# Thread: Niagara AX- Need a Pressure Temperature Conversion block

1. Professional Member
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This can be done with kitControl math blocks and a little help from excel's Trendline feature. Copy and paste the temperature vs pressure values in to excel. Convert to PSIA and Deg R (curve fitting works better). Create a graph and try the various Trendlines until you get a good fit. I came up with this for R134a. y = 0.00003561 x^3 - 0.01308796 x^2 + 2.12259171 x + 421.11910836 With x = PSIA and a range of 20.7 to 149.7 and y = deg R.

2. Could I get a copy of the program objects also, email is in my profile, Thank you.

3. Originally Posted by DaveCR
I came up with this for R134a. y = 0.00003561 x^3 - 0.01308796 x^2 + 2.12259171 x + 421.11910836 ]
nice work ... though I think it maybe time to make a generic curve-fit Program Object to the 4th or 5th order.

...maybe even have an Enum setting for different refrigerants

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Thanks. For 134a:
y = 9.20621E-10 x^5 - 6.26875E-07 x^4 + 1.65989E-04 x^3 - 2.26106E-02 x^2 + 2.14070E+00 x - 1.32707E+01
Input pressure range (PSIA) 14.7 to 244.7. Output °R. This turns out to be quite a good fit with R squared = 0.9999
Last edited by DaveCR; 01-27-2013 at 11:44 AM. Reason: punctuation

5. Originally Posted by DaveCR
This can be done with kitControl math blocks and a little help from excel's Trendline feature. Copy and paste the temperature vs pressure values in to excel. Convert to PSIA and Deg R (curve fitting works better). Create a graph and try the various Trendlines until you get a good fit. I came up with this for R134a. y = 0.00003561 x^3 - 0.01308796 x^2 + 2.12259171 x + 421.11910836 With x = PSIA and a range of 20.7 to 149.7 and y = deg R.
I've been attempting to set this up all morning for R410A and I can't seem to figure out for the life of me how to get it to output properly. I know lynxspring has an actual conversion block in their lynxKitControl, but unfortunately it only works with their certificate on the JACE.

Anyone else sucessfully made this work for 410?

6. Originally Posted by noskilltech
I've been attempting to set this up all morning for R410A and I can't seem to figure out for the life of me how to get it to output properly. I know lynxspring has an actual conversion block in their lynxKitControl, but unfortunately it only works with their certificate on the JACE.

Anyone else sucessfully made this work for 410?
I have a program object for 134 that you could probably change the pressure-temp tables in for 410.

7. I'll send you an email here in just a second. Thanks

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Does anyone have a program object for refrigerant pressure temperature (R410a) ?

9. I have one, send me your email.

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