Handskit T12 hotair/heat gun (t12 clone) - is it safe? [DONT BUY IT]

[dinth]

Hi. I just received a Chinese t12 hotair station. After unpacking it I thought that I will check what is inside and found out that the the electric grid L is most likely permanently wired to the handle. Is it safe? Or maybe I'm mistaken about the handle being wired to the electric grid? Do you see any other concerning design faults or problems here?

[tszaboo]

Looking at this two pictures, I cannot decide what's worse. The design or the assembly...

[dinth]

Is there anything i can fix myself on this board? Will it be safe to use?

[nvmR]

Regarding assembly, Q1 would enjoy some more solder on the tab.

Regarding safety, (with the device turned off and out of the electricity), try to buzz with a multimeter the L, H and the metal parts on the handle, and anything else metal that you can touch while using.
There is an optocoupler on the board, so at least somethings been done right.

[dinth]

The ground pin is not connected to anything, including the metal parts of the case - im not sure what PAT category this device belongs to and if it should have grounded case.
I have tried measuring continuity between L, N and various exposed parts of the case and there's no continuity anywhere. I can dig out a professional testing meter which can measure isolation resistance at 500 and 1000V if thats gonna be helpful and will not damage the soldering station.
But when the handle is disconnected, there's a direct connection (0Ohm) between L and the middle pin of the handle socket, which is exposed without the handle connected.

[Gyro]

Looking at this two pictures, I cannot decide what's worse. The design or the assembly...

I've seen worse. Sure the hand soldering isn't the neatest but the board clearances seem mostly respectable, it uses a fused IEC connector (or maybe switched - I can't tell. Check the fuse rating).

The main thing I notice is that the permanent live track runs close to the connector earth connection, and rather more importantly, the Earth connection doesn't seem to go anywhere, just to a couple of plated through holes on the PCB. Without seeing the head and case It's impossible to say whether it's a Class II double insulated product or not. If not, then there should certainly be earth wire connections to the case, if it is metal, and any exposed metalwork on the head (I'm not familiar with the T12 hot-air).

Regarding permanent live going straight to the element in the head (and the Triac in the Neutral), it's debatable, I suppose ideally it would be in the Live feed,  but Triacs can fail short circuit too, and it puts less dielectric stress on what may or may not be a high quality opto.

The safely, or not, mainly rests in the design of the head and whether there is some form of safe connector between to two (or whether it is direct wired).


EDIT: From your above post, it sounds as if you definitely have a problem with connector safety and non-earthed metal case. The second is easy, the first not so much (unless you can permanently secure the plug).

If it has a connection in the head cable that goes to the head metalwork then you should definitely earth it. Otherwise, if it doesn't pass an insulation test at 500V, then it is unsafe to use anyway (regardless of whether it breaks it).

[Ian.M]

The worrying thing is the two unsoldered holes at the end of the ground (mains PE) track in the bottom photo.  It doesn't go anywhere top-side so I am certain nothing is properly grounded.  Edit: I see you've just confirmed that.

The hot air tool is likely to have exposed metalwork and if ungrounded it *MUST* have reinforced insulation between any mains circuits and the exposed metalwork.   If you post teardown photos of the tool we can check if it appears to have appropriate insulation, and creepage and clearance distances.  If not, we may be able to suggest how it could be grounded to make it safe. 

Similarly front panel metalwork (if any) must either have reinforced insulation or be grounded, so we need to see photos of it, both exterior and inside. Edit: including a closeup of the socket for the tool with the plug removed.

As adequate creepage and clearance distances are important, please take the photos with a ruler with millimeter divisions in each, at the same distance from the camera as the part being photographed.

[dinth]

More photos including the handle

[Ian.M]

That's unsafe with no way to make it safe except if you can replace the tool connector on the front panel with a female connector rated for 250V AC, put a matching male connector on the tool cable + ground all the exposed metalwork.

It looks like there *may* be a ground wire to the tool heater barrel, going to the yellow wire in the cord, but as it isn't connected to mains PE it isn't doing any good.  You'd need to trace the circuit at the controller end to see if that wire could be tied to PE to ground the barrel.

[tszaboo]

Regarding assembly, Q1 would enjoy some more solder on the tab.

Regarding safety, (with the device turned off and out of the electricity), try to buzz with a multimeter the L, H and the metal parts on the handle, and anything else metal that you can touch while using.
There is an optocoupler on the board, so at least somethings been done right.

The TO220 package is not designed to be soldered down. I don't think it has the necessary platings to be able to be properly wetted by solder.

Looking at this two pictures, I cannot decide what's worse. The design or the assembly...

