Coordinating Backup Settings

[Brucep]

I am the new owner of a recently installed Seton W-180. I am heating an 8,000 sf home insulated with 6 inches of icynene pillow foam. All floors are hydronic with extra attention to exterior thermal breaks where concrete went against an outside wall. The house is supplied by two 1 1/4" Pex lines insulated with one foot diamater of 2 pound dense rigid foam in a sheet of plastic burried at least 24"...distance of run aproximately 200 ft. It goes to a 250k BTU heat exchanger in the house. I have a Taco 0011 hardwired to circulate continuously the boiler loop. The unit will eventually heat snow melt as well as a pool and shop....for now just the house. D/t the economy I postponed my shop, pool and sm and built a 10x16 ft wood shed that houses the boiler. My settings are as follows:
Temp at boiler (setting) 190
Incoming side at heat exchanger 190 (amazingly undetectable heat loss)
Outgoing side 153

Main circulation loop on house side of Heat Exchanger 160
Leaves exchanger at 180

I am attributing the difference in temperature differentials to asynchronous flow rates.

My original system is a 260kBTU Knight boiler hooked to the same loop that the house side of the heat exchanger is on. I have attached a few pictures for clarification (or more confusion

My dillema is trying to coordinate the backup boiler. When the Knight kicks on it basically cuts any existing differential on the boiler side of the heat exchanger to zero and it rises to activate the blow off on the boiler. Given the current quality of my wood...North Idaho pine/larch and cedar I am not able to get burn times that get me through the night. My goal is to have the knight fill those gaps but still extract the remaining being produced by the Seton. This may not be possible since output temp of the Knight is 180 and it will result in actually pushing heat to the boiler. Right now we have an aquastat connected to the line comeing from the boiler set at 140....so as the boiler starts to fizzle, the knight kicks on but that is the end of my wood heat. Not sure if attached photos help clarify my existing system. Any help on settings or replumbing if necessary appreciatted.

Also I have searched, but was unable to find any information on a simple device/methodology to have me paged when the temp drops below a preset level on the boiler incoming line. There is an online computer nearbye...I'm sure someone must have done this...just can't find it.

 

[jebatty]

...heating an 8,000 sf home...will eventually heat snow melt as well as a pool and shop....for now just the house. D/t the economy I postponed my shop, pool

Applaud you for using a sustainable energy source, which we do too. This is our 19th season of heating with wood. We also have chosen to extend our sustainability goal by continuing to strive for moderation in all other areas of our lifestyle. Even so, our carbon footprint remains much higher than the average European, and is shockingly high when compared to the average world citizen. My wife and I have lots of work yet to do to on our goal of an environmentally sustainable lifestyle.

 

[Nofossil]

This is one of those complex control tasks that require some ingenuity to accomplish with off-the-shelf parts.

You might look at timer relays as part of the solution - don't allow the Knight to come on until the wood boiler has been below a minimum setpoint for some period of time.

As far as alerting you, would a break-on-rise aquastat do it?