[en] An improved zero-dimensional model which includes a coronal non-equilibrium treatment of impurities and which takes into account the ionization energies of deuterium and of the impurities in the energy balance for a Reversed Field Pinch (RFP) device, is applied to the study of the ZT-H device. The ZT-H device is designed to operate at 4MA and the simulations focus on 4MA operation. The studies include: (i) the effects of different (IN); (ii) the effects of changing /tau//sub pi/, the particle lifetime of the i/sup th/ impurity species; (iii) the effects of having different levels of carbon inpurity; (iv) the sensitivity of the model to C/sub 4RP/, the multiplicative coefficient for the ramping phase which is used in the ion heating term; and (v) the effect of keeping β/sub theta/ fixed at 0.1 in /tau//sub Epsilon/ rather than computing β/sub theta/ from its definition. The results show that T/sub e/ and T/sub i/ are essentially identical and vary approximately proportionately to (IN). The effect of doubling the impurity recycling time /tau//sub pi/, from 5 ms to 10 ms, results in T increasing by a factor of approximately 1.6. High levels of carbon impurity are damaging to temperature behavior, e.g., increasing the carbon impurity from 5% to 10% of the n/sub e/, requires increased ohmic heating by 20% in order to reach T = 3130 eV for (IN) = 6.0 /times/ 10/sup /minus/14/ A/minus/m. The model is not sensitive to small changes in the ramp coefficient C/sub 4RP/. The effect of keeping β/sub theta/ constant at 0.1 is to produce higher temperatures over the cases where β/sub theta/ is not held constant. For example when (IN) = 3.0 /times/ 10/sup /minus/14/ A/minus/m and /tau//sub pi/ = 5.0 ms, there is an increase in T by a factor of more than two. Also with β/sub theta/ constant at 0.1, the confinement times are higher. 5 refs., 29 figs., 3 tabs