navien ncb 240

I had a plumber replaced my boiler and water heater for a Navien combi. I have nothing but problems. the house is a multi family house, currently 4 apartments. The heat is not hot enough to heat each apartments. the plumber is telling me that due to a high demand of hot water, the boiler can't...

I have a Navien NCB 240E combi-boiler set up for hydro space heating and domestic hot water (installed 2019) I am having an ongoing issue and can't figure it out. My domestic hot water side is set to around 125 F. When I turn on a faucet to call for hot water, the flow rate is 0.6 GPM. The...