The steam pushes the air out through the vents at the ends of the main, and, in the case of a one-pipe system
like this one, on the radiators.
Another central ground loop type is the one-pipe system
shown in the lower left portion of Figure 3.
In a one-pipe system (Figure 2), the main loop flow is provided by a pair of parallel flow pumps.
The disparity in the curves arises from a combination of the part-load performance of the variable speed pumping system and the reduced head losses associated with the one-pipe system.
At peak design conditions, heat pumps operating within a one-pipe system are less efficient than traditional variable flow systems.
The system EER and COP performance of a two-pipe variable flow system versus a one-pipe system is comparable.
In a one-pipe system, the flow to the individual units is managed through the unit mounted circulator.
Therefore, the radiator trap now handles all of the venting jobs that were accomplished by the vent in the one-pipe system.
These are called one-pipe systems because there is only one pipe connection at the radiator.
Because the supply valve cannot be throttled, zoning in one-pipe systems is difficult, although not impossible.
have one supply pipe and return from each coil connected back into that same pipe.