I've seen worse. Sure the hand soldering isn't the neatest but the board clearances seem mostly respectable, it uses a fused IEC connector (or maybe switched - I can't tell. Check the fuse rating).

The main thing I notice is that the permanent live track runs close to the connector earth connection, and rather more importantly, the Earth connection doesn't seem to go anywhere, just to a couple of plated through holes on the PCB. Without seeing the head and case It's impossible to say whether it's a Class II double insulated product or not. If not, then there should certainly be earth wire connections to the case, if it is metal, and any exposed metalwork on the head (I'm not familiar with the T12 hot-air).

Regarding permanent live going straight to the element in the head (and the Triac in the Neutral), it's debatable, I suppose ideally it would be in the Live feed,  but Triacs can fail short circuit too, and it puts less dielectric stress on what may or may not be a high quality opto.

The safely, or not, mainly rests in the design of the head and whether there is some form of safe connector between to two (or whether it is direct wired).


EDIT: From your above post, it sounds as if you definitely have a problem with connector safety and non-earthed metal case. The second is easy, the first not so much (unless you can permanently secure the plug).

If it has a connection in the head cable that goes to the head metalwork then you should definitely earth it. Otherwise, if it doesn't pass an insulation test at 500V, then it is unsafe to use anyway (regardless of whether it breaks it).

There should be something, like 10MOhm between the tip and earth as minimum. That isolation is a joke. Someone made the effort to place a slot in the board and then the earth is routed within a millimeter? And the isolation slot doesn't cover all the way?
The entire construction is a joke. They cut into the solder on the pins?
It would make a good exercise to see who can spot more issues with it.

[Gyro]

Ouch, yes. That connector is a thing of nightmares! 

Finding a touchproof replacement of similar size, with the right number of pins is unlikely (a male female swap might be a possibility, but I don't think they make them. Tightening the locking ring after applying a permanent threadlocking compound might be a possibility, with an appropriate warning label, for personal use. It's a one way process though as you would no longer be able to get to the cable terminations.

Yes, it does look as if there may be a ground wire connection to the heater barrel. You would want that directly connected to earth - a heater insulation breakdown would need a low impedance fault path. Speaking of which, running the barrel earth connection though that blob soldered PCB isn't ideal, it would be better to use a crimped or mechanically sound and soldered, heatshrinked connection.

With those, and the earth connection to the case addressed, you might be set for reasonable personal use (not left unattended with mains power switch on). Returning and buying a genuine (hopefully better) alternative is the other path.

[dinth]

Thank you for your help!
Just as a warning here is the link to the product page on Aliexpress: https://www.aliexpress.com/item/1005002965789645.html?spm=a2g0o.order_list.0.0.45e2d2d6yDj6D1
To be fair, on one of the photos there is a warning that there is 230V on the connector, but i assumed that this will be 230V going through some kind of isolation transformer, not connected directly to the mains.

[Gyro]

That photo is rather an admission of guilt and premeditation rather than a warning. A responsible manufacturer removes such a product from the market after a customer (presumably) reports it. I guess it was some sort indication to a knowledgeable buyer that immediate remedial action would be required though.

At least they put the mains live on the centre pin. It means maximum isolation from the connector shell (which is of course currently floating) if you can make it permanently non-recoverable.


P.S. It does look as if they've made a reasonable attempt at element insulation. There is a minimum of 2 layers of glass or mineral fibre sheet between the element former and barrel, but you're heavily dependent on assembly quality. You would want the barrel earthed for ESD purposes in any case.

[dinth]

Do you have any recommendations for a cheap and small hot air station though?
I used to have a bigger (and probably better) one in the past, but i sold it because didnt have space + i avoid anything SMD.
But now i do have a small SMD job (removing a few caps), which i cannot do with a normal soldering station, so i bought this hot air station just to do that (and potentially in the future for other small smd jobs).

[BrokenYugo]

Quick 957DW+ seems to be the bottom dollar for something somewhat reputable, not sure if that comes in 240V though.

Avoid entirely the blower in handle stuff, AFAIK they're all like that with mains in the handle and generally crappy/hazardous design/build.

[dinth]

Just a couple of screenshots from the conversation with the seller.
A couple of hours ago he was trying to persuade me that the output voltage is only 24V so there is no shock risk, showing me a photo of his own unit as a proof...

and now he's trying to prove to me that the unit is properly grounded, again showing me a photo of his unit... which now has a ground cable soldered to the earth pin 

What kind of joke is this?

[mastershake]

this looks a lot like the older earlier ksger ones. they re did their hot air ones. still not the best but much nicer then this at least the newer style ones are.