Dear @MikeJH,
You can use FSV 5051 yes, it’s the same. However, I don’t know if only setting 5051 sets any cap of the compressor frequency. I previously read that there’s only 2 options to cap the compressor once 5051 is set to enabled. It’s either through a 0-10V entry on the MIM board, or by setting the 42F1 modbus register.
Either it’s that there is an implicit cap value (I’ll confirm that), or that the weather condition changed…
Given my experiment and monitoring, quiet mode is somewhat a FRC, but it has adverse effect. Also FRC is enabled also for DHW cycles. On my setup (gen 7 r290 5kw), it takes longer to heat up the water tank, but it never consumes more than 1kw, and the CoP is much better, as it takes longer to reach the top water flow temperature compared to uncapped behavior.
Cheers
