I have an oil furnace that has a tank-less hot water that supplies my hot water. I am looking to install an electric hot water heater in series with my oil furnace. I have read multiple threads of people that have installed an electric water heater by hooking up the hot water return from the oil furnace to the inlet of the electric water heater. Then they would turn off the furnace during the non heating season, and during the heating season they would turn on the boiler. This allows the electric water heater to be fed with hot water from the furnace during the winter months (while the furnace is being used anyways) to help heat the hot water to save electricity. During the summer months the hot water would be heated completely with electricity so the oil furnace can be shut off thus saving the cost of oil being used just to heat the hot water.
My question is has anybody ever installed an electric water heater by installing the return of the electric water heater to the supply of the oil furnace tank-less supply? The reason why I would like to install the water heater before the oil furnace tank-less is because even during the winter months the water that supplies the oil furnace tank-less will already be hot and therefore save oil consumption my helping to keep the burner hot. If I install the electric water heater in series after the oil furnace then the oil furnace would still turn on when I am using hot water. Before anyone states that this is a waste of money because the electricity will be more expensive then oil, let me state that I have solar panels and will never use up the amount of electricity they are creating. Thus if I install the electric water heater in series with the oil burner (before the oil furnace instead of afterwards like most post suggest) during the winter months I would have the added benefit of helping to keep the oil furnace hot. My only cost would be the purchase of an electric water heater and then I would be completely saving money.
I would be interested in hearing people's thoughts about this. Also if you have done this and it is working for you, I would also enjoy hearing from you. Last but not least although this would not be a normal installation, does anyone know if this will pass plumbing codes? All replies will be greatly appreciated and thanks in advance.