Help Me Prevent and Air Bleeding Nightmare

Mike T., Swampeast MO

I must add a large radiant floor area to a gravity conversion system. Four small radiant floor areas are already installed and working properly.

Due to the boiler used, the control philosophy <I>and the nature of the original system</I> I must ensure that the head loss in the piping of the new radiant area is essentially zero at normal flow rates--just as it is with the TRVd radiators and existing radiant floors.

Depending on the the heat transfer method used (I'm leaning to Raupanel over a fairly equivalent custom construction) I'll need between 11 and 15 circuits (about 35' each) for this floor.

While I can guarantee that the circuits will be utterly flat with leads directly down to connections, I cannot guarantee that they will be level--even to within 3 pipe diameters of 3/8" tube.

The initial air purge of the 4 existing radiant floor loops is time consuming, messy and usually frustrating for one. (At least there are zero air problems after.)

How do I do ensure I can bleed this without extreme complexity and expense (shut-off and air purge at supply/return for each circuit) yet still ensure positive results?

Things I fairly well assume:

1) The "manifolds" serving the radiant loops will be installed at the end of one gravity main pair and can have shut-off valves installed before the first branches as well as interconnections (with valves) at either or both ends. Drains and air bleeders can be installed nearly anywhere as well. Pitch of the "manifolds" will be maintained just as for the gravity mains unless there is some compelling reason to reverse the pitch in either or both.

2) The FHV (similar to TRV) that will control flow in this area is unrestricted as to position. It can be installed in any practical place in either the supply or return. It will be wall mounted at convenient height and will feature an integral air bleeded.

3) The "extra" pipe required to make the room-length "manifolds" reverse-return will be used since in this case a single two-way valve is serving a large house worth of circuits and I want to ensure that I have "the same nearly zero head loss" at the points the "manifolds" connect to the gravity mains.

When I "think like air", the minimum I can imagine for guaranteed results is shut-off valves at either the supply or return for each circuit plus a way to isolate this section from the rest of the system until it is filled and then use the existing altitude difference (about 10' above this level) to "power purge" each circuit via air vent(s) in the "manifolds". Plus, perhaps, some interconnection (with valve) between these manifolds. Reasonable? Voice of experience from similar experience likely on a far larger scale?