Driving a Delta Load with a Wye
There is no problem when connecting a Delta configured load to a Wye source. 
In that case you do not connect the neutral wire. The wire to be connected to the metal case of the heater should be your earth connection. Somewhere down the line the earth and neutral come together again. That however is not visible here. 

Beware of the voltages the delta load voltages. The voltage measured across the lines must be the same. Therefore not the WYe voltages against the neutral.

The information at the end of your question is not clear at all.