There is no preferential payment if an old creditor is just replaced w/ a new one.  Ex.  Owe Creditor A 50k and get loan from Creditor B to pay creditor A.
a.    Debtor needs to not have control over any of the debt.  For this to work, need to clearly indicate in loan documents that money will go directly to A—never under dominion and control of the debtor and so never his property.  If the debtor simply tells the bank to pay—that looks like he had control, and the doctrine won’t apply.
b.    If new creditor gets SI, when old creditor had none, trustee will try to avoid that SI as an indirect preference.  In above example, say that B got a 20k SI and A had no SI.  The 20k SI won’t look like a transfer for antecedent debt b/c it was only given when 50k provided by B.  Trustee will argue that it was for the benefit of A, and thus transferred on account of antecedent debt—so should be avoided as indirect preference making B unsecured.  At that point, B may try to sue A to get money back since this is not what he bargained for.