connected to earth yourself this will not affect the majority of the electronic, but if you add the iron actually not connected to earth either you will have an infinite potential and will kill some components (ask how I know) (the components will not be affected if the electronic is totally not powered at the time, but if you want to do any soldering on a powered board (insulated from  the main or on battery, you need the solder iron to be earth but you don't want the earthing to bite you in case of electrical problem for example.
Also nitrile gloves don't avoid you pushing some statics electricity to your pcs, you have a simple proof about that by the fact you can use your phone with this type of gloves.
So in conclusion it's interesting to see not everyone is ok about what values we should use for the resistor (I was thinking it was a basic question 😅 because I see a lot of video talking about it but no one saying more than your solder iron Tips should be connected to earth.

[Irilia]

So what do you consider is best 100K or 470K ?

[madires]

It depends on your goal. For example, for just handling ESD 1 MOhm would be standard.

[Irilia]

Yes it's what I was asking, so it looks perfect at 1M