Three types of systems discussed in the ASHRAE GSHP text are the unitary system, the common loop system, and the one-pipe system
. This comparison considers the common loop GSHP using five common loops each connected to eight to 10 heat pumps with a total of 46 units serving the building.
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.
: in this arrangement, a single pipe supplies steam to the heat emitters and returns condensate to the boiler.
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. Efficient off-peak performance is key to reducing annual energy use.
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.
Therefore, the radiator trap now handles all of the venting jobs that were accomplished by the vent in the one-pipe system. The trap also provides a way for condensate to drain without interfering with the steam flow.
These are called one-pipe systems because there is only one pipe connection at the radiator.
with classroom units have been demonstrated to be effective in school applications for dramatic energy reductions, improved comfort and acoustics, and installation cost without the typical premium for GCHP systems (Monahan and Boswell 2007).
have one supply pipe and return from each coil connected back into that same pipe.