13 Pa.C.S. § 2612: "Installment contract"; breach.

(a) Definition of "installment contract".--An "installment contract" is one which requires or authorizes the delivery of goods in separate lots to be separately accepted, even though the contract contains a clause "each delivery is a separate contract" or its equivalent.

(b) Right to reject nonconforming installment.--The buyer may reject any installment which is nonconforming if the nonconformity substantially impairs the value of that installment and cannot be cured or if the nonconformity is a defect in the required documents; but if the nonconformity does not fall within subsection (c) and the seller gives adequate assurance of its cure the buyer must accept that installment.

(c) Breach.--Whenever nonconformity or default with respect to one or more installments substantially impairs the value of the whole contract there is a breach of the whole. But the aggrieved party reinstates the contract if he accepts a nonconforming installment without seasonably notifying of cancellation or if he brings an action with respect only to past installments or demands performance as to future installments.