Indirect water heater addition.

[tmudd]

Howdy trusted gang of information. I cant describe enough what a great forum this is once you get the boiler bug. I am in the process of hooking up a used indirect that I came onto . After studying the Caleffi diagrams( pg. 44 Zdronics Domestic water heating /July 2012) on how to hook up in tandem with existing electric water heater, I have aquestion. Will it provide just preheated water to the water heater or will the indirect heat both of the tanks? The diagram relates to a solar application for the heat source. My heat source will be a supply /return off of primary loop from boiler hooked up to the heat exchanger inside the indirect . The diagram shows the domestic cold supply coming into the bottom of the indirect tank, and hot produced from the indirect going out the top of the tank to the cold side supply of the electric water heater. It then leaves the electic water heater hot side to the load and uses a mixing vlave to balance temperature. for domestic hot water use. If water is drawn out of the domestic electric water heater , I see how hot water can enter the electic tank. What I fail to comprehend is how the water will thermosiphon into the electric water heater without domestic hot water use. i was hoping to created an arrangment so that when the temperatures got below 120, that my electirc elements would pick up the slack and provide hot water.Can anybody verify that this arrangemnt works? or better yet can Bob Rohr chime in, I know he is a Caleffi afficianado and have used much of his advice on my primary secondary systems. thanks to anyone who can take a stab at this before I start piping.
Tom

 

[Clarkbug]

Tom,

You would leave the elements alone in the electric hot water heater. They have a thermostat that would kick on to heat the water if it dropped below their setpoint.

The idea is that the indirect would be hot, and when you draw any hot water in your house by lets say taking a shower, the "cold" water that would fill the electric is actually the water heated by your indirect. That way the only time your electric would run is if you have lots of standby losses, and it needs to maintain temp, or if your boiler is off, and the water in the indirect is also cold.

You are essentially pre-heating the supply water to your electric heater only. There wouldnt be any thermosiphon involved or required.

Hope that helps!

 

[avc8130]

When I plumbed my indirect in, I did it in parallel with my electric. I can use either or. For winter I throw some valves and my indirect supplies DHW powered by the boiler. For summer, I throw the opposite valves and the electric hot water heat supplies DHW.

The other method is to plumb them in series. The cold supply should go into the Indirect first, then the hot from the indirect into the cold of the electric and then the hot to the house. I would set the indirect 10F warmer than the electric thermostat during boiler operation. That should prevent the electric from ever coming on (unless you have a LONG period of now demand and standby losses beat you). Then in the summer your indirect will be filled with well/town temp water and the electric will do all of the heating.

ac