Can the NEC PM use PD comments on the design to instruct changes? The Principal Designer in this case works for the same company as the NEC PM, as the Employer has sub contract both services to them. Specific context being that the design is compliant with CDM and the Works Information but the NEC PM and by association the PD are of the opinion that changes would improve maintenance requirements. The changes are minor but fairly frequent and result in re-draft after re-draft of the design. The PM has instructed many of the changes however within the instruction references that they are Principal Designer recommendations and thus are not a CE to the Contractor.
If the PM is instructing you to do the change suggested by the Principal Designer, then it is a compensation event under clause 60.1(1) regardless (but assuming it is not due to the two bullets in that clause).
If the Principal Designer is making ‘nice to have’ comments and your existing design COMPLIES (in capitals because that is the important word) with the Works Information and CDM, then the change would not arise from your fault, so it you would be entitled to not just the direct changes but also the re-work and any subsequent delay.
If however, it didn’t, and the PM was instructing changes to make it compliant, then while it would be a CE, it would arise from your fault with a zero assessment under clause 61.4
So answering your question literally, ‘Yes’ the PM can