diff --git a/tardis/plasma_array.py b/tardis/plasma_array.py
index 17f94953129..ecddb932d9b 100644
--- a/tardis/plasma_array.py
+++ b/tardis/plasma_array.py
@@ -374,8 +374,12 @@ def calculate_saha_nebular(self, delta=None):
         try:
             zeta = interpolate.interp1d(zeta_data.columns.values, zeta_data.ix[phis.index].values)(self.t_rads)
         except ValueError:
-            raise ValueError('Outside of interpolation area %s' % self.t_rads)
-        finally:
+            raise ValueError('t_rads outside of zeta factor interpolation'
+                             ' zeta_min={0:.2f} zeta_max={1:.2f} '
+                             '- requested {2}'.format(
+                zeta_data.columns.values.min(), zeta_data.columns.values.max(),
+                self.t_rads))
+        else:
             # fixing missing nan data
             # issue created - fix with warning some other day
             zeta[np.isnan(zeta)] = 1.0
diff --git a/tardis/tests/test_plasma.py b/tardis/tests/test_plasma_nlte.py
similarity index 99%
rename from tardis/tests/test_plasma.py
rename to tardis/tests/test_plasma_nlte.py
index 6837d295dd5..2ce54802d14 100644
--- a/tardis/tests/test_plasma.py
+++ b/tardis/tests/test_plasma_nlte.py
@@ -34,11 +34,11 @@ def pytest_generate_tests(metafunc):
     metafunc.parametrize(argnames, [[funcargs[name] for name in argnames]
             for funcargs in funcarglist])
 
-class TestNLTELTEApproximtion(object):
+class TestNLTELTEApproximation(object):
 
     params = {"test_He_ltelevelpops" : [dict(ion_number = 0),
                                         dict(ion_number = 1)]}
-    
+
     def setup(self):
         self.nlte_species=[(2,0),(2,1)]
         self.nlte_config = TARDISConfigurationNameSpace({'species':
@@ -100,3 +100,5 @@ def test_He_dilutelevelpops(self, dummy):
     def test_He_dilutelevelpops_isnotLTE(self, ion_number):
         lte_pops = self.atom_data.levels["g"].ix[(2,ion_number)].values * np.exp(- self.atom_data.levels["energy"].ix[(2,ion_number)].values * u.erg / const.k_B / self.plasma.t_rads / u.K).value
         assert not np.allclose(lte_pops, self.atom_data.levels["g"].ix[(2,ion_number)][0]*self.plasma.level_populations[0].ix[(2,ion_number)].values, atol=0)
+
+
diff --git a/tardis/tests/test_plasma_simple.py b/tardis/tests/test_plasma_simple.py
new file mode 100644
index 00000000000..1076acb8139
--- /dev/null
+++ b/tardis/tests/test_plasma_simple.py
@@ -0,0 +1,24 @@
+from astropy import constants as const, units as u
+import os
+import tardis
+from tardis import plasma_array, atomic
+import pytest
+#from numpy.testing import assert_allclose
+data_path = os.path.join(tardis.__path__[0], 'tests', 'data')
+helium_test_db = os.path.join(data_path, 'chianti_he_db.h5')
+
+
+class TestNebularPlasma(object):
+
+    def setup(self):
+        atom_data = atomic.AtomData.from_hdf5(helium_test_db)
+        self.plasma = plasma_array.BasePlasmaArray.from_abundance(
+            {'He':1.0}, 1e-15*u.Unit('g/cm3'), atom_data, 10 * u.day,
+            ionization_mode='nebular', excitation_mode='dilute-lte')
+
+    def test_high_temperature(self):
+        with pytest.raises(ValueError) as excinfo:
+            self.plasma.update_radiationfield([100000.], [1.])
+
+        assert excinfo.value.message.startswith('t_rads outside of zeta '
+                                                'factor interpolation')
\ No newline at end of file