Now that Fall has come to Warrington, PA, the system is switched over to heating.  Like last winter, condensation is rapidly forming on the pipes and the manifold. 

I have about 25 feet of PEXa that comes across the basement ceiling and down into the manifold.  Much of that is covered is Armacell, but the armacell is held on with those zip ties.  If I stick my finger into the insulation (into the cut that runs the length of the armacell) I can feel a little water.  Plus, water drips out both ends of the armacell sleeves. 

The manifold is even worse.  It's brass, and the Supply side, being so cold, is covered with water.  This is an unconditioned basement with a sump pit in the opposite corner.  The pit almost always has some standing water.  There is a cover, but it's not tight fitting.  Water positively drips down the loops, forms on the manifold, then drips onto the basement floor.

The manifold is then connected with short flexible pipes to the flow center.  Water condenses on the supply pipe, trickles onto the flow center, then down onto the floor.

There is laundry in the basement, but the dryer is securely vented to the outside.  The AirTap did provide some humidification, but with the system on for heating more, the AirTap doesn't run much anymore, and when it does, not enough to dry the air.

I'm thinking a mini-gutter under the manifold to catch the water, connected to the condensate line which then goes to the sump pit.

Every system,every install, has it's pro's and cons. You have just discovered some of yours. Running lines through unconditioned space is bound to present problems and running individual loop lines in that space was an issue that needed to be addresed from the beginning. No real problem?
If there is no threat of real damage due to the sweating the work around can be as simple or complex as you choose. If the mini gutter is an effective solution that is acceptable to you, great! If not, other options could be as simple as conditioning the space in question, or a different type of insulation on the pipeing that is more sealed.
hope this helps
Eric

Pipes should be able to be insulated so that they don't sweat. Armaflex is available in a whole host of diameters and wall thicknesses. There is an adhesive available for it. There is also 2x1/8" Armaflex foam tape that can bridge gaps. Keep air from circulating between the Armaflex and the line it insulates and that'll stop condensate.

The Armaflex on our pipes were slid on during installation (no slit running the long dimension of the insulation.) The butt joints (where one piece of Armaflex ends and another piece begins) has what looks like black duct tape around the joint. I have no idea if the pipes are sweating under the Armaflex. I really don't want to know. :-)

The originally installer nailed brackets to hold the pipes into the ceiling joists. He put the armaflex on afterward, so every so often there's a break with a metal bracket. I'm tempted to remove all the brackets, get that armaflex that has the pre-glued joints, wrap the pipes from end to end, tape the joins, then reattach them to the ceiling again. I just don't want to screw anything up. A few of the pipes turn a tightish corner as they go down to the manifold. I don't want to over-flex them. I'm concerned that some of the pipes that are above the ductwork are NOT covered and could be dripping onto the ductboard.

I also may want to wait until spring now, because the pipes are all moist, and I probably shouldn't be insulating them when they are wet. Sigh...it's always something.

The condensate will keep forming unless you seal it up to prevent the endless supply of higher dew point air from getting to the colder pipes. I say you remove the brackets and get complete coverage along the runs, seal at all ends, etc. Put on larger brakets on top of the insulation afterwards. Hard to insulate things can be wrapped with the self adhesive foam tape stuff. It does not have to be perfect, but the better the seals the less condensate will form. You may be able to re-use the old insulation if you seal the seam.

Chris