Are you using a thermostat in the engine coolant to keep the engine hot, about 190F or just straight thermosiphoning ?
The engine has a 190f thermostat and the water exiting the engine will run into a coil loop inside the solar tank.
After exiting the tank there is a small radiator heat dump which activates if the return water is too hot.
The tank is a well insulated solar hot water collector with dual internal heat exchange coils and a backup heating element.
My main reason for doing this project is twofold.
1] I have all the components collecting dust and want to put them to use. This will offset the cost of the existing heater when the roid is running on WVO. I can learn a lot about hydronic systems at the same time.
2]Greenhouse. Once the system proves itself the fan/coil heater will be moved to the greenhouse on the outside of the garage wall.
My experiments with an electric heater this autumn showed that this heat will be enough to extend my growing season by 1.5 to 2 months on either end of summer by keeping the space warm through the night. That part has been proven the past several growing seasons.
3] This system can be expanded with a second tank once I get my 2 evacuated tube collectors mounted and producing heat.
The system is totally scale-able.
Back to my original question, does the logic seem sound for my method of stretching the heat over a 12 hour period?
(a question perhaps more suited to the Micro-Cogen forum but nobody looks there anymore)