Making progress of my DIY hydronic system and was able to run a test on Sunday and will first post what worked!

I filled it slowly with water today from a low point and it has 20 gallons of storage and topped out somewhere around 23 gallons which seems right.

Absolutely none of the PEX connections that I put together using the expansion tool leaked!!!



Fired up my diesel heater and observed the following behavior:

1. It sat there for a bit of time while I think it did its startup sequence of warming up the glow plug, testing water flow and fan speed.
2. It started clicking the pump loudly which muted down as the pump filled with fuel.
3. Exhaust pipe output a little bit of white diesel smoke.
4. Internal fan speed ramped up and the exhaust started to roar and the output fluid pipe was about 170 degrees (no muffler at this time).
5. When turned off it went through a shutdown and cool down cycle for about 3-5 minutes before fully shutting down.

So I believe that the diesel boiler is functional.