UL Listing - no switch, no fuse on a heating device? - Page 1
Forum section: electronics / general

author: rx8pilot
author_rank: Super Contributor
timestamp: August 20, 2015, 04:07:22 am
content: I just purchased a thermal wire stripper from a company called Patco. They are a USA based companyhttp://patcoinc.net/PTS-10.htmlThis is likely the lowest cost thermal stripper available.The device did the job I needed it to do. I stripped about 500 wires on the first day and it was so much easier than the mechanical strippers I had been using and there are no nicks or missing strands. That is the good part.Of course like most here, I was curious what they put in it. Four screws later - I found out. Not much at all. The mains wires go directly into the case with no strain relief and no switch. as I slid the guts out, I see the sole component is a transformer 120v to 4v. The mains wires go direct to it and the secondary goes direct to the heating element. No fuse, no power indicator, no switch, no thermal protection. Somehow they decided to put a UL logo on the back but I cannot imagine that this thing is not violating nearly every rule.Does anyone else think this a major flaw in a commercial product?Here is a photo:

author: amyk
author_rank: Super Contributor
timestamp: August 20, 2015, 05:31:12 am
content: The thermal+current fuse is buried inside the transformer.

author: rx8pilot
author_rank: Super Contributor
timestamp: August 20, 2015, 06:18:03 am
content: That sounds better. How do you tell visually? Is it assumed or an obvious feature?

author: amyk
author_rank: Super Contributor
timestamp: August 20, 2015, 01:52:05 pm
content: If the UL listing was real, it would probably be the case.Transformers with integrated fuses are quite common.http://www.imajeenyus.com/electronics/20121001_fixing_transformer_thermal_cutout/index.shtml

author: wraper
author_rank: Unknown
timestamp: August 20, 2015, 01:58:25 pm
content: Quote from: rx8pilot on August 20, 2015, 06:18:03 amIf the device is only transformer (+rectifier) in the box, that is almost 100% giveaway there is thermal fuse in the transformer.

author: SeanB
author_rank: Super Contributor
timestamp: August 20, 2015, 07:43:44 pm
content: Easy to see by the thick overwrapping of tape around the primary side by the leads. This covers a cardboard cover which in turn covers the thermal one time cutout. Probably a 130C 2A thermal fuse in there, under the tape and in good thermal contact with the outer layer of the primary winding.

author: rx8pilot
author_rank: Super Contributor
timestamp: August 20, 2015, 07:46:29 pm
content: I did not see any rectifier anywhere but I guess that could be wrapped up in the xformer as well.This kind of sucks though. If the thermal fuse is tripped, replacing it is either a pain or impossible. The other issues of not having a switch or strain releif on the mains wire entry is not good. Not even an indicator to remind me if its on or off.I now know why it is the lowest cost option for thermal wire strippers.Sent from my SAMSUNG-SM-G890A using Tapatalk

author: SeanB
author_rank: Super Contributor
timestamp: August 20, 2015, 08:34:36 pm
content: Why a rectifier on a heater element? If you want an indicator use a red LED and a 1k series resistor on the secondary, it will flicker a little but will work. that fuse can be replaced, after a little digging and cutting of the tapes to get it out. then put a new one in and use some kapton tape to cover it again.

author: wraper
author_rank: Unknown
timestamp: August 21, 2015, 09:44:19 am
content: Quote from: rx8pilot on August 20, 2015, 07:46:29 pmThere is no need for rectifier.

author: zapta
author_rank: Super Contributor
timestamp: August 27, 2015, 01:40:17 pm
content: Quote from: rx8pilot on August 20, 2015, 07:46:29 pmI have the Teledyne one and if I remember correctly it also doesn't have a visible fuse, just a momentary switch.Safety standards are sometimes surprising but if it is really UL approved it should be fine.