Eko 40 install & a few more questions. thermostat wiring & return temp control circ

[Stlshrk]

Well, I've been working on my install & am trying to make some serious headway before the new baby arrives Labor Day weekend. No irony there, eh?

Here we go again.

You guys rock btw!

1 - My main house supply loop will feed the water/air heat exchanger in the outlet duct of my electric central heat/air system. The original thermostat I have on the system will not support a heat call only turning on the fan (and not the actual heat side of the electric system). I need to be able to call for heat and only engage the fan, but still allow for the electric heat to come on if the temp drops to whatever the lower set temp is. Do I need to replace this with 2 different thermostats to accomplish this or with a single 2 heat/1 cool thermostat? If there is another thread covering this with any specifics, then I seem to be searching incorrectly... There are so many thermostats available, but I don't think that a lot of them are going to work with this type of set up.

2 - I like the idea of having an additional circ to control return temp to the boiler, rather than a mixing valve.
https://www.hearth.com/talk/threads/20980/
Yeah, I know it is an econoburn thread, but I'm hoping to make it work with the Eko 40.
Is it just me or would I need to wire the power supply to the boiler return circ from the boiler control that powers on the primary boiler circulator so that the boiler return circ would not continue to pump water through the boiler the entire time that it is not up to temp? Somehow it would need to only allow the aqua-stat to power on the return circ when the primary boiler circ is also running & then return temp is not high enough. Or, is there another relay that I need to connect here? Entirely possible I'm missing something big picture here.

Thanks folks, looking forward to your input!

 

[Stlshrk]

The existing thermostat has the following connections.

Y,G,R,O,W2,E, AND C

 

[RJP Electric]

I can see why you are in a pickle here, If you continuously pump hot water through your coil in your FHA unit, your limits will automatically turn on your fan. Please excuse the drawing that I butchered, I would use a second thermostat connected to a Taco SR501-1 and put in 24 volt electronic valves as shown, the bypass would be normally open and the one for your heater would be normally closed. When your second thermostat calls it will flip the valves in opposite directions bringing the hot water in your unit. Then I would put on a aquastat near my FHA coil so when the water was up to temperature the fan would come on (connected to red and green low voltage in your unit)