psychrometric chart question

[thunderspeed]

I'm trying to understand the following :

I have for a point :
tdb = 84.7 F
twb = 75.6 F
when i enter then [(IP units)psychro chart] to get enthalpy , it comes out to be :
h=39.1 btu/lb
now i need my enthalpy to be in (SI units) to I convert the 39.1 to be :
h= 90.94 KJ/Kg
ok , now I worked this another way ,
I transformed tdb and twb from F to C
tdb = 29.27778C
twb = 24.22222C
then entered the [(SI units)psychro chart] to get enthalpy the outcome is :
h= 73.3 KJ/Kg

I cant figure out what is the reason for the huge difference between the 73 and 90 of h in SI
can anyone help ?

[The MG Pony]

Dude don't be an A-hole and spam, seriously

[thunderspeed]

Dude don't be spam, seriously

you are only allowed to answer the question if you know the reason of this problem ,
so if you find it something that easy , go ahead and clarify . no one knows every thing .
other wise you'd better shut up and behave till someone answers .

[Brian_UK]

you are only allowed to answer the question if you know the reason of this problem ,
so if you find it something that easy , go ahead and clarify . no one knows every thing .
other wise you'd better shut up and behave till someone answers .To reiterate his comment, only post a single question once​​​, ​do not multi post the same question across the forum like spam.

[Magoo]

Thunderspeed.
search http://www.kwangu.com/work/psychrometric.htm

[sterl]

The base points are different for the (2) charts....Neither of them are working in absolute numbers, each has a different definition for "zero enthalpy". See:
http://www.engineeringtoolbox.com/enthalpy-moist-air-d_683.html