How to pipe a HW heater with a tankless heater in the boiler. I want to use both sometimes and just the HW heater sometimes. Where to place the valves?

How to pipe a HW heater with a tankless heater in the boiler. I want to use both sometimes and just the HW heater sometimes. Where to place the valves?
Are you asking for a by-pass set up where you can cut a heater in and out of the system like a water softener by-pass, (see imige)? To cut the heater into the system open valves one and three and leave valve two closed. To cut the heater out of the system close valves one and three and open up valve two. Be advised that while this set upwill work it's not good practice to seal off both hot and cold supplies and still keep the power on to the heater.Good luck, Tom

Speedball1

I presently have a oil fired hot water boiler with a tankless heater for the domestic hot water. I would like to install a new electric hot water heater and use it primarily in the summer months and turn off the oil fired boiler, valve off the tankless heater and drain the coil. I would also like to keep the electric water heater in the circuit during the winter months and have the tankless heater feed hot water into the tank. I'm not sure where to put the winter/summer shut-off valves and perhaps check valves. Can you help me?

mtetter

Speedball1

I presently have a oil fired hot water boiler with a tankless heater for the domestic hot water. I would like to install a new electric hot water heater and use it primarily in the summer months and turn off the oil fired boiler, valve off the tankless heater and drain the coil. I would also like to keep the electric water heater in the circuit during the winter months and have the tankless heater feed hot water into the tank. I'm not sure where to put the winter/summer shut-off valves and perhaps check valves. Can you help me?

Mtetter


I would also like to keep the electric water heater in the circuit during the winter months and have the tankless heater feed hot water into the tank. This isn't going to fly. Are you proposing to run the tankless into the boiler and use the boiler as a storage tank in the summer? Your tankless is a "on demand " heater. What's going to keep the water hot in the boiler when the tankless isn't calling for a draw? It's like joining two systems together, one "on demand" and the other "storage". It could work , after a fashion. With a regular electric water heater because you have two storage boilers but not with a tankless. Sorry, tom

Speedball1

What I have is this. An oil fired boiler that generates hot water for my house baseboard heating system. Contained within the boiler is a tankless heater that is heated by way of the firebox in the boiler. The tankless heater is used only for domestic hot water. It has a separate CW supply to the heater and is not in any way connected to the house heating system. The hot water exits the tankless heater and into a mixing valve and thence to the house plumbing fixtures. This is the only hot water source for the house and therefore the boiler has to run 365 days/year. I would like to install a NEW electric hot water heater and pipe it into the existing cold water supply and the existing domestic hot water to provide hot water during the summer months and turn off the boiler, thereby avoiding the $800.00 fuel oil bill that I incurr for the summer. I can pipe the EWH into the existing system with values to bypass the boiler tankless heater. What I need help in doing is how to pipe the system and still use the boiler tankless heater as well as the EWH during the winter months. I invision a HW pipe from the tankless heater into the CW supply of the EWH. Would I need a check valve to prevent HW from back feeding into the CW system? Your help in resolving this situation would be appreciated.

mtetter