Heater blanket

[SM2GXN]

Hi!

Here's some thoughts
My curiosity lead me to open a rubber block containing the thermostat on a heater blanket that didn't work well, the blanket which is made of rubber is used to warm up a R134a refrigerant tube for car A/C in order to speed up the refrigerant R134 transfer from the tube you simply wrap it arround the tube.
The blanket is made in just about the same manner as floor heating but wires are much closer to get a more even spread of the heat, I think.
Inside the rubber block I found 2 thermostats in series, started to check for data sheets on the web and found them 120VAC 6A for each, check this link: http://www.elfa.se/pdf/69/06937981.pdf.
Now, what do you think? Did the designer put these thermostats in series in order for the blanket to work safe on 230Vac or did he just do it for fun?
I belive that there are no thermostats that will close and open exactley at the same time even if they are pretty well matched, I'm talking bimetallic thermostats.
My conclusion is that one of the thermostats will have to take the whole mighty 230Vac cause they will not close nor open at the same time.
This blanket is made in US, could this version with two thermostats in series be for countries with 230Vac? 
Let me know what you think...

 

[ante1]

Hi,

Car A/C service? Haven’t checked your outside temperature lately? ;D
I don’t think this would in any way compensate for the voltage. But it might be as an extra safety measure. How much current is put trough the circuit? It might be possible that at 3A or a little less these switches are suppose to survive 230V. Anyway I think this is bad engineering and I doubt the Swedish board of electric safety has seen this!

 

[SM2GXN]

Hi Ante!

Well it's -2 to here so it's time to switch on the A/C  ;D

Anyway I think this is bad engineering and I doubt the Swedish board of electric safety has seen this! Shocked

I don't think so it might have got in to Sweden by the "unknown black freighter"  ;D
I don't remember but not much current passes through those switches, maybe 2-3 amps (as you were guessing) I was more worried about the maximum voltage.
yes indeed it is bad engineering at highest level, here's what I did I bought another thermostat from Elfa 37-920-09 and some silcone rubber, made a small box with double sided pcb over the blanket thermostat and filled it with rubber silicone it took nearly 2 weeks to dry  ;D but it sure works.

 

[ante1]

Well, it sounds like we could put the “S” marking on it as soon as the silicone has dried! 

 

[SM2GXN]

;D ;D
Honestly I liked the old "S" marking better, this CE and all the other labels they put on all electronic devices means nothing to me, you don't know if they just have a big pile of labels in a box and when they think it's ok they just put on theirs product, not to talk about EMC it's a big joke  ;D
Ooops!!!

 

[ante1]

I feel that sometimes they don’t have the knowledge or the common sense to make the wise decisions that this requires.  :-\