Superheat Correction facter for R12-TXV - R134a?

[The MG Pony]

Ok I have a Singer M:207C TXV for R-12 (Same as the american Control company TXV) it comes preset to 9F (-12C) superheat.

It is a 6,000BTU/hr unit (1.76 KW/hr) liquid cross charged head internaly equilized


I'm thinking I need to set the super heat higher for it to work correctly with R-134a correct?

Thanks guys for any Help.

Head pressure during pull down is 150PSI

[US Iceman]

it comes preset to ... (-12C) superheat. ...
I'm thinking I need to set the super heat higher for it to work correctly


You must have made some kind of error in your calculations.:confused:

If you are running a negative superheat, that is a unique kind of refrigeration system you are working on.:rolleyes:

If the evaporator has any appreciable pressure drop, the internally equalized valve may not remain stable no matter where it is set at.

[Josip]

Ok I have a Singer M:207C TXV for R-12 (Same as the american Control company TXV) it comes preset to 9F (-12C) superheat.

It is a 6,000BTU/hr unit (1.76 KW/hr) liquid cross charged head internaly equilized


I'm thinking I need to set the super heat higher for it to work correctly with R-134a correct?

Thanks guys for any Help.

Head pressure during pull down is 150PSI

Hi, The MG Pony :)

I think in this case this 9F means 5K or 5C but only like a difference, because the superheat we always write in K and K is always positive number, there is not negative temp shown in K scale at all.

So if you run your sistem at 9F(-12,778C) your superheat will be 18F(-7,778C) (difference of 9F or 5K or 5C)

For *****s it is Ok to have min of 5K, with ammonia you can go to 0K.

Best regards, Josip :)

[The MG Pony]

This is what I read off the TXVs manual it is presset to 9degrees fehren?

I guess there is no sort of correction facter eh? just a good thermometer and a set of guages and some time tuning it all?

But if it is going as a differance then is there some basic way to set it correctly to work with R-134a? IE Increasing super heat or reducing it slightly to match the R-12 curve.