Flow regulating valve necessary?

zepfan

We need to replace a tankless heater coil on a 20 year old oil fired boiler, residential The manufacturer shows a flow regulating valve on the line line for the cold water inlet to the heater. Is this necessary, and if so what is the purpose of it? The reason I ask is there isn’t one currently, and it seems to have been ok without it for 20 years. The piping does have an existing adjustable three way mixing/tempering valve that was recently replaced. Thanks to all

bburd

The flow regulating valve ensures that the hot water flow rate does not exceed the ability of the coil to heat it to an adequate temperature.

This dates back to the days before low flow showerheads. It is probably less of an issue today.