gravity hot water heat traps

leonz

I recently came across something quite interesting in the Engineering Tool Box with regard to gravity hot water systems using both the reverse return and no reverse return to the boiler sump.

The two drawings they have for two types of gravity hot water heating systems illustrate what they refer to as a "heat lock".

The drawings illustrate how the plumbing was done for this in this manner;
The piping began with the hot water riser coming off the top of the steam chest and then Tee'd with the branch going to the heating load in both drawings and then a short nipple coming off the top of the Tee then connecting to an elbow then to a second short nipple and then another elbow and then a short nipple pointing downward connected to a third elbow connecting another short nipple to the elbow that connects to the riser that eventually connects to the base of the open to air steel expansion tank.

Would a heat trap like this still work with the loop pipe coming off the bottom of the steel expansion tank to keep the water moving to avoid freezing in the tank and still move fast enough in the return pipe to the boiler sump?

thanks

EBEBRATT-Ed

I can picture part of what you describe but to me the piping to the expansion tank should come off the top of the boiler with no "heat trap" You want any air in the system to bubble up into the expansion tank. Air does not want to go down

leonz

Hell Ed,

I agree completely that is why I wanted to post it here and ask the question.

Makes me think perhaps it is best used with the air purged from the system when the heating season starts and the radiators have been bled of air before they get toasty?