return grilles pressure loss

[nausicaa]

where can i find the the return grille fitting loss
i m trying to calc. the pressure loss in the duct work from return air duct to heat pump

thanks

[nausicaa]

the size is 26 by 33 in. i dont really know the spacing. how do i check if there is any volume damper on it?

[johnl45]

We use .03 iwc