Boiler Piping Flow & Pipe Sizing | HVAC Hydronics
Boiler Flow Rates Explained - Local Boiler Quotes
9 litres of water weighs 9 kilos, so the flow is 0.15 kg per second. So we get 0.15 x 50 x 4.2 = 31.5 kJ/sec (1 kiloJoule per sec = 1 kiloWatt) ( rapidtables.com/convert/electric/kj-to-kw) Which broadly means you need something like a 31.5 kilowatt power output on your boiler without allowing for any inefficiencies.
A big danger that is posed by faulty heaters is the risk of carbon monoxide poisoning which occurs when a gas heater is not properly ventilated. You can expect a tanked water heater to last for about 12 years while tankless water heaters last for 20 years. The cost of replacing a tankless heater is high although the cost of maintaining it is low.
4 Signs Your Faulty Boiler Could be Dangerous
What Is The Best Combi Boiler Flow Rate | Protech Boilers