M380 Hurricane Heater

[Itchintogo]

From what Chuck explained and from what I can see with the picture (and I don't know squat about Hurricane heaters BTW) I think Chuck could take the Zone 2 hose ( the one with no valve at the TEE and I will come back to this) off and shut the red valve. Then he could flush only zone 2 out and the coolant would empty out of the left hand hose bib. Similarly he could flush through zone 1 by disconnecting the hose with the yellow handle and with the red valve off it too would evacuate from the left hose bib.

Then he could back flush the heating unit by reverse flushing from the hot feed and still with the red valve shut he could open the right hose bib and evacuate from there and not contaminate the zones. Or attach a hose to the right bib and flush out the heater and evacuate at the feed line just before the Tee. Depending which direction he wanted to go.

All of this and because there are so few hours usage makes me think there is a valve somewhere in zone 2 that is shut off. Air is a good thought as well. I wonder why BB would install a yellow valve for Zone 1 and nothing for Zone 2? If you had a leak in zone 2 you would have no way of shutting it off. That does not make sense to me. So at a minimum I would install a yellow valve in zone 2 for that. But I suspect there is one somewhere you have not found yet.

Chuck I don't know who you bought the coach from but any chance you can phone the PO? This valve or valves may be closer to the register or at the return tee where it goes back to one return line. Just my thoughts. Hope it helps.