Using indirect as a primary

i07nyc

I installed a odr and my return temp is low. Cast iron boiler with no primary loop. I know I can raise the low temp and solve the problem that way but curious if I was to take the check valve out of the indirect circulator so there would be some gravity flow via the indirect. My thought is that it would borrow heat from the indirect then pay it back at the end of the heating cycle.

hot_rod

It's possible that the heat in the indirect will thermoisiphon back to the boiler, but it will lower the indirect temperature and call on the boiler IF it does.

Add a boiler return device, either a mixing valve, or other temperature responsive valve.