In well-crystallized zeolites, the distribution of silicon atoms among Q(4)(nAl) clusters containing up to n = 4 framework aluminum (FAl) is well documented. Upon replacement of the alkali charge-balancing cations by protons and thermal activation of the original sieve, a solid acid is obtained. There are Lewis sites in nanoparticles of nonframework alumina (NFAl) created by the thermal treatment. The Bronsted sites are OH groups bridging framework silicon and aluminum. First, it is demonstrated that it is possible to estimate semiquantitatively heteronuclear second moments M(2)(Si-H) in acid zeolites having chemisorbed ammonia using an adapted Si-29 CP REDOR (cross-polarization rotational echo double resonance) technique. Then we show that, on this basis and with comparison with simple models, two kinds of bridging OH groups are distinguishable : (i) one donating its proton to NH3, forming NH4+ reorienting isotropically rapidly, and (ii) one operating as a proton donor to a strongly hydrogen-bonded ammonia. The strong Bronsted sites of the first kind are mostly located on Q(4)(nAl) with n = 1 while the hydrogen-bonded species as mostly associated with Q(4)(nAl) with n > 1. The higher the rate of polarization transfer is, the larger M(2)(Si-H). The largest M(2)(Si-H) is associated with the sites on which NH3 is hydrogen bonded. It is suggested that a noticeable fraction of the acidic OHs react with, and therefore are neutralized by, nonframework alumina. Moreover, preliminary information on an exchange process involving NH4+ is presented.