MCA and accurate sizing of transformers

[WastefulMiser]

Based solely on MCA information from an HVAC vendor what is the best method for sizing a transformer to keep it as minimum as possible without undersizing the transformer?

Is it safe to use (0.8*MCA)=A? Or should they provide FLA for the HVAC?

 

[shamsdebout]

Based solely on MCA information from an HVAC vendor what is the best method for sizing a transformer to keep it as minimum as possible without undersizing the transformer?

Is it safe to use (0.8*MCA)=A? Or should they provide FLA for the HVAC?

It is safe to use 0.8*MCA, however it maybe that your FLA is actually much less. I do think that without the FLA info that is a good approximation. I have seen people use the MCA for the rated current, I am not comfortable with it.