The difficulty with this configuration is that in order for the tankless water heating unit to turn on the burner it requires flowing water. The recirculating pump does not draw enough water to guarantee that the burners turn on so for that reason another option needs to be produced to have a hot water configuration that includes a tankless water heater and a recirculating pump. Tough water will damage a tankless water heating unit. Obstacles with a tankless water heating system is that they require a flow of water to turn the burner on. I can then turn on the hot water and not notice any cooling of the water due to the fact that the tankless water heating unit is mixing water into the recirculating loop.

Plumbing Care, Inc.