I have a Peerless 85-140-WPC-H (or WRS) boiler. I use it for a heat pump backup, domestic hot water, and a heater for my small shop. I am getting a new heat pump and a tankless hot water heater. I would like to keep the boiler as a backup for the new heat pump. One tech told me that was his recommendation. Another wanted to install 2 tankless systems and use one for the heat pump backup, as he said the water in the boiler would always be hot, even when I wasn't using it. Which one is right?