Quick Question - re combi boiler/tankless hot water heater

[Haim1824]

Hello - I am in the process of a whole home renovation in Maryland which includes all new plumbing. Home will have 6 bedrooms, 4 full baths (3 shower, 1 tub), 2 sets of washer/dryers. It is possible that on any given morning two people will be showering at the same time the washer and dishwasher will be running. It seems from my calculations (assuming ~60 degree temp rise) that I will need more (around a minimum of 8.5GPM. It looks like the NFC-250/200H can provide 6GPM at 60 degree rise. Plubmer suggested that the NFC-250/200H should be more than capable to heat the radiators in the house and be sufficient to provide hot water for showers, dishwasher, etc. Are my calculations wrong? Plumber mentioned the possibility of a linked storage tank. Wouldnt it make more sense to add another tankless heater to provide enough GPM?

Thanks,
Adam

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[Breplum]

It is often said that separate heat sources makes servicing so much simpler.
As a plumber who does not do hydronic heating professionally but has worked on numerous combi units to repair, I have to say that separate makes life simpler and easier to diagnose too. The repairs if needed are easier when separate because the mfr is not trying to cram everything into one case.
Always go with the highest AFUE you can afford, such as Navien NPE A2 series for domestic hot water.