If this panel u mention is your main panel they MUST be connected and as you describe is right. However if this is a sub panel they MUST NOT be connected.
My bet is the appliance guy does not know what is wrong and is trying to pass the buck It sounds like the electricians have got your back.
My bet is the appliance guy does not know what is wrong and is trying to pass the buck It sounds like the electricians have got your back.