vent placement if pump is on return

archibald tuttle

spirovent, caleffi etc. propose lowest pressure highest temp as vent location.

so if i have the pump on the return then these two points are diametrically opposed as you've got the coolest temps at the lowest pressure.

most diagrams show the pump on the feed but past the vent meaning the vent should take care of any undissolved air showing up at high temp and low pressure although i was kind of getting used to the 'it's alright to put the pump on the return as long as you are still pumping away from the PONPC' school of thought.

assuming I stick to that idea should i favor before the pump on the return or after the boiler for vent location in the esteemed opinion of those here gathere.

hot_rod

The highest temperature point is the best. If you have a good microbubble type air sep at the boiler supply outlet, that small delta P that is being seen at the sep location is not a dealbreaker.
The lowest pressure will be at the highest point, if you have piping above the boiler, an auto type float vent can help also. mostly that high point catches air that migrates up when everything shuts down. Hot air rises